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                        REGISTRATION RIGHTS AGREEMENT


        THIS AGREEMENT, dated as of October 30, 1998, is entered
into by and among Cistron Biotechnology, Inc., a corporation 
organized under the laws of Delaware (the "Company") and Pasteur 
Merieux Serums & Vaccins, S.A., a societe anonyme organized under 
the laws of France (the "Shareholder").

                             W I T N E S S E T H:

        WHEREAS, on the date hereof, the Company and the 
Shareholder are entering into a Common Stock and Warrant Purchase 
Agreement (the "Common Stock and Warrant Purchase Agreement"), 
relating to the Shareholder's investment in the Company; and

        WHEREAS, the Company, as partial inducement for the
Shareholder to enter into the Common Stock and Warrant Purchase 
Agreement, has elected to grant to the Shareholder the 
registration rights provided for herein.

        NOW, THEREFORE, in consideration of the premises, mutual
covenants and agreements herein contained and for other good and 
valuable consideration, the receipt and adequacy of which are 
hereby acknowledged, the parties hereto hereby agree as follows:

ARTICLE 1. Certain Definitions.
           --------------------

           (a) For the purposes of this Agreement, the following
terms shall have the respective meanings set forth below:

        "Advice" is as defined in Section 2.5.

        "Agreement" means this Agreement, as from time to time
assigned, supplemented, amended or modified in accordance with the 
terms hereof.

        "Common Stock and Warrant Purchase Agreement" is as defined
in the recitals.

        "Company" is as defined in the preamble.

        "Demand Registration" is as defined in Section 2.1.

        "Demand Request" is as defined in Section 2.1.

        "Exchange Act" means the United States Securities Exchange
Act of 1934, as amended, or any similar federal law then in force.

        "Indemnified Person" is as defined in Section 2.9(a).

        "Material Adverse Effect" is as defined in Section 2.3(a).

        "NASD" is as defined in Section 2.4(p).

        "Proposed Registration" is as defined in Section 2.2(a).

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        "Restricted Shares" means any Shares or other securities of
the Company which have not been registered under the Securities 
Act and which are owned by the Shareholder.

        "SEC" means the United States Securities and Exchange
Commission.

        "Securities Act" means the United States Securities Act of
1933, as amended, or any similar federal law then in force.

        "Shareholder" is as defined in the preamble.

        "Shares" means common stock of the Company, par value $.01
per share.

        "Suspension Notice" is as defined in Section 2.5.

           (b) Capitalized terms used herein but not defined
herein shall have the meaning set forth in the Common Stock and 
Warrant Purchase Agreement.

ARTICLE 2. Registration Rights.
           --------------------

            2.1. Demand Registration.  At any time after October 30,
2000 the Shareholder may require the Company (pursuant to a 
written notice to the Company) to effect the registration under 
the Securities Act of Shares of the Company (a "Demand 
Registration"). Such request (a "Demand Request") by the 
Shareholder shall (i) specify the class and number of Shares which 
the Shareholder intends to sell or dispose of, and (ii) state the 
intended method or methods by which the Shareholder intends to 
sell or dispose of such Shares.  In connection with any 
underwritten public offering, the underwriter thereof shall be 
selected by the Company, subject to the consent of the 
Shareholder, which shall not be unreasonably withheld.  Upon 
receipt of a Demand Request, the Company shall (as requested) (i) 
cause to be filed, within seventy-five (75) calendar days of the 
date of delivery to the Company of the request, a registration 
statement covering such Shares which the Company has been so 
requested to register, providing for the registration under the 
Securities Act of such Shares to the extent necessary to permit 
the disposition of such Shares so to be registered in accordance 
with the intended method of distribution specified in such request 
(provided, further, that in either case the Company may delay 
making such filing or taking such action by not more than sixty 
(60) calendar days if the Company, prior to the time it would 
otherwise have been required to file such registration statement 
or take such action, determines in good faith that the filing of 
such registration statement or the taking of such action would 
require the disclosure of material nonpublic information that, in 
the reasonable judgment of the Company, would be detrimental to 
the Company if so disclosed (and a delay would be likely to reduce 
the detrimental effect of such disclosure or obviate the need for 
such disclosure to be made), or would otherwise adversely affect a 
financing, acquisition, disposition, merger or other material 
transaction), and shall use its best efforts to have such 
registration statement declared effective by the SEC as soon as 
practicable thereafter. The Shareholder shall have the right to 
exercise up to one (1) such Demand Registration right.

            2.2. Piggyback Rights.
                 -----------------

             (a) Each time that the Company proposes (either
unilaterally or pursuant to the exercise of demand registration 
rights by any other third party) for any reason to register any of 
its securities under the Securities Act (a "Proposed 
Registration"), other than pursuant to a registration statement on 
Form F-4 or Form F-8 or similar or successor forms, the Company 
shall promptly give
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written notice of such Proposed Registration to the Shareholder
(which notice shall be given not less than thirty (30) calendar
days prior to the effective date of the Company's registration
statement) and such holders shall have the right, on a pro rata
basis, to request inclusion of any of the Shareholder's Shares
in the Proposed Registration.  No registration pursuant to this
Section 2.2 shall relieve the Company of its obligation to register
Shares pursuant to Section 2.1.

