Structure of an antigen-specific suppressor factor produced by a hybrid T-cell line

Abstract

THE preceding report¹ described the production by the hybrid T-cell line A1 of a suppressor factor with specificity for sheep red blood cells (SRBC). The factor, which binds specifically to SRBC and suppresses the antibody response to this antigen in culture, does not react with anti-mouse immunoglobulin (mIg) reagents, but is removed by mouse alloantisera (anti-H–2). In these respects it resembles the antigen-specific T-cell factors which have been obtained from T cells after stimulation by antigen and which play an important part in regulation of the antibody response^2,3. We report here our study of the structure of the A1 suppressor molecule by incorporation of ³H-leucine, followed by SDS–polyacrylamide-gel electrophoresis (SDS–PAGE). The molecule seems to be composed of two types of polypeptide chain in noncovalent association, a large chain of molecular weight 85,000 and a small chain of 25,000. The MW of the native molecule is about 200,000. The isolated large chain binds to SRBC. The H–2 determinants are apparently present on the small chain.