Nucleotide sequences of rat cDNA clones coding heavy chain class I major histocompatibility complex proteins.

Abstract The membrane-bound class I major histocompatibility complex (MHC) dimer is composed of a heavy chain (45-kd) that is noncovalently associated with a β 2 -microglobulin ( β 2 -m; 12-kd) light chain. 1 The heavy chain of the class I MHC dimer contains the membranedistal polymorphic α 1 (90 amino acids; AA) and α 2 (92 AA) domains, each of which forms an a-helix and four anti-parallel β-pleated strands. The α 2 domain is attached to a membrane-proximal α 3 (92 AA) domain, which is less polymorphic, and followed by the conserved transmembrane (25 AA) and cytoplasmic (30 AA) domains. The α 1 and α 2 domains of the rat class I MHC RT1.A a molecule bear highly polymorphic sequences which are immunogenic and induce allograft rejection. Two peptides were derived from the helical regions of the rat class I MHC RT1A a sequence. One peptide was localized in the a, helical region (56–72 AA and 72–83 AA), and one was localized in the α 2 helical region (145–155 AA). Both peptides elicited the proliferative response of alloantigen-specific T cells. 2 Our studies showed that the α 1 helical region of the RT1.A 1 molecule contains a potent immunogenic epitope localized at AA positions 62, 63, 65, and 69. 3 To examine the localization of other immunogenic epitopes, we isolated and sequenced additional rat class I MHC cDNAs.