             (b) The Shareholder shall have twenty-five (25)
calendar days from the receipt of such notice to deliver to the 
Company a written request specifying the number of Shares the 
Shareholder intends to sell and the Shareholder's intended method 
of disposition.  The Shareholder shall have the right to withdraw 
its request for inclusion of such Shares in any registration 
statement pursuant to this Section 2.2 by giving written notice to 
the Company of such withdrawal.  Subject to Section 2.3 below, the 
Company shall include in such registration statement all such 
Shares so requested to be included therein; provided, however, 
that the Company may at any time withdraw or cease proceeding with 
any such piggyback registration if it shall at the same time 
withdraw or cease proceeding with the registration of all other 
equity securities originally proposed to be registered.

             (c) In the event that the Proposed Registration by the
Company is, in whole or in part, an underwritten public offering 
of securities of the Company, any request under Section 2.2(b) 
hereof must specify that the Shares be included in the 
underwriting on the same terms and conditions as the Shares 
otherwise being sold through underwriters under such registration.

            2.3. Priority on Registrations.
                 --------------------------

             (a) Notwithstanding the foregoing, if the Shares
requested to be included in the Proposed Registration pursuant to 
Section 2.2 hereof by the Shareholder differ from the type of 
securities proposed to be registered by the Company and the 
managing underwriter advises the Company that due to such 
differences the inclusion of such Shares would materially and 
adversely affect the price or success of the offering (a "Material 
Adverse Effect"), then (i) the number of the Shareholder' Shares 
to be included in the registration statement shall be reduced to 
an amount which, in the judgment of the managing underwriter, 
would eliminate such Material Adverse Effect or (ii) if no such 
reduction would, in the judgment of the managing underwriter, 
eliminate such Material Adverse Effect, then the Company shall 
have the right to exclude all such Shares from such registration 
statement provided no other securities of such type are included 
and offered for the account of any other person in such 
registration statement. Any partial reduction in the number of 
Shares to be included in the registration statement pursuant to 
clause (i) of the immediately preceding sentence shall be effected 
pro rata based on the ratio which the Shareholder's requested 
Shares bears to the total number of Shares requested to be 
included in such registration statement by all other persons who 
have requested that their Shares be included in such registration 
statement.  

           (b) If the Shares requested to be included in the
registration statement are of the same type as the securities 
being registered by the Company and the managing underwriter 
advises the Company that the inclusion of such Shares would cause 
a Material Adverse Effect, the Company will be obligated to 
include in such registration statement, as to the Shareholder 
(subject to the priority rules set forth below), the greater of 
(i) that portion of the Shares the Shareholder has requested be 
registered which the managing underwriter believes may be included 
(together with only securities to be offered by the Company) 
without causing a Material Adverse Effect, or (ii) that portion of 
the Shares the Shareholder has requested to be registered equal to 
the ratio which the Shareholder's requested Shares bears to the 
total number of Shares requested to be included in such 
registration statement by all other persons (other than (i) the 
Company, if such registration has been

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initiated by the Company for securities to be offered by the Company
or (ii) the Shareholder, if such registration has been initiated by it 
pursuant to Section 2.1 hereof) who have requested that their 
Shares be included in such registration statement.  It is 
acknowledged by the Shareholder that pursuant to the foregoing 
provision, the securities to be included in such registration 
shall be allocated (A) if the Company initiates the Proposed 
Registration (either unilaterally or pursuant to the exercise of 
demand registration rights by any other third party), (1) first, 
to the Company or such other third party exercising demand 
registration rights, (2) second, to the Shareholder (in accordance 
with the above described ratio if all Shares proposed to be 
included in the Proposed Registration cannot be so included) and 
(3) third, to all other persons requesting securities to be 
included therein (in accordance with the above described ratio if 
all Shares proposed to be included in the Proposed Registration 
cannot be so included) and  (B) if the Shareholder exercises a 
right to cause a Demand Registration, (1) first, to the 
Shareholder and (2) second, to all other persons requesting 
securities to be included therein (in accordance with the above 
described ratio if all Shares proposed to be included in the 
Proposed Registration cannot be so included).  If as a result of 
the provisions of this Section 2.3(b) the Shareholder shall not be 
entitled to include all of its Shares in a registration that the 
Shareholder has requested to be so included, the Shareholder may 
withdraw the Shareholder's request to include Shares in such 
registration statement.  The Shares that are excluded from the 
underwritten public offering pursuant to the preceding sentence 
shall be withheld from the market by the Shareholder for a period, 
not to exceed one hundred eighty (180) calendar days from the 
closing of such underwritten public offering, that the managing 
underwriter(s) determines as necessary in order to effect such 
underwritten public offering.  In granting any future registration 
rights the Company will include the priority of registration 
herein.

           (c)  The Shareholder may not participate in any
registration statement hereunder unless the Shareholder completes, 
executes and delivers all questionnaires, powers of attorney, 
indemnities, underwriting agreements, and other documents 
reasonably required under the terms of such underwriting 
arrangements, including an opinion of its counsel; provided, 
however, that the Shareholder shall not be required to make any 
representations or warranties in connection with any such 
registration other than representations and warranties as to (i) 
the Shareholder's ownership of its Shares to be sold or 
transferred free and clear of all liens, (ii) the Shareholder's 
power and authority to effect such transfer, and (iii) such 
matters pertaining to compliance with securities laws as may be 
reasonably requested.

