Serotyping for MLC gene products: I. Presumptive evidence that ABCIL may detect MLC factors.

Serum from a grand multiparous Inuit (Eskimo) woman, who is HL-A identical but stimulatory in MLC with cells of her husband, contains strong ABCIL reactivity. This serum is operationally monospecific against a cell membrane determinant on lymphocytes, but not platelets, of some unrelated persons. Cells of those who are ABCIL positive with this serum always give a lower MLC stimulation index compared with their MLC responsiveness to cells that are ABCIL negative. This serum also contains good MLC inhibitory activity but only in those one way MLC reactions in which it reacts, by ABCIL, with the stimulating cells. It is postulated that the ABCIL activity is directed against a common MLC factor on lymphocytes.