Chemical features of an antigen-specific suppressor T cell factor composed of two polypeptide chains.

A [35S]methionine-labelled antigen-specific suppressor factor (TsF) was extracted from a T cell hybridoma by freezing and thawing. It was purified by use of immunoadsorbent columns or plates conjugated with antigens or antibodies, and was analysed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis. The TsF was found to be composed of two distinct and non-covalently associated polypeptide chains with molecular weights of 45 and 27 kilodaltons (kd). The heavy chain possesses both antigen-binding capacity and constant-region determinants (Ct) detected by monoclonal BALB/c anti-CB-20 antibodies (anti-Ct). The light chain was defined by conventional or monoclonal anti-I-J antibodies [B10.A(5R) anti-B10.A(3R)]. Functional analyses have also shown that the keyhole-limpet-hemocyanin-specific TsF composed of 45-kd and 27-kd molecules purified on plates coated with monoclonal anti-Ct or anti-I-J antibodies suppresses antibody response in an antigen-specific fashion.