<PAGE>   1
     AS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION ON MARCH 31, 1998

                                                             FILE NO. 333-______
================================================================================

                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

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

                                    FORM S-8
                          REGISTRATION STATEMENT UNDER
                           THE SECURITIES ACT OF 1933

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

                                 LEUKOSITE, INC.
             (Exact Name of Registrant as Specified in its Charter)

                  DELAWARE                                      04-3173859
(State or Other Jurisdiction of Incorporation                (I.R.S. Employer
              or Organization)                              Identification No.)

                      215 FIRST STREET, CAMBRIDGE, MA 02142
               (Address of Principal Executive Offices) (Zip Code)

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

                                 LEUKOSITE, INC.
                        1997 EMPLOYEE STOCK PURCHASE PLAN
                            (Full Title of the Plan)

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

                         CHRISTOPHER K. MIRABELLI, Ph.D.
                       Chairman of the Board of Directors,
                      President and Chief Executive Officer
                                 LEUKOSITE, INC.
                                215 First Street
                         Cambridge, Massachusetts 02142
                     (Name and Address of Agent for Service)

                                 (617) 621-9350
           Telephone Number, Including Area Code, of Agent for Service

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

                                   Copies to:

                            JUSTIN P. MORREALE, ESQ.
                               JULIO E. VEGA, ESQ.
                                BINGHAM DANA LLP
                               150 Federal Street
                              Boston, MA 02110-1726
                                 (617) 951-8000

                         CALCULATION OF REGISTRATION FEE

<TABLE>
<CAPTION>
<S>                           <C>          <C>              <C>                 <C>
=============================================================================================
                                              PROPOSED           PROPOSED
                                AMOUNT        MAXIMUM            MAXIMUM          AMOUNT OF
          TITLE OF              TO BE      OFFERING PRICE       AGGREGATE       REGISTRATION
SECURITIES TO BE REGISTERED   REGISTERED     PER SHARE      OFFERING PRICE(1)       FEE
---------------------------------------------------------------------------------------------
Common Stock,
$.01 par value................ 150,000          N/A           $1,396,875           $412.08
=============================================================================================
</TABLE>

     (1) The proposed maximum offering price has been estimated pursuant to Rule
457(h) solely for the purpose of calculating the registration fee. It is not
known how many shares will be purchased under the Plan or at what price such
shares will be purchased. The estimate of the proposed maximum aggregate
offering price has been calculated based on the offering of 150,000 shares,
being the aggregate number of shares of Common Stock available for issuance upon
exercise of options to be granted under the Plan, at an exercise price of $9.313
per share, which is the average of the high and low prices of the Registrant's
Common Stock as listed on the National Association of Securities Dealers
Automated Quotation ("Nasdaq") National Market System on March 27, 1998.

<PAGE>   2

                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT


ITEM 3. INCORPORATION OF DOCUMENTS BY REFERENCE.

        The following documents filed by LeukoSite, Inc. (the "REGISTRANT") with
the Securities and Exchange Commission (the "SEC") are hereby incorporated by
reference in this Registration Statement: (1) the Registrant's Annual Report on
Form 10-K for the fiscal year ended December 31, 1997; (2) all reports filed by
the Registrant pursuant to Section 13(a) or 15(d) of the Securities Exchange Act
of 1934, as amended (the "EXCHANGE ACT"), since the end of the Registrant's 1997
fiscal year; and (3) the description of the Common Stock contained in the
Registrant's registration statement on Form 8-A filed with the SEC under Section
12(g) of the Exchange Act, including any amendment or report filed for the
purpose of updating such description.

        In addition, all documents subsequently filed by the Registrant pursuant
to Sections 13(a), 13(c), 14 and 15(d) of the Exchange Act, prior to the filing
of a post-effective amendment which indicates that all securities offered hereby
have been sold or which deregisters all of such securities then remaining
unsold, shall be deemed to be incorporated by reference into this Registration
Statement and to be a part hereof from the date of filing of such documents.


ITEM 4. DESCRIPTION OF SECURITIES

        Not applicable.


ITEM 5. INTERESTS OF NAMED EXPERTS OR COUNSEL

        Not applicable.


