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                                                                   EXHIBIT 10.16

                             XCYTE THERAPIES, INC.

                                 2000 STOCK PLAN

        1. PURPOSES OF THE PLAN. The purposes of this 2000 Stock Plan are to
attract and retain the best available personnel for positions of substantial
responsibility, to provide additional incentive to Employees and Consultants and
to promote the success of the Company's business. Options granted under the Plan
may be Incentive Stock Options or Nonstatutory Stock Options, as determined by
the Administrator at the time of grant of an option and subject to the
applicable provisions of Section 422 of the Code and the regulations promulgated
thereunder. Stock purchase rights may also be granted under the Plan.

        2. DEFINITIONS. As used herein, the following definitions shall apply:

           (a) "ADMINISTRATOR" means the Board or its Committee appointed
pursuant to Section 4 of the Plan.

           (b) "AFFILIATE" means an entity other than a Subsidiary (as defined
below) which, together with the Company, is under common control of a third
person or entity.

           (c) "APPLICABLE LAWS" means the legal requirements relating to the
administration of stock option and restricted stock purchase plans under
applicable U.S. state corporate laws, U.S. federal and applicable state
securities laws, the Code, any Stock Exchange rules or regulations and the
applicable laws of any other country or jurisdiction where Options or Stock
Purchase Rights are granted under the Plan, as such laws, rules, regulations and
requirements shall be in place from time to time.

           (d) "BOARD" means the Board of Directors of the Company.

           (e) "CHANGE OF CONTROL" means a sale of all or substantially all of
the Company's assets, or any merger or consolidation of the Company with or into
another corporation other than a merger or consolidation in which the holders of
more than 50% of the shares of capital stock of the Company outstanding
immediately prior to such transaction continue to hold (either by the voting
securities remaining outstanding or by their being converted into voting
securities of the surviving entity) more than 50% of the total voting power
represented by the voting securities of the Company, or such surviving entity,
outstanding immediately after such transaction.

           (f) "CODE" means the Internal Revenue Code of 1986, as amended.

           (g) "COMMITTEE" means one or more committees or subcommittees of the
Board appointed by the Board to administer the Plan in accordance with Section 4
below.

           (h) "COMMON STOCK" means the Common Stock of the Company.

           (i) "COMPANY" means Xcyte Therapies, Inc., a Delaware corporation.

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           (j) "CONSULTANT" means any person, including an advisor, who is
engaged by the Company or any Parent, Subsidiary or Affiliate to render services
and is compensated for such services, and any director of the Company whether
compensated for such services or not.

           (k) "CONTINUOUS SERVICE STATUS" means the absence of any interruption
or termination of service as an Employee or Consultant. Continuous Service
Status as an Employee or Consultant shall not be considered interrupted in the
case of: (i) sick leave; (ii) military leave; (iii) any other leave of absence
approved by the Administrator, provided that such leave is for a period of not
more than ninety (90) days, unless reemployment upon the expiration of such
leave is guaranteed by contract or statute, or unless provided otherwise
pursuant to Company policy adopted from time to time; or (iv) in the case of
transfers between locations of the Company or between the Company, its Parents,
Subsidiaries, Affiliates or their respective successors. A change in status from
an Employee to a Consultant or from a Consultant to an Employee will not
constitute an interruption of Continuous Service Status.

           (l) "CORPORATE TRANSACTION" means a sale of all or substantially all
of the Company's assets, or a merger, consolidation or other capital
reorganization of the Company with or into another corporation and includes a
Change of Control.

           (m) "DIRECTOR" means a member of the Board.

           (n) "EMPLOYEE" means any person employed by the Company or any
Parent, Subsidiary or Affiliate, with the status of employment determined based
upon such factors as are deemed appropriate by the Administrator in its
discretion, subject to any requirements of the Code or the Applicable Laws. The
payment by the Company of a director's fee to a Director shall not be sufficient
to constitute "employment" of such Director by the Company.

           (o) "EXCHANGE ACT" means the Securities Exchange Act of 1934, as
amended.

           (p) "FAIR MARKET VALUE" means, as of any date, the fair market value
of the Common Stock, as determined by the Administrator in good faith on such
basis as it deems appropriate and applied consistently with respect to
Participants. Whenever possible, the determination of Fair Market Value shall be
based upon the closing price for the Shares as reported in the Wall Street
Journal for the applicable date.

           (q) "INCENTIVE STOCK OPTION" means an Option intended to qualify as
an incentive stock option within the meaning of Section 422 of the Code, as
designated in the applicable Option Agreement.

           (r) "LISTED SECURITY" means any security of the Company that is
listed or approved for listing on a national securities exchange or designated
or approved for designation as a national market system security on an
interdealer quotation system by the National Association of Securities Dealers,
Inc.

           (s) "NAMED EXECUTIVE" means any individual who, on the last day of
the Company's fiscal year, is the chief executive officer of the Company (or is
acting in such

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capacity) or among the four most highly compensated officers of the Company
(other than the chief executive officer). Such officer status shall be
determined pursuant to the executive compensation disclosure rules under the
Exchange Act.

           (t) "NONSTATUTORY STOCK OPTION" means an Option not intended to
qualify as an Incentive Stock Option, as designated in the applicable Option
Agreement.

           (u) "OPTION" means a stock option granted pursuant to the Plan.

           (v) "OPTION AGREEMENT" means a written document, the form(s) of which
shall be approved from time to time by the Administrator, reflecting the terms
of an Option granted under the Plan and includes any documents attached to or
incorporated into such Option Agreement, including, but not limited to, a notice
of stock option grant and a form of exercise notice.

           (w) "OPTION EXCHANGE PROGRAM" means a program approved by the
Administrator whereby outstanding Options are exchanged for Options with a lower
exercise price or are amended to decrease the exercise price as a result of a
decline in the Fair Market Value of the Common Stock.

           (x) "OPTIONED STOCK" means the Common Stock subject to an Option.

           (y) "OPTIONEE" means an Employee or Consultant who receives an
Option.

           (z) "PARENT" means a "parent corporation," whether now or hereafter
existing, as defined in Section 424(e) of the Code, or any successor provision.

           (aa) "PARTICIPANT" means any holder of one or more Options or Stock
Purchase Rights, or the Shares issuable or issued upon exercise of such awards,
under the Plan.

           (bb) "PLAN" means this 2000 Stock Plan.

           (cc) "REPORTING PERSON" means an officer, Director, or greater than
ten percent stockholder of the Company within the meaning of Rule 16a-2 under
the Exchange Act, who is required to file reports pursuant to Rule 16a-3 under
the Exchange Act.

           (dd) "RESTRICTED STOCK" means Shares of Common Stock acquired
pursuant to a grant of a Stock Purchase Right under Section 11 below.

           (ee) "RESTRICTED STOCK PURCHASE AGREEMENT" means a written document,
the form(s) of which shall be approved from time to time by the Administrator,
reflecting the terms of a Stock Purchase Right granted under the Plan and
includes any documents attached to such agreement.

           (ff) "RULE 16B-3" means Rule 16b-3 promulgated under the Exchange
Act, as amended from time to time, or any successor provision.

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           (gg) "SHARE" means a share of the Common Stock, as adjusted in
accordance with Section 14 of the Plan.

           (hh) "STOCK EXCHANGE" means any stock exchange or consolidated stock
price reporting system on which prices for the Common Stock are quoted at any
given time.

           (ii) "STOCK PURCHASE RIGHT" means the right to purchase Common Stock
pursuant to Section 11 below.

           (jj) "SUBSIDIARY" means a "subsidiary corporation," whether now or
hereafter existing, as defined in Section 424(f) of the Code, or any successor
provision.

           (kk) "TEN PERCENT HOLDER" means a person who owns stock representing
more than ten percent (10%) of the voting power of all classes of stock of the
Company or any Parent or Subsidiary.

        3. STOCK SUBJECT TO THE PLAN. Subject to the provisions of Section 14 of
the Plan, the maximum aggregate number of Shares that may be sold under the Plan
is 2,100,000 Shares of Common Stock plus an annual increase on the first day of
each of the Company's fiscal years beginning in 2002 and ending in 2008 equal to
the lesser of (a) 500,000 Shares, (b) 3 % of the Shares outstanding on the last
day of the immediately preceding fiscal year, or (c) such lesser number of
Shares as the Board shall determine. The Shares may be authorized but unissued,
or reacquired Common Stock. If an award should expire or become unexercisable
for any reason without having been exercised in full, or is surrendered pursuant
to an Option Exchange Program, the unpurchased Shares that were subject thereto
shall, unless the Plan shall have been terminated, become available for future
grant under the Plan. In addition, any Shares of Common Stock which are retained
by the Company upon exercise of an award in order to satisfy the exercise or
purchase price for such award or any withholding taxes due with respect to such
exercise or purchase shall be treated as not issued and shall continue to be
available under the Plan. Shares issued under the Plan and later repurchased by
the Company pursuant to any repurchase right which the Company may have shall
not be available for future grant under the Plan.

        4. ADMINISTRATION OF THE PLAN.

           (a) GENERAL. The Plan shall be administered by the Board or a
Committee, or a combination thereof, as determined by the Board. The Plan may be
administered by different administrative bodies with respect to different
classes of Participants and, if permitted by the Applicable Laws, the Board may
authorize one or more officers to make awards under the Plan.

           (b) COMMITTEE COMPOSITION. If a Committee has been appointed pursuant
to this Section 4, such Committee shall continue to serve in its designated
capacity until otherwise directed by the Board. From time to time the Board may
increase the size of any Committee and appoint additional members thereof,
remove members (with or without cause) and appoint new members in substitution
therefor, fill vacancies (however caused) and remove all members of a Committee
and thereafter directly administer the Plan, all to the extent permitted by the

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Applicable Laws and, in the case of a Committee administering the Plan in
accordance with the requirements of Rule 16b-3 or Section 162(m) of the Code, to
the extent permitted or required by such provisions.

           (c) POWERS OF THE ADMINISTRATOR. Subject to the provisions of the
Plan and in the case of a Committee, the specific duties delegated by the Board
to such Committee, the Administrator shall have the authority, in its
discretion:

               (i) to determine the Fair Market Value of the Common Stock, in
accordance with Section 2(p) of the Plan, provided that such determination shall
be applied consistently with respect to Participants under the Plan;

               (ii) to select the Employees and Consultants to whom Options and
Stock Purchase Rights may from time to time be granted;

               (iii) to determine whether and to what extent Options and Stock
Purchase Rights are granted;

               (iv) to determine the number of Shares of Common Stock to be
covered by each award granted;

               (v) to approve the form(s) of agreement(s) used under the Plan;

               (vi) to determine the terms and conditions, not inconsistent with
the terms of the Plan, of any award granted hereunder, which terms and
conditions include but are not limited to the exercise or purchase price, the
time or times when awards may be exercised (which may be based on performance
criteria), any vesting acceleration or waiver of forfeiture restrictions, and
any restriction or limitation regarding any Option, Optioned Stock, Stock
Purchase Right or Restricted Stock, based in each case on such factors as the
Administrator, in its sole discretion, shall determine;

               (vii) to determine whether and under what circumstances an Option
may be settled in cash under Section 10(c) instead of Common Stock;

               (viii) to implement an Option Exchange Program on such terms and
conditions as the Administrator in its discretion deems appropriate, provided
that no amendment or adjustment to an Option that would materially and adversely
affect the rights of any Optionee shall be made without the prior written
consent of the Optionee;

               (ix) to adjust the vesting of an Option held by an Employee or
Consultant as a result of a change in the terms or conditions under which such
person is providing services to the Company;

               (x) to construe and interpret the terms of the Plan and awards
granted under the Plan, which constructions, interpretations and decisions shall
be final and binding on all Participants; and

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               (xi) in order to fulfill the purposes of the Plan and without
amending the Plan, to modify grants of Options or Stock Purchase Rights to
Participants who are foreign nationals or employed outside of the United States
in order to recognize differences in local law, tax policies or customs.

