Cord IgM antibody specific for human killer T cells: T lymphocytotoxic human fetal antibody (TLFA) recognizing maternal killer T cells proliferating in the presence of interleukin 2.

T lymphocytotoxic human fetal antibody- (TLFA) containing cord IgM (TLFA IgM) was purified from cord blood. The proliferation of maternal mixed lymphocyte culture-(MLC) induced and long-term cultured T cells (LCT) specific to the paternal non-T cells in the presence of interleukin 2 (IL 2) was inhibited by treatment with the respective TLFA IgM plus complement (C). Sixty-six to 78% of Leu-2a-positive maternal LCT were stained with the respective TLFA IgM, as determined by anti-Leu antibodies and TLFA IgM double-staining. Moreover, TLFA IgM plus C treatment reduced the killer activity of the respective maternal LCT against the PHA-induced paternal target cells. Therefore, TLFA-positive killer T cells of maternal LCT belong to certain killer T cell subsets of Leu-2a-positive pan-killer T cells, and TLFA contains a potential antibody against maternal killer T cells.