            2.4. Registration Procedures.  Whenever the Shareholder
has requested that any Shares be registered pursuant to the 
provisions of this Article 2, the Company will use its 
commercially reasonable efforts to effect the registration and the 
sale of such Shares in accordance with the intended method of 
disposition thereof as set forth in the written request, and 
pursuant thereto the Company shall:  

             (a) prepare and file with the SEC a registration
statement with respect to such securities on the appropriate 
forms, and use its best efforts to cause such registration 
statement(s) to become and remain effective in accordance with 
Section 2.4(b) hereof and in accordance with all laws, rules and 
regulations applicable thereto; 

             (b) prepare and file with the SEC such amendments and
supplements to such registration statements and the prospectus 
used in connection therewith as may be necessary to keep such 
registration statement effective until the earlier of (i) the sale 
of all Shares covered thereby or (ii) the expiration of nine 
months from the effective date of the registration statement, and to

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comply with the provisions of the Securities Act with respect
to the sale or other disposition of all Shares covered by such 
registration statement; 

             (c) furnish to the Shareholder pursuant to Section 2.1
or Section 2.2 such number of copies of any summary prospectus or 
other prospectus, including a preliminary prospectus, in 
conformity with the requirements of the Securities Act, and such 
other documents as the Shareholder may reasonably request in order 
to facilitate the public sale or other disposition of such Shares;

             (d) use its best efforts to register or qualify the
Shares covered by such registration statement under the securities 
or blue sky laws of such jurisdictions as the Shareholder shall 
reasonably request and do any and all other acts or things which 
may be necessary or advisable to enable the Shareholder to 
consummate the public sale or other disposition in such 
jurisdictions of such Shares; provided, however, that the Company 
shall not be required to consent to general service of process for 
all purposes in any jurisdiction where it is not then subject to 
process, qualify to do business as a foreign company where it 
would not be otherwise required to qualify or submit to liability 
for state or local taxes where it is not otherwise liable for such 
taxes;

             (e) at any time when a prospectus relating thereto
covered by such registration statement is required to be delivered 
under the Securities Act within the appropriate period mentioned 
in Section 2.4(b) hereof, promptly notify the Shareholder and each 
underwriter and (if requested by the Shareholder) confirm such 
notice in writing (i) when a prospectus or any prospectus 
supplement or post-effective amendment has been filed and, with 
respect to a registration statement or any post-effective 
amendment, when the same has become effective, (ii) of the 
issuance by any state securities or other regulatory authority of 
any order suspending the qualification or exemption from 
qualification of any of the Shares under state securities or blue 
sky laws or the initiation of any proceedings for that purpose, 
and (iii) of the happening of any event as a result of which the 
prospectus included in such registration, as then in effect, 
includes an untrue statement of a material fact or omits to state 
a material fact required to be stated therein or necessary to make 
the statements therein not misleading in light of the 
circumstances then existing and, at the request of the  
Shareholder, prepare, file and furnish to the Shareholder a 
reasonable number of copies of a supplement to or an amendment of 
such prospectus as may be necessary so that, as thereafter 
delivered to the purchasers of such shares, such prospectus shall 
not include an untrue statement of a material fact or omit 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 then existing;

             (f) if the Company has delivered preliminary or final
prospectuses to the Shareholder and after having done so the 
prospectus is amended to comply with the requirements of the 
Securities Act, the Company shall promptly notify the Shareholder 
and, if requested, the Shareholder shall immediately cease making 
offers of Shares and return all prospectuses to the Company.  The 
Company shall promptly provide the Shareholder with revised 
prospectuses and, following receipt of the revised prospectuses, 
the Shareholder shall be free to resume making offers of the 
Shares; 

             (g) furnish, at the request of the Shareholder on the
date such Shares are delivered to the underwriters for sale in 
connection with a registration pursuant to this Article 2, if such 
securities are being sold through underwriters, or, if such 
securities are not being sold through underwriters, on the date 
that the registration statement with respect to such securities 
becomes effective, (i) an opinion, dated such date, of the counsel 
representing the Company for the purposes

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<PAGE>6

of such registration, in form and substance as is customarily given
to underwriters in an underwritten public offering, addressed to the
underwriters, if any, and to the Shareholder and (ii) a letter dated
such date, from the independent certified public accountants of the
Company, in form and substance as is customarily given by independent 
certified public accountants to underwriters in an underwritten 
public offering, addressed to the underwriters, if any, and the 
Shareholder;

             (h) if any proposed registration effected pursuant to
Section 2.1 or Section 2.2 involves an underwritten public 
offering, (i) subject to Section 2.1, select a reputable managing 
underwriter to underwrite such public offering, (ii) cause all 
Shares to be listed for trading on the principal national 
securities exchange where the Company's common stock is listed for 
trading, and (iii) enter into (A) an underwriting agreement with 
the underwriter providing for such representations, warranties, 
covenants, conditions and indemnities as may be requested by the 
underwriter and (B) a deposit agreement with a depositary, if 
applicable, providing for such representations, warranties, 
covenants, conditions and indemnities as may be requested by the 
depositary;