ITEM 6. INDEMNIFICATION OF DIRECTORS AND OFFICERS

        Section 145 of the Delaware General Corporation Law empowers a Delaware
corporation to indemnify its officers and directors and certain other persons to
the extent and under the circumstances set forth therein.

        The Restated Certificate of Incorporation and the Amended and Restated
By-Laws of the Registrant, copies of which are filed herein as Exhibits 4.1 and
4.2, provide for advancement of expenses and indemnification of officers and
directors of the Registrant and certain other persons against liabilities and
expenses incurred by any of them in certain stated proceedings and under certain
stated conditions to the fullest extent permissible under Delaware law.

        The Registrant intends to maintain insurance for the benefit of its
directors and officers insuring such persons against certain liabilities,
including liabilities under the securities laws.


ITEM 7. EXEMPTION FROM REGISTRATION CLAIMED

        Not applicable.


<PAGE>   3

ITEM 8. EXHIBITS

        The following exhibits are filed as part of this Registration Statement:

         4.1    Restated Certificate of Incorporation of the Registrant.
                Incorporated by reference to Exhibit 3.3 to the Registrant's
                Registration Statement on Form S-1 (File No. 333-30213).

         4.2    Amended and Restated By-Laws of the Registrant. Incorporated by
                reference to Exhibit 3.4 to the Registrant's Registration
                Statement on Form S-1 (File No. 333-30213).

           5    Opinion and Consent of Bingham Dana LLP with respect to
                the legality of the shares being registered.

        23.1    Consent of Bingham Dana LLP (included in Exhibit 5).

        23.2    Consent of Arthur Andersen LLP.

          24    Power of Attorney (included in signature page to Registration
                Statement).

ITEM 9. UNDERTAKINGS

        The undersigned Registrant hereby undertakes:

(1)     To file, during any period in which offers or sales are being made, a
        post-effective amendment to this Registration Statement to include any
        material information with respect to the plan of distribution not
        previously disclosed in this Registration Statement or any material
        change to such information in this Registration Statement;

(2)     That, for the purpose of determining any liability under the Securities
        Act of 1933, as amended (the "SECURITIES ACT"), each such post-effective
        amendment shall be deemed to be a new registration statement relating to
        the securities offered therein, and the offering of such securities at
        that time shall be deemed to be the initial bona fide offering thereof;

(3)     To remove from registration by means of a post-effective amendment any
        of the securities being registered which remain unsold at the
        termination of the offering;

(4)     That, for purposes of determining any liability under the Securities
        Act, each filing of the Registrant's annual report pursuant to Section
        13(a) or 15(d) of the Exchange Act (and, where applicable, each filing
        of an employee benefit plan's annual report pursuant to Section 15(d) of
        the Exchange Act) that is incorporated by reference in the Registration
        Statement shall be deemed to be a new registration statement relating to
        the securities offered therein, and the offering of such securities at
        that time shall be deemed to be the initial bona fide offering thereof;
        and

(5)     Insofar as indemnification for liabilities arising under the Securities
        Act may be permitted to directors, officers and controlling persons of
        the Registrant pursuant to the foregoing provisions, or otherwise, the
        Registrant has been advised that in the opinion of the SEC such
        indemnification is against public policy as expressed in the Securities
        Act and is, therefore, unenforceable. In the event that a claim for
        indemnification against such liabilities (other than the payment by the
        Registrant of expenses incurred or paid by a director, officer or
        controlling person of the Registrant in the successful defense of any
        action, suit or proceeding) is asserted by such director, officer or
        controlling person in connection with the securities being registered,
        the Registrant will, unless in the opinion of its counsel the matter has
        been settled by controlling precedent, submit to a court of appropriate
        jurisdiction the question whether such indemnification by it is against
        public policy as expressed in the Securities Act and will be governed by
        the final adjudication of such issue.



                                       2

<PAGE>   4

                                   SIGNATURES

        Pursuant to the requirements of the Securities Act of 1933, as amended,
the Registrant certifies that it has reasonable grounds to believe that it meets
all of the requirements for filing on Form S-8 and has duly caused this
Registration Statement to be signed on its behalf by the undersigned, thereunto
duly authorized, in the City of Cambridge, Commonwealth of Massachusetts, on
this 31st day of March, 1998.