        5. ELIGIBILITY.

           (a) RECIPIENTS OF GRANTS. Nonstatutory Stock Options and Stock
Purchase Rights may be granted to Employees and Consultants. Incentive Stock
Options may be granted only to Employees, provided that Employees of Affiliates
shall not be eligible to receive Incentive Stock Options.

           (b) TYPE OF OPTION. Each Option shall be designated in the Option
Agreement as either an Incentive Stock Option or a Nonstatutory Stock Option.

           (c) ISO $100,000 LIMITATION. Notwithstanding any designation under
Section 5(b), to the extent that the aggregate Fair Market Value of Shares with
respect to which Options designated as Incentive Stock Options are exercisable
for the first time by any Optionee during any calendar year (under all plans of
the Company or any Parent or Subsidiary) exceeds $100,000, such excess Options
shall be treated as Nonstatutory Stock Options. For purposes of this Section
5(c), Incentive Stock Options shall be taken into account in the order in which
they were granted, and the Fair Market Value of the Shares subject to an
Incentive Stock Option shall be determined as of the date of the grant of such
Option.

           (d) NO EMPLOYMENT RIGHTS. The Plan shall not confer upon any
Participant any right with respect to continuation of an employment or
consulting relationship with the Company, nor shall it interfere in any way with
such Participant's right or the Company's right to terminate his or her
employment or consulting relationship at any time, with or without Cause.

        6. TERM OF PLAN. The Plan shall become effective upon its adoption by
the Board of Directors. It shall continue in effect for a term of ten (10) years
unless sooner terminated under Section 16 of the Plan.

        7. TERM OF OPTION. The term of each Option shall be the term stated in
the Option Agreement; provided that the term shall be no more than ten years
from the date of grant thereof or such shorter term as may be provided in the
Option Agreement and provided further that, in the case of an Incentive Stock
Option granted to a person who at the time of such grant is a Ten Percent
Holder, the term of the Option shall be five years from the date of grant
thereof or such shorter term as may be provided in the Option Agreement.

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        8. LIMITATION ON GRANTS TO EMPLOYEES. Subject to adjustment as provided
in Section 14 below, the maximum number of Shares that may be subject to Options
and Stock Purchase Rights granted to any one Employee under this Plan for any
fiscal year of the Company shall be 1,000,000, provided that this Section 8
shall apply only after such time, if any, as the Common Stock becomes a Listed
Security.

        9. OPTION EXERCISE PRICE AND CONSIDERATION.

           (a) EXERCISE PRICE. The per Share exercise price for the Shares to be
issued pursuant to exercise of an Option shall be such price as is determined by
the Administrator and set forth in the Option Agreement, but shall be subject to
the following:

               (i) In the case of an Incentive Stock Option

                   (A) granted to an Employee who at the time of grant is a Ten
Percent Holder, the per Share exercise price shall be no less than 110% of the
Fair Market Value per Share on the date of grant; or

                   (B) granted to any other Employee, the per Share exercise
price shall be no less than 100% of the Fair Market Value per Share on the date
of grant.

               (ii) In the case of a Nonstatutory Stock Option, the per share
Exercise Price shall be such price as determined by the Administrator provided
that if such eligible person is, at the time of the grant of such Option, a
Named Executive of the Company, the per share Exercise Price shall be no less
than 100% of the Fair Market Value on the date of grant if such Option is
intended to qualify as performance-based compensation under Section 162(m) of
the Code.

               (iii) Notwithstanding the foregoing, Options may be granted with
a per Share exercise price other than as required above pursuant to a merger or
other corporate transaction.

           (b) PERMISSIBLE CONSIDERATION. The consideration to be paid for the
Shares to be issued upon exercise of an Option, including the method of payment,
shall be determined by the Administrator (and, in the case of an Incentive Stock
Option, shall be determined at the time of grant) and may consist entirely of
(1) cash; (2) check; (3) delivery of Optionee's promissory note with such
recourse, interest, security and redemption provisions as the Administrator
determines to be appropriate (subject to the provisions of Section 153 of the
Delaware General Corporation Law); (4) cancellation of indebtedness; (5) other
Shares that have a Fair Market Value on the date of surrender equal to the
aggregate exercise price of the Shares as to which the Option is exercised,
provided that in the case of Shares acquired, directly or indirectly, from the
Company, such Shares must have been owned by the Optionee for more than six
months on the date of surrender (or such other period as may be required to
avoid the Company's incurring an adverse accounting charge); (6) delivery of a
properly executed exercise notice together with such other documentation as the
Administrator and a securities broker approved by the Company shall require to
effect exercise of the Option and prompt delivery to

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the Company of the sale or loan proceeds required to pay the exercise price and
any applicable withholding taxes; or (7) any combination of the foregoing
methods of payment. In making its determination as to the type of consideration
to accept, the Administrator shall consider if acceptance of such consideration
may be reasonably expected to benefit the Company and the Administrator may, in
its sole discretion, refuse to accept a particular form of consideration at the
time of any Option exercise.

        10. EXERCISE OF OPTION.

           (a) GENERAL.

               (i) EXERCISABILITY. Any Option granted hereunder shall be
exercisable at such times and under such conditions as determined by the
Administrator, consistent with the term of the Plan and reflected in the Option
Agreement, including vesting requirements and/or performance criteria with
respect to the Company and/or the Optionee. The Administrator shall have the
discretion to determine whether and to what extent the vesting of Options shall
be tolled during any unpaid leave of absence; provided however that in the
absence of such determination, vesting of Options shall be tolled during any
such leave.

               (ii) MINIMUM EXERCISE REQUIREMENTS. An Option may not be
exercised for a fraction of a Share. The Administrator may require that an
Option be exercised as to a minimum number of Shares, provided that such
requirement shall not prevent an Optionee from exercising the full number of
Shares as to which the Option is then exercisable.

               (iii) PROCEDURES FOR AND RESULTS OF EXERCISE. An Option shall be
deemed exercised when written notice of such exercise has been given to the
Company in accordance with the terms of the Option by the person entitled to
exercise the Option and the Company has received full payment for the Shares
with respect to which the Option is exercised. Full payment may, as authorized
by the Administrator, consist of any consideration and method of payment
allowable under Section 9(b) of the Plan, provided that the Administrator may,
in its sole discretion, refuse to accept any form of consideration at the time
of any Option exercise.

        Exercise of an Option in any manner shall result in a decrease in the
number of Shares that thereafter may be available, both for purposes of the Plan
and for sale under the Option, by the number of Shares as to which the Option is
exercised.

               (iv) RIGHTS AS STOCKHOLDER. Until the issuance of the Shares (as
evidenced by the appropriate entry on the books of the Company or of a duly
authorized transfer agent of the Company), no right to vote or receive dividends
or any other rights as a stockholder shall exist with respect to the Optioned
Stock, notwithstanding the exercise of the Option. No adjustment will be made
for a dividend or other right for which the record date is prior to the date the
stock certificate is issued, except as provided in Section 14 of the Plan.

           (b) TERMINATION OF EMPLOYMENT OR CONSULTING RELATIONSHIP. Except as
otherwise set forth in this Section 10(b), the Administrator shall establish and
set forth in the applicable Option Agreement the terms and conditions upon which
an Option shall remain

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exercisable, if at all, following termination of an Optionee's Continuous
Service Status, which provisions may be waived or modified by the Administrator
at any time in the Administrator's sole discretion. To the extent that the
Optionee is not entitled to exercise an Option at the date of his or her
termination of Continuous Service Status, or if the Optionee (or other person
entitled to exercise the Option) does not exercise the Option to the extent so
entitled within the time specified in the Option Agreement or below (as
applicable), the Option shall terminate and the Optioned Stock underlying the
unexercised portion of the Option shall revert to the Plan. In no event may any
Option be exercised after the expiration of the Option term as set forth in the
Option Agreement (and subject to Section 7). In the event the period for
exercise of an Option following the termination of the Optionee's Continuous
Service Status, as provided in the Option Agreement or below, is longer than the
period permitted under Code Section 422 for an Incentive Stock Option, upon the
expiration of the period permitted under Code Section 422 such Option, if
designated as an Incentive Stock Option, shall be treated as a Nonstatutory
Stock Option.

        The following provisions shall apply to the extent an Option Agreement
does not specify the terms and conditions upon which an Option shall terminate
upon termination of an Optionee's Continuous Service Status:

               (i) TERMINATION OTHER THAN UPON DISABILITY OR DEATH. In the event
of termination of an Optionee's Continuous Service Status other than as a result
of disability or death, such Optionee may exercise an Option for three months
following such termination to the extent the Optionee was entitled to exercise
it at the date of such termination.

               (ii) DISABILITY OF OPTIONEE. In the event of termination of an
Optionee's Continuous Service Status as a result of his or her disability
(including a disability within the meaning of Section 22(e)(3) of the Code),
such Optionee may exercise an Option at any time within twelve months following
such termination to the extent the Optionee was entitled to exercise it at the
date of such termination.

               (iii) DEATH OF OPTIONEE. In the event of the death of an Optionee
during the period of Continuous Service Status, or within 30 days following
termination of Optionee's Continuous Service Status, the Option may be exercised
by Optionee's estate or by a person who acquired the right to exercise the
Option by bequest or inheritance at any time within twelve months following the
date of death, but only to the extent of the right to exercise that had accrued
at the date the Optionee's Continuous Service Status terminated.

           (c) BUYOUT PROVISIONS. The Administrator may at any time offer to buy
out for a payment in cash or Shares an Option previously granted under the Plan
based on such terms and conditions as the Administrator shall establish and
communicate to the Optionee at the time that such offer is made.

        11. STOCK PURCHASE RIGHTS.

           (a) RIGHTS TO PURCHASE. When the Administrator determines that it
will offer Stock Purchase Rights under the Plan, it shall advise the offeree in
writing of the terms, conditions and restrictions related to the offer,
including the number of Shares that such person

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shall be entitled to purchase, the price to be paid, and the time within which
such person must accept such offer. The offer to purchase Shares subject to
Stock Purchase Rights shall be accepted by execution of a Restricted Stock
Purchase Agreement in the form determined by the Administrator.

           (b) REPURCHASE OPTION.

               (i) GENERAL. Unless the Administrator determines otherwise, the
Restricted Stock Purchase Agreement shall grant the Company a repurchase option
exercisable upon the voluntary or involuntary termination of the purchaser's
employment with the Company for any reason (including death or disability). The
purchase price for Shares repurchased pursuant to the Restricted Stock Purchase
Agreement shall be the original purchase price paid by the purchaser and may be
paid by cancellation of any indebtedness of the purchaser to the Company. The
repurchase option shall lapse at such rate as the Administrator may determine.

               (ii) TERMINATION FOR CAUSE. In the event of termination of a
Participant's Continuous Service for Cause, the Company shall have the right to
repurchase from the Participant vested Shares issued upon exercise of a Stock
Purchase Right at the Participant's original cost for the Shares. Such
repurchase shall be effected pursuant to such terms and conditions, and at such
time, as the Administrator shall determine. Nothing in this Section 11(b)(ii)
shall in any way limit the Company's right to purchase unvested Shares as set
forth in the applicable Restricted Stock Purchase Agreement.

