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The HLA complex codes for three distinct 44000 dalton molecules associated with beta2 microglobulin--HLA-A, B and C--each with its own multiallelic series of private antigens. The HLA-B molecule is exceptional in that it also carries a diallelic system, Bw4 and Bw6. One of these, Bw4, is often associated with the A-locus specificity A9. This finding has usually been ascribed to linkage disequilibrium between A- and B-locus antigens. We have shown, however, that an epitope called LHe is actually shared by A-locus and B-locus molecules. This epitope is found on all HLA-B molecules bearing the Bw4 determinant and is also found on all HLA-A molecules carrying the A9 (Aw23 and Aw24) or Aw32 specificities. We consider this a "public" HLA antigen; the possible molecular basis for both subtypic and public antigens on a single glycoprotein is discussed.

We describe here two monoclonal antibodies with HLA-DR7 serologic specificity. The antibodies, SFR16-DR7M, a cytotoxic rat IgM antibody of high affinity, and SFR16-DR7G, a noncytotoxic antibody of the rat IgG 2a class, react with only DR7-positive cells in radioimmunoassay. The cytotoxic activity of SFR16-DR7M correlates completely with the presence of the DR7 specificity, and segregates with the DR7-bearing haplotype in a family. SFR16-DR7M precipitates a class II molecule with the electrophoretic characteristics of DR molecules from LG-10, an HLA-DR7 homozygous cell line. SFR16-DR7G completely inhibits the cytotoxicity of SFR16-DR7M, but only partially inhibits the cytotoxicity of a chimpanzee antiserum with DR7 specificity, Gay/Swei. In binding-inhibition studies, binding of SFR16-DR7M to LG-10 cells is only partially inhibited by the chimpanzee antiserum and vice versa. Both SFR16-DR7M and Gay/Swei reciprocally deplete the same class II molecules from a 35S-methionine-labeled detergent-solubilized membrane preparation of the LG-10 cell line. The chimpanzee serum Gay contains antibodies reactive with epitopes on separated DR7 beta chains, while both SFR16-DR7M and SFR16-DR7G bind only to DR7 alpha-beta complexes. These data suggest that at least two allogeneic epitopes exist which result in the same serologic specificity, and that these epitopes differ in their requirement for alpha-beta complex formation.

SUMMARYHuman lymphocytes treated with Vibrio cholerae neuraminidase (VCN) are more susceptible to cytotoxic human alloantisera than are sham treated cells. Sera from most normal or immunized donors showing no detectable anti-HL-A activity gave strong positive reactions with almost all VCN-treated is

The complexity of the human class II molecules is well established. A minimum of four distinct serologically defined molecular subunits have been identified (DR, BR, DQ, DP). We report here a new serologically defined B cell specificity designated MA4. The absorption data is consistent with the interpretation that the MA4 specificity is located on a molecule or chain distinct from DR, BR, DQ, DP.

Publisher Summary This chapter discusses the genetic and antigenetic aspects of human histocompatibility systems. The chapter provides an overview of the genetic and antigenetic aspects of human histocompatibility systems. Histocompatibility antigens are the substances that are associated with the plasma membrane of tissue cells of some—but not all—members of a species. Tissue or cell suspensions carrying such antigens induce an immune response when introduced into another member of the same species. The immunity can be measured in several ways such as by the detection of antibodies in the serum of an individual rejecting a transplant, by a more rapid rejection of a second graft from the same donor, or by demonstration of increased immunological reactivity in lymphoid cells of the recipient. From immunological studies and from more limited chemical characterizations of antigens of different systems, it appears that a wide variety of substances can function as H antigens. In many respects, H antigens resemble blood group antigens with the distinction that blood group antigens are by definition found on the red cell and may also be present on other cells and tissues, whereas H antigens are found on tissues and may or may not be present on the red cell.