                                       LEUKOSITE, INC.


                                       By: /s/ Christopher K. Mirabelli, Ph.D.
                                           -------------------------------------
                                           Christopher K. Mirabelli, Ph.D.
                                           Chairman of the Board of Directors,
                                           President and Chief Executive Officer


                                POWER OF ATTORNEY

        Each person whose signature appears below hereby appoints Christopher K.
Mirabelli and Augustine Lawlor and each of them severally, acting alone and
without the other, his/her true and lawful attorney-in-fact with the authority
to execute in the name of each such person, and to file with the Securities and
Exchange Commission, together with any exhibits thereto and other documents
therewith, any and all amendments (including without limitation post-effective
amendments) to this Registration Statement on Form S-8 necessary or advisable to
enable the Registrant to comply with the Securities Act of 1933, as amended, and
any rules, regulations, and requirements of the Securities and Exchange
Commission in respect thereof, which amendments may make such other changes in
the Registration Statement as the aforesaid attorney-in-fact executing the same
deems appropriate.

        Pursuant to the requirements of the Securities Act of 1933, this
Registration Statement has been signed by the following persons in the
capacities and on the date indicated.

<TABLE>
<CAPTION>
        SIGNATURE                                 TITLE                               DATE
        ---------                                 -----                               ----
<S>                               <C>                                              <C>

/s/ Christopher K. Mirabelli
-------------------------------   Chairman of the Board of Directors, President    March 31, 1998
Christopher K. Mirabelli, Ph.D.   and Chief Executive Officer
                                  (Principal Executive Officer)

/s/ Augustine Lawlor
-------------------------------   Vice President,  Corporate  Development          March 31, 1998
       Augustine Lawlor           and Chief Financial Officer
                                  (Principal Financial and Accounting Officer)

/s/ Kate Bingham
-------------------------------   Director                                         March 31, 1998
         Kate Bingham

/s/ Yasunori Kaneko, M.D.
-------------------------------   Director                                         March 31, 1998
    Yasunori Kaneko, M.D.

/s/ John W Littlechild
-------------------------------   Director                                         March 31, 1998
     John W. Littlechild
</TABLE>



                                       3

<PAGE>   5

<TABLE>
<S>                               <C>                                              <C>
/s/ Martin Peretz, Ph.D.
-------------------------------   Director                                         March 31, 1998
     Martin Peretz, Ph.D.

/s/ Mark Skaletsky
-------------------------------   Director                                         March 31, 1998
     Mark Skaletsky

/s/ Timothy A. Springer, Ph.D.
-------------------------------   Director                                         March 31, 1998
  Timothy A. Springer, Ph.D.

/s/ Christopher T. Walsh, Ph.D.
-------------------------------   Director                                         March 31, 1998
 Christopher T. Walsh, Ph.D.
</TABLE>



                                       4

<PAGE>   6

                                INDEX TO EXHIBITS


<TABLE>
<CAPTION>
EXHIBIT                                                                              SEQUENTIAL
NUMBER                             DESCRIPTION                                        PAGE NO.
-------                            -----------                                       ----------
<S>         <C>                                                                      <C>

  4.1       Restated Certificate of Incorporation of the Registrant.
            Incorporated by reference to Exhibit 3.3 to the Registrant's
            Registration Statement Form S-1 (File No. 333-30213).                        --

  4.2       Amended and Restated By-Laws of the Registrant. Incorporated by
            reference to Exhibit 3.4 to the Registrant's Registration Statement
            on Form S-1 (File No. 333-30213).                                            --

   5        Opinion and Consent of Bingham Dana LLP with respect to the legality
            of the shares being registered.                                              7

  23.1      Consent of Bingham Dana LLP (included in Exhibit 5).                         8

  23.2      Consent of Arthur Andersen LLP                                               9

   24       Power of Attorney (included in signature page to Registration
            Statement).                                                                  4
</TABLE>






