Serologic Cross-Reactivity Between H-2 and HL-A Antigens

Abstract

Soluble HL-A antigen extracted from cultured human lymphoid cells (RPMI 1788, HL-A 2, 10, 7, W14) by the 3M KCl method was injected into rabbits. The rabbit anti-HL-A sera contained antibodies against all the HL-A specificities present on the immunogen. Moreover, these same xenoantibodies reacted also with certain murine lymphocytes bearing distinct H-2 specificities in the direct complement dependent lymphocytotoxic test. Absorption studies confirmed this selected reactivity and led to the conclusion that mainly antigenic determinants of the D region of H-2^d and the K region of H-2^b are involved in this cross-reactivity. Rabbit anti-HL-A sera absorbed with cells of different mouse strains were tested against a large panel of human lymphocytes from unrelated donors for remaining cytotoxic activity. The results indicate that absorption with cells of the genotypes H-2^b (K^bD^b) and H-2^a (K^kD^d) remove antibodies against determinants of the first segregant series (cross-reacting with HL-A 2 and 10). These data suggest a specific cross-reactivity between human and murine histocompatibility antigens and suggest a certain structural homology between these cell surface antigens and perhaps even a similar organization of the genetic fine structure of the HL-A and H-2 systems.