Structural identity of the TL antigen homologues derived from strain 2 and strain 13 guinea pigs.

Strain 2 and strain 13 guinea pig thymocytes have been shown to bear a molecule that by several criteria appears to be a homologue of the murine TL antigen. The existence of a TL polymorphism in the mouse system as evidenced by TL- strains and various TL phenotypes in TL+ strains prompted a study to determine if a similar polymorphism could be demonstrated in the guinea pig system. By using two-dimensional gel electrophoresis, the thymocytes of a third inbred strain, DHCBA, were shown to bear a TL antigen, and the TL antigens of strains 2 and DHCBA were shown to give identical patterns of spots. A biochemical comparison of the strain 2 and strain 13 TL antigen heavy chains by tryptic and chymotryptic peptide mapping demonstrated that these molecules have identical peptides. Thus, no polymorphism could be demonstrated within the guinea pig TL system for the three inbred strains studied. Comparative tryptic peptide mapping of the guinea pig TL and class I B.1+S antigens demonstrated 43% homology, significantly higher than that reported for murine H-2 and TL antigens. These results provide suggestive evidence that the gene duplication giving rise to the genes determining the class I and TL antigens may have occurred more recently in the guinea pig than in the mouse.