Cross-reactivity among the products of three nonallelic H-2 loci, H-2Ld, H-2Dq, and H-2Kk.

Cross-reactions of the products of three nonallelic H-2 loci, H-2K, H-2D, and H-2L, have been studied by serological, immunochemical, and cellular immune techniques. Immunoprecipitation experiments revealed a determinant shared between Ld and Dq molecules but absent on Dd molecules, By cytotoxic screening of sera from individual mice an exceptional anti-Ld serum was found which cross-reacted with an H-2k antigen. Genetic mapping studies suggested that the basis of this activity was an Ld-Kk serological cross-reaction. Cytotoxic T cells generated to Ld alloantigens were also found to recognize a cross-reacting Kk determinant. These studies therefore suggest that L, D, and K are three structurally homologous cell surface glycoproteins that have evolved from a common primordial gene.