Distinct epitopes of Ik gene products identified by monoclonal antibodies.
Analysis of reactivity of monoclonal anti-Iak alloantibodies, obtained by fusion between NS 1 myeloma and spleen cells from alloimmune A. TH mice, permitted the identification of 9 distinct determinants of the Ik gene products. Competitive binding experiments indicated that 2 private epitopes (defined by H8-109.13 and H8-138.4 antibodies) of the I-Ak product could be separated, thereby apparently splitting the Ia.2 specificity. A public determinant of the I-Ak molecule (identified by H8-15.9 antibody) was found expressed not only on the I-A products of the H-2b, H-2d, H-2ja, H-2p and H-2q murine haplotypes, but also on human HLA-DR antigens. Four determinants of the I-E/Ck antigen (defined by H7-8.26, H10-81.10, H10-93.2 and H8-86.2 antibodies) had a  strain distribution analogues to the Ia.7 specificity. However, competitive binding experiments, and the cross-reactivity pattern with Ia-like antigens from other species (e.g. human HLA-DR antigens) indicated that these antibodies detected distinct determinants on the I-E/Ck molecule, thereby subdividing the broad Ia. 7 specificity. Two other determinants (defined by H9-14.8 and H9-15.4 antibodies) had a strain distribution that did not permit a precise assignment to a given Ia antigen, even though preliminary data suggested that they could detect separate determinants on the I-E/Ck  product. All these monoclonal antibodies identified membrane antigens with the expected Ia tissue distribution pattern, and most of them could precipitate a molecule containing two chains of 28kD and 35kD, from mouse spleen cell lysates.
D000818:Animals; D000906:Antibodies; D011232:Chemical Precipitation; D002999:Clone Cells / Q000276:immunology; D003429:Cross Reactions; D003602:Cytotoxicity, Immunologic; D000939:Epitopes; D005260:Female; D000949:Histocompatibility Antigens Class II / Q000235:genetics* / Q000276:immunology; D007111:Immunity, Cellular; D008297:Male; D051379:Mice; D008805:Mice, Inbred A; D008808:Mice, Inbred CBA; D014176:Protein Biosynthesis; D011817:Rabbits
D000906:Antibodies; D000939:Epitopes; D000949:Histocompatibility Antigens Class II