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Cellular events mediated by antigen-specific soluble factor extracted from carrier-primed suppressor T cells (TsF) in the suppressive interaction was studied. Keyhole limpet hemocyanin (KLH)-specific TsF directly acts on KLH-primed, I-J positive, nylon-wool-adherent T cells that have an acceptor site for TsF. The nylon-wool-adherent T cells, after accepting TsF in the presence of specific antigen, generate new suppressor T cells acting as an actual effector cell type. Antigen-specificity and syngeneity at I-J between TsF and acceptor T cells are both required for the induction of new suppressor T cells. Newly induced suppressor T cells, however, suppress both syngeneic and allogeneic responses in an antigen-nonspecific fashion.

No abstract available.

Partial sequences of three immunologically distinct group A streptococcal M proteins (M5, M6, and M24) revealed significant homology with each other, certain amino acid residues being conserved within the three molecules. In addition, a common feature of the sequenced regions of these M proteins was their high alpha-helical potential and the presence of a repeating seven residue periodicity that is characteristic of the double helical coiled-coil molecule, tropomyosin. The existence of a tropomyosin-like seven residue periodicity strongly suggests that regions of these three M proteins may participate in intra- and/or intermolecular coiled-coil interactions. Because of the constraints imposed by such a repeating periodicity, certain conserved residues within the M proteins would occupy spatially equivalent positions in the tertiary structure of these molecules. This common characteristic could play an important role in the common antiphagocytic property of the immunologically diverse M molecules. In addition to similarities in the secondary structure of M proteins and tropomyosin, significant sequence homology has also been observed between certain regions of these molecules with up to 50% identical residues. As a result of the striking structural similarity with tropomyosin, M proteins may play a regulatory role in the contractile mechanisms involved in phagocytosis.

Ia specificities 22 and 23 were found to be determinants on hybrid Ia molecules by serological and biochemical studies. Lipopolysaccharide-stimulated splenic lymphocytes from (B10 X B10.D2)F1 expressed Ia.22 although both the parents were negative. Similarly [D2.GD X B10.A(5R)]F1 cells expressed Ia.23, whereas D2.GD and B10.A(5R) lacked it. Ia.22 can be generated by gene complementation of Ak-Ek, Ab-Ed, Ab-Ek, As-Ed, and As-Ek, whereas Ia.23 can be generated by Ad-Ed, Ad-Ek, and Ad-Ep. Other possible complementing combinations are under study. The role of Ia.22 and 23 in mixed lymphocyte reactions and immune responses are discussed.