           (c) OTHER PROVISIONS. The Restricted Stock Purchase Agreement shall
contain such other terms, provisions and conditions not inconsistent with the
Plan as may be determined by the Administrator in its sole discretion. In
addition, the provisions of Restricted Stock Purchase Agreements need not be the
same with respect to each purchaser.

           (d) RIGHTS AS A STOCKHOLDER. Once the Stock Purchase Right is
exercised, the purchaser shall have the rights equivalent to those of a
stockholder, and shall be a stockholder when his or her purchase is entered upon
the records of the duly authorized transfer agent of the Company. No adjustment
will be made for a dividend or other right for which the record date is prior to
the date the Stock Purchase Right is exercised, except as provided in Section 14
of the Plan.

        12. TAXES.

           (a) As a condition of the exercise of an Option or Stock Purchase
Right granted under the Plan, the Participant (or in the case of the
Participant's death, the person exercising the Option or Stock Purchase Right)
shall make such arrangements as the Administrator may require for the
satisfaction of any applicable federal, state, local or foreign withholding tax
obligations that may arise in connection with the exercise of the Option or
Stock Purchase Right and the issuance of Shares. The Company shall not be
required to issue any Shares under the Plan until such obligations are
satisfied. If the Administrator allows the withholding or surrender of Shares to
satisfy a Participant's tax withholding obligations under this Section 12
(whether pursuant to Section 12(c), (d) or (e), or otherwise), the Administrator

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shall not allow Shares to be withheld in an amount that exceeds the minimum
statutory withholding rates for federal and state tax purposes, including
payroll taxes.

           (b) In the case of an Employee and in the absence of any other
arrangement, the Employee shall be deemed to have directed the Company to
withhold or collect from his or her compensation an amount sufficient to satisfy
such tax obligations from the next payroll payment otherwise payable after the
date of an exercise of the Option or Stock Purchase Right.

           (c) This Section 12(c) shall apply only after the date, if any, upon
which the Common Stock becomes a Listed Security. In the case of Participant
other than an Employee (or in the case of an Employee where the next payroll
payment is not sufficient to satisfy such tax obligations, with respect to any
remaining tax obligations), in the absence of any other arrangement and to the
extent permitted under the Applicable Laws, the Participant shall be deemed to
have elected to have the Company withhold from the Shares to be issued upon
exercise of the Option or Stock Purchase Right that number of Shares having a
Fair Market Value determined as of the applicable Tax Date (as defined below)
equal to the amount required to be withheld. For purposes of this Section 12,
the Fair Market Value of the Shares to be withheld shall be determined on the
date that the amount of tax to be withheld is to be determined under the
Applicable Laws (the "Tax Date").

           (d) If permitted by the Administrator, in its discretion, a
Participant may satisfy his or her tax withholding obligations upon exercise of
an Option or Stock Purchase Right by surrendering to the Company Shares that
have a Fair Market Value determined as of the applicable Tax Date equal to the
amount required to be withheld. In the case of shares previously acquired from
the Company that are surrendered under this Section 12(d), such Shares must have
been owned by the Participant for more than six (6) months on the date of
surrender (or such other period of time as is required for the Company to avoid
adverse accounting charges).

           (e) Any election or deemed election by a Participant to have Shares
withheld to satisfy tax withholding obligations under Section 12(c) or (d) above
shall be irrevocable as to the particular Shares as to which the election is
made and shall be subject to the consent or disapproval of the Administrator.
Any election by a Participant under Section 12(d) above must be made on or prior
to the applicable Tax Date.

           (f) In the event an election to have Shares withheld is made by a
Participant and the Tax Date is deferred under Section 83 of the Code because no
election is filed under Section 83(b) of the Code, the Participant shall receive
the full number of Shares with respect to which the Option or Stock Purchase
Right is exercised but such Participant shall be unconditionally obligated to
tender back to the Company the proper number of Shares on the Tax Date.

        13. NON-TRANSFERABILITY OF OPTIONS AND STOCK PURCHASE RIGHTS.

           (a) GENERAL. Except as set forth in this Section 13, Options and
Stock Purchase Rights may not be sold, pledged, assigned, hypothecated,
transferred or disposed of in

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any manner other than by will or by the laws of descent or distribution. The
designation of a beneficiary by an Optionee will not constitute a transfer. An
Option or Stock Purchase Right may be exercised, during the lifetime of the
holder of an Option or Stock Purchase Right, only by such holder or a transferee
permitted by this Section 13.

           (b) LIMITED TRANSFERABILITY RIGHTS. Notwithstanding anything else in
this Section 13, prior to the date, if any, on which the Common Stock becomes a
Listed Security, the Administrator may in its discretion grant Nonstatutory
Stock Options that may be transferred by instrument to an inter vivos or
testamentary trust in which the Options are to be passed to beneficiaries upon
the death of the trustor (settlor) or by gift to "Immediate Family" (as defined
below), on such terms and conditions as the Administrator deems appropriate.
Following the date, if any, on which the Common Stock becomes a Listed Security,
the Administrator may in its discretion grant transferable Nonstatutory Stock
Options pursuant to Option Agreements specifying the manner in which such
Nonstatutory Stock Options are transferable. "Immediate Family" means any child,
stepchild, grandchild, parent, stepparent, grandparent, spouse, sibling,
mother-in-law, father-in-law, son-in-law, daughter-in-law, brother-in-law, or
sister-in-law, and shall include adoptive relationships.

        14. ADJUSTMENTS UPON CHANGES IN CAPITALIZATION, MERGER OR CERTAIN OTHER
TRANSACTIONS.

           (a) CHANGES IN CAPITALIZATION. Subject to any required action by the
stockholders of the Company, the number of Shares of Common Stock covered by
each outstanding Option or Stock Purchase Right, the numbers of Shares set forth
in Sections 3(a) and 8 above, and the number of Shares of Common Stock that have
been authorized for issuance under the Plan but as to which no Options or Stock
Purchase Rights have yet been granted or that have been returned to the Plan
upon cancellation or expiration of an Option or Stock Purchase Right, as well as
the price per Share of Common Stock covered by each such outstanding Option or
Stock Purchase Right, shall be proportionately adjusted for any increase or
decrease in the number of issued Shares of Common Stock resulting from a stock
split, reverse stock split, stock dividend, combination, recapitalization or
reclassification of the Common Stock, or any other increase or decrease in the
number of issued Shares of Common Stock effected without receipt of
consideration by the Company; provided, however, that conversion of any
convertible securities of the Company shall not be deemed to have been "effected
without receipt of consideration." Such adjustment shall be made by the
Administrator, whose determination in that respect shall be final, binding and
conclusive. Except as expressly provided herein, no issuance by the Company of
shares of stock of any class, or securities convertible into shares of stock of
any class, shall affect, and no adjustment by reason thereof shall be made with
respect to, the number or price of Shares of Common Stock subject to an Option
or Stock Purchase Right.

           (b) DISSOLUTION OR LIQUIDATION. In the event of the dissolution or
liquidation of the Company, each Option and Stock Purchase Right will terminate
immediately prior to the consummation of such action, unless otherwise
determined by the Administrator.

           (c) CORPORATE TRANSACTION.

                                      -12-
<PAGE>   13

               (i) In the event of a Corporate Transaction, each outstanding
Option and Stock Purchase Right shall be assumed or an equivalent option or
right shall be substituted by the successor corporation or a Parent or
Subsidiary of such successor corporation, unless such successor corporation does
not agree to assume the outstanding Options or Stock Purchase Rights or to
substitute equivalent options or rights, in which case such Options or Stock
Purchase Rights shall terminate upon the consummation of the transaction.

               (ii) In the event of a Change of Control, if the successor
corporation or a Parent or Subsidiary of such successor corporation agrees to
assume unexercised Options or Stock Purchase Rights or to substitute them with
equivalent options or stock purchase rights, the vesting and exercisability of
each outstanding Option and Stock Purchase Right shall accelerate such that the
Options and Stock Purchase Rights shall become vested and exercisable as to the
lesser of 25% of the Shares subject to the Option or Stock Purchase Right or the
remaining unvested Shares, and any repurchase right of the Company with respect
to Shares issued upon exercise of an Option or Stock Purchase Right shall lapse
as to the lesser of 25% of the Shares initially subject to the Company
repurchase right or the remaining Shares subject to the Company repurchase
right. The acceleration of vesting and lapse of repurchase rights provided for
in this Section 15(c)(ii) shall occur immediately prior to consummation of the
Change of Control and shall apply to Shares that would have vested last under
the vesting schedule applicable to the option or the shares subject to Company
repurchase right.

               (iii) In addition to the acceleration of vesting and lapse of
repurchase rights provided for in Section 15(c)(ii), in the event of the
Involuntary Termination within twelve (12) months of the Change of Control of a
Participant holding an Option or Stock Purchase Right that is assumed or
substituted by the Successor Corporation in the Change of Control, or holding
Restricted Stock issued upon exercise of an Option or Stock Purchase Right with
respect to which the Successor Corporation has succeeded to a repurchase right
as a result of the Change of Control, then any assumed or substituted Option or
Stock Purchase Right held by such Participant at the time of the Involuntary
Termination shall accelerate and become exercisable as to the lesser of 25% of
the Shares subject to the Option or Stock Purchase Right or the remaining
unvested Shares, and any repurchase right of the Company with respect to Shares
issued upon exercise of an Option or Stock Purchase Right shall lapse as to the
lesser of 25% of the Shares initially subject to the Company repurchase right or
the remaining Shares subject to the Company repurchase right. The acceleration
of vesting and lapse of repurchase rights provided for in this Section
15(c)(iii) shall occur as of the Participant's last day of Continuous Service
Status.

               (iv) In the event the Successor Corporation does not agree to
assume unexercised Options, or to substitute them with equivalent options or
stock purchase rights, the vesting and exercisability of each outstanding Option
and Stock Purchase Right shall accelerate such that the Options and Stock
Purchase Rights shall become vested and exercisable as to 100% of the remaining
unvested Shares, and any repurchase right of the Company with respect to Shares
issued upon exercise of an Option or Stock Purchase Right shall lapse as to 100%
of the remaining Shares subject to the Company repurchase right. The
acceleration of vesting and lapse

                                      -13-
<PAGE>   14

of repurchase rights provided for in this Section 15(c)(iv) shall occur
immediately prior to consummation of the Change of Control.

               (v) For purposes of this Section 15(c), an Option or a Stock
Purchase Right shall be considered assumed, without limitation, if, at the time
of issuance of the stock or other consideration upon a Corporate Transaction or
a Change of Control, as the case may be, each holder of an Option or Stock
Purchase Right would be entitled to receive upon exercise of the Option or Stock
Purchase Right the same number and kind of shares of stock or the same amount of
property, cash or securities as such holder would have been entitled to receive
upon the occurrence of the transaction if the holder had been, immediately prior
to such transaction, the holder of the number of Shares of Common Stock covered
by the Option or the Stock Purchase Right at such time (after giving effect to
any adjustments in the number of Shares covered by the Option or Stock Purchase
Right as provided for in this Section 15); provided however that if such
consideration received in the transaction is not solely common stock of the
successor corporation or its Parent, the Administrator may, with the consent of
the successor corporation, provide for the consideration to be received upon
exercise of the Option or Stock Purchase Right to be solely common stock of the
successor corporation or its Parent equal to the Fair Market Value of the per
Share consideration received by holders of Common Stock in the transaction.

