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                                                                    EXHIBIT 10.1

                                  TOLERRX, INC.

                              AMENDED AND RESTATED
                           2000 EQUITY INCENTIVE PLAN

1.   PURPOSE

     This Plan is intended to encourage ownership of Common Stock by employees,
consultants and directors of the Company and its Affiliates and to provide
additional incentive for them to promote the success of the Company's business.
The Plan is intended to be an incentive stock option plan within the meaning of
Section 422 of the Code but not all Awards granted hereunder are required to be
Incentive Options.

2.   DEFINITIONS

     As used in the Plan the following terms shall have the respective meanings
set out below, unless the context clearly requires otherwise:

     2.1.  ACCELERATE, ACCELERATED, and ACCELERATION, when used with respect to
an Option, means that as of the time of reference such Option will become
exercisable with respect to some or all of the shares of Common Stock for which
it was not then otherwise exercisable by its terms, and, when used with respect
to Restricted Stock, means that the Risk of Forfeiture otherwise applicable to
such Common Stock shall expire with respect to some or all of the shares of
Restricted Stock then still otherwise subject to the Risk of Forfeiture.

     2.2.  ACQUIRING PERSON means, with respect to any Transaction or any
acquisition described in clause (ii) of the definition of Change of Control, the
surviving or acquiring person or entity in connection with such Transaction or
acquisition, as the case may be, PROVIDED THAT if such surviving or acquiring
person or entity is controlled, directly or indirectly, by any other person or
entity (an "ULTIMATE PARENT ENTITY") that is not itself controlled by any entity
or person that is not a natural person, the term "ACQUIRING PERSON" shall mean
such Ultimate Parent Entity.

     2.3.  AFFILIATE means, with respect to any person or entity, any other
person or entity controlling, controlled by or under common control with the
first person or entity.

     2.4.  AWARD means any grant or sale pursuant to the Plan of Options,
Restricted Stock, or Stock Grants.

     2.5.  AWARD AGREEMENT means an agreement between the Company and the
recipient of an Award, setting forth the terms and conditions of the Award.

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     2.6.  BENEFICIAL OWNERSHIP has the meaning ascribed to such term in Rule
13d-3, or any successor rule thereto, promulgated by the Securities and Exchange
Commission pursuant to the Exchange Act.

     2.7.  BOARD means the Company's Board of Directors.

     2.8.  CHANGE OF CONTROL means (i) the closing of any Sale of the Company
Transaction or (ii) the direct or indirect acquisition, in a single transaction
or a series of related transactions, by any person or Group (other than the
Company or a Controlled Affiliate of the Company) of Beneficial Ownership of
previously outstanding shares of capital stock of the Company if (A) immediately
after such acquisition, such person or Group, together with their respective
Affiliates, shall own or hold shares of capital stock of the Company possessing
at least twenty-five percent (25%) of the total voting power of the outstanding
capital stock of the Company, (B) immediately prior to such acquisition, such
person or Group, together with their respective Affiliates, did not own or hold
shares of capital stock of the Company possessing at least twenty-five percent
(25%) of the total voting power of the outstanding capital stock of the Company,
and (C) within thirty (30) days after the Company is notified or first becomes
aware of such acquisition, whichever is earlier, a majority of the members of
the Board of Directors of the Company as constituted immediately prior to such
acquisition do not consent in writing to exclude such acquisition from the scope
of this definition.

     2.9.  CODE means the Internal Revenue Code of 1986, as amended from time to
time, or any successor statute thereto, and any regulations issued from time to
time thereunder.

     2.10. CONTROLLED AFFILIATE means, with respect to any person or entity, any
other person or entity that is controlled by such person or entity.

     2.11. COMMITTEE means any committee of the Board delegated responsibility
by the Board for the administration of the Plan, as provided in Section 5 of the
Plan. For any period during which no such committee is in existence, "Committee"
shall mean the Board and all authority and responsibility assigned the Committee
under the Plan shall be exercised, if at all, by the Board.

     2.12. COMMON STOCK means common stock, par value $0.001 per share, of the
Company.

     2.13. COMPANY means TolerRx, Inc., a corporation organized under the laws
of the State of Delaware.

     2.14. EXCHANGE ACT means the Securities Exchange Act of 1934, as amended.

     2.15. GRANT DATE means the date as of which an Option is granted, as
determined under Section 7.1(a).

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     2.16. GROUP has the meaning ascribed to such term in Section 13(d)(3) of
the Exchange Act or any successor section thereto.

     2.17. INCENTIVE OPTION means an Option which by its terms is to be treated
as an "incentive stock option" within the meaning of Section 422 of the Code.

     2.18. MARKET VALUE means the value of a share of Common Stock on any date
as determined by the Committee.

     2.19. NONSTATUTORY OPTION means any Option that is not an Incentive Option.

     2.20. OPTION means an option to purchase shares of Common Stock.

     2.21. OPTIONEE means a Participant to whom an Option shall have been
granted under the Plan.

     2.22. PARTICIPANT means any holder of an outstanding Award under the Plan.

     2.23. PLAN means this Amended and Restated 2000 Equity Incentive Plan of
the Company, as amended and in effect from time to time.

     2.24. RESTRICTED STOCK means a grant or sale of shares of Common Stock to a
Participant subject to a Risk of Forfeiture.

     2.25. RESTRICTION PERIOD means the period of time, established by the
Committee in connection with an Award of Restricted Stock, during which the
shares of Restricted Stock are subject to a Risk of Forfeiture described in the
applicable Award Agreement.

     2.26. RISK OF FORFEITURE means a limitation on the right of a Participant
to retain an Award of Restricted Stock, including a right in the Company to
reacquire such Restricted Stock at less than its then Market Value, arising
because of the occurrence or non-occurrence of specified events or conditions.

     2.27. SALE OF THE COMPANY TRANSACTION means any Transaction in which the
stockholders of the Company immediately prior to such Transaction, together with
any and all of such stockholders' Affiliates, do not own or hold, immediately
after consummation of such Transaction, shares of capital stock of the Acquiring
Person in connection with such Transaction possessing at least a majority of the
total voting power of the outstanding capital stock of such Acquiring Person.

     2.28. SECURITIES ACT means the Securities Act of 1933, as amended.

     2.29. STOCK GRANT means the grant of shares of Common Stock not subject to
restrictions or other forfeiture conditions.

     2.30. TEN PERCENT OWNER means a person who owns, or is deemed within the
meaning of Section 422(b)(6) of the Code to own, stock possessing more than 10%
of the total combined voting power of all classes of stock of the Company (or
any parent or

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subsidiary corporations of the Company, as defined in Section 424(e) and (f),
respectively, of the Code). Whether a person is a Ten Percent Owner shall be
determined with respect to each Option based on the facts existing immediately
prior to the Grant Date of such Option.

     2.31. TRANSACTION means any merger or consolidation of the Company with or
into another person or entity or the sale or transfer of all or substantially
all of the assets of the Company, in each case in a single transaction or in a
series of related transactions.

3.   TERM OF THE PLAN

     Unless the Plan shall have been earlier terminated by the Board, Awards may
be granted under this Plan at any time in the period commencing on the effective
date of approval of the Plan by the Board and ending immediately prior to the
tenth anniversary of the earlier of the adoption of the Plan by the Board or
approval of the Plan by the Company's stockholders. Awards granted pursuant to
the Plan within such period shall not expire solely by reason of the termination
of the Plan. Awards of Incentive Options granted prior to stockholder approval
of the Plan are hereby expressly conditioned upon such approval, but in the
event of the failure of the stockholders to approve the Plan shall thereafter
and for all purposes be deemed to constitute Nonstatutory Options.

4.   STOCK SUBJECT TO THE PLAN

     Subject to adjustment in accordance with the provisions of Section 8 of the
Plan, the aggregate number of shares of Common Stock that may initially be
issued pursuant to or subject to outstanding Awards granted under the Plan will
not exceed _______________.(1/) Notwithstanding the foregoing, and subject to
adjustment in accordance with the provisions of Section 8 of the Plan, no more
than an aggregate of __________(2/) shares of Stock may be issued pursuant to
the exercise of Incentive Stock Options granted under the Plan. For purposes of
applying the foregoing limitations, if any Option expires, terminates, or is
cancelled for any reason without having been exercised in full, or if any Award
of Restricted Stock is forfeited by the recipient, the shares not purchased by
the Optionee or forfeited by the recipient shall again be available for Awards
thereafter to be granted under the Plan. Shares of Common Stock issued pursuant
to the Plan may be either authorized but unissued shares or shares held by the
Company in its treasury.

