Comparative Studies of Mouse (H-2) and Human (HL-A) Histocompatibility Antigens

A purification procedure applied to H-2 antigens (controlled by the H-2 locus) was used for the characterization of HL-A substances (HL-A2 and HL-A7) (controlled by the HL-A locus) solubilized from lymphoid cell membranes by delipidation. Upon Sephadex chromatography the serologically active material had an apparent Mr of 32000, and displayed, in relation to H-2 antigens, a faster electrophoretic mobility and higher pI values. One sulfhydryl group and one (intrachain) disulfide bond were present in partially purified HL-A preparations. Reduction and aminoethylation in 4 M urea did not influence the electrophoretic migration of HL-A active substances, suggesting that, as already demonstrated for H-2 alloantigens, in HL-A molecules the genetic determinants are present on single polypeptide chains. Highly purified HL-A alloantigens, like H-2 substances, revealed a high degree of microheterogeneity. These findings further support the concept of the genetic and structural homology of the main histocompatibility systems in mouse and man.