             (i) before filing a registration statement or amendment
thereto, furnish to each Shareholder and its counsel and other 
representatives and the underwriters, if any, copies of each such 
registration statement or amendment proposed to be filed, which 
documents shall be made available on a timely basis for review and 
comment by the Shareholder, the underwriters (if any) and their 
respective representatives;

             (j) make generally available to the Company's security
holders an earnings statement satisfying the provisions of Section 
11(a) of the Securities Act no later than thirty (30) calendar 
days after the end of the 12-month period beginning with the first 
day of the Company's first fiscal quarter commencing after the 
effective date of a registration statement, which earnings 
statement shall cover said 12-month period, and which requirement 
will be deemed to be satisfied if the Company timely files 
complete and accurate information on Forms 20-F and 6-K under the 
Exchange Act and otherwise complies with Rule 158 under the 
Securities Act;

             (k) if requested by the managing underwriter or the
Shareholder, promptly incorporate in a prospectus supplement or 
post-effective amendment such information as the managing 
underwriter or the Shareholder reasonably requests to be included 
therein, including, without limitation, with respect to the Shares 
being sold by the Shareholder, the purchase price being paid 
therefor by the underwriters and with respect to any other terms 
of the underwritten offering of the Shares to be sold in such 
offering, and promptly make all required filings of such 
prospectus supplement or post-effective amendment;

            (l) as promptly as practicable after filing with the
SEC of any document which is incorporated by reference into a 
registration statement (in the form in which it was incorporated), 
deliver a copy of each such document to the Shareholder;

             (m) cooperate with the Shareholder and the managing
underwriter to facilitate the timely preparation and delivery of 
certificates (which shall not bear any restrictive legends unless 
required under applicable law) representing securities sold under 
any registration statement (if any), and enable such securities to 
be in such denominations and registered in such names as the 
managing underwriter or such sellers may request and keep 
available and make available to the Company's transfer agent prior 
to the effectiveness of such registration statement a supply of 
such certificates;
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             (n) in the event that the Shareholder may be considered
to be a "control person," promptly make available for inspection 
by the Shareholder, any underwriter participating in any 
disposition pursuant to any registration statement, and any 
attorney, accountant or other agent or representative retained by 
any the Shareholder or underwriter (collectively, the 
"Inspectors"), all financial and other records, pertinent 
corporate documents and properties of the Company (collectively, 
the "Records"), as shall be reasonably necessary to enable them to 
exercise their due diligence responsibility, and cause the 
Company's officers, directors and employees to supply all 
information requested by any such Inspector in connection with 
such registration statement; provided, that, unless the disclosure 
of such Records is necessary to avoid or correct a misstatement or 
omission in the registration statement or the release of such 
Records is ordered pursuant to a subpoena or other order from a 
court of competent jurisdiction, the Company shall not be required 
to provide any information under this subparagraph (n) if (i) the 
Company believes, after consultation with counsel for the Company, 
that to do so would cause the Company to forfeit an attorney-
client privilege that was applicable to such information or (ii) 
if either (A) the Company has requested and been granted from the 
SEC confidential treatment of such information contained in any 
filing with the SEC of documents provided supplementally or 
otherwise or (B) the Company reasonably determines in good faith 
that such Records are confidential and so notifies the Inspectors 
in writing unless prior to furnishing any such information with 
respect to (i) or (ii) the Shareholder requesting such information 
agrees to enter into a confidentiality agreement in customary form 
and subject to customary exceptions; and provided, further, that 
the Shareholder agrees that it will, upon learning that disclosure 
of such Records is sought in a court of competent jurisdiction, 
give notice to the Company and allow the Company at its expense, 
to undertake appropriate action and to prevent disclosure of the 
Records deemed confidential;

             (o) provide, if required, a CUSIP number for the Shares
included in any registration statement not later than the 
effective date of such registration statement;

             (p) cooperate with the Shareholder and each underwriter
participating in the disposition of such Shares and their 
respective counsel in connection with any filings required to be 
made with the National Association of Securities Dealers, Inc. 
("NASD");

             (q) during the period when the prospectus is required
to be delivered under the Securities Act, promptly file all 
documents required to be filed with the SEC pursuant to Sections 
13(a), 13(c), 14 or 15(d) of the Exchange Act;

             (r) notify the Shareholder promptly of any request by
the SEC for the amending or supplementing of such registration 
statement or prospectus or for additional information;

             (s) prepare and file with the SEC promptly any
amendments or supplements to such registration statement or 
prospectus which, in the opinion of counsel for the Company or the 
managing underwriter, is required in connection with the 
distribution of the Shares;

            (t) advise the Shareholder, promptly after it shall
have received notice or obtain knowledge thereof, of the issuance 
of any stop order by the SEC suspending the effectiveness of such 
registration statement or the initiation or threatening of any 
proceeding for such purpose and promptly use its best efforts to 
prevent the issuance of any stop order or to obtain its withdrawal 
at the earliest possible moment if such stop order should be 
issued; and
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<PAGE>8
            (u) in the case of a Demand Request pursuant to Section
2.1 if the Shareholder so requests, to request acceleration of 
effectiveness of the registration statement from the SEC, provided 
at the time of such request the Company does not, in good faith, 
believe it is necessary to amend further the registration 
statement in order to comply with the provisions of this Section 
2.4.  If the Company wishes to further amend the registration 
statement prior to requesting acceleration, it shall have five (5) 
Business Days to so amend prior to requesting acceleration.