5.   ADMINISTRATION

     The Plan shall be administered by the Committee; PROVIDED, HOWEVER, that at
any time and on any one or more occasions the Board may itself exercise any of
the powers and responsibilities assigned the Committee under the Plan and when
so acting shall have

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     (1/) This number will represent 15% of the Company immediately after the
IPO.

     (2/) This number will represent 25% of the Company immediately after the
IPO.

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the benefit of all of the provisions of the Plan pertaining to the Committee's
exercise of its authorities hereunder; AND PROVIDED FURTHER that the Committee
may delegate to an executive officer or officers the authority to grant Awards
hereunder to employees who are not officers, and to consultants, in accordance
with such guidelines as the Committee shall set forth at any time or from time
to time. Subject to the provisions of the Plan, the Committee shall have
complete authority, in its discretion, to make or to select the manner of making
all determinations with respect to each Award to be granted by the Company under
the Plan in addition to any other determination allowed the Committee under the
Plan including, without limitation: (a) the employee, consultant or director to
receive the Award; (b) the form of Award; (c) whether an Option (if granted to
an employee) will be an Incentive Option or a Nonstatutory Option; (d) the time
of granting an Award; (e) the number of shares subject to an Award; (f) the
exercise price of an Option or purchase price for shares of Restricted Stock or
for a Stock Grant and the method of payment of such exercise price or such
purchase price; (g) the term of an Option; (h) the vesting period of shares of
Restricted Stock and any acceleration thereof; (i) the exercise date or dates of
an Option and any acceleration thereof; and (j) the effect of termination of any
employment, consulting or Board member relationship with the Company or any of
its Affiliates on the subsequent exercisability of an Option or on the Risk of
Forfeiture of Restricted Stock. In making such determinations, the Committee may
take into account the nature of the services rendered by the respective
employees, consultants and directors, their present and potential contributions
to the success of the Company and its Affiliates, and such other factors as the
Committee in its discretion shall deem relevant. Subject to the provisions of
the Plan, the Committee shall also have complete authority to interpret the
Plan, to prescribe, amend and rescind rules and regulations relating to it, to
determine the terms and provisions of the respective Award Agreements (which
need not be identical), and to make all other determinations necessary or
advisable for the administration of the Plan. The Committee's determinations
made in good faith on matters referred to in this Plan shall be final, binding
and conclusive on all persons having or claiming any interest under the Plan or
an Award made pursuant to hereto.

6.   AUTHORIZATION AND ELIGIBILITY

     The Committee may grant from time to time and at any time prior to the
termination of the Plan one or more Awards, either alone or in combination with
any other Awards, to any employee of or consultant to one or more of the Company
and its Affiliates or to any non-employee member of the Board or of any board of
directors (or similar governing authority) of any Affiliate. However, only
employees of the Company, and of any parent or subsidiary corporations of the
Company, as defined in Sections 424(e) and (f), respectively, of the Code, shall
be eligible for the grant of an Incentive Option. Further, in no event shall the
number of shares of Common Stock covered by Options or other Awards granted to
any one person in any one calendar year (or portion of a year) ending after such
date exceed thirty (30%) of the aggregate number of shares of Common Stock
subject to the Plan.

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     Each grant of an Award shall be subject to all applicable terms and
conditions of the Plan (including but not limited to any specific terms and
conditions applicable to that type of Award set out in the following Section),
and such other terms and conditions, not inconsistent with the terms of the
Plan, as the Committee may prescribe. No prospective Participant shall have any
rights with respect to an Award, unless and until such Participant has executed
an agreement evidencing the Award, delivered a fully executed copy thereof to
the Company, and otherwise complied with the applicable terms and conditions of
such Award.

7.   SPECIFIC TERMS OF AWARDS

     7.1.  OPTIONS.

           (a)  DATE OF GRANT. The granting of an Option shall take place at the
time specified in the Award Agreement. Only if expressly so provided in the
applicable Award Agreement shall the Grant Date be the date on which the Award
Agreement shall have been duly executed and delivered by the Company and the
Optionee.

           (b)  EXERCISE PRICE. The price at which shares of Common Stock may be
acquired under each Incentive Option shall be not less than 100% of the Market
Value of Common Stock on the Grant Date, or not less than 110% of the Market
Value of Common Stock on the Grant Date if the Optionee is a Ten Percent Owner.
The price at which shares may be acquired under each Nonstatutory Option shall
not be so limited solely by reason of this Section.

           (c)  OPTION PERIOD. No Incentive Option may be exercised on or after
the tenth anniversary of the Grant Date, or on or after the fifth anniversary of
the Grant Date if the Optionee is a Ten Percent Owner. The Option period under
each Nonstatutory Option shall not be so limited solely by reason of this
Section.

           (d)  EXERCISABILITY. An Option may be immediately exercisable or
become exercisable in such installments, cumulative or non-cumulative, as the
Committee may determine. In the case of an Option not otherwise immediately
exercisable in full, the Committee may Accelerate such Option in whole or in
part at any time; PROVIDED, HOWEVER, that in the case of an Incentive Option,
any such Acceleration of such Incentive Option would not cause such Incentive
Option to fail to comply with the provisions of Section 422 of the Code or the
Optionee consents to such Acceleration.

           (e)  EFFECT OF TERMINATION OF EMPLOYMENT, CONSULTING OR BOARD MEMBER
RELATIONSHIP. Unless the Committee shall provide otherwise with respect to any
Option, if the Optionee's employment, consulting or Board member relationship
with the Company and its Affiliates ends for any reason, including because an
entity with which the Optionee has an employment, consulting or Board member
relationship ceases to be an Affiliate of the Company, any outstanding Option
held by the Optionee shall cease to be exercisable in any respect not later than
ninety (90) days following that event and, for the period it remains exercisable
following that event, shall be exercisable only to the extent exercisable at the
date of that event. Military or sick leave or other bona fide leave

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shall not be deemed a termination of employment, PROVIDED that it does not
exceed the longer of ninety (90) days or the period during which the absent
Optionee's reemployment rights, if any, are guaranteed by statute or by
contract.

           (f)  TRANSFERABILITY. Except as otherwise provided in this subsection
(f), Options shall not be transferable, and no Option or interest therein may be
sold, transferred, pledged, assigned, or otherwise alienated or hypothecated,
other than by will or by the laws of descent and distribution. Except as
otherwise provided in this subsection (f), all of a Participant's rights in any
Option may be exercised during the life of the Participant only by the
Participant or the Participant's legal representative. However, the Committee
may, at or after the grant of a Nonstatutory Option, provide that such Option
may be transferred by the recipient to a family member; PROVIDED, HOWEVER, that
any such transfer is without payment of any consideration whatsoever and that no
transfer of an Option shall be valid unless first approved by the Committee,
acting in its sole discretion. For this purpose, "family member" means any
child, stepchild, grandchild, parent, stepparent, spouse, former spouse,
sibling, niece, nephew, mother-in-law, father-in-law, son-in-law,
daughter-in-law, brother-in-law, or sister-in-law, including adoptive
relationships, any person sharing the Participant's household (other than a
tenant or employee), a trust in which the foregoing persons have more than fifty
percent (50%) of the beneficial interests, a foundation in which the foregoing
persons (or the Participant) control the management of assets, and any other
entity in which these persons (or the Participant) own more than fifty percent
(50%) of the voting interests.

