Antigen-specific T lymphocyte clones. III. Papain splits purified T suppressor molecules into two functional domains.

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Abstract
Purified molecules (70,000 MW) from a mouse T suppressor (Ts) clone bind to sheep erythrocyte glycophorin and specifically suppress the response to this antigen. Papain splits purified 70,000 MW Ts molecules into 3 peptides: MW 45,000 and 24,000. The 45,000 MW peptide nonspecifically suppresses antibody responses to several antigens and lacks antigen-binding activity. The 24,000 MW peptide does not suppress but retains antigen-binding activity. Papain apparently splits the Ts molecule into a constant region responsible for function and a variable region responsible for antigen-binding. Since binding of the 70,000 MW molecule to antigen also results in release of the 45,000 MW subunit, this cleavage may allow Ts molecules specific for 1 determinant to suppress immunity to complex foreign proteins.