           2.5. Suspension of Dispositions.  The Shareholder agrees
that upon receipt of any notice (a "Suspension Notice") from the 
Company of the happening of any event of the kind described in 
Section 2.4(e)(iii), the Shareholder will forthwith discontinue 
disposition of Shares until the Shareholder's receipt of the 
copies of the supplemented or amended prospectus, or until it is 
advised in writing (the "Advice") by the Company that the use of 
the prospectus may be resumed, and has received copies of any 
additional or supplemental filings which are incorporated by 
reference in the prospectus, and, if so directed by the Company, 
the Shareholder will deliver to the Company all copies, other than 
permanent file copies then in the Shareholder's possession, of the 
prospectus covering such Shares current at the time of receipt of 
such Suspension Notice.  In the event the Company shall give any 
such Suspension Notice, the time period regarding the 
effectiveness of registration statements set forth in Section 
2.4(b) hereof shall be extended by the number of days during the 
period from and including the date of the giving of the Suspension 
Notice to and including the date when each seller of Shares 
covered by such registration statement shall have received the 
copies of the supplemented or amended prospectus or the Advice. 
The Company shall use its commercially reasonable efforts and take 
such actions as are reasonably necessary to render the Advice as 
promptly as practicable.

           2.6. Cooperation upon a Registration.  The Shareholder
and the Company agree that, in connection with any exercise of 
registration rights pursuant to this Article 2, the Shareholder 
will authorize, and will authorize and direct the Company to take, 
such actions as are necessary or appropriate to effectuate such 
registration.  In addition, the Shareholder agrees to cooperate 
fully with the Company and the underwriters of any underwritten 
public offering in the preparation of all documentation necessary 
or desirable to effectuate any registration of any Shares under 
the Securities Act pursuant to this Article 2, or registration or 
qualification of any Shares pursuant to Section 2.4(d) hereof.  In 
addition, the Company agrees to cooperate fully with the 
Shareholder in connection with any such registration or 
qualification.  

           2.7. Limitations.  Notwithstanding anything in this
Agreement to the contrary, if requested in writing by the managing 
underwriter(s), if any, of any underwritten public offering of the 
Company's capital stock pursuant to this Article 2, the 
Shareholder agrees not to offer, sell, contract to sell or 
otherwise dispose of any shares of capital stock of the Company 
except as part of such underwritten public offering within thirty 
(30) calendar days before or one hundred eighty (180) calendar 
days after the effective date of the registration statement filed 
with respect to said offering, unless expressly authorized to do 
so by the managing underwriter(s). 

           2.8. Expenses.  The Company shall pay all expenses
incurred by the Company in complying with Sections 2.1, 2.2 and 
2.4 hereof, including, without limitation, all registration and 
filing fees (including all expenses incident to filing with the 
NASD), fees and expenses of complying with the securities or blue 
sky laws of all such jurisdictions in which the Shares are 
proposed to be offered and sold (including reasonable fees and 
disbursements of counsel in connection with blue sky qualification 
of Shares), rating agency fees, printing expenses, messenger and 
delivery expenses, the Company's internal expenses (including 
without limitation all salaries

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<PAGE>9

and expenses of its officers and employees performing legal or
accounting duties), fees and expenses incurred in connection with
any listing of the Shares, fees and expenses of counsel for the
Company and its independent certified public accountants (including
the expenses of any special audit or cold comfort letters required by
or incident to such performance), securities act liability insurance
(if the Company elects to obtain such insurance) and fees and 
disbursements of underwriters (to the extent the Company is liable 
therefor under the terms of any underwriting agreement), whether 
or not any registration statement becomes effective; provided, 
however, that all underwriting discounts and selling commissions 
applicable to the Shares covered by registrations effected 
pursuant to Section 2.1 or Section 2.2 hereof shall be borne by 
the Shareholder, in proportion to the number of Shares sold by the 
Shareholder, and except as expressly provided in this Section 2.8, 
in no event shall the Company pay any fees or expenses 
attributable to any counsel, accountants or other persons retained 
or employed by the Shareholder.