           (g)  METHOD OF EXERCISE. An Option may be exercised by the Optionee
giving written notice, in the manner provided in Section 15, specifying the
number of shares of Common Stock with respect to which the Option is then being
exercised. The notice shall be accompanied by payment in the form of cash or
check payable to the order of the Company in an amount equal to the exercise
price of the shares of Common Stock to be purchased or, if the Committee had so
authorized on the grant of an Incentive Option or on or after grant of a
Nonstatutory Option (and subject to such conditions, if any, as the Committee
may deem necessary to avoid adverse accounting effects to the Company) by
delivery to the Company of shares of Common Stock having a Market Value equal to
the exercise price of the shares to be purchased. Payment may also be made
through and under the terms and conditions of any formal cashless exercise
program authorized by the Company entailing the sale of Common Stock subject to
an Option in a brokered transaction (other than to the Company). Receipt by the
Company of such notice and payment in any authorized or combination of
authorized means shall constitute the exercise of the Option. Within thirty (30)
days thereafter but subject to the remaining provisions of the Plan, the Company
shall deliver or cause to be delivered to the Optionee or his agent a
certificate or certificates for the number of shares then being purchased. Such
shares shall be fully paid and nonassessable. Notwithstanding any of the
foregoing provisions in this subsection (g) to the contrary, (A) no Option shall
be considered to have been exercised unless and until all of the provisions
governing such exercise specified in the Plan and in the relevant Award
Agreement shall have been duly complied with; and (B) the obligation of the
Company to issue any shares upon exercise

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of an Option is subject to the provisions of Section 9.1 hereof and to
compliance by the Optionee with all of the provisions of the Plan and the
relevant Award Agreement.

           (h)  LIMIT ON INCENTIVE OPTION CHARACTERIZATION. An Incentive Option
shall be considered to be an Incentive Option only to the extent that the number
of shares of Common Stock for which the Option first becomes exercisable in a
calendar year do not have an aggregate Market Value (as of the date of the grant
of the Option) in excess of the "current limit". The current limit for any
Optionee for any calendar year shall be $100,000 MINUS the aggregate Market
Value at the date of grant of the number of shares of Common Stock available for
purchase for the first time in the same year under each other Incentive Option
previously granted to the Optionee under the Plan, and under each other
incentive stock option previously granted to the Optionee under any other
incentive stock option plan of the Company and its Affiliates. Any shares of
Common Stock which would cause the foregoing limit to be violated shall be
deemed to have been granted under a separate Nonstatutory Option, otherwise
identical in its terms to those of the Incentive Option.

           (i)  NOTIFICATION OF DISPOSITION. Each person exercising any
Incentive Option granted under the Plan shall be deemed to have covenanted with
the Company to report to the Company any disposition of such shares prior to the
expiration of the holding periods specified by Section 422(a)(1) of the Code
and, if and to the extent that the realization of income in such a disposition
imposes upon the Company federal, state, local or other withholding tax
requirements, or any such withholding is required to secure for the Company an
otherwise available tax deduction, to remit to the Company an amount in cash
sufficient to satisfy those requirements.

           (j)  RIGHTS PENDING EXERCISE. No person holding an Option shall be
deemed for any purpose to be a stockholder of the Company with respect to any of
the shares of Common Stock issuable pursuant to his Option, except to the extent
that the Option shall have been exercised with respect thereto and, in addition,
a certificate shall have been issued therefor and delivered to such holder or
his agent.

     7.2.  RESTRICTED STOCK.

           (a)  PURCHASE PRICE. Shares of Restricted Stock shall be issued under
the Plan for such consideration, in cash, other property or services, or any
combination thereof, as is determined by the Committee.

           (b)  ISSUANCE OF CERTIFICATES. Subject to subsection (c) below, each
Participant receiving an Award of Restricted Stock shall be issued a stock
certificate in respect of such shares of Restricted Stock. Such certificate
shall be registered in the name of such Participant, and, if applicable, shall
bear an appropriate legend referring to the terms, conditions, and restrictions
applicable to such Award substantially in the following form:

     The transferability of this certificate and the shares represented by this
     certificate are subject to the terms and conditions of the TolerRx, Inc.

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     Amended and Restated 2000 Equity Incentive Plan and an Award Agreement
     entered into by the registered owner and TolerRx, Inc. Copies of such Plan
     and Agreement are on file in the offices of TolerRx, Inc.

           (c)  ESCROW OF SHARES. The Committee may require that the stock
certificates evidencing shares of Restricted Stock be held in custody by a
designated escrow agent (which may but need not be the Company) until the
restrictions thereon shall have lapsed, and that the Participant deliver a stock
power, endorsed in blank, relating to the Common Stock covered by such Award.

           (d)  RESTRICTIONS AND RESTRICTION PERIOD. During the Restriction
Period applicable to shares of Restricted Stock, such shares shall be subject to
limitations on transferability and a Risk of Forfeiture arising on the basis of
such conditions related to the performance of services, Company or Affiliate
performance or otherwise as the Committee may determine and provide for in the
applicable Award Agreement. Any such Risk of Forfeiture may be waived or
terminated, or the Restriction Period shortened, at any time by the Committee on
such basis as it deems appropriate.

           (e)  RIGHTS PENDING LAPSE OF RISK OF FORFEITURE OR FORFEITURE OF
AWARD. Except as otherwise provided in the Plan or the applicable Award
Agreement, at all times prior to lapse of any Risk of Forfeiture applicable to,
or forfeiture of, an Award of Restricted Stock, the Participant shall have all
of the rights of a stockholder of the Company, including the right to vote the
shares of Restricted Stock.

           (f)  EFFECT OF TERMINATION OF EMPLOYMENT, CONSULTING OR BOARD MEMBER
RELATIONSHIP. Unless otherwise determined by the Committee at or after grant and
subject to the applicable provisions of the Award Agreement, if a Participant's
employment, consulting or Board member relationship with the Company and its
Affiliates ends for any reason during the Restriction Period, including because
an entity with which the Participant has an employment, consulting or Board
member relationship ceases to be an Affiliate of the Company, all shares of
Restricted Stock still subject to Risk of Forfeiture shall be forfeited or
otherwise subject to return to or repurchase by the Company on the terms
specified in the Award Agreement; PROVIDED, HOWEVER, that military or sick leave
or other bona fide leave shall not be deemed a termination of employment, if it
does not exceed the longer of ninety (90) days or the period during which the
absent Participant's reemployment rights, if any, are guaranteed by statute or
by contract.

           (g)  LAPSE OF RESTRICTIONS. If and when the Restriction Period
expires without a prior forfeiture of the Restricted Stock, the certificates for
such shares shall be delivered to the Participant promptly if not theretofore so
delivered.

     7.3.  STOCK GRANTS.

           (a)  IN GENERAL. Stock Grants shall be issued for such consideration,
in cash, other property or services, or any combination thereof, as is
determined by the Committee. Without limiting the generality of the foregoing,
Stock Grants may be

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awarded in such circumstances as the Committee deems appropriate, including
without limitation in recognition of significant contributions to the success of
the Company or its Affiliates or in lieu of compensation otherwise already due.
Stock Grants shall be made without forfeiture conditions of any kind.

           (b)  ISSUANCE OF CERTIFICATES. Each Participant receiving a Stock
Grant shall be issued a stock certificate in respect of such Stock Grant. Such
certificate shall be registered in the name of such Participant, and, if
applicable, shall bear an appropriate legend referring to the terms, conditions,
and restrictions applicable to such Award substantially in the following form:

     The transferability of this certificate and the shares represented by this
     certificate are subject to the terms and conditions of the TolerRx, Inc.
     Amended and Restated 2000 Equity Incentive Plan. A copy of such Plan is on
     file in the offices of TolerRx, Inc.

     7.4.  AWARDS TO PARTICIPANTS OUTSIDE THE UNITED STATES. The Committee may
modify the terms of any Award under the Plan granted to a Participant who is, at
the time of grant or during the term of the Award, resident or primarily
employed outside of the United States in any manner deemed by the Committee to
be necessary or appropriate in order that such Award shall conform to laws,
regulations, and customs of the country in which the Participant is then
resident or primarily employed, or so that the value and other benefits of the
Award to the Participant, as affected by foreign tax laws and other restrictions
applicable as a result of the Participant's residence or employment abroad,
shall be comparable to the value of such an Award to a Participant who is
resident or primarily employed in the United States. An Award may be modified
under this Section 7.4 in a manner that is inconsistent with the express terms
of the Plan, so long as such modifications will not contravene any applicable
law or regulation.

     7.5.  AUTOMATIC GRANTS TO OUTSIDE DIRECTORS.

           (a)  Each outside director shall be granted upon his election to the
board an Award covering [100,000](3/) shares of Common Stock, which Award shall
be, at the election of each outside director, in the form of either (i) an
Option which shall become exercisable, cumulatively, in a series of three (3)
successive, equal annual installments, with the first installment to become
exercisable on, or at any time after, the first year anniversary of the Grant
Date or (ii) Restricted Stock for which the Risk of Forfeiture shall expire in a
series of three (3) successive, equal annual installments, with the first
installment to expire on, or at any time after, the first year anniversary of
the grant date of the Award.