               (vi) For purposes of this Section 15(c) "Involuntary Termination"
means termination of a Participant's Continuous Service under the following
circumstances: (A) termination without Cause by the Company or a Subsidiary,
Parent, Affiliate or successor thereto, as appropriate; or (B) voluntary
resignation by the Participant within 30 days following (I) a reduction in the
Participant's then-current base salary of more than 20%, other than in
connection with a similar reduction in the base salaries of similarly situated
employees or consultants as part of a general salary level reduction; or (II)
relocation by the Company or a Subsidiary, Parent, Affiliate or successor
thereto, as appropriate, of the Participant's work site to a facility or
location by more than 50 miles from the Participant's principal work site
immediately prior to such relocation.

               (vii) For purposes of this Section 15(c), "Cause" for termination
of a Participant's Continuous Service Status will exist if the Participant is
terminated for any of the following reasons: (A) Participant's material breach
of any of the terms of any written agreement between the Participant and the
Company; (B) Participant's conviction of a felony harmful to the reputation of
the Company or of a crime involving moral turpitude; (C) Participant's willful
misconduct in the performance of his or her duties and responsibilities to the
Company; (D) Participant's violation of his or her duty of loyalty or his or her
obligations with respect to proprietary information or trade secrets of the
Company or to any party to whom the Participant owes an obligation of
nondisclosure as a result of his or her relationship with the Company; (E)
Participant's violation of the Company's nondiscrimination policies or policies
prohibiting harassment; or (F) Participant's commission of any other intentional
wrongful act that could cause the Company to be liable to a third party. The
determination as to whether a Participant's Continuous Service is terminated for
Cause shall be made in good faith by the Company and shall be final and binding
on the Participant. The foregoing definition does not in any way limit

                                      -14-
<PAGE>   15

the Company's ability to terminate a Participant's employment or consulting
relationship at any time as provided in Section 5(d) above. The term "Company"
will be interpreted to include any Subsidiary, Parent, Affiliate or successor
thereto, as appropriate.

           (d) CERTAIN DISTRIBUTIONS. In the event of any distribution to the
Company's stockholders of securities of any other entity or other assets (other
than dividends payable in cash or stock of the Company) without receipt of
consideration by the Company, the Administrator may, in its discretion,
appropriately adjust the price per Share of Common Stock covered by each
outstanding Option or Stock Purchase Right to reflect the effect of such
distribution.

        15. TIME OF GRANTING OPTIONS AND STOCK PURCHASE RIGHTS. The date of
grant of an Option or Stock Purchase Right shall, for all purposes, be the date
on which the Administrator makes the determination granting such Option or Stock
Purchase Right, or such other date as is determined by the Administrator,
provided that in the case of any Incentive Stock Option, the grant date shall be
the later of the date on which the Administrator makes the determination
granting such Incentive Stock Option or the date of commencement of the
Optionee's employment relationship with the Company. Notice of the determination
shall be given to each Employee or Consultant to whom an Option or Stock
Purchase Right is so granted within a reasonable time after the date of such
grant.

        16. AMENDMENT AND TERMINATION OF THE PLAN.

           (a) AUTHORITY TO AMEND OR TERMINATE. The Board may at any time amend,
alter, suspend or discontinue the Plan, but no amendment, alteration, suspension
or discontinuation (other than an adjustment pursuant to Section 14 above) shall
be made that would materially and adversely affect the rights of any Optionee or
holder of Stock Purchase Rights under any outstanding grant, without his or her
consent. In addition, to the extent necessary and desirable to comply with the
Applicable Laws, the Company shall obtain stockholder approval of any Plan
amendment in such a manner and to such a degree as required.

           (b) EFFECT OF AMENDMENT OR TERMINATION. No amendment or termination
of the Plan shall materially and adversely affect Options or Stock Purchase
Rights already granted, unless mutually agreed otherwise between the Optionee or
holder of the Stock Purchase Rights and the Administrator, which agreement must
be in writing and signed by the Optionee or holder and the Company.

        17. CONDITIONS UPON ISSUANCE OF SHARES. Notwithstanding any other
provision of the Plan or any agreement entered into by the Company pursuant to
the Plan, the Company shall not be obligated, and shall have no liability for
failure, to issue or deliver any Shares under the Plan unless such issuance or
delivery would comply with the Applicable Laws, with such compliance determined
by the Company in consultation with its legal counsel. As a condition to the
exercise of an Option or Stock Purchase Right, the Company may require the
person exercising the award to represent and warrant at the time of any such
exercise that the Shares are being purchased only for investment and without any
present intention to sell or distribute such Shares if, in the opinion of
counsel for the Company, such a representation is required by law.

                                      -15-
<PAGE>   16

        18. RESERVATION OF SHARES. The Company, during the term of this Plan,
will at all times reserve and keep available such number of Shares as shall be
sufficient to satisfy the requirements of the Plan.

        19. AGREEMENTS. Options and Stock Purchase Rights shall be evidenced by
Option Agreements and Restricted Stock Purchase Agreements, respectively, in
such form(s) as the Administrator shall from time to time approve.

        20. STOCKHOLDER APPROVAL. If required by the Applicable Laws,
continuance of the Plan shall be subject to approval by the stockholders of the
Company within twelve (12) months before or after the date the Plan is adopted.
Such stockholder approval shall be obtained in the manner and to the degree
required under the Applicable Laws.

        21. INFORMATION AND DOCUMENTS TO OPTIONEES AND PURCHASERS. Prior to the
date, if any, upon which the Common Stock becomes a Listed Security and if
required by the Applicable Laws, the Company shall provide financial statements
at least annually to each Optionee and to each individual who acquired Shares
pursuant to the Plan, during the period such Optionee or purchaser has one or
more Options or Stock Purchase Rights outstanding, and in the case of an
individual who acquired Shares pursuant to the Plan, during the period such
individual owns such Shares. The Company shall not be required to provide such
information if the issuance of Options or Stock Purchase Rights under the Plan
is limited to key employees whose duties in connection with the Company assure
their access to equivalent information.

        22. AWARDS GRANTED TO CALIFORNIA RESIDENTS. Prior to the date, if any,
upon which the Common Stock becomes a Listed Security, Options or Stock Purchase
Rights granted under the Plan to persons resident in California shall be subject
to the provisions set forth in Attachment A hereto. To the extent the provisions
of the Plan conflict with the provisions set forth on Attachment A, the
provisions on Attachment A shall govern the terms of such Options.

                                      -16-
<PAGE>   17

                                  ATTACHMENT A
                    PROVISIONS APPLICABLE TO AWARD RECIPIENTS
                             RESIDENT IN CALIFORNIA

        Until such time as any security of the Company becomes a Listed Security
and if required by Applicable Laws, the following additional terms shall apply
to Options and Stock Purchase Rights, and Shares issued upon exercise of such
awards, granted under the 2000 Stock Plan (the "Plan") to persons resident in
California as of the grant date of any such award (each such person, a
"California Recipient"):

        1. In the case of an Option, whether an Incentive Stock Option or a
Nonqualified Stock Option, that is granted to a California Recipient who, at the
time of the grant of such Option, owns stock representing more than 10% of the
total combined voting power of all classes of stock of the Company or any Parent
or Subsidiary, the per Share exercise price shall be no less than 110% of the
Fair Market Value on the grant date.

        2. In the case of a Nonqualified Stock Option that is granted to any
other California Recipient, the per Share exercise price shall be no less than
85% of the Fair Market Value per Share on the grant date.

        3. In the case of a Stock Purchase Right granted to a California
Recipient, the purchase price applicable to stock purchased under such Stock
Award shall not be less than 85% of the Fair Market Value of the Shares as of
the Grant Date, or, in the case of a person owning stock representing more than
10% of the total combined voting power of all classes of stock of the Company or
any Parent or Subsidiary, the price shall not be less than 100% of the Fair
Market Value of the Shares as of the grant date.

        4. With respect to an Option or Stock Purchase Right issued to any
California Recipient who is not an Officer, Director or Consultant, such Option
or Stock Purchase Right shall become exercisable, or any repurchase option in
favor of the Company shall lapse, at the rate of at least 20% of the Shares per
year over five years from the grant date.

        5. The following rules shall apply to an Option issued to any California
Recipient or to stock issued to a California Recipient upon exercise of a Stock
Purchase Right, in the event of termination of the California Recipient's
employment or services with the Company:

           (a) If such termination was for reasons other than death or
disability, the California Recipient shall have at least 30 days after the date
of such termination (but in no event later than the expiration of the term of
such Option established by the Plan Administrator as of the grant date) to
exercise such Option.

           (b) If such termination was on account of the death or disability of
the California Recipient, the holder of the Option may, but only within six
months from the date of such termination (but in no event later than the
expiration date of the term of such Option established by the Plan Administrator
as of the grant date), exercise the Option to the extent the California
Recipient was otherwise entitled to exercise it at the date of such termination.
To the extent that the California Recipient was not entitled to exercise the
Option at the date of

<PAGE>   18

termination, or if the holder does not exercise such Option to the extent so
entitled within six months from the date of termination, the Option shall
terminate and the Common Stock underlying the unexercised portion of the Option
shall revert to the Plan.

        6. The Company shall provide financial statements at least annually to
each California Recipient during the period such person has one or more Options
or Stock Awards outstanding, and in the case of an individual who acquired
Shares pursuant to the Plan, during the period such individual owns such Shares.
The Company shall not be required to provide such information if the issuance of
awards under the Plan is limited to key employees whose duties in connection
with the Company assure their access to equivalent information.

        7. Unless defined below or otherwise in this Attachment, Capitalized
terms shall have the meanings set forth in the Plan. For purposes of this
Attachment, "Officer" means a person who is an officer of the Company within the
meaning of Section 16(a) of the Exchange Act and the rules and regulations
promulgated thereunder.

                                      -ii-<PAGE>   1
                                                                   EXHIBIT 10.17

                             XCYTE THERAPIES, INC.

                        2000 EMPLOYEE STOCK PURCHASE PLAN

        The following constitute the provisions of the 2000 Employee Stock
Purchase Plan of Xcyte Therapies, Inc.

        1. PURPOSE. The purpose of the Plan is to provide employees of the
Company and its Designated Subsidiaries with an opportunity to purchase Common
Stock of the Company. It is the intention of the Company to have the Plan
qualify as an "Employee Stock Purchase Plan" under Section 423 of the Code. The
provisions of the Plan shall, accordingly, be construed so as to extend and
limit participation in a manner consistent with the requirements of that section
of the Code.

        2. DEFINITIONS.

               (a) "BOARD" means the Board of Directors of the Company.

               (b) "CODE" means the Internal Revenue Code of 1986, as amended.

               (c) "COMMON STOCK" means the Common Stock of the Company.

               (d) "COMPANY" means Xcyte Therapies, Inc., a Delaware
corporation.

               (e) "COMPENSATION" means all earnings reported as wages on Form
W-2, including straight time pay, payments for overtime, shift premiums,
incentive compensation, incentive payments, bonuses, commissions and other
compensation.

                (f) "CONTINUOUS STATUS AS AN EMPLOYEE" means the absence of any
interruption or termination of service as an Employee. Continuous Status as an
Employee shall not be considered interrupted in the case of (i) sick leave; (ii)
military leave; (iii) any other leave of absence approved by the Administrator,
provided that such leave is for a period of not more than 90 days, unless
reemployment upon the expiration of such leave is guaranteed by contract or
statute, or unless provided otherwise pursuant to Company policy adopted from
time to time; or (iv) transfers between locations of the Company, between the
Company and its Subsidiaries or between the Company's Subsidiaries.