           2.9. Indemification.
                ---------------

            (a) In the event of any registration of any Shares
under the Securities Act pursuant to this Article 2 or 
registration or qualification of any Shares pursuant to Section 
2.4(d) hereof, the Company shall indemnify and hold harmless the 
Shareholder, each underwriter of such shares, if any, each broker 
or any other person acting on behalf of the Shareholders, each 
director, officer, employee and partner of any of the foregoing 
and each other person, if any, who controls any of the foregoing 
persons, within the meaning of the Securities Act (each, an 
"Indemnified Person"), against any losses, claims, damages, 
liabilities or expenses, joint or several, to which any of the 
foregoing persons may become subject under the Securities Act or 
otherwise, insofar as such losses, claims, damages or liabilities 
(or actions in respect thereof) arise out of, are related to, 
result from or are based upon an untrue statement or alleged 
untrue statement of a material fact contained in any registration 
statement under which such Shares were registered under the 
Securities Act, any preliminary prospectus or final prospectus 
contained therein, or any amendment or supplement thereto, or any 
document incident to registration or qualification of any Shares 
pursuant to Section 2.4(d) hereof, or arise out of, are related 
to, result from or are based upon the omission or alleged omission 
to state therein a material fact required to be stated therein or 
necessary to make the statements therein not misleading or, with 
respect to any prospectus, necessary to make the statements 
therein, in light of the circumstances under which they were made, 
not misleading, or any violation by the Company of the state 
securities or blue sky laws applicable to the Company and relating 
to action or inaction required of the Company in connection with 
such registration or qualification under such state securities or 
blue sky laws.  The Company shall reimburse on demand each 
Indemnified Person for any legal or any other costs and expenses 
reasonably incurred by any of them in connection with 
investigating, preparing for, defending or settling any such loss, 
claim, damage, liability or action by any governmental agency or 
body; provided, however, that the Company shall not be liable in 
any such case to the extent that any such loss, claim, damage, 
liability or expense arises out of or is based upon an untrue 
statement or alleged untrue statement or omission or alleged 
omission made in said registration statement, preliminary or final 
prospectus or amendment or supplement thereto or any document 
incident to registration or qualification of any Shares pursuant 
to Section 2.4(d) hereof, in reliance upon and in conformity with 
written information furnished to the Company by the Shareholder, 
underwriter, broker, other person or controlling person 
specifically for use in the preparation thereof or arises out of 
or is based upon the Indemnified Person's failure to deliver a 
copy of the registration statement or prospectus or any amendments 
or supplements thereto after the Company has furnished such 
Indemnified Person with a sufficient number of copies of the same.

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<PAGE>10
            (b) Before Shares shall be included in any registration
pursuant to this Article 2, the Shareholder will furnish to the 
Company in writing such information and affidavits as the Company 
reasonably requests for use in connection with any such 
registration statement and prospectus, and the Shareholder and any 
underwriter acting on its behalf shall have agreed to indemnify 
and hold harmless (in the same manner and to the same extent as 
set forth in paragraph (a) above) the Company, each member of the 
Board of Directors of the Company, each officer of the Company who 
signs such registration statement, every other participating 
shareholder and any person who controls the Company within the 
meaning of the Securities Act, with respect to any untrue 
statement or omission from such registration statement, any 
preliminary prospectus or final prospectus contained therein, or 
any amendment or supplement thereto, if such untrue statement or 
omission was made in reliance upon and in conformity with such 
written information furnished to the Company by the Shareholder or 
such underwriter for use in the preparation of such registration 
statement, preliminary prospectus, final prospectus or amendment 
or supplement; provided, however, that the maximum amount of 
liability in respect of such indemnification shall be limited to 
an amount equal to the net proceeds actually received by the 
Shareholder from the sale of Shares effected pursuant to such 
registration.

            (c) Promptly after receipt by an Indemnified Person of
notice of the commencement of any action involving a claim 
referred to in Section 2.9(a) or (b) hereof, such Indemnified 
Person will, if a claim in respect thereof is to be made against 
the indemnifying party under this Section 2.9, give written notice 
to the latter of the commencement of such action (provided that 
the failure to give such notice shall not limit the rights of such 
Indemnified Person to the extent that such failure or delay in 
notifying the indemnifying party does not prevent the indemnifying 
party from presenting a proper defense against the claim).  In 
case any such action is brought against an Indemnified Person, the 
indemnifying party will be entitled to participate in and to 
assume the defense thereof, jointly with any other indemnifying 
party similarly notified to the extent that it may wish, with 
counsel reasonably satisfactory to such Indemnified Person, and, 
after notice to such Indemnified Person from the indemnifying 
party of its election to assume the defense thereof; provided, 
however, that, if any Indemnified Person shall have reasonably 
concluded that there may be one or more legal defenses available 
to such Indemnified Person which are different from, in conflict 
with or additional to those available to the indemnifying party, 
or that such claim or litigation involves or could have an effect 
upon matters beyond the scope of the indemnity agreement provided 
in this Section 2.9, or if the indemnifying party fails to take 
diligent action to defend such claim within twenty (20) calendar 
days following notice thereof from the Indemnified Person, the 
indemnifying party shall not have the right to assume the defense 
of such action on behalf of such Indemnified Person, and such 
indemnifying party shall reimburse such Indemnified Person and any 
person controlling such Indemnified Person for the fees and 
expenses of counsel retained by the Indemnified Person which are 
reasonably related to the matters covered by the indemnity 
agreement provided in this Section 2.9.  If the indemnifying party 
does assume its own defense as permitted hereunder, from such time 
the Indemnified Person shall bear the expenses of its own separate 
counsel.  If such defense is not assumed by the indemnifying party 
as permitted hereunder, the indemnifying party will not be subject 
to any liability for any settlement made by the Indemnified Person 
without its written consent, which consent shall not be 
unreasonably withheld.  If such defense is assumed by the 
indemnifying party pursuant to the provisions hereof, such 
indemnifying party shall not make any settlement of the applicable 
claim indemnified against hereunder without the written consent of 
the Indemnified Person or persons, which consent shall not be 
unreasonably withheld.  An indemnifying party who is not entitled 
to, or elects not to, assume the defense of a claim will not be 
obligated to pay the fees and expenses of more than one counsel 
for all parties indemnified by such indemnifying party with 
respect to such claim, unless in the 

                            -10-
<PAGE>11

reasonable judgment of any Indemnified Person, a conflict
of interest may exist between such Indemnified Person and any
other such Indemnified Person with respect to such claim, in
which event the indemnifying party shall be obligated to pay the
reasonable fees and disbursements of such additional counsel or
counsels.