           (b)  Each outside director shall be granted automatically each year
on the anniversary of the first date of his or her term of service on the Board
an Award

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     (3/) 100,000 is on a pre-split, pre-IPO basis. The grant will be for an
equivalent number on a post-split, post-IPO basis.

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covering [15,000](4/) shares of Common Stock, which Award shall be, at the
election of each outside director, in the form of either (i) an Option which
shall become fully exercisable on the first year anniversary of the Grant Date
or (ii) Restricted Stock for which the Risk of Forfeiture shall expire on the
first year anniversary of the grant date of the Award.

8.   ADJUSTMENT PROVISIONS

     8.1.  ADJUSTMENT FOR CORPORATE ACTIONS. All of the share numbers set forth
in the Plan reflect the capital structure of the Company as of
__________________, 2003. Subject to the provisions of Section 8.2, if
subsequent to such date the outstanding shares of Common Stock (or any other
securities covered by the Plan by reason of the prior application of this
Section) are increased, decreased, or exchanged for a different number or kind
of shares or other securities, or if additional shares or new or different
shares or other securities are distributed with respect to such shares of Common
Stock or other securities, through merger, consolidation, sale of all or
substantially all the property of the Company, reorganization, recapitalization,
reclassification, stock dividend, stock split, reverse stock split, or other
distribution with respect to such shares of Common Stock, or other securities,
an appropriate and proportionate adjustment will be made in (i) the maximum
numbers and kinds of shares provided in Section 4, (ii) the numbers and kinds of
shares or other securities subject to the then outstanding Awards, (iii) the
exercise price for each share or other unit of any other securities subject to
then outstanding Options (without change in the aggregate purchase price as to
which such Options remain exercisable), and (iv) the repurchase price of each
share of Restricted Stock then subject to a Risk of Forfeiture in the form of a
Company repurchase right.

        8.2.  CHANGE OF CONTROL. Subject to the applicable provisions of the
Award Agreement, in the event of a Change of Control, the Board of Directors
shall have the discretion, exercisable in advance of, at the time of, or
(except to the extent otherwise provided below) at any time after, such
Change of Control, to provide for any or all of the following (subject to and
upon such terms as the Board of Directors may deem appropriate): (A) the
Acceleration of any or all outstanding Options (including Options that are
assumed or replaced pursuant to clause (C) below) that are not exercisable in
full at the time the Change of Control, such Acceleration to become effective
at the time of the Change of Control, or at such time following the Change of
Control that the employment, consulting or Board member relationship of the
applicable Optionee or Optionees with the Company and its Affiliates
terminates, or at such other time or times as the Board of Directors shall
determine; (B) the termination of any or all of the Company's repurchase
rights with respect to Restricted Stock Awards, such termination to become
effective at the time of the Change of Control, or at such time following the
Change of Control that the employment, consulting or Board member
relationship with the Company and its Affiliates of the Participant or
Participants that hold such Restricted

----------

     (4/) 15,000 is on a pre-split, pre-IPO basis. The grant will be for an
equivalent number on a post-split, post-IPO basis.

<Page>

                                     - 12 -

Stock Awards terminates, or at such other time or times as the Board of
Directors shall determine; (C) the assumption of outstanding Options, or the
substitution of outstanding Options with equivalent options, by the acquiring
or succeeding corporation or entity (or an affiliate thereof); or (D) the
termination of all Options (other than Options that are assumed or
substituted pursuant to clause (C) above) that remain outstanding at the time
of the consummation of the Change of Control, PROVIDED THAT, the Board of
Directors shall have made the determination to effect such termination prior
to the consummation of the Change of Control and the Board of Directors shall
have given, or caused to be given, to all Optionees written notice of such
potential termination at least five (5) business days prior to the
consummation of the Change of Control. Notwithstanding the foregoing, subject
to the applicable provisions of the Award Agreement, in the event of the
closing of a Sale of the Company Transaction in which the acquiring or
succeeding corporation or entity does not have an equity incentive plan under
which all outstanding Options may be assumed or pursuant to which options may
be issued in substitution of all outstanding Options, the vesting of all
outstanding Options shall Accelerate by one year, such Acceleration to become
effective upon the closing of the Sale of the Company Transaction. The
provisions of this Section 8.2 shall not be construed as to limit or restrict
in any way the Committee's general authority under Sections 7.1(d) or 7.2(d)
hereof to Accelerate Options in whole or in part at any time or to waive or
terminate at any time any Risk of Forfeiture applicable to shares of
Restricted Stock. Each outstanding Option that is assumed in connection with
a Change of Control, or is otherwise to continue in effect subsequent to a
Change of Control, will be appropriately adjusted, immediately after the
Change of Control, as to the number and class of securities and the price at
which it may be exercised in accordance with Section 8.1.

     8.3.  DISSOLUTION OR LIQUIDATION.   Upon dissolution or liquidation of the
Company, each outstanding Option shall terminate, but the Optionee (if at the
time he or she has an employment, consulting or Board member relationship with
the Company or any of its Affiliates) shall have the right, immediately prior to
such dissolution or liquidation, to exercise the Option to the extent
exercisable on the date of such dissolution or liquidation.

     8.4.  RELATED MATTERS.   Any adjustment in Awards made pursuant to this
Section 8 shall be determined and made, if at all, by the Committee and shall
include any correlative modification of terms, including of Option exercise
prices, rates of vesting or exercisability, Risks of Forfeiture and applicable
repurchase prices for Restricted Stock, which the Committee may deem necessary
or appropriate so as to ensure that the rights of the Participants in their
respective Awards are not substantially diminished nor enlarged as a result of
the adjustment and corporate action other than as expressly contemplated in this
Section 8. No fraction of a share shall be purchasable or deliverable upon
exercise, but in the event any adjustment hereunder of the number of shares
covered by an Award shall cause such number to include a fraction of a share,
such number of shares shall be adjusted to the nearest smaller whole number of
shares. No adjustment of an Option exercise price per share pursuant to this
Section 8 shall result in an exercise price which is less than the par value of
the Common Stock.

<Page>

                                     - 13 -

9.   SETTLEMENT OF AWARDS

     9.1.  VIOLATION OF LAW. Notwithstanding any other provision of the Plan or
the relevant Award Agreement, if, at any time, in the reasonable opinion of the
Company, the issuance of shares of Common Stock covered by an Award may
constitute a violation of law, then the Company may delay such issuance and the
delivery of a certificate for such shares until (i) approval shall have been
obtained from such governmental agencies, other than the Securities and Exchange
Commission, as may be required under any applicable law, rule, or regulation and
(ii) in the case where such issuance would constitute a violation of a law
administered by or a regulation of the Securities and Exchange Commission, one
of the following conditions shall have been satisfied:

           (a)  the shares are at the time of the issue of such shares
effectively registered under the Securities Act; or

           (b)  the Company shall have determined, on such basis as it deems
appropriate (including an opinion of counsel in form and substance satisfactory
to the Company) that the sale, transfer, assignment, pledge, encumbrance or
other disposition of such shares or such beneficial interest, as the case may
be, does not require registration under the Securities Act or any applicable
state securities laws.

     9.2.  RESTRICTIONS ON RIGHTS IN STOCK. Any Common Stock to be issued
pursuant to Awards granted under the Plan shall be subject to such stop-transfer
orders and other restrictions as the Committee may deem advisable under the
rules, regulations, and other requirements of any stock exchange upon which the
Common Stock is then listed, and any applicable federal or state securities law,
and the Committee may cause a legend or legends to be put on any such
certificates to make appropriate reference to such restrictions.

     9.3.  INVESTMENT REPRESENTATIONS. The Company shall be under no obligation
to issue any shares covered by an Award unless the shares to be issued pursuant
to Awards granted under the Plan have been effectively registered under the
Securities Act or the Participant shall have made such written representations
to the Company (upon which the Company believes it may reasonably rely) as the
Company may deem necessary or appropriate for purposes of confirming that the
issuance of such shares will be exempt from the registration requirements of
that Act and any applicable state securities laws and otherwise in compliance
with all applicable laws, rules and regulations, including but not limited to
that the Participant is acquiring shares for his or her own account for the
purpose of investment and not with a view to, or for sale in connection with,
the distribution of any such shares.

