The biochemical genetics of TL antigens on mouse thymocytes

Abstract

Molecules bearing thymus leukemia (TL) alloantigen were isolated by immuno‐precipitation from detergent‐solubilized thymocyte lysates. Antisera used included monoclonal antibodies (anti‐TL. M1, anti‐TL.m2, anti‐TL.m3), monospecific anti‐TL.5 alloantisera and multispecific anti‐TL.1,2,3,5 antiserum. Apparently, each of these reagents immunoprecipitates the same single 45 000 molecular weight Tla gene product as shown by identity on sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS‐PAGE), isoelectric focusing and by sequential precipitation studies. Allelic TL molecules, coded by the Tla^a and Tla^d genes, were shown to be distinguishable by SDS‐PAGE, and tryptic peptide mapping experiments. Both allelic TL molecules could be isolated from thymocytes of (Tla^a x Tla^d)F₁ mice. These results suggest that, at least for the Tla^a‐Tla^d allelic differences, the polymorphism and antigenicity of TL is determined by variation in amino acid composition.