               (g) "CONTRIBUTIONS" means all amounts credited to the account of
a participant pursuant to the Plan.

               (h) "CORPORATE TRANSACTION" means a sale of all or substantially
all of the Company's assets, or a merger, consolidation or other capital
reorganization of the Company with or into another corporation.

               (i) "DESIGNATED SUBSIDIARIES" means the Subsidiaries which have
been designated by the Board from time to time in its sole discretion as
eligible to participate in the Plan; provided however that the Board shall only
have the discretion to designate Subsidiaries if

<PAGE>   2
the issuance of options to such Subsidiary's Employees pursuant to the Plan
would not cause the Company to incur adverse accounting charges.

               (j) "EMPLOYEE" means any person, including an Officer, who is
treated as an employee of the Company for payroll tax purposes and who is
customarily employed for at least twenty (20) hours per week and more than five
(5) months in a calendar year by the Company or one of its Designated
Subsidiaries.

               (k) "EXCHANGE ACT" means the Securities Exchange Act of 1934, as
amended.

               (l) "FAIR MARKET VALUE" means, as of any date, the value of
Common Stock determined by the Board in its discretion provided that, to the
extent the Common Stock is trading on the Nasdaq National Market, (A) the Fair
Market Value as of an Offering Date shall be the closing sales price of the
Common Stock as reported by the Nasdaq National Market for the last trading day
immediately preceding the Offering Date, and (B) the Fair Market Value of the
Common Stock as of a Purchase Date shall be the closing sales price of the
Common Stock as reported on the Nasdaq National Market for the Purchase Date or,
if the Common Stock is not traded on such date, the last trading day immediately
preceding the Purchase Date, in each case as reported in The Wall Street
Journal. For purposes of the Offering Date under the first Offering Period under
the Plan, the Fair Market Value of a share of the Common Stock of the Company
shall be the Price to Public as set forth in the final prospectus filed with the
Securities and Exchange Commission pursuant to Rule 424 under the Securities Act
of 1933, as amended.

               (m) "OFFERING DATE" means the first business day of each Offering
Period of the Plan.

               (n) "OFFERING PERIOD" means a period of up to twenty-seven (27)
months as set forth in Section 4(a) of the Plan. The duration and timing of the
Offering Periods may be changed pursuant to Section 4(a), Section 20 and Section
21 of the Plan.

               (o) "OFFICER" means a person who is an officer of the Company
within the meaning of Section 16 of the Exchange Act and the rules and
regulations promulgated thereunder.

               (p) "PLAN" means this Employee Stock Purchase Plan.

               (q) "PURCHASE DATE" means the last day of each Purchase Period of
the Plan.

               (r) "PURCHASE PERIOD" means a period of approximately six (6)
months within or coincident with an Offering Period, except for the first
Purchase Period as set forth in Section 4(b). The duration and timing of the
Purchase Periods may be changed pursuant to Section 4(b), Section 19 and Section
20 of the Plan.

               (s) "PURCHASE PRICE" means with respect to a Purchase Period an
amount equal to 85% of the Fair Market Value (as defined in Section 2(l) above)
of a Share of Common Stock on the Offering Date or on the Purchase Date,
whichever is lower; provided, however, that

                                      -2-
<PAGE>   3
in the event (i) of any increase in the number of Shares available for issuance
under the Plan as a result of a stockholder-approved amendment to the Plan, and
(ii) all or a portion of such additional Shares are to be issued with respect to
one or more Offering Periods that are underway at the time of such increase
("Additional Shares"), and (iii) the Fair Market Value of a Share of Common
Stock on the date of such increase (the "Approval Date Fair Market Value") is
higher than the Fair Market Value on the Offering Date for any such Offering
Period, then in such instance the Purchase Price with respect to Additional
Shares shall be 85% of the Approval Date Fair Market Value or the Fair Market
Value of a Share of Common Stock on the Purchase Date, whichever is lower.

               (t) "SHARE" means a share of Common Stock, as adjusted in
accordance with Section 19 of the Plan.

               (u) "SUBSIDIARY" means a corporation, domestic or foreign, of
which not less than 50% of the voting shares are held by the Company or a
Subsidiary, whether or not such corporation now exists or is hereafter organized
or acquired by the Company or a Subsidiary.

        3. ELIGIBILITY. Any person who is an Employee as of the Offering Date of
a given Offering Period shall be eligible to participate in such Offering Period
under the Plan, subject to the requirements of Section 5 and the limitations of
Section 5(c), Section 6(c) and Section 6(d), and the limitations imposed by
Section 423(b) of the Code.

        4. OFFERING PERIODS AND PURCHASE PERIODS.

               (a) OFFERING PERIODS. The Plan shall be implemented by a series
of Offering Periods of approximately six (6) months duration, with new Offering
Periods commencing on or about February 1 and August 1 of each year and ending,
respectively, on the next following July 31 and January 31 (or at such other
time or times as may be determined by the Board of Directors). If and to the
extent the Board takes action prior to the effective date of the Company's
Registration Statement on Form S-1 for the initial public offering of the
Company's Common Stock (the "IPO Date") to grant eligible Employees options to
participate in an Offering Period beginning on the IPO Date (such period, the
"IPO Offering Period"), then such period shall begin on the IPO Date and
continue until July 31, 2001. Offering Periods shall commence on a continuing
successive basis (and overlapping, if the Board of Directors establishes
Offering Periods of twelve (12) or more months' duration) until the Plan is
terminated in accordance with Section 20 or 23 hereof. The Board of Directors of
the Company shall have the power to change the duration and/or the frequency of
Offering Periods with respect to future offerings without stockholder approval
if such change is announced at least five (5) days prior to the scheduled
beginning of the first Offering Period to be affected.

               (b) PURCHASE PERIODS. Each Offering Period of approximately six
(6) months' duration shall consist of a single Purchase Period coincident with
such Offering Period. If the Board of Directors establishes Offering Periods of
twelve (12) or more months' duration, each such Offering Period shall consist of
consecutive Purchase Periods of approximately six (6) months duration. The last
day of each Purchase Period shall be the "Purchase Date" for such Purchase
Period. A Purchase Period commencing on February 1 shall end on the next July 31

                                      -3-
<PAGE>   4
and Purchase Period commencing on August 1 shall end on the next January 31. If
the Board takes action to cause there to be an IPO Offering Period, then the
first Purchase Period shall commence on the IPO Date and shall end on January
31, 2001. The Board of Directors of the Company shall have the power to change
the duration and/or frequency of Purchase Periods with respect to future
purchases without stockholder approval if such change is announced at least five
(5) days prior to the scheduled beginning of the first Purchase Period to be
affected.

        5. PARTICIPATION; SUBSCRIPTION AGREEMENT.

               (a) With respect to the IPO Offering Period, if any, an eligible
Employee will become a participant in the Plan by the Board's taking action
prior to the IPO Date to grant such persons options to purchase Shares pursuant
to the Plan. To the extent that a participant purchases Shares on the first
Purchase Date of the IPO Offering Period, if any, by delivering a check to the
Company as set forth in Section 7(c)(i), such delivery and purchase shall
operate, unless the participant withdraws from the Plan pursuant to Section 10
or 11, as an election by the participant to continue participating in the Plan
in each successive Offering Period on the payroll deduction basis described in
Section 7(c)(ii) and the Company shall withhold from the participant's
Compensation beginning with the first payroll paid following such first Purchase
Date at a Contribution rate equal to the ratio that the aggregate purchase price
paid for Shares purchased on such Purchase Date bears to the participant's total
Compensation during that Purchase Period (which rate shall not exceed the
percentage specified in Section 5(c) below). A participant may at any time after
the commencement of the IPO Offering Period, if any, file a subscription
agreement as described in Section 5(c) to make contributions to the Plan for
such IPO Offering Period on a payroll deduction basis.

               (b) Except with respect to the IPO Offering Period, if any, an
eligible Employee may become a participant in the Plan by completing a
subscription agreement as described in Section 5(c) below on the form provided
by the Company and filing it with the Company as directed on such form prior to
the applicable Offering Date.

               (c) A participant's subscription agreement shall set forth the
percentage of the participant's Compensation to be paid as Contributions
pursuant to the Plan, which percentage shall be not less than one percent (1%)
and not more than fifteen percent (15%) (or such other maximum percentage as the
Board may establish from time to time before an Offering Date) of such
participant's Compensation on each payday during the Offering Period. If the
Board of Directors establishes overlapping Offering Periods of twelve (12) or
more months' duration, to the extent a participant is participating in more than
one Offering Period, the maximum aggregate percentage of Compensation that he or
she may contribute under the Plan shall be fifteen percent (15%) (or such other
maximum percentage as the Board may establish from time to time before an
Offering Date) and the Employee's Contributions under the earliest-filed
subscription agreement shall be reduced as necessary to prevent his or her
Contributions in the aggregate from exceeding such maximum percentage.

               (d) A participant's subscription shall be effective for the
Offering Period with respect to which it is filed, and also shall be
automatically effective for each successive Offering

                                      -4-
<PAGE>   5
Period that commences at the end of the Offering Period for which it is filed
(or that commences at the end of any such successive Offering Period), unless
the participant files a new subscription to decrease the amount of his or her
contributions as set forth in Section 5(e) below, withdraws in accordance with
Section 10 or 11, or is otherwise ineligible to participate in such successive
Offering Period.

               (e) A participant may discontinue his or her participation in the
Plan as provided in Section 10, or, on one occasion only during a Purchase
Period may decrease the rate of his or her Contributions with respect to an
Offering Period, by completing and filing with the Company a new subscription
agreement authorizing a change in the payroll deduction rate. Any change in rate
of Contributions pursuant to the preceding sentence shall be effective as of the
beginning of the next calendar month following the date of filing of the new
subscription agreement, provided the agreement indicating such change is filed
at least ten (10) business days prior to such date and, if not, then as of the
beginning of the next succeeding calendar month. With respect to the IPO
Offering Period, any election by a participant to commence payroll deductions
under the Plan following the IPO Date in accordance with Section 7(c)(ii) at a
rate of Compensation that would result in his or her purchasing less than the
full amount of Shares that he or she could purchase under the option granted to
him or her by the Board shall not count as a decrease in participation for
purposes of the first sentence of this Section 5(e).

        6. GRANT OF OPTION; LIMITATIONS.

               (a) With respect to the IPO Offering Period, if any, each
eligible Employee shall be granted an option to purchase on each Purchase Date a
number of Shares of the Company's Common Stock determined by dividing the
maximum amount specified by the Board in granting the option (which amount shall
be a percentage of such Employee's Compensation) by the applicable Purchase
Price, subject to the limitations in subsections (c) and (d) of this Section 6.

               (b) Except with respect to the IPO Offering Period, if any, and
subject to the limitations in subsections (c) and (d) of this Section 6 and
Section 13(b), on the Offering Date of each Offering Period, each eligible
Employee participating in such Offering Period shall be granted an option to
purchase on each Purchase Date a number of Shares of the Company's Common Stock
determined by dividing such Employee's Contributions accumulated prior to such
Purchase Date and retained in the participant's account as of the Purchase Date
by the applicable Purchase Price.

               (c) Notwithstanding the above, the maximum number of Shares an
Employee may purchase during each Purchase Period of any Offering Period
(including the IPO Offering Period) shall be 2,500 Shares (subject to any
adjustment pursuant to Section 19 below), and provided further that such
purchase shall be subject to the limitations set forth in Sections 13(b). In
addition to the limits on an Employee's participation in the Plan set forth
herein, the Board may establish limits on the number of shares an Employee may
elect to purchase with respect to any Offering Period if such limit is announced
at least fifteen (15) days prior to the scheduled beginning of the first
Offering Period to be affected.