     9.4.  REGISTRATION. If the Company shall deem it necessary or desirable to
register under the Securities Act or other applicable statutes any shares of
Common Stock issued or to be issued pursuant to Awards granted under the Plan,
or to qualify any such shares of Common Stock for exemption from the Securities
Act or other applicable statutes, then the Company shall take such action at its
own expense. The Company may

<Page>

                                     - 14 -

require from each recipient of an Award, or each holder of shares of Common
Stock acquired pursuant to the Plan, such information in writing for use in any
registration statement, prospectus, preliminary prospectus or offering circular
as is reasonably necessary for such purpose and may require reasonable indemnity
to the Company and its officers and directors from such holder against all
losses, claims, damage and liabilities arising from such use of the information
so furnished and caused by any untrue statement of any material fact therein or
caused by the omission to state a material fact required to be stated therein or
necessary to make the statements therein not misleading in the light of the
circumstances under which they were made.

     9.5.  LOCK-UP. Without the prior written consent of the Company or the
managing underwriter in any public offering of shares of Common Stock, no
Participant shall sell, make any short sale of, loan, grant any option for the
purchase of, pledge or otherwise encumber, or otherwise dispose of, any shares
of Common Stock during the one hundred-eighty (180) day period commencing on the
effective date of the registration statement relating to any underwritten public
offering of securities of the Company. The foregoing restrictions are intended
and shall be construed so as to preclude any Participant from engaging in any
hedging or other transaction that is designed to or reasonably could be expected
to lead to or result in, a sale or disposition of any shares of Common Stock
during such period even if such shares of Common Stock are or would be disposed
of by someone other than such Participant. Such prohibited hedging or other
transactions would include, without limitation, any short sale (whether or not
against the box) or any purchase, sale or grant of any right (including without
limitation any put or call option) with respect to any shares of Common Stock or
with respect to any security that includes, relates to, or derives any
significant part of its value from any shares of Common Stock. Without limiting
the generality of the foregoing provisions of this Section 9.5, if, in
connection with any underwritten public offering of securities of the Company,
the managing underwriter of such offering requires that the Company's directors
and officers enter into a lock-up agreement containing provisions that are more
restrictive than the provisions set forth in the preceding sentence, then (a)
each Participant (regardless of whether or not such Participant has complied or
complies with the provisions of clause (b) below) shall be bound by, and shall
be deemed to have agreed to, the same lock-up terms as those to which the
Company's directors and officers are required to adhere; and (b) at the request
of the Company or such managing underwriter, each Participant shall execute and
deliver a lock-up agreement in form and substance equivalent to that which is
required to be executed by the Company's directors and officers.

     9.6.  PLACEMENT OF LEGENDS; STOP ORDERS; ETC. Each share of Common Stock to
be issued pursuant to Awards granted under the Plan may bear a reference to the
investment representations made in accordance with Section 9.3 in addition to
any other applicable restrictions under the Plan, the terms of the Award and to
the fact that no registration statement has been filed with the Securities and
Exchange Commission in respect to such shares of Common Stock. All certificates
for shares of Common Stock or other securities delivered under the Plan shall be
subject to such stock transfer orders and other restrictions as the Committee
may deem advisable under the rules, regulations, and

<Page>

                                     - 15 -

other requirements of any stock exchange upon which the Common Stock is then
listed, and any applicable federal or state securities law, and the Committee
may cause a legend or legends to be placed on any such certificates to make
appropriate reference to such restrictions.

     9.7.  TAX WITHHOLDING. Whenever shares of Common Stock are issued or to be
issued pursuant to Awards granted under the Plan, the Company shall have the
right to require the recipient to remit to the Company an amount sufficient to
satisfy federal, state, local or other withholding tax requirements if, when,
and to the extent required by law (whether so required to secure for the Company
an otherwise available tax deduction or otherwise) prior to the delivery of any
certificate or certificates for such shares. The obligations of the Company
under the Plan shall be conditional on satisfaction of all such withholding
obligations and the Company shall, to the extent permitted by law, have the
right to deduct any such taxes from any payment of any kind otherwise due to the
recipient of an Award.

10.  RESERVATION OF STOCK

     The Company shall at all times during the term of the Plan and any
outstanding Options granted hereunder reserve or otherwise keep available such
number of shares of Common Stock as will be sufficient to satisfy the
requirements of the Plan (if then in effect) and such Options and shall pay all
fees and expenses necessarily incurred by the Company in connection therewith.

11.  NO SPECIAL SERVICE RIGHTS

     Nothing contained in the Plan or in any Award Agreement shall confer upon
any recipient of an Award any right with respect to the continuation of his or
her employment, consulting or Board member relationship with the Company (or any
Affiliate), or interfere in any way with the right of the Company (or any
Affiliate), subject to the terms of any separate employment, consulting or Board
member agreement or provision of law or corporate articles or by-laws to the
contrary, at any time to terminate such employment, consulting or Board member
agreement or to increase or decrease, or otherwise adjust, the other terms and
conditions of the recipient's employment, consulting or Board member
relationship with the Company and its Affiliates.

12.  NONEXCLUSIVITY OF THE PLAN

     Neither the adoption of the Plan by the Board nor the submission of the
Plan to the stockholders of the Company shall be construed as creating any
limitations on the power of the Board to adopt such other incentive arrangements
as it may deem desirable, including without limitation, the granting of stock
options and restricted stock other than under the Plan, and such arrangements
may be either applicable generally or only in specific cases.

<Page>

                                     - 16 -

13.  TERMINATION AND AMENDMENT OF THE PLAN

     The Board may at any time terminate the Plan or make such amendments or
modifications of the Plan as it shall deem advisable. In the event of the
termination of the Plan, the terms of the Plan shall survive any such
termination with respect to any Award that is outstanding on the date of such
termination, unless the holder of such Award agrees in writing to terminate such
Award or to terminate all or any of the provisions of the Plan that apply to
such Award. Unless the Board otherwise expressly provides, any amendment or
modification of the Plan shall affect the terms of any Award outstanding on the
date of such amendment or modification as well as the terms of any Award made
from and after the date of such amendment or modification; PROVIDED, HOWEVER,
that, except to the extent otherwise provided in the last sentence of this
paragraph, (i) no amendment or modification of the Plan shall apply to any Award
that is outstanding on the date of such amendment or modification if such
amendment or modification would reduce the number of shares subject to such
Award, increase the purchase price applicable to shares subject to such Award or
materially adversely affect the provisions applicable to such Award that relate
to the vesting or exercisability of such Award or of the shares subject to such
Award, (ii) no amendment or modification of the Plan shall apply to any
Incentive Option that is outstanding on the date of such amendment or
modification if such amendment or modification would result in such Incentive
Option no longer being treated as an "incentive stock option" within the meaning
of Section 422 of the Code and (iii) no amendment or modification of the Plan
shall apply to any Award that is outstanding on the date of such amendment or
modification unless such amendment or modification of the Plan shall also apply
to all other Awards outstanding on the date of such amendment or modification.
In the event of any amendment or modification of the Plan that is described in
clause (i), (ii) or (iii) of the foregoing proviso, such amendment or
modification of the Plan shall apply to any Award outstanding on the date of
such amendment or modification only if the recipient of such Award consents in
writing thereto.

     The Committee may amend or modify, prospectively or retroactively, the
terms of any Award theretofore granted without amending or modifying the terms
of the Plan itself, PROVIDED that as amended or modified such Award is
consistent with the terms of the Plan as in effect at the time of the amendment
or modification of such Award, but no such amendment or modification of such
Award shall, without the written consent of the recipient of such Award, reduce
the number of shares subject to such Award, increase the purchase price
applicable to shares subject to such Award, adversely affect the provisions
applicable to such Award that relate to the vesting or exercisability of such
Award or of the shares subject to such Award, otherwise materially adversely
affect the terms of such Award (except for amendments or modifications to the
terms of such Award or of the stock subject to such Award that are expressly
permitted by the terms of the Plan or that result from any amendment or
modification of the Plan in accordance with the provisions of the first
paragraph of this Section 13), or, if such Award is an Incentive Option, result
in such Incentive Option no longer being treated as an "incentive stock option"
within the meaning of Section 422 of the Code.