                                       5
[{"type": "S-8", "sequence": "1", "description": "LEUKOSITE, INC.", "secsgml_size_bytes": 16006}]
{"company-data": {"conformed-name": "LEUKOSITE INC", "cik": "0000915320", "assigned-sic": "2834", "irs-number": "043173859", "state-of-incorporation": "DE", "fiscal-year-end": "1231"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-48993", "film-number": "98583389"}, "business-address": {"street1": "215 FIRST ST", "city": "CAMBRIDGE", "state": "MA", "zip": "02142"}, "mail-address": {"street1": "215 FIRST STREET", "city": "CAMBRIDGE", "state": "MA", "zip": "02142"}}
1
     AS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION ON MARCH 31, 1998

                                                             FILE NO. 333-______
================================================================================

                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

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

                                    FORM S-8
                          REGISTRATION STATEMENT UNDER
                           THE SECURITIES ACT OF 1933

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

                                 LEUKOSITE, INC.
             (Exact Name of Registrant as Specified in its Charter)

                  DELAWARE                                      04-3173859
(State or Other Jurisdiction of Incorporation                (I.R.S. Employer
              or Organization)                              Identification No.)

                      215 FIRST STREET, CAMBRIDGE, MA 02142
               (Address of Principal Executive Offices) (Zip Code)

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

                                 LEUKOSITE, INC.
                        1997 EMPLOYEE STOCK PURCHASE PLAN
                            (Full Title of the Plan)

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

                         CHRISTOPHER K. MIRABELLI, Ph.D.
                       Chairman of the Board of Directors,
                      President and Chief Executive Officer
                                 LEUKOSITE, INC.
                                215 First Street
                         Cambridge, Massachusetts 02142
                     (Name and Address of Agent for Service)

                                 (617) 621-9350
           Telephone Number, Including Area Code, of Agent for Service

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

                                   Copies to:

                            JUSTIN P. MORREALE, ESQ.
                               JULIO E. VEGA, ESQ.
                                BINGHAM DANA LLP
                               150 Federal Street
                              Boston, MA 02110-1726
                                 (617) 951-8000

                         CALCULATION OF REGISTRATION FEE
=============================================================================================
                                              PROPOSED           PROPOSED
                                AMOUNT        MAXIMUM            MAXIMUM          AMOUNT OF
          TITLE OF              TO BE      OFFERING PRICE       AGGREGATE       REGISTRATION
SECURITIES TO BE REGISTERED   REGISTERED     PER SHARE      OFFERING PRICE(1)       FEE
---------------------------------------------------------------------------------------------
Common Stock,
$.01 par value................ 150,000          N/A           $1,396,875           $412.08
=============================================================================================
(1) The proposed maximum offering price has been estimated pursuant to Rule
457(h) solely for the purpose of calculating the registration fee. It is not
known how many shares will be purchased under the Plan or at what price such
shares will be purchased. The estimate of the proposed maximum aggregate
offering price has been calculated based on the offering of 150,000 shares,
being the aggregate number of shares of Common Stock available for issuance upon
exercise of options to be granted under the Plan, at an exercise price of $9.313
per share, which is the average of the high and low prices of the Registrant's
Common Stock as listed on the National Association of Securities Dealers
Automated Quotation ("Nasdaq") National Market System on March 27, 1998.
2

                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

ITEM 3. INCORPORATION OF DOCUMENTS BY REFERENCE.

        The following documents filed by LeukoSite, Inc. (the "REGISTRANT") with
the Securities and Exchange Commission (the "SEC") are hereby incorporated by
reference in this Registration Statement: (1) the Registrant's Annual Report on
Form 10-K for the fiscal year ended December 31, 1997; (2) all reports filed by
the Registrant pursuant to Section 13(a) or 15(d) of the Securities Exchange Act
of 1934, as amended (the "EXCHANGE ACT"), since the end of the Registrant's 1997
fiscal year; and (3) the description of the Common Stock contained in the
Registrant's registration statement on Form 8-A filed with the SEC under Section
12(g) of the Exchange Act, including any amendment or report filed for the
purpose of updating such description.

