A monoclonal antibody directed against a synthetic peptide reacts with a cell surface rabbit class I MHC molecule.

Monoclonal antibodies were prepared against synthetic peptides synthetized on the basis of nucleotide sequence from cDNA and genomic clones encoding a class I antigen expressed by the rabbit RL-5 cell line. Using a peptide corresponding to positions 61-73 of the N domain, we were able to obtain an hybridoma producing monoclonal antibody which recognized the peptide as well as the native class I antigen. This hybridoma, designated anti-61, reacted with cell surface molecules on RL-5 cells and on human HeLa cells transfected with the 19-1 gene encoding RL-5 class I antigen. No reactivity with HeLa cells prior to transfection could be detected by radioimmunoassay or by fluorescent activated cell sorter analyses, although these cells were strongly positive in both assays with anti-human class I reagents. Antibody reaction to positive cells could be inhibited by the homologous peptide but not by unrelated peptides. Anti-61 antibody precipitated a 41,000 mol. wt molecule from RL-5 cells with an N-terminal amino acid sequence corresponding to the RL-5 class I antigen.