A novel type of T-T cell interaction removes the requirement for I-B region in the H-2 complex.

Abstract

When tested in the in vitro T cell proliferation assay, [mouse] H-2a cells are nonresponders to lactate dehydrogenase B (LDH-B; L-lactate:NAD+ oxidoreductase, EC 1.1.1.27) and to IgG2a myeloma protein. The cells can be converted into responders by the addition to the culture of monoclonal anti-Ia.m7 antibody, or by the removal from the culture of Lyt-2+ [T lymphocyte associated-alloantigen (Lyt)-2 positive] lymphocytes. In both instances, the responsiveness can be suppressed again by the addition to the culture of monoclonal antibodies to I region-associated (Ia) molecules controlled by the I-A subregion. In some H-2 haplotypes, the response to LDH-B and IgG2a probably is the result of interaction between the I-A and I-E subregions. The H-2a haplotype carries a responder allele at the I-A subregion, but the responsiveness of H-2a cells is normally suppressed by T cells recognizing the antigen in the context of the I-E molecules. When the recognition of I-E molecules is blocked by an antiserum or when the cells capable of this recognition are removed, the H-2a cells become responders. A nonresponder turned responder by antibody inhibition was demonstrated. The postulate of the I-B subregion is no longer necessary, additional evidence was provided that the Ia molecules are the products of the immune response (Ir) genes.