[letterhead of Bingham Dana]

                            August 2, 1999

LeukoSite, Inc.
215 First Street
Cambridge, MA 02142


Ladies and Gentlemen:

     We have acted as counsel to LeukoSite, Inc., a Delaware corporation (the
"Company") in connection with the registration under the Securities Act of
1933, as amended (the "Act"), of up to an additional 1,566,938 shares (the
"Shares") of the Company's Common Stock, $0.01 par value per share, to be
offered by certain stockholders of the Company (the "Selling Stockholders"),
pursuant to a Registration Statement on Form S-3, initially filed by the
Company with the Securities and Exchange Commission on April 13, 1999.

     As such counsel, we have reviewed the corporate proceedings taken by the
Company with respect to the authorization of the issuance of the Shares. We
have also examined and relied upon originals or copies, certified or
otherwise authenticated to our satisfaction, of such corporate records,
documents, agreements or other instruments of the Company. As to all matters
of fact (including factual conclusions and characterizations and descriptions
of purpose, intention or other state of mind), we have entirely relied upon
certificates of officers of the Company, and have assumed, without
independent inquiry, the accuracy of those certificates.

     We have assumed the genuineness of all signatures, the conformity to the
originals of all documents reviewed by us as copies, the authenticity and
completeness of all original documents reviewed by us in original or copy
form and the legal competence of each individual executing a document. We
have also assumed that the registration requirements of the Act and all
applicable requirements of state laws regulating the sale of securities will
have been duly satisfied.

     With respect to our opinion set forth below with respect to the Shares,
we have assumed that the Company has received the specified purchase price or
other consideration therefor set forth in that certain Agreement and Plan of
Merger and Reorganization, dated January 4, 1999.


August 2, 1999
Page 2


     This opinion is limited solely to the Delaware General Corporation Law
as applied by courts located in the State of Delaware.

     Subject to the foregoing, it is our opinion that the Shares have been
duly authorized, validly issued and fully paid and are non-assessable.

     We hereby consent to the filing of this opinion as an exhibit to the
Registration Statement.

                                     Very truly yours,

                                     /s/ Bingham Dana LLP

                                     BINGHAM DANA LLP