Two-chain structure of T-suppressor factor: antigen-specific T-suppressor factor occurs as a single molecule and as separate antigen-binding and I-J+ parts, both of which are required for biological activity.
Antigen-specific T-suppressor factor (TsF), which acts at the expression stage of the contract sensitivity reaction, was produced by culturing the lymphoid cells of mice injected with picryl-sulphonic (trinitrobenzenesulphonic) acid and then painted with picryl chloride. Supernatant activity was found around 50-60 and 90 kDa on Sephadex gel filtration. The activity at 50-60 kDa was due to two separate (or readily separable) molecules, one antigen binding and the other bearing I-J determinants as shown by affinity chromatography on insolubilized antigen and anti-I-J. These two separate molecules were inactive alone but complemented each other and may be designated as the variable chain of TsF (TsFv) and the I-J+ chain. The use of gel filtration and sequential absorption of individual pools on anti-I-J antibody followed by antigen, together with a complementation assay, also showed a TSFv chain at 30-40 kDa and an I-J+ chain at 20-30 kDa. The higher-molecular-weight activity around 90 kDa was due to a single molecule which was both antigen binding and I-J+. This molecule dissociated on treatment with the reducing agent dithioerythritol followed by alkylation into two separate chains, one antigen binding and the other I-J+, both of which were required for activity. There was a requirement for genetic matching between the antigen-binding chain (TsFv) and the I-J+ chain for biological activity. These data support a two-chain model of TsF in which TsFv and the I-J+ chain occur as a single disulphide-bonded molecule around 90 kDa, or as two separate (or readily separable) chains of lower molecular weight which were inactive alone but complemented each other.
D000818:Animals; D000936:Antigen-Antibody Complex; D002478:Cells, Cultured; D000939:Epitopes / Q000032:analysis*; D007144:Immunoglobulin J-Chains / Q000032:analysis*; D008214:Lymphocytes / Q000276:immunology; D008222:Lymphokines / Q000276:immunology* / Q000302:isolation & purification; D051379:Mice; D008970:Molecular Weight; D011948:Receptors, Antigen, T-Cell / Q000276:immunology; D013491:Suppressor Factors, Immunologic; D013601:T-Lymphocytes / Q000276:immunology*
D000936:Antigen-Antibody Complex; D000939:Epitopes; D007144:Immunoglobulin J-Chains; D008222:Lymphokines; D011948:Receptors, Antigen, T-Cell; D013491:Suppressor Factors, Immunologic