                                      -5-
<PAGE>   6
               (d) Any provisions of the Plan to the contrary notwithstanding,
no Employee shall be granted an option under the Plan (i) if, immediately after
the grant, such Employee (or any other person whose stock would be attributed to
such Employee pursuant to Section 424(d) of the Code) would own capital stock of
the Company and/or hold outstanding options to purchase stock possessing five
percent (5%) or more of the total combined voting power or value of all classes
of stock of the Company or of any subsidiary of the Company, or (ii) if such
option would permit his or her rights to purchase stock under all employee stock
purchase plans (described in Section 423 of the Code) of the Company and its
Subsidiaries to accrue at a rate which exceeds twenty-five thousand dollars
($25,000) of the Fair Market Value (as defined in Section 2(l) above) of such
stock (determined at the time such option is granted) for each calendar year in
which such option is outstanding at any time.

        7. METHOD OF PAYMENT FOR PURCHASE OF SHARES.

               (a) Except with respect to the IPO Offering Period, if any, this
Plan shall be operated as a payroll deduction plan. Once a participant is
participating in the Plan on a payroll deduction basis, he or she may not make
any additional lump sum cash payments into such account. Payroll deductions
shall commence on the first payroll paid following the Offering Date and shall
end on the last payroll paid on or prior to the last Purchase Period of the
Offering Period to which the participant's subscription agreement is applicable,
unless the participant withdraws as provided in Section 10 or 11. All payroll
deductions made by a participant shall be credited to his or her account under
the Plan.

               (b) With respect to the IPO Offering Period, payroll deductions
shall commence on the first payroll date following the date, if any, on which
the participant elects pursuant to Section 5(a) to have amounts withheld from
his or her Compensation.

               (c) A participant in the IPO Offering Period shall make payment
for the purchase of Shares by (i) making a lump sum cash payment to the Company
on or prior to the Purchase Date for such Offering Period for the amount of the
purchase price for the Shares being purchased (after which date an Employee
wishing to continue participating in the Plan shall participate on a payroll
deduction basis unless the participant withdraws from the Plan under Section 10
or 11), or (ii) electing, following the IPO Date, to have amounts directly
withheld from the Employee's Compensation by filing a subscription agreement
pursuant to Section 5(c).

               (d) Notwithstanding the foregoing, to the extent necessary to
comply with Section 423(b)(8) of the Code and the limitations of this Section 6,
a participant's payroll deductions may be decreased by the Company to zero
percent (0%) at any time during a Purchase Period. Payroll deductions shall
re-commence at the rate provided in such participant's subscription agreement at
the beginning of the next Purchase Period or, in the case of the limitation of
Section 6(d), the first Purchase Period which is scheduled to end in the
following calendar year, unless the participant withdraws in accordance with
Section 10 or 11 or is otherwise ineligible to participate in such Purchase
Period.

                                      -6-
<PAGE>   7
               (e) At the time the option is exercised, in whole or in part, or
at the time some or all of the Company's Common Stock issued under the Plan is
disposed of, the participant must make adequate provision for the Company's
federal, state, or other tax withholding obligations, if any, which arise upon
the exercise of the option or the disposition of the Common Stock. At any time,
the Company may, but shall not be obligated to, withhold from the participant's
compensation the amount necessary for the Company to meet applicable withholding
obligations, including any withholding required to make available to the Company
any tax deductions or benefits attributable to sale or early disposition of
Common Stock by the participant.

        8. EXERCISE OF OPTION.

               (a) Except with respect to the first Purchase Period of the IPO
Offering Period, if any, and unless a participant withdraws from the Plan as
provided in Section 10 or 11, his or her option for the purchase of Shares will
be exercised automatically on each Purchase Date of an Offering Period, and
unless otherwise limited by Section 6 or Section 13(b), the maximum number of
full Shares subject to the option will be purchased at the applicable Purchase
Price with the accumulated Contributions in his or her account. With respect to
the first Purchase Period of the IPO Offering Period, a participant's option
thereunder shall either be exercised as provided in the preceding sentence or by
the participant's delivering to the Company a check for the full amount of the
purchase price of the Shares being purchased (which number of Shares may be less
than the entire number of Shares subject to the option granted by the Board)
prior to the time of purchase for such Purchase Date. No fractional Shares shall
be issued. The Shares purchased upon exercise of an option hereunder shall be
deemed to be transferred to the participant on the Purchase Date. During his or
her lifetime, a participant's option to purchase Shares hereunder is exercisable
only by him or her.

               (b) No fractional Shares shall be purchased. Any payroll
deductions accumulated in a participant's account which are not sufficient to
purchase a full Share shall be retained in the participant's account for the
subsequent Purchase Period or Offering Period, subject to earlier withdrawal by
the participant as provided in Section 10 or 11 below. Any other amounts left
over in a participant's account after a Purchase Date shall be returned to the
participant.

        9. DELIVERY. As promptly as practicable after each Purchase Date of each
Offering Period, the Company shall arrange the delivery to each participant, as
appropriate, of the Shares purchased upon exercise of his or her option.
Notwithstanding the foregoing, the Board may require that all Shares purchased
under the Plan be held in an account (the participant's "ESPP Stock Account")
established in the name of the participant (or in the name of the participant
and his or her spouse, as designated by the participant on his or her
subscription agreement), subject to such rules as determined by the Board and
uniformly applied to all participants, including designation of a brokerage or
other financial services firm (an "ESPP Broker") to hold such Shares for the
participant's ESPP Stock Account with registration of such Shares in the name of

                                      -7-
<PAGE>   8
such ESPP Broker for the benefit of the participant (or for the benefit of the
participant and his or her spouse, as designated by the participant on his or
her subscription agreement).

        10. VOLUNTARY WITHDRAWAL; TERMINATION OF EMPLOYMENT.

               (a) A participant may withdraw all but not less than all the
Contributions credited to his or her account under the Plan at any time prior to
each Purchase Date by giving written notice to the Company. All of the
participant's Contributions credited to his or her account will be paid to him
or her promptly after receipt of his or her notice of withdrawal and his or her
option for the current period will be automatically terminated, and no further
Contributions for the purchase of Shares will be made during the Offering
Period. With respect to the IPO Offering Period, a participant who has not
previously chosen to have amounts withheld from his or her Compensation shall be
considered to have withdrawn from such period if he or she fails to exercise the
options granted hereunder by delivering to the Company the full amount of the
purchase price for the Shares being purchased (which number of Shares may be
less than the entire number of Shares subject to the option granted by the
Board) for the first Purchase Period within the IPO Offering Period.

               (b) A participant's withdrawal from an offering will not have any
effect upon his or her eligibility to participate in a succeeding Offering
Period or in any similar plan which may hereafter be adopted by the Company.

        11. AUTOMATIC WITHDRAWAL.

               (a) In the event an Employee fails to remain in Continuous Status
as an Employee of the Company for at least twenty (20) hours per week during the
Offering Period in which the employee is a participant, unless such Employee is
on an approved leave of absence or a temporary reduction of hours, he or she
will be deemed to have elected to withdraw from the Plan and the Contributions
credited to his or her account will be returned to him or her and his or her
option terminated.

               (b) Upon termination of the participant's Continuous Status as an
Employee prior to the Purchase Date of an Offering Period for any reason,
including retirement or death, the Contributions credited to his or her account
will be returned to him or her or, in the case of his or her death, to the
person or persons entitled thereto under Section 15, and his or her option will
be automatically terminated.

               (c) If the Board of Directors has established Offering Periods of
12 months' duration, to the extent permitted by any applicable laws, regulations
or stock exchange rules, if the Fair Market Value of the Shares on an Offering
Date for an Offering Period (the "New Offering Period") commencing within an
Offering Period (the "Ongoing Offering Period") then in progress, is lower than
was the Fair Market Value of the Shares on the Offering Date for the Ongoing
Offering Period, then every participant in the Ongoing Offering Period shall
automatically be deemed to have (i) withdrawn from the Ongoing Offering Period
at the close of the Purchase Period immediately preceding the New Offering
Period, and (ii) to have enrolled in such New Offering Period.

                                      -8-
<PAGE>   9
        12. INTEREST. No interest shall accrue on the Contributions of a
participant in the Plan.

        13. STOCK.

               (a) Subject to adjustment as provided in Section 19, the maximum
number of Shares which shall be made available for sale under the Plan shall be
600,000 Shares, plus an annual increase on the first day of each of the
Company's fiscal years beginning in 2002 through 2008 equal to the lesser of (i)
300,000 Shares (before giving effect to a stock split effected in connection
with the Company's initial public offering), (ii) one percent (1%) of the Shares
outstanding on the last day of the immediately preceding fiscal year, or (iii)
such lesser number of Shares as is determined by the Board.

               (b) If the Board determines that, on a given Purchase Date, the
number of shares with respect to which options are to be exercised may exceed
(i) the number of shares of Common Stock that were available for sale under the
Plan on the Offering Date of the applicable Offering Period, or (ii) the number
of shares available for sale under the Plan on such Purchase Date, the Board may
in its sole discretion provide (x) that the Company shall make a pro rata
allocation of the Shares of Common Stock available for purchase on such Offering
Date or Purchase Date, as applicable, in as uniform a manner as shall be
practicable and as it shall determine in its sole discretion to be equitable
among all participants exercising options to purchase Common Stock on such
Purchase Date, and continue all Offering Periods then in effect, or (y) that the
Company shall make a pro rata allocation of the shares available for purchase on
such Offering Date or Purchase Date, as applicable, in as uniform a manner as
shall be practicable and as it shall determine in its sole discretion to be
equitable among all participants exercising options to purchase Common Stock on
such Purchase Date, and terminate any or all Offering Periods then in effect
pursuant to Section 20 below. The Company may make pro rata allocation of the
Shares available on the Offering Date of any applicable Offering Period pursuant
to the preceding sentence, notwithstanding any authorization of additional
Shares for issuance under the Plan by the Company's stockholders subsequent to
such Offering Date.

               (c) The participant shall have no interest or voting right in
Shares covered by his or her option until such option has been exercised.

               (d) Shares to be delivered to a participant under the Plan will
be registered in the name of the participant or in the name of the participant
and his or her spouse; provided that if the Board has determined that Shares
shall be held in an ESPP Stock Account held by an ESPP Broker in accordance with
Section 9, Shares shall be registered in the name of such ESPP Broker for the
benefit of the participant (or the participant and his or her spouse, as
designated by the participant in his or her subscription agreement).

        14. ADMINISTRATION. The Board, or a committee named by the Board, shall
supervise and administer the Plan and shall have full power to adopt, amend and
rescind any rules deemed desirable and appropriate for the administration of the
Plan and not inconsistent with the Plan, to construe and interpret the Plan, and
to make all other determinations necessary or advisable for the administration
of the Plan.

                                      -9-
<PAGE>   10
        15. DESIGNATION OF BENEFICIARY.

               (a) A participant may file a written designation of a beneficiary
who is to receive any Shares and cash, if any, from the participant's account
under the Plan in the event of such participant's death subsequent to the end of
a Purchase Period but prior to delivery to him or her of such Shares and cash.
In addition, a participant may file a written designation of a beneficiary who
is to receive any cash from the participant's account under the Plan in the
event of such participant's death prior to the Purchase Date of an Offering
Period. If a participant is married and the designated beneficiary is not the
spouse, spousal consent shall be required for such designation to be effective.

