Recognition of HLA class I molecules by antisera directed to synthetic peptides corresponding to different regions of the HLA-B7 heavy chain.

Antisera have been prepared in rabbits and in mice against different peptides corresponding to four hydrophilic and variable regions of HLA-B7 heavy chain (65-82, 99-118, 138-157, and 164-187). Specific antipeptide sera have been obtained with all synthetic peptides; for three of them which were more than 20 amino acids long, highly potent sera were elicited by injection of the free peptide. Three overlapping peptides included in region 138-157 have been used, and two different antigenic sites were detected in this region. HLA molecules solubilized in nonionic detergent were precipitated by antipeptide sera directed against regions 65-82, 138-157, and 164-187, but not by antipeptide serum directed against the less hydrophilic region 99-118. Analysis by two-dimensional electrophoresis of the isolated molecules confirmed the anti-HLA specificity of the antipeptide 65-82 and 138-157 sera. Variable numbers of HLA-related spots were found according to the antisera used. Antipeptide 138-157 serum precipitated numerous HLA molecules and therefore probably reacted with monomorphic determinants whereas antipeptide 65-82 appeared specific for a more limited number of HLA antigens. Such reagents directed against well-defined regions of the HLA class I heavy chain are of considerable interest, notably for the mapping of antigenic epitopes on the molecule and for the study of relationships between structure and function.