Functional characterization of a naturally occurring antibody cytotoxic for a subpopulation of splenic T cells.

Sera from old (greater than 6 months) New Zealand Black (NZB) mice were shown to contain an IgM antibody which was cytotoxic for thymus-derived (T) lymphocytes in the presence of rabbit complement. This antibody in the presence of complement markedly decreased the response of normal spleen cells to the T cell mitogen concanvalin A (Con A) but not to another T cell mitogen phytohemagglutinin-P (PHA-P). Responses of these treated cells to the polyclonal B cell mitogens, bacterial lipopolysaccharide (LPS), and polyriboinosinic-polyribocytidylic acid (poly[I]-poly[C]) were unimpaired. This naturally occurring NZB antibody was different from conventional anti-theta serum which abolished the response to both PHA-P and Con A. Moreover, the NZB serum affected spleen cells from both theta-C3H and theta-AKR mice. The ability of such serum to influence, differentially, Con A reactive cells as opposed to PHA-P-reactive cells, suggest that the NZB antiserum recognizes a subpopulation of T lymphocytes.