        In addition, all documents subsequently filed by the Registrant pursuant
to Sections 13(a), 13(c), 14 and 15(d) of the Exchange Act, prior to the filing
of a post-effective amendment which indicates that all securities offered hereby
have been sold or which deregisters all of such securities then remaining
unsold, shall be deemed to be incorporated by reference into this Registration
Statement and to be a part hereof from the date of filing of such documents.

ITEM 4. DESCRIPTION OF SECURITIES

        Not applicable.

ITEM 5. INTERESTS OF NAMED EXPERTS OR COUNSEL

        Not applicable.

ITEM 6. INDEMNIFICATION OF DIRECTORS AND OFFICERS

        Section 145 of the Delaware General Corporation Law empowers a Delaware
corporation to indemnify its officers and directors and certain other persons to
the extent and under the circumstances set forth therein.

        The Restated Certificate of Incorporation and the Amended and Restated
By-Laws of the Registrant, copies of which are filed herein as Exhibits 4.1 and
4.2, provide for advancement of expenses and indemnification of officers and
directors of the Registrant and certain other persons against liabilities and
expenses incurred by any of them in certain stated proceedings and under certain
stated conditions to the fullest extent permissible under Delaware law.

        The Registrant intends to maintain insurance for the benefit of its
directors and officers insuring such persons against certain liabilities,
including liabilities under the securities laws.

ITEM 7. EXEMPTION FROM REGISTRATION CLAIMED

        Not applicable.
3

ITEM 8. EXHIBITS

        The following exhibits are filed as part of this Registration Statement:

         4.1    Restated Certificate of Incorporation of the Registrant.
                Incorporated by reference to Exhibit 3.3 to the Registrant's
                Registration Statement on Form S-1 (File No. 333-30213).

         4.2    Amended and Restated By-Laws of the Registrant. Incorporated by
                reference to Exhibit 3.4 to the Registrant's Registration
                Statement on Form S-1 (File No. 333-30213).

           5    Opinion and Consent of Bingham Dana LLP with respect to
                the legality of the shares being registered.

        23.1    Consent of Bingham Dana LLP (included in Exhibit 5).

        23.2    Consent of Arthur Andersen LLP.

          24    Power of Attorney (included in signature page to Registration
                Statement).

ITEM 9. UNDERTAKINGS

        The undersigned Registrant hereby undertakes:

(1)     To file, during any period in which offers or sales are being made, a
        post-effective amendment to this Registration Statement to include any
        material information with respect to the plan of distribution not
        previously disclosed in this Registration Statement or any material
        change to such information in this Registration Statement;

(2)     That, for the purpose of determining any liability under the Securities
        Act of 1933, as amended (the "SECURITIES ACT"), each such post-effective
        amendment shall be deemed to be a new registration statement relating to
        the securities offered therein, and the offering of such securities at
        that time shall be deemed to be the initial bona fide offering thereof;

(3)     To remove from registration by means of a post-effective amendment any
        of the securities being registered which remain unsold at the
        termination of the offering;

(4)     That, for purposes of determining any liability under the Securities
        Act, each filing of the Registrant's annual report pursuant to Section
        13(a) or 15(d) of the Exchange Act (and, where applicable, each filing
        of an employee benefit plan's annual report pursuant to Section 15(d) of
        the Exchange Act) that is incorporated by reference in the Registration
        Statement shall be deemed to be a new registration statement relating to
        the securities offered therein, and the offering of such securities at
        that time shall be deemed to be the initial bona fide offering thereof;
        and

(5)     Insofar as indemnification for liabilities arising under the Securities
        Act may be permitted to directors, officers and controlling persons of
        the Registrant pursuant to the foregoing provisions, or otherwise, the
        Registrant has been advised that in the opinion of the SEC such
        indemnification is against public policy as expressed in the Securities
        Act and is, therefore, unenforceable. In the event that a claim for
        indemnification against such liabilities (other than the payment by the
        Registrant of expenses incurred or paid by a director, officer or
        controlling person of the Registrant in the successful defense of any
        action, suit or proceeding) is asserted by such director, officer or
        controlling person in connection with the securities being registered,
        the Registrant will, unless in the opinion of its counsel the matter has
        been settled by controlling precedent, submit to a court of appropriate
        jurisdiction the question whether such indemnification by it is against
        public policy as expressed in the Securities Act and will be governed by
        the final adjudication of such issue.