            (d) In order to provide for just and equitable
contribution to joint liability under the Securities Act in any 
case in which an Indemnified Person makes a claim for 
indemnification pursuant to this Section 2.9, but it is judicially 
determined (by the entry of a final judgment or decree by a court 
of competent jurisdiction and the expiration of time to appeal or 
the denial of the last right of appeal) that such indemnification 
may not be enforced in such case notwithstanding the fact that 
this Section 2.9 provides for indemnification in such case, then 
the Company and the Shareholder will contribute to the aggregate 
losses, claims, damages or liabilities to which they may be 
subject as is appropriate to reflect, as between the Company and 
the Shareholder, on the one hand, and the underwriter on the other 
hand, the relative fault of the Company and the Shareholder in 
connection with the statements or omissions which resulted in such 
losses, claims, damages or liabilities, it being understood that 
the parties acknowledge that the overriding equitable 
consideration to be given effect in connection with this provision 
is the ability of one party or the other to correct the statement 
or omission which resulted in such losses, claims, damages or 
liabilities, and that it would not be just and equitable if 
contribution pursuant hereto were to be determined by pro rata 
allocation or by any other method of allocation which does not 
take into consideration the foregoing equitable considerations.  
Notwithstanding the foregoing, (i) the Shareholder will not be 
required to contribute any amount in excess of the net proceeds to 
it of all Shares sold by it pursuant to such registration 
statement, (ii) no underwriter shall be required to contribute any 
amount in excess of the proceeds to it from the offering pursuant 
to such registration statement, and (iii) no person guilty of 
fraudulent misrepresentation, within the meaning of Section 11(f) 
of the Securities Act, shall be entitled to contribution from any 
person who is not guilty of such fraudulent misrepresentation.  If 
indemnification is available under this Section 2.9, the 
indemnifying parties shall indemnify each Indemnified Person to 
the full extent provided in Section 2.9(a) and Section 2.9(b) 
without regard to the relative fault of said indemnifying party or 
Indemnified Person or any other equitable consideration provided 
for in this Section 2.9(d).

           (e) Notwithstanding any of the foregoing, if in
connection with an underwritten public offering of any Shares, the 
Company, the Shareholder and the underwriters enter into an 
underwriting or purchase agreement relating to such offering which 
contains provisions covering indemnification among the parties, 
the indemnification provided thereunder shall be in addition to 
(and not in lieu of) the indemnification provided to the 
Shareholders hereunder.

           (f) The indemnification and contribution required by
this Section 2.9 shall be made by periodic payment of the amount 
thereof during the course of the investigation or defense, as and 
when bills are received or expense, loss, damage or liability is 
incurred; provided, that if a court of competent jurisdiction 
finally determines that any Indemnified Person which has received 
payments hereunder does not have an indemnification right under 
this Section 2.9 for any reason, then such Indemnified Person 
shall within five (5) calendar days of such final determination, 
refund all amounts received hereunder to the Company or the 
Shareholder, as the case may be.

           (g) The indemnification and contribution provided for
hereunder will remain in full force and effect regardless of any 
investigation made by or on behalf of any Indemnified Person and 
will survive the transfer of Shares.

                                 -11-
<PAGE>12

ARTICLE 3. Miscellaneous
           -------------

           3.1. Notices.  Any and all notices, consents, offers,
acceptances, or any other communication provided for herein shall 
be sufficient if given in writing and deemed received when 
delivered by first class, registered or certified mail, postage 
prepaid or overnight courier or hand delivery, or when sent by 
facsimile transmission (confirmed by facsimile machine report and 
with a confirmation letter sent by first class mail, postage 
prepaid) which shall be addressed, or sent to the address or 
telecopier number of the party set forth below its signature 
hereto or, in each case, such other address or telecopier number, 
as the case may be, as such party may from time to time designate 
in writing to the other parties.

           3.2. Amendment and Waiver.  No change or modification
of, or waiver of compliance with, this Agreement shall be valid 
unless the same shall be in writing and signed by all of the 
parties hereto.

           3.3. Termination.  This Agreement may be terminated at
any time by an instrument in writing signed by all of the parties 
hereto.  This Agreement shall terminate automatically in the event 
that (i) the Shareholder transfers all of its Restricted Shares, 
or (ii) the Shareholder may sell all of its Restricted Shares 
pursuant to Rule 144(k) of the Securities Act.  Unless sooner 
terminated, this Agreement shall terminate fifteen (15) years from 
the date hereof, unless, at any time within one (1) year prior to 
such date, both of the parties extend its duration for as many 
additional periods, each not to exceed ten (10) years, as they may 
desire.

           3.4. No Waiver.  No failure or delay on the part of the
Company or the Shareholder in exercising any right, between the 
Company and the Shareholder shall operate as a waiver thereof nor 
shall any single or partial exercise of any right, power or 
privilege hereunder preclude the simultaneous or later exercise of 
any other right, power or privilege.  The rights and remedies 
herein expressly provided are cumulative and not exclusive of any 
rights or remedies which the Company or the Shareholder would 
otherwise have.  No notice to or demand on the Company or the 
Shareholder, as the case may be, in any case shall entitle the 
Company or the Shareholder, as the case may be, to any other or 
further notice or demand in similar or other circumstances or 
constitute a waiver of the rights of the Company or the 
Shareholder to take any other or further action in any 
circumstances without notice or demand.

