Cytotoxic antibodies against surface immunoglobulin.

The reactivity of B lymphocytes, null lymphocytes, T lymphocytes, chronic lymphocytic leukemia (CLL) cells, B and T cultured cell lines, monocytes, and granulocytes was tested against a panel of antisera under cold conditions of 5 C incubation followed by 25 C incubation in complement. The degree of cold cytotoxic activity against these cell types was in the order given above, with the C cells being the most sensitive. Surface immunoglobulin (SIg) staining followed the same distribution sequence, with the B cells containing the most SIg. Human IgM inhibited cold cytotoxic antisera but human IgG or human serum albumin (HSA) did not. IgM did not inhibit HLA antisera. We conclude that at least some cold cytotoxic antibodies react against surface IgM.