LEASE ASSIGNMENT

        In connection with the Commercial Lease dated October 13, 1994 (the
"Lease"), between T-Cell Diagnostics, Inc., a Delaware corporation ("Lessee"),
and Cummings Properties Management, Inc. ("Lessor"), concerning premises at 8-H,
8-K, 8-F and 8-G and 6-X and 6-AA Gill Street, Woburn, Massachusetts (the
"Leased Premises"), and in consideration of one dollar ($1.00) and other mutual
benefits to be derived herefrom, Lessee and Endogen, Inc., a Massachusetts
corporation ("Assignee"), hereby agree as follows:

        1.    Lessee hereby assigns and transfers all of its right, title and
              interest in the Lease and the Leased Premises to Assignee as of
              the Effective Date (as hereinafter defined). Assignee hereby
              accepts such assignment and assumes all of the obligations of
              Lessee as tenant under the Lease arising or accruing on or after
              the Effective Date.

        2.    Lessee shall indemnify, defend and hold harmless Assignee from and
              against all claims, liabilities, expenses, losses and damages
              arising out of a breach or default by Lessee in its obligations as
              the lessee under the Lease which arise or accrue on or before the
              Effective Date. Assignee shall indemnify, defend and hold harmless
              Lessee from and against all claims, liabilities, expenses, losses
              and damages arising out of a breach or default by Assignee in its
              obligations as the lessee under the Lease which arise or accrue
              after the Effective Date.

        3.    The Assignment shall be effective as of the end of the day on
              March 4, 1996 (the "Effective Date").

        IN WITNESS WHEREOF, Lessee and Assignee have hereunto set their hands
and common seals this 4th day of March, 1996.

                              T CELL DIAGNOSTICS, INC.

                              By: /s/ Alan W. Tuck
                                  -------------------------------
                                  Alan W. Tuck
                                  President


                              ENDOGEN, INC.

                              By: /s/ Owen A. Dempsey
                                  -------------------------------
                                  Owen A. Dempsey
                                  President and Chief Executive Officer