               (b) Such designation of beneficiary may be changed by the
participant (and his or her spouse, if any) at any time by written notice. In
the event of the death of a participant and in the absence of a beneficiary
validly designated under the Plan who is living at the time of such
participant's death, the Company shall deliver such Shares and/or cash to the
executor or administrator of the estate of the participant, or if no such
executor or administrator has been appointed (to the knowledge of the Company),
the Company, in its discretion, may deliver such Shares and/or cash to the
spouse or to any one or more dependents or relatives of the participant, or if
no spouse, dependent or relative is known to the Company, then to such other
person as the Company may designate.

        16. TRANSFERABILITY. Neither Contributions credited to a participant's
account nor any rights with regard to the exercise of an option or to receive
Shares under the Plan may be assigned, transferred, pledged or otherwise
disposed of in any way (other than by will, the laws of descent and
distribution, or as provided in Section 15) by the participant. Any such attempt
at assignment, transfer, pledge or other disposition shall be without effect,
except that the Company may treat such act as an election to withdraw funds in
accordance with Section 10.

        17. USE OF FUNDS. The Company may use all Contributions received or held
by the Company under the Plan for any corporate purpose, and the Company shall
not be obligated to segregate such Contributions.

        18. REPORTS. Individual accounts will be maintained for each participant
in the Plan. Statements of account will be given to participating Employees at
least annually, which statements will set forth the amounts of Contributions,
the per Share Purchase Price, the number of Shares purchased and the remaining
cash balance, if any.

        19. ADJUSTMENTS UPON CHANGES IN CAPITALIZATION; CORPORATE TRANSACTIONS.

               (a) ADJUSTMENT. Subject to any required action by the
stockholders of the Company, the number of Shares covered by each option under
the Plan which has not yet been exercised and the number of Shares which have
been authorized for issuance under the Plan but have not yet been placed under
option (collectively, the "Reserves"), as well as the maximum number of shares
of Common Stock which may be purchased by a participant in a Purchase Period,
the number of shares of Common Stock set forth in Section 13(a) above, and the
per Share Purchase Price covered by each option under the Plan which has not yet
been exercised,

                                      -10-
<PAGE>   11
shall be proportionately adjusted for any increase or decrease in the number of
issued Shares resulting from a stock split, reverse stock split, stock dividend,
combination or reclassification of the Common Stock (including any such change
in the number of Shares of Common Stock effected in connection with a change in
domicile of the Company), or any other increase or decrease in the number of
Shares effected without receipt of consideration by the Company; provided
however that conversion of any convertible securities of the Company shall not
be deemed to have been "effected without receipt of consideration." Such
adjustment shall be made by the Board, whose determination in that respect shall
be final, binding and conclusive. Except as expressly provided herein, no issue
by the Company of shares of stock of any class, or securities convertible into
shares of stock of any class, shall affect, and no adjustment by reason thereof
shall be made with respect to, the number or price of Shares subject to an
option.

               (b) CORPORATE TRANSACTIONS.

                      (i) In the event of a dissolution or liquidation of the
Company, any Purchase Period and Offering Period then in progress will terminate
immediately prior to the consummation of such action, unless otherwise provided
by the Board. In the event of a Corporate Transaction, each option outstanding
under the Plan shall be assumed or an equivalent option shall be substituted by
the successor corporation or a parent or Subsidiary of such successor
corporation. In the event that the successor corporation refuses to assume or
substitute for outstanding options, each Purchase Period and Offering Period
then in progress shall be shortened and a new Purchase Date shall be set (the
"New Purchase Date"), as of which date any Purchase Period and Offering Period
then in progress will terminate. The New Purchase Date shall be on or before the
date of consummation of the transaction and the Board shall notify each
participant in writing, at least ten (10) days prior to the New Purchase Date,
that the Purchase Date for his or her option has been changed to the New
Purchase Date and that his or her option will be exercised automatically on the
New Purchase Date, unless prior to such date he or she has withdrawn from the
Offering Period as provided in Section 10 or 11.

                      (ii) For purposes of this Section 19, an option granted
under the Plan shall be deemed to be assumed, without limitation, if, at the
time of issuance of the stock or other consideration upon a Corporate
Transaction, each holder of an option under the Plan would be entitled to
receive upon exercise of the option the same number and kind of shares of stock
or the same amount of property, cash or securities as such holder would have
been entitled to receive upon the occurrence of the transaction if the holder
had been, immediately prior to the transaction, the holder of the number of
Shares of Common Stock covered by the option at such time (after giving effect
to any adjustments in the number of Shares covered by the option as provided for
in this Section 19); provided however that if the consideration received in the
transaction is not solely common stock of the successor corporation or its
parent (as defined in Section 424(e) of the Code), the Board may, with the
consent of the successor corporation, provide for the consideration to be
received upon exercise of the option to be solely common stock of the successor
corporation or its parent equal in Fair Market Value to the per Share
consideration received by holders of Common Stock in the transaction.

                                      -11-
<PAGE>   12
                      (iii) The Board may, if it so determines in the exercise
of its sole discretion, also make provision for adjusting the Reserves, as well
as the price per Share of Common Stock covered by each outstanding option, in
the event that the Company effects one or more reorganizations,
recapitalizations, rights offerings or other increases or reductions of Shares
of its outstanding Common Stock, and in the event of the Company's being
consolidated with or merged into any other corporation.

        20. AMENDMENT OR TERMINATION.

               (a) The Board may at any time and for any reason terminate or
amend the Plan. Except as provided in Section 19, no such termination of the
Plan may affect options previously granted, provided that the Plan or an
Offering Period may be terminated by the Board on a Purchase Date or by the
Board's setting a new Purchase Date with respect to an Offering Period and
Purchase Period then in progress if the Board determines that termination of the
Plan and/or the Offering Period is in the best interests of the Company and the
stockholders or if continuation of the Plan and/or the Offering Period would
cause the Company to incur adverse accounting charges as a result of a change
after the effective date of the Plan in the generally accepted accounting rules
applicable to the Plan. Except as provided in Section 19 and in this Section 20,
no amendment to the Plan shall make any change in any option previously granted
which adversely affects the rights of any participant. In addition, to the
extent necessary to comply with Rule 16b-3 under the Exchange Act, or under
Section 423 of the Code (or any successor rule or provision or any applicable
law or regulation), the Company shall obtain stockholder approval in such a
manner and to such a degree as so required.

               (b) Without stockholder consent and without regard to whether any
participant rights may be considered to have been adversely affected, the Board
(or its committee) shall be entitled to change the Offering Periods and Purchase
Periods, limit the frequency and/or number of changes in the amount withheld
during an Offering Period, establish the exchange ratio applicable to amounts
withheld in a currency other than U.S. dollars, permit payroll withholding in
excess of the amount designated by a participant in order to adjust for delays
or mistakes in the Company's processing of properly completed withholding
elections, establish reasonable waiting and adjustment periods and/or accounting
and crediting procedures to ensure that amounts applied toward the purchase of
Common Stock for each participant properly correspond with amounts withheld from
the participant's Compensation, and establish such other limitations or
procedures as the Board (or its committee) determines in its sole discretion
advisable which are consistent with the Plan.

        21. NOTICES. All notices or other communications by a participant to the
Company under or in connection with the Plan shall be deemed to have been duly
given when received in the form specified by the Company at the location, or by
the person, designated by the Company for the receipt thereof.

        22. CONDITIONS UPON ISSUANCE OF SHARES. Shares shall not be issued with
respect to an option unless the exercise of such option and the issuance and
delivery of such Shares pursuant thereto shall comply with all applicable
provisions of law, domestic or foreign,

                                      -12-
<PAGE>   13
including, without limitation, the Securities Act of 1933, as amended, the
Exchange Act, the rules and regulations promulgated thereunder, applicable state
securities laws and the requirements of any stock exchange upon which the Shares
may then be listed, and shall be further subject to the approval of counsel for
the Company with respect to such compliance.

        As a condition to the exercise of an option, the Company may require the
person exercising such option to represent and warrant at the time of any such
exercise that the Shares are being purchased only for investment and without any
present intention to sell or distribute such Shares if, in the opinion of
counsel for the Company, such a representation is required by any of the
aforementioned applicable provisions of law.

        23. TERM OF PLAN; EFFECTIVE DATE. The Plan shall become effective upon
the IPO Date. It shall continue in effect for a term of twenty (20) years unless
sooner terminated under Section 20.

                                      -13-
<PAGE>   14
                              XCYTE THERAPIES, INC.

                        2000 EMPLOYEE STOCK PURCHASE PLAN
                             SUBSCRIPTION AGREEMENT

                  (Offering Periods After IPO Offering Period)

                                                             New Election ______
                                                       Change of Election ______

        1. I, ________________________, hereby elect to participate in the Xcyte
Therapies, Inc. 2000 Employee Stock Purchase Plan (the "Plan") for the Offering
Period ______________, ____ to _______________, ____, and subscribe to purchase
shares of the Company's Common Stock in accordance with this Subscription
Agreement and the an.

        2. I elect to have Contributions in the amount of ____% of my
Compensation, as those terms are defined in the Plan, applied to this purchase.
I understand that this amount must not be less than 1% and not more than 15% of
my Compensation during the Offering Period. (Please note that no fractional
percentages are permitted).

        3. I hereby authorize payroll deductions from each paycheck during the
Offering Period at the rate stated in Item 2 of this Subscription Agreement. I
understand that all payroll deductions made by me shall be credited to my
account under the Plan and that I may not make any additional payments into such
account. I understand that all payments made by me shall be accumulated for the
purchase of shares of Common Stock at the applicable purchase price determined
in accordance with the Plan. I further understand that, except as otherwise set
forth in the Plan, shares will be purchased for me automatically on the Purchase
Date of each Offering Period unless I otherwise withdraw from the Plan by giving
written notice to the Company for such purpose.

        4. I understand that I may discontinue at any time prior to the Purchase
Date my participation in the Plan as provided in Section 10 of the Plan. I also
understand that I can decrease the rate of my Contributions once during an
Offering Period by completing and filing with the Company a new Subscription
Agreement with such decrease taking effect as of the beginning of the next
following calendar month, if filed at least ten (10) business days prior to the
beginning of such month. Further, I may change the rate of deductions for future
Offering Periods by filing a new Subscription Agreement, and any such change
will be effective as of the beginning of the next Offering Period. In addition,
I acknowledge that, unless I withdraw from the Plan as provided in Section 10 or
11 of the Plan, my election will continue to be effective for each successive
Offering Period.

<PAGE>   15
        5. I have received a copy of the Company's most recent description of
the Plan and a copy of the complete "Xcyte Therapies, Inc. 2000 Employee Stock
Purchase Plan." I understand that my participation in the Plan is in all
respects subject to the terms of the Plan.

        6. Shares purchased for me under the Plan should be issued in the
name(s) of (name of employee or employee and spouse only):

                                            ------------------------------------

                                            ------------------------------------

        7. I understand that if I dispose of any shares received by me pursuant
to the Plan within 2 years after the Offering Date (the first day of the
Offering Period during which I purchased such shares) or within 1 year after the
Purchase Date, I will be treated for federal income tax purposes as having
received ordinary compensation income at the time of such disposition in an
amount equal to the excess of the fair market value of the shares on the
Purchase Date over the price which I paid for the shares, regardless of whether
I disposed of the shares at a price less than their fair market value at the
Purchase Date. The remainder of the gain or loss, if any, recognized on such
disposition will be treated as capital gain or loss.