<Page>

                                     - 17 -

14.  INTERPRETATION OF THE PLAN

     In the event of any conflict between the provisions of this Plan and the
provisions of any applicable Award Agreement, the provisions of such Award
Agreement shall control, but insofar as possible the provisions of the Plan and
such Award Agreement shall be construed so as to give full force and effect to
all such provisions.

15.  NOTICES AND OTHER COMMUNICATIONS

     Any notice, demand, request or other communication hereunder to any party
shall be deemed to be sufficient if contained in a written instrument delivered
in person or duly sent by first class registered, certified or overnight mail,
postage prepaid, or telecopied with a confirmation copy by regular, certified or
overnight mail, addressed or telecopied, as the case may be, (i) if to the
recipient of an Award, at his or her residence address last filed with the
Company and (ii) if to the Company, at its principal place of business,
addressed to the attention of its Chief Executive Officer, or to such other
address or telecopier number, as the case may be, as the addressee may have
designated by notice to the addressor. All such notices, requests, demands and
other communications shall be deemed to have been received: (i) in the case of
personal delivery, on the date of such delivery; (ii) in the case of mailing,
when received by the addressee; and (iii) in the case of facsimile transmission,
when confirmed by facsimile machine report.

16.  GOVERNING LAW

     The Plan and all Award Agreements and actions taken thereunder shall be
governed, interpreted and enforced in accordance with the laws of the
Commonwealth of Massachusetts, without regard to the conflict of laws principles
thereof.

<Page>
                                  TOLERRX, INC.

                       NONSTATUTORY STOCK OPTION AGREEMENT

         NONSTATUTORY STOCK OPTION AGREEMENT, dated as of _______________ (this
"Agreement"), between TolerRx, Inc., a Delaware corporation (the "Company"), and
___________________ (the "Optionee").

         1. GRANT OF OPTION.

         Pursuant to the Company's Amended and Restated 2000 Equity Incentive
Plan, as amended from time to time (the "Plan"), a copy of which is attached
hereto as Exhibit A, the Company grants to the Optionee an option (the "Option")
to purchase from the Company all or any part of a total of _____________ shares
(the "Optioned Shares") of the Company's common stock, $.001 par value, at a
price of $____________ per share. The Option is granted as of _________________
(the "Grant Date").

         2. CHARACTER OF OPTION.

         The Option is not intended to be treated as an "incentive stock option"
within the meaning of Section 422 of the Internal Revenue Code of 1986, as
amended (the "Code"), but as a nonstatutory stock option within the meaning of
the Code.

         3. DURATION OF OPTION.

         Unless subject to earlier expiration pursuant to the terms of the Plan,
the Option shall expire on ___________.

         4. EXERCISE OF OPTION.

         Until its  expiration  pursuant to Section 3 hereof,  the Option may be
exercised  in the manner  specified  in Section  7.1(f) of the Plan as  follows:
[INSERT VESTING SCHEDULE].

         5. TRANSFER OF OPTIONS.

         The Option may not be transferred except by prior written consent of
the Company.

         6. INCORPORATION OF PLAN TERMS.

         The Option is granted subject to all of the applicable terms and
provisions of the Plan, including but not limited to the limitations on the
Company's obligation to deliver the Optioned Shares upon exercise thereof as set
forth in Section 9 of the Plan.
<Page>
         7. MISCELLANEOUS.

         This Agreement shall be construed and enforced in accordance with the
laws of the Commonwealth of Massachusetts and shall be binding upon and inure to
the benefit of any successor or assign of the Company and any assign, executor,
administrator, trustee, guardian, or other legal representative of the Optionee.

         IN WITNESS WHEREOF, the parties have executed this Agreement as a
sealed instrument as of the date first above written.

TOLERRX, INC.                                 OPTIONEE

By:
     --------------------------------         --------------------------------
        Douglas J. Ringler                       [Insert Name of Optionee]
        President

                                              Address:

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

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

                                              --------------------------------
<Page>
                                  TOLERRX, INC.

                        INCENTIVE STOCK OPTION AGREEMENT

         INCENTIVE STOCK OPTION AGREEMENT, dated as of ___________ (this
"Agreement"), between TolerRx, Inc., a Delaware corporation (the "Company"), and
_________________ (the "Optionee").

         1. GRANT OF OPTION.

         Pursuant to the Company's Amended and Restated 2000 Equity Incentive
Plan, as amended from time to time (the "Plan"), a copy of which is attached
hereto as Exhibit A, the Company grants to the Optionee an option (the "Option")
to purchase from the Company all or any part of a total of _________________
shares (the "Optioned Shares") of the Company's common stock, $.001 par value,
at a price of $_____________ per share. The Option is granted as of
_______________ (the "Grant Date").

         2. CHARACTER OF OPTION.

         The Option is intended to be treated as an "incentive stock option"
within the meaning of Section 422 of the Internal Revenue Code of 1986, as
amended.

         3. DURATION OF OPTION.

         Unless subject to earlier expiration pursuant to the terms of the Plan,
the Option shall expire on the earlier of (i) the tenth anniversary of the Grant
Date or (ii) the 90th day following the termination of the Optionee's employment
with the Company for any reason.

         4. EXERCISE OF OPTION.

         Until its expiration pursuant to Section 3 hereof, the Option may be
exercised in the manner specified in Section 7.1(f) of the Plan as follows:
[INSERT VESTING SCHEDULE (e.g., (i) ____________ percent (___%) of the Optioned
Shares shall vest on and after _________ __, 200_, and (ii) the remaining
_______________ percent (___%) of the Optioned Shares shall vest in a series of
____________ (___) equal installments, in portions of whole shares as nearly
equal as practicable, with each installment vesting on _____________, until all
of the Optioned Shares are fully vested.]

         5. Transfer of Options.

         The Option may not be transferred except by will or the laws of descent
and distribution, and, during the lifetime of the Optionee, may be exercised
only by the Optionee.
<Page>
         6. INCORPORATION OF PLAN TERMS.

         The Option is granted subject to all of the applicable terms and
provisions of the Plan, including but not limited to the limitations on the
Company's obligation to deliver Optioned Shares upon exercise thereof as set
forth in Section 9 of the Plan.

         7. MISCELLANEOUS.

         This Agreement shall be construed and enforced in accordance with the
laws of the Commonwealth of Massachusetts and shall be binding upon and inure to
the benefit of any successor or assign of the Company and any executor,
administrator, trustee, guardian, or other legal representative of the Optionee.

         IN WITNESS WHEREOF, the parties have executed this Agreement as a
sealed instrument as of the date first above written.

TOLERRX, INC.                                 OPTIONEE

By:  --------------------------------         --------------------------------
        Douglas J. Ringler                       [Insert Name of Optionee]
        President

                                              Address:

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

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

                                              --------------------------------<Page>

                                                                    EXHIBIT 10.2

                                  TOLERRX, INC.

                        2003 EMPLOYEE STOCK PURCHASE PLAN

<Page>

<Table>
<S>                                                                           <C>
1.   Purpose..................................................................1

2.   Definitions..............................................................1

3.   Eligibility..............................................................3

4.   Offering Periods.........................................................3

5.   Participation............................................................3

6.   Method of Payment of Contributions.......................................4

7.   Grant of Option..........................................................5

8.   Exercise of Option.......................................................6

9.   Delivery.................................................................6

10.  Voluntary Withdrawal; Termination of Employment..........................6

11.  Interest.................................................................7

12.  Stock....................................................................7

13.  Administration...........................................................7

14.  Designation of Beneficiary...............................................7

15.  Transferability of Options and Shares....................................8

16.  Use of Funds.............................................................8

17.  Reports..................................................................8

18.  Adjustments Upon Changes in Capitalization; Corporate Transactions.......8

19.  Amendment or Termination.................................................10

20.  Notices..................................................................10

21.  Conditions to Issuance of Shares.........................................10

22.  Term of Plan; Effective Date.............................................11
</Table>

<Page>

                                  TOLERRX, INC.

                        2003 EMPLOYEE STOCK PURCHASE PLAN

     The following constitute the provisions of the 2003 Employee Stock Purchase
Plan of TolerRx, 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

     2.1.  BOARD means the Board of Directors of the Company.

     2.2.  CODE means the Internal Revenue Code of 1986, as amended.

     2.3.  COMMON STOCK means the Common Stock, par value $0.001 per share, of
the Company.

     2.4.  COMPANY means TolerRx, Inc., a Delaware corporation.

     2.5.  COMPENSATION means all regular straight time compensation including
commissions but shall not include payments for overtime, shift premium,
incentive compensation, incentive payments, bonuses and other irregular or
infrequent compensation or benefits.