                                       2
4

                                   SIGNATURES

        Pursuant to the requirements of the Securities Act of 1933, as amended,
the Registrant certifies that it has reasonable grounds to believe that it meets
all of the requirements for filing on Form S-8 and has duly caused this
Registration Statement to be signed on its behalf by the undersigned, thereunto
duly authorized, in the City of Cambridge, Commonwealth of Massachusetts, on
this 31st day of March, 1998.

                                       LEUKOSITE, INC.

                                       By: /s/ Christopher K. Mirabelli, Ph.D.
                                           -------------------------------------
                                           Christopher K. Mirabelli, Ph.D.
                                           Chairman of the Board of Directors,
                                           President and Chief Executive Officer

                                POWER OF ATTORNEY

        Each person whose signature appears below hereby appoints Christopher K.
Mirabelli and Augustine Lawlor and each of them severally, acting alone and
without the other, his/her true and lawful attorney-in-fact with the authority
to execute in the name of each such person, and to file with the Securities and
Exchange Commission, together with any exhibits thereto and other documents
therewith, any and all amendments (including without limitation post-effective
amendments) to this Registration Statement on Form S-8 necessary or advisable to
enable the Registrant to comply with the Securities Act of 1933, as amended, and
any rules, regulations, and requirements of the Securities and Exchange
Commission in respect thereof, which amendments may make such other changes in
the Registration Statement as the aforesaid attorney-in-fact executing the same
deems appropriate.

        Pursuant to the requirements of the Securities Act of 1933, this
Registration Statement has been signed by the following persons in the
capacities and on the date indicated.
SIGNATURE                                 TITLE                               DATE
        ---------                                 -----                               ----
/s/ Christopher K. Mirabelli
-------------------------------   Chairman of the Board of Directors, President    March 31, 1998
Christopher K. Mirabelli, Ph.D.   and Chief Executive Officer
                                  (Principal Executive Officer)

/s/ Augustine Lawlor
-------------------------------   Vice President,  Corporate  Development          March 31, 1998
       Augustine Lawlor           and Chief Financial Officer
                                  (Principal Financial and Accounting Officer)

/s/ Kate Bingham
-------------------------------   Director                                         March 31, 1998
         Kate Bingham

/s/ Yasunori Kaneko, M.D.
-------------------------------   Director                                         March 31, 1998
    Yasunori Kaneko, M.D.

/s/ John W Littlechild
-------------------------------   Director                                         March 31, 1998
     John W. Littlechild
3
5
/s/ Martin Peretz, Ph.D.
-------------------------------   Director                                         March 31, 1998
     Martin Peretz, Ph.D.

/s/ Mark Skaletsky
-------------------------------   Director                                         March 31, 1998
     Mark Skaletsky

/s/ Timothy A. Springer, Ph.D.
-------------------------------   Director                                         March 31, 1998
  Timothy A. Springer, Ph.D.

/s/ Christopher T. Walsh, Ph.D.
-------------------------------   Director                                         March 31, 1998
 Christopher T. Walsh, Ph.D.
4
6

                                INDEX TO EXHIBITS
EXHIBIT                                                                              SEQUENTIAL
NUMBER                             DESCRIPTION                                        PAGE NO.
-------                            -----------                                       ----------
4.1       Restated Certificate of Incorporation of the Registrant.
            Incorporated by reference to Exhibit 3.3 to the Registrant's
            Registration Statement Form S-1 (File No. 333-30213).                        --

  4.2       Amended and Restated By-Laws of the Registrant. Incorporated by
            reference to Exhibit 3.4 to the Registrant's Registration Statement
            on Form S-1 (File No. 333-30213).                                            --

   5        Opinion and Consent of Bingham Dana LLP with respect to the legality
            of the shares being registered.                                              7

  23.1      Consent of Bingham Dana LLP (included in Exhibit 5).                         8

  23.2      Consent of Arthur Andersen LLP                                               9

   24       Power of Attorney (included in signature page to Registration
            Statement).                                                                  4
5