Anti-HLA antibodies of predetermined specificity: a chemically synthesized peptide induces antibodies specific for HLA-A,B heavy chain.

A chemically synthesized dodecapeptide (Asp-Ala-Ala-Ser-Pro-Arg-Glu-Glu-Pro-Arg-Ala-Pro), consisting of residues 39 through 50 of the HLA-B7 heavy chain sequence and containing a highly hydrophilic hexapeptide segment (Pro-Arg-Glu-Glu-Pro-Arg), induced antibodies that bound specifically to free HLA-A, and HLA-B heavy chains and to the soluble dodecapeptide. Although these antibodies reacted with free HLA-A,B heavy chains in blots on nitrocellulose, they failed to immunoprecipitate the HLA-A,B-beta 2-microglobulin antigen complex solubilized from human lymphoblastoid cells by nonionic detergents. These observations suggest that the physical characteristics of this particular soluble hydrophilic dodecapeptide may closely resemble nonallotypic determinants expressed by free HLA-A,B heavy chains and that such antigenic sites may be modified by conformational changes in the native HLA-A,B heavy chain-beta 2-microglobulin complex.