     2.6.  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) in the case of transfers between locations of the Company
or between the Company and its Designated Subsidiaries.

     2.7.  CONTRIBUTIONS means all amounts credited to the account of a
participant pursuant to the Plan.

     2.8.  CORPORATE TRANSACTION means a merger or consolidation of the Company
with and into another person or the sale, transfer, or other disposition of all
or

<Page>

                                       -2-

substantially all of the Company's assets to one or more persons (other than any
wholly-owned subsidiary of the Company) in a single transaction or series of
related transactions.

     2.9.  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.

     2.10. EMPLOYEE means any person, including an Officer, 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.

     2.11. EXCHANGE ACT means the Securities Exchange Act of 1934, as amended.

     2.12  INITIAL OFFERING PERIOD means the first Offering Period of the Plan.

     2.13. OFFERING COMMENCEMENT DATE means the first business day of each
Offering Period of the Plan.

     2.14. OFFERING PERIOD means any of the periods, generally of six (6) months
duration, as set forth in Section 4.

     2.15. 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.

     2.16. OFFERING TERMINATION DATE means the last business day of each
Offering Period of the Plan.

     2.17. PLAN means this Employee Stock Purchase Plan.

     2.18. PURCHASE PRICE means with respect to an Offering Period an amount
equal to 85% of the Fair Market Value (as defined in Section 7.2 below) of a
Share on the Offering Commencement Date or on the Offering Termination Date,
whichever is lower; provided, however, that (i) if there is an increase in the
number of Shares available for issuance under the Plan as a result of a
stockholder-approved amendment to the Plan, (ii) all or a portion of such
additional Shares are to be issued with respect to the Offering Period 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
Commencement Date for 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 Offering
Termination Date, whichever is lower.

     2.19. SHARE means a share of Common Stock, as adjusted in accordance with
Section 18 of the Plan.

<Page>

                                       -3-

     2.20. 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

     3.1.  Any person who is an Employee as of the Offering Commencement Date of
a given Offering Period shall be eligible to participate in such Offering Period
under the Plan, subject to the requirements of Sections 5.1 and 5.3 and the
limitations imposed by Section 423(b) of the Code.

     3.2.  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 (taking into account stock which 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 7.2 below) of such
stock (determined at the time such option is granted) for each calendar year in
which such option is outstanding at any time.

4.   OFFERING PERIODS

     Each Offering Period will begin on January 1 or July 1 and end on the next
following June 30 or December 31, respectively. However, the first Offering
Period shall commence on the beginning of the effective date of the Registration
Statement on Form S-1 for the initial public offering of the Company's Common
Stock (the "IPO Date") and continue until December 31, 2003. At any time and
from time to time, the Board may change the duration and/or the frequency of
Offering Periods with respect to future Offering Periods or suspend operation of
the Plan with respect to Offering Periods not yet commenced.

5.   PARTICIPATION

     5.1.  An eligible Employee may become a participant in the Plan by
completing a subscription agreement on the form provided by the Company and
filing it with the Company's payroll office prior to the applicable Offering
Commencement Date, unless a later time for filing the subscription agreement is
set by the Board for all eligible Employees with respect to a given Offering
Period. The subscription agreement shall set forth the percentage of the
participant's Compensation (subject to Section 6.1 below) to be paid as
Contributions pursuant to the Plan.

<Page>

                                       -4-

     5.2.  Payroll deductions shall commence on the first payroll following the
Offering Commencement Date and shall end on the last payroll paid on or prior to
the Offering Termination Date of the Offering Period to which the subscription
agreement is applicable, unless sooner terminated by the participant as provided
in Section 10.

     5.3.  Participation in the Plan for the Initial Offering Period shall be on
the same terms and conditions as are set forth in the Plan in respect of
Offering Periods generally, except as and to the extent otherwise expressly set
forth in this Section 5.3:

           (a)  All eligible Employees as of the Offering Commencement Date of
the Initial Offering Period shall automatically participate in the Plan and be
granted an option pursuant to the Plan as of such Offering Commencement Date.
Eligible Employees shall neither be required to submit a subscription agreement
to participate in the Initial Offering Period nor be permitted to decline to
participate in the Initial Offering Period (but any Contributions of a
participant for the Initial Offering Period may be withdrawn as provided in
Section 10). However, any participation as to subsequent Offering Periods shall
require submission of a subscription agreement and compliance with all other
applicable provisions of the Plan.

           (b)  For purposes of determining the exercise price of options
granted on the Offering Commencement Date of the Initial Offering Period, the
Fair Market Value of a Share as of such Offering Commencement Date 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.

           (c)  At any time after the effectiveness of the Company's
Registration Statement on Form S-8 with respect to the Plan and prior to the
Offering Termination Date, a participant in the Plan for the Initial Offering
Period may deliver by payment in cash or personal check amounts for credit as
Contributions under the Plan with respect to the Initial Offering Period.

           (d)  The total Contributions credited to a participant's account
under the Plan for the Initial Offering Period pursuant to subsection (c) above,
shall not exceed ten percent (10%) of the participant's Compensation for the
Initial Offering Period. Any excess shall be promptly refunded to the
participant following the Offering Termination Date of the Initial Offering
Period.

6.   METHOD OF PAYMENT OF CONTRIBUTIONS

     6.1.  A participant shall elect to have payroll deductions made on each
payday during the Offering Period in an amount not less than one percent (1%)
and not more than ten percent (10%) (or such other percentage as the Board may
establish from time to time before an Offering Commencement Date) of such
participant's Compensation on each payday during the Offering Period. All
payroll deductions made by a participant shall be

<Page>

                                       -5-

credited to his or her account under the Plan. A participant may not make any
additional payments into such account.

     6.2.  A participant may discontinue his or her participation in the Plan as
provided in Section 10. In addition, if the Board has so announced to Employees
at least five (5) days prior to the scheduled beginning of the next Offering
Period to be affected by the Board's determination, a participant may, on one
occasion only during each Offering Period, change the rate of his or her
Contributions with respect to the Offering Period by completing and filing with
the Company a new subscription agreement authorizing a change in the payroll
deduction rate. Any such change in rate shall be effective as of the first
payroll period following the date of filing of the new subscription agreement,
if the agreement is filed at least ten (10) business days prior to such period
and, if not, as of the second following payroll period.

     6.3.  Notwithstanding the foregoing, to the extent necessary to comply with
Section 423(b)(8) of the Code and Section 3.2 herein, a participant's payroll
deductions may be decreased during any Offering Period scheduled to end during
the current calendar year to 0%. Payroll deductions reduced to 0% in compliance
with this Section 6.3 shall re-commence automatically at the rate provided in
such participant's subscription agreement at the beginning of the first Offering
Period which is scheduled to end in the following calendar year, unless
terminated by the participant as provided in Section 10.

7.   GRANT OF OPTION

     7.1.  On the Offering Commencement Date of each Offering Period, each
eligible Employee participating in such Offering Period shall be granted an
option to purchase on the Offering Termination Date of that Offering Period a
number of Shares determined by dividing such Employee's Contributions
accumulated prior to such Offering Termination Date and retained in the
participant's account as of the Offering Termination Date by the applicable
Purchase Price. However, the maximum number of Shares an Employee may purchase
during each Offering Period shall be 2,500 shares, and provided further that
such purchase shall be subject to the limitations set forth in Sections 3.2 and
12.

     7.2.  The fair market value of the Company's Common Stock on a given date
(the "Fair Market Value") shall be determined by the Board in its discretion
based on the closing sales price of the Common Stock for such date (or, in the
event that the Common Stock is not traded on such date, on the immediately
preceding trading date), as reported by the National Association of Securities
Dealers Automated Quotation ("Nasdaq") National Market or, if such price is not
reported, the mean of the bid and asked prices per share of the Common Stock as
reported by Nasdaq or, in the event the Common Stock is listed on a stock
exchange, the closing sales price on such exchange on such date (or, in the
event that the Common Stock is not traded on such date, on the immediately
preceding trading date), as reported in The Wall Street Journal.