        I hereby agree to notify the Company in writing within 30 days after the
date of any such disposition, and I will make adequate provision for federal,
state or other tax withholding obligations, if any, which arise upon the
disposition of the Common Stock. The Company shall be entitled, to the extent
required by applicable law, to withhold from my Compensation any amount
necessary to comply with applicable tax withholding requirements with respect to
the purchase or sale of shares under the Plan.

        8. If I dispose of such shares at any time after expiration of the
2-year and 1-year holding periods, I understand that I will be treated for
federal income tax purposes as having received compensation income only to the
extent of an amount equal to the lesser of (a) the excess of the fair market
value of the shares at the time of such disposition over the purchase price
which I paid for the shares under the option, or (b) 15% of the fair market
value of the shares on the Offering Date. The remainder of the gain or loss, if
any, recognized on such disposition will be treated as capital gain or loss.

        I understand that this tax summary is only a summary and is subject to
change. I further understand that I should consult a tax advisor concerning the
tax implications of the purchase and sale of stock under the Plan.

        9. In connection with the initial public offering of the Company's
securities and upon request of the Company or the underwriters managing any
underwritten offering of the Company's securities, I agree not to sell, make any
short sale of, loan, grant any option for the purchase of, or otherwise dispose
of any securities of the Company, however or whenever I acquired them, without
the prior written consent of the Company or such underwriters, as the case may
be, for such period of time (not to exceed 180 days) from the effective date of
such registration as may be requested by the Company or such managing
underwriters and to execute

                                       -2-
<PAGE>   16
an agreement reflecting the foregoing as may be requested by the underwriters at
the time of the public offering.

        10. I hereby agree to be bound by the terms of the Plan. The
effectiveness of this Subscription Agreement is dependent upon my eligibility to
participate in the Plan.

NAME (print):
             --------------------------
SIGNATURE:
          -----------------------------
SOCIAL SECURITY #:
                  ---------------------
DATE:
      ---------------------------------

SPOUSE'S SIGNATURE (necessary
if beneficiary is not spouse):

---------------------------------------
(Signature)

---------------------------------------
(Print name)

                                       -3-
<PAGE>   17
                              XCYTE THERAPIES, INC.

                        2000 EMPLOYEE STOCK PURCHASE PLAN
                             SUBSCRIPTION AGREEMENT

                              (IPO Offering Period)

                                                             New Election ______
                                                       Change of Election ______

        1. I have received an option to purchase shares of the Company's Common
Stock under the Xcyte Therapies, Inc. 2000 Employee Stock Purchase Plan (the
"Plan") for the Offering Period that commenced on [__________ ___,] 2001 and
ends on July 31, 2001 (the "Initial Offering Period").

        2. I hereby elect to participate in the Plan by having Contributions in
the amount of ____% of my Compensation, as those terms are defined in the Plan,
applied to purchases under the Plan. I understand that this amount (together
with any other amounts I am contributing under the Plan) must not be less than
1% and not more than 15% of my Compensation during any Offering Period. (Please
note that no fractional percentages are permitted). I also understand that, as a
result of making this election to participate in the Plan on a payroll-deduction
basis, I am no longer eligible to have purchase Shares by delivering to the
Company a check for the amount of any purchases made on my behalf under the Plan
and that I shall at all times in the future be able to participate in the Plan
solely on a payroll-deduction basis on the terms set forth in the Plan.

        3. I hereby authorize payroll deductions from each paycheck during the
Offering Period at the rate stated in Item 2 of this Subscription Agreement. I
understand that all payroll deductions made by me shall be credited to my
account under the Plan and that I may not make any additional payments into such
account. I understand that all payments made by me shall be accumulated for the
purchase of shares of Common Stock at the applicable purchase price determined
in accordance with the Plan. I further understand that, except as otherwise set
forth in the Plan, shares will be purchased for me automatically on the Purchase
Date of each Offering Period unless I otherwise withdraw from the Plan by giving
written notice to the Company for such purpose.

        4. I understand that I may discontinue at any time prior to the Purchase
Date my participation in the Plan as provided in Section 10 of the Plan. I also
understand that I can increase or decrease the rate of my Contributions on one
occasion only with respect to any increase and one occasion only with respect to
any decrease during any Purchase Period by completing and filing a new
Subscription Agreement with such increase or decrease taking effect as of the
beginning of the calendar month following the date of filing of the new
Subscription

<PAGE>   18
        Agreement, if filed at least ten (10) business days prior to the
beginning of such month. Further, I may change the rate of deductions for future
Offering Periods by filing a new Subscription Agreement, and any such change
will be effective as of the beginning of the next Offering Period. In addition,
I acknowledge that, unless I withdraw from the Plan as provided in Section 10 or
11 of the Plan, my election will continue to be effective for each successive
Offering Period.

        5. I have received a copy of the Company's most recent description of
the Plan and a copy of the complete "Xcyte Therapies, Inc. 2000 Employee Stock
Purchase Plan." I understand that my participation in the Plan is in all
respects subject to the terms of the Plan.

        6. Shares purchased for me under the Plan should be issued in the
name(s) of (name of employee or employee and spouse only):

                                            ------------------------------------

                                            ------------------------------------

        7. I understand that if I dispose of any shares received by me pursuant
to the Plan within 2 years after the Offering Date (the first day of the
Offering Period during which I purchased such shares) or within 1 year after the
Purchase Date, I will be treated for federal income tax purposes as having
received ordinary compensation income at the time of such disposition in an
amount equal to the excess of the fair market value of the shares on the
Purchase Date over the price which I paid for the shares, regardless of whether
I disposed of the shares at a price less than their fair market value at the
Purchase Date. The remainder of the gain or loss, if any, recognized on such
disposition will be treated as capital gain or loss.

        I hereby agree to notify the Company in writing within 30 days after the
date of any such disposition, and I will make adequate provision for federal,
state or other tax withholding obligations, if any, which arise upon the
disposition of the Common Stock. The Company may, but will not be obligated to,
withhold from my compensation the amount necessary to meet any applicable
withholding obligation including any withholding necessary to make available to
the Company any tax deductions or benefits attributable to the sale or early
disposition of Common Stock by me.

        8. If I dispose of such shares at any time after expiration of the
2-year and 1-year holding periods, I understand that I will be treated for
federal income tax purposes as having received compensation income only to the
extent of an amount equal to the lesser of (a) the excess of the fair market
value of the shares at the time of such disposition over the purchase price
which I paid for the shares under the option, or (b) 15% of the fair market
value of the shares on the Offering Date. The remainder of the gain or loss, if
any, recognized on such disposition will be treated as capital gain or loss.

        I understand that this tax summary is only a summary and is subject to
change. I further understand that I should consult a tax advisor concerning the
tax implications of the purchase and sale of stock under the Plan.

                                      -2-
<PAGE>   19
        9. In connection with the initial public offering of the Company's
securities and upon request of the Company or the underwriters managing any
underwritten offering of the Company's securities, I agree not to sell, make any
short sale of, loan, grant any option for the purchase of, or otherwise dispose
of any securities of the Company, however or whenever I acquired them, without
the prior written consent of the Company or such underwriters, as the case may
be, for such period of time (not to exceed 180 days) from the effective date of
such registration as may be requested by the Company or such managing
underwriters and to execute an agreement reflecting the foregoing as may be
requested by the underwriters at the time of the public offering.

        10. I hereby agree to be bound by the terms of the Plan. The
effectiveness of this Subscription Agreement is dependent upon my eligibility to
participate in the Plan.

SIGNATURE:
          --------------------------
SOCIAL SECURITY #:
                   -----------------
DATE:
     -------------------------------

SPOUSE'S SIGNATURE (necessary
if beneficiary is not spouse):

------------------------------------
(Signature)

------------------------------------
(Print name)

                                      -3-
<PAGE>   20
                              XCYTE THERAPIES, INC.

                        2000 EMPLOYEE STOCK PURCHASE PLAN

                              ELECTION TO PURCHASE

                              (IPO Offering Period)

        I, __________________________, hereby elect to purchase Shares pursuant
to the option granted to me on __________, __, 2001 under the Xcyte Therapies,
Inc. 2000 Employee Stock Purchase Plan (the "Plan"). Accompanying this Election
to Purchase is a check in the amount of $___________ and I elect to purchase
that number of Shares that is calculated by dividing such amount by the
applicable Purchase Price as specified in the Plan with respect to the purchase
being made on July 31, 2001. I understand that the amount I specified above may
not exceed 15% of my Compensation for the period beginning on _________, __,
2000 and ending on July 31, 2001 or result in my purchasing a number of Shares
in excess of the limits specified in Sections 6 and ___ of the Plan.

        I understand that, as a result of my delivering the amount specified in
the preceding paragraph to the Company, I shall be deemed to have elected to
continue participating in the Plan on a payroll deduction basis (on the terms
described in the Plan) and that, beginning with the first payroll paid following
July 31, 2001 and unless I specify another percentage Contribution rate by
filling out a Subscription Agreement, the Company shall withhold a percentage of
my Compensation equal to the ratio that the above amount bears to my
Compensation for the period beginning on _________, __, 2000 and ending on July
31, 2001.

Dated:
      -------------------              -----------------------------------------
                                       Signature of Employee

Check, payable to Xcyte Therapies, Inc., is  enclosed.

<PAGE>   21
                              XCYTE THERAPIES, INC.

                        2000 EMPLOYEE STOCK PURCHASE PLAN

                              NOTICE OF WITHDRAWAL

        I, __________________________, hereby elect to withdraw my participation
in the Xcyte Therapies 2000 Employee Stock Purchase Plan (the "Plan") for the
Offering Period that began on _________ ___, _____. This withdrawal covers all
Contributions credited to my account and is effective on the date designated
below.

        I understand that all Contributions credited to my account will be paid
to me within ten (10) business days of receipt by the Company of this Notice of
Withdrawal and that my option for the current period will automatically
terminate, and that no further Contributions for the purchase of shares can be
made by me during the Offering Period.

        The undersigned further understands and agrees that he or she shall be
eligible to participate in succeeding offering periods only by delivering to the
Company a new Subscription agreement.

Dated:
      --------------------------       -----------------------------------------
                                       Signature of Employee

                                       -----------------------------------------
                                       Social Security Number

<PAGE>   22
                              XCYTE THERAPIES, INC.

                        2000 EMPLOYEE STOCK PURCHASE PLAN

                             BENEFICIARY DESIGNATION

        In the event of my death, I hereby designate the following as my
beneficiary to receive all payments and shares due to me under the Xcyte
Therapies, Inc. 2000 Employee Stock Purchase Plan. I understand that my
Beneficiary Designation will be effective upon acknowledgement of receipt by
Xcyte Therapies, Inc.

BENEFICIARY:

NAME:  (Please print)

-------------------------------------   ----------------------------------------
(First)       (Middle)        (Last)    Relationship:

------------------------------------
 (Address)

------------------------------------

SIGNATURE:                             DATE:
           -----------------------          ------------------------------------
Print Name:
           -----------------------

SOCIAL SECURITY #:
                  ----------------

SPOUSE'S SIGNATURE (necessary if beneficiary is not Employee's spouse):

-----------------------------------
(Signature)

-----------------------------------
(Print name)

MAIL OR DELIVER THIS FORM TO:

ACKNOWLEDGEMENT OF RECEIPT BY XCYTE THERAPIES, INC.:

By:                                 Dated:
    -------------------------------       --------------------------------------
Title:

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