           3.5. Specific Performance.  Each party to this Agreement
acknowledges that the other parties will suffer irreparable injury 
in the event of any breach of any provision of this Agreement and 
that therefore the remedy at law for any breach or threatened 
breach of any such provision of this Agreement will be inadequate.  
Accordingly, upon a breach or threatened breach of any such 
provision of this Agreement by any party hereto, the other parties 
shall, in addition and without prejudice to any of the rights and 
remedies they may have, be entitled as a matter of right, without 
proof of actual damages, to seek specific performance of such 
provisions of this Agreement and to such other injunctive or 
equitable relief to enforce, or prevent any violations (whether 
anticipatory, continuing or future) of, such provisions of this 
Agreement.

           3.6. Counterparts and Headings.  This Agreement may be
executed in two or more counterparts, each of which shall be 
deemed to be an original, but all of which together shall 
constitute one and the same instrument.  All headings and any 
cover page are inserted for convenience or reference only and 
shall not affect its meaning or interpretation.

                             -12-
<PAGE>13

           3.7. Nouns and Pronouns.  Whenever the context may
require, any pronouns used herein shall include the corresponding 
masculine, feminine or neuter forms, and the singular form of 
nouns and pronouns shall include the plural and vice-versa.

           3.8. Expenses.  Except as provided in Section 2.8
hereto, each of the parties to this Agreement shall bear its own 
expenses, including, without limitation, the fees and 
disbursements of its respective counsel, in connection with the 
negotiation and execution of this Agreement and the consummation 
of the transactions contemplated hereby.

           3.9. Governing Law.  This Agreement will be governed by,
and construed and enforced in accordance with, the laws of the 
State of New York, U.S.A., without regard to its conflict of law 
rules.

           3.10. Successors and Assigns.  This Agreement shall
be binding upon and shall inure to the benefit of the Company and 
its successors, and the Shareholder and its successors and 
assigns; provided that the rights and obligations of the 
Shareholder hereunder shall inure to the benefit of and be binding 
upon any transferee of the Shareholder only if such transferee (i) 
is an affiliate of the Shareholder and (ii) agrees in writing to 
be bound by the provisions of this Agreement.  

           3.11. Severability.  In the event that any provision
of this Agreement becomes or is declared by a court of competent 
jurisdiction to be illegal, invalid or unenforceable, the 
remaining provisions hereof shall nevertheless continue in full 
force and effect as though the illegal, invalid or unenforceable 
provisions were not a part hereof, and the parties shall exert 
their best efforts to amend this Agreement to include a provision 
which is legal, valid and enforceable, or to take such other 
action, which in either case carries out the original intent of 
the parties.

           3.12. Complete Agreement.  This Agreement contains
the entire agreement among the parties with respect to the subject 
matter hereof and supersedes all prior and contemporaneous 
arrangements or understandings, whether written or oral, between 
or among any of the parties hereto, with respect to the subject 
matter hereof.

           3.13. Further Assurances.  Each of the parties to
this Agreement agrees to execute such other documents and take 
such other action as may be reasonably necessary to implement and 
carry out the intent of this agreement.

                              -13-
<PAGE>14

        IN WITNESS WHEREOF, the parties hereto have signed this 
Agreement as of the day and year first above written.


CISTRON BIOTECHNOLOGY, INC.


By: /s/BRUCE C. GALTON
    ------------------
Name:  BRUCE C. GLATON
Title: Chairman of the Board
       and Chief Executive Officer
Notice Address: 

        Cistron Biotechnology, Inc.
        101 Bloomfield Avenue
        Pine Brook, NJ  07058
        Attention:  Chairman 
        Telecopier: (973) 575-4854
							

with a copy to:

        Seth I. Truwit, Esq.
        Epstein Becker & Green, PC
        250 Park Avenue
        New York, NY  10177
        Telephone:  (212) 351-4709
        Telecopier:  (212) 661-0989

Pasteur Merieux Serums & Vaccins, S.A.


By: /s/DAVID J. WILLIAMS
    --------------------
Name:  DAVOD J. WILLIAMS
Title: President
       and Chief Operating Officer

Notice Address: 


with a copy to:

        Pasteur Merieux Serums & Vaccins, S.A.
        58, avenue Leclerc
        69007 Lyon, France
        Attention:  Senior Vice President, Legal and
        Corporate Affairs
        Telecopier:  011 33 4 72 73 77 84

        Pasteur Merieux Connaught - USA 

                                 -14-
<PAGE>15

        Route 611
        Swiftwater, PA  18370
        Attention:  Vice President, 
        Business Development
        Telecopier:  (717) 839-4600

        and

        Akin, Gump, Strauss, Hauer & Feld, LLP
        590 Madison Avenue
        New York, New York 10022
        Attention:  L. Kevin O'Mara, Jr., Esq.
        Telephone:  (212) 872-1021
        Telecopier:  (212) 872-1002


                                  -15-