<Page>

                                       -6-

8.   EXERCISE OF OPTION

     Unless a participant withdraws from the Plan as provided in Section 10, his
or her option for the purchase of Shares will be exercised automatically on the
Offering Termination Date of an Offering Period, and 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. 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 Offering Termination Date.
During his or her lifetime, a participant's option to purchase Shares hereunder
is exercisable only by him or her.

9.   DELIVERY

     As promptly as practicable after each Offering Termination Date of each
Offering Period, the Company shall arrange the delivery to each participant, as
appropriate, of a certificate representing the Shares purchased upon exercise of
his or her option. 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 Offering Period, subject to earlier
withdrawal by the participant as provided in Section 10 below.  Any other
amounts left over in a participant's account after an Offering Termination Date
shall be returned to the participant.

10.  VOLUNTARY WITHDRAWAL; TERMINATION OF EMPLOYMENT

     10.1. A participant may withdraw all but not less than all of the
Contributions credited to his or her account under the Plan at any time prior to
each Offering Termination 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 Offering Period will be automatically terminated, and
no further Contributions for the purchase of Shares will be made during the
Offering Period.

     10.2. Upon termination of the participant's Continuous Status as an
Employee prior to the Offering Termination 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 14, and his or her option
will be automatically terminated.

     10.3. 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, 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.

     10.4. A participant's withdrawal during an Offering Period 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.

<Page>

                                       -7-

11.  INTEREST

     No interest shall accrue on the Contributions of a participant in the Plan.

12.  STOCK

     12.1. Subject to adjustment as provided in Section 18, the maximum number
of Shares which shall be made available for sale under the Plan shall be 150,000
Shares. Notwithstanding the foregoing, and subject to adjustment in accordance
with Section 18 no more than an aggregate of 150,000 Shares may be issued
pursuant to this Plan. If the Board determines that, on a given Offering
Termination 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 Commencement Date, or (ii) the
number of shares available for sale under the Plan on such Offering Termination
Date, the Board may in its sole discretion provide that the Company shall make a
pro rata allocation of the Shares available for purchase on such Offering
Commencement Date or Offering Termination 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 Offering Termination Date. The Company may make pro rata
allocation of the Shares available on the Offering Commencement Date of the
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 Commencement Date.

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

     12.3. 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, as directed by the participant.

13.  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. The Board's determinations made in good faith on matters referred to in
this Plan shall be final, binding and conclusive on all persons having or
claiming any interest under this Plan.

14.  DESIGNATION OF BENEFICIARY

     14.1. 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 an
Offering Period but prior to

<Page>

                                       -8-

delivery to him or her of such Shares and cash. Any such beneficiary shall also
be entitled to receive any cash from the participant's account under the Plan in
the event of such participant's death prior to the Offering Termination Date of
an Offering Period.

     14.2. Such designation of beneficiary may be changed by the participant 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.

15.  TRANSFERABILITY OF OPTIONS AND SHARES

     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
14) 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. In
addition, if the Board has so announced to Employees at least five (5) days
prior to the scheduled beginning of the next Offering Period to be affected by
the Board's determination, any Shares acquired on the Offering Termination Date
of such Offering Period may be subject to restrictions specified by the Board on
the transfer of such Shares.

16.  USE OF FUNDS

     All Contributions received or held by the Company under the Plan may be
used by the Company for any corporate purpose, and the Company shall not be
obligated to segregate such Contributions from its other assets.

17.  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.

18.  ADJUSTMENTS UPON CHANGES IN CAPITALIZATION; CORPORATE TRANSACTIONS

     18.1. 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

<Page>

                                       -9-

as the maximum number of shares of Common Stock which may be purchased by a
participant in an Offering Period, the number of shares of Common Stock set
forth in Section 12.1 above, and the price per Share of Common Stock covered by
each option under the Plan which has not yet been exercised, shall be
proportionately adjusted for any increase or decrease in the number of the
Company's 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.

     18.2. CORPORATE TRANSACTIONS. In the event of a dissolution or liquidation
of the Company, the 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, the Offering Period then in progress shall be shortened and
a new Offering Termination Date shall be set (the "New Offering Termination
Date"), as of which date the Offering Period then in progress will terminate.
The New Offering Termination 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 Offering Termination Date, that the
Offering Termination Date for his or her option has been changed to the New
Offering Termination Date and that his or her option will be exercised
automatically on the New Offering Termination Date, unless prior to such date he
or she has withdrawn from the Offering Period as provided in Section 10. For
purposes of this Section 18, 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 18); 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.

<Page>

                                      -10-

     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.

19.  AMENDMENT OR TERMINATION

     19.1. The Board may at any time and for any reason terminate or amend the
Plan. Except as provided in Section 18, 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 an Offering Termination Date or by the Board's
setting a new Offering Termination Date with respect to an Offering 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 its 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 the Plan. Except as provided
in Section 18 and in this Section 19, no amendment to the Plan shall make any
change in any option previously granted which adversely affects the rights of
any participant.

     19.2. 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, 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.

20.  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.

21.  CONDITIONS TO 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, including,
without limitation, the

<Page>

                                      -11-

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.

22.  TERM OF PLAN; EFFECTIVE DATE

     The Plan shall become effective upon the IPO Date. It shall continue in
effect for a term of five (5) years unless sooner terminated under Section 19.

<Page>

                                                                          SAMPLE

                                  TOLERRX, INC.

                        2003 EMPLOYEE STOCK PURCHASE PLAN

                             SUBSCRIPTION AGREEMENT

                                                               New Election ____

                                                         Change of Election ____

     1.    I, __________________, hereby elect to participate in the TolerRx,
Inc. 2003 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 Plan.

     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 10% 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, without
interest or earnings, 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 Offering Termination 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 Offering
Termination Date my participation in the Plan as provided in Section 10 of the
Plan. I acknowledge that, unless I discontinue my participation in the Plan as
provided in Section 10 of the Plan, my election will continue to be effective
for each successive Offering Period.

     5.    I have received a copy of the complete TolerRx, Inc. 2003 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):

<Page>

                                       -2-

                                               _________________________________

                                               _________________________________

     7.    In the event of my death, I hereby designate the following as my
beneficiary(ies) to receive all payments and shares due to me under the Plan:

NAME: (Please print)
                                               _________________________________
                                               (First)      (Middle)     (Last)

__________________________                     _________________________________
(Relationship)                                 (Address)

                                               _________________________________

     8.    I understand that if I dispose of any shares received by me pursuant
to the Plan within 2 years after the Offering Commencement Date (the first day
of the Offering Period during which I purchased such shares) or within 1 year
after the Offering Termination 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 Offering Termination 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 Offering Termination 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.

     9.    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 (1) 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 (2) 15% of the fair market
value of the shares on the Offering Commencement 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
certain tax implications of the purchase and sale of stock under the Plan.

<Page>

                                       -3-

     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:
      -------------------------------------

<Page>

                                                                          SAMPLE

                                  TOLERRX, INC.

                        2003 EMPLOYEE STOCK PURCHASE PLAN

               EXERCISE AGREEMENT FOR THE INITIAL OFFERING PERIOD

     1.    I have received a copy of the complete TolerRx, Inc. 2003 Employee
Stock Purchase Plan. I understand that my participation in the Plan is in all
respects subject to the terms of the Plan.

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

                                               _________________________________

                                               _________________________________

     3.    In the event of my death, I hereby designate the following as my
beneficiary(ies) to receive all shares due to me under the Plan:

NAME: (Please print)
                                        ________________________________________
                                               (First)      (Middle)     (Last)

__________________________                     _________________________________
(Relationship)                                 (Address)

                                               _________________________________

     4.    I understand that if I dispose of any shares received by me pursuant
to the Plan within 2 years after the Offering Commencement Date (the first day
of the Offering Period during which I purchased such shares) or within 1 year
after the Offering Termination 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 Offering Termination 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 Offering Termination 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

<Page>

                                       -2-

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.

     5.    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 (1) 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 (2) 15% of the fair market
value of the shares on the Offering Commencement 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
certain tax implications of the purchase and sale of stock under the Plan.

     6.    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:
       ------------------------------------

<Page>

                                                                          SAMPLE

                                  TOLERRX, INC.

                        2003 EMPLOYEE STOCK PURCHASE PLAN

                              NOTICE OF WITHDRAWAL

     I, _____________, hereby elect to withdraw my participation in the TolerRx,
Inc. 2003 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

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