Recognition of Immunoglobulin Idiotypes by Thymus-Derived Lymphocytes

The ability of thymus-derived lymphocytes (T cells) from BALB/c mice to recognize the individually specific antigenic determinants (idiotypes) of BALB/c myeloma proteins was tested. Spleen cells from donor mice immunized with a given myeloma protein greatly augmented the response of hapten-specific bone-marrow-derived, thymus-independent lymphocytes (B cells) to a hapten conjugate of the immunizing myeloma protein. This helper effect was specific for the myeloma protein idiotype; responses to hapten conjugates of similar myeloma proteins, bearing different idiotypic determinants, were not augmented by these spleen cells. That the helper cell is a T cell was shown by its marked sensitivity to cytolysis with an isoantiserum specific for T cells (anti-Thy-1.2) and complement. The discrimination between idiotypes by such T cells is roughly comparable to that of the antibody produced by the donors of the helper cells.