Shared chemical properties of different murine thymus-leukemia antigens.

Immunochemical studies of murine thymus-leukemia antigens (TLA) have confirmed that the subunit structure consists of a 45,000-dalton heavy chain and a beta 2 microglobulin (beta 2m) light chain. Similar structural features are exhibited by the TLA from thymocytes of Tlaa, Tlac, Tlad, and a leukemia cell derived from C57BL/6, a Tlab strain. In addition to the similar subunit structure from the four haplotypes, each TLA shows a similar pattern of trypsin proteolysis. This procedure yields a major heavy chain cleavage product of approximately 37,000 daltons that remains associated with beta 2m and retains most or all of the antigenic determinants of the intact TLA. Evidence is presented that TLA do not exhibit Fc receptor properties, nor do they adsorb to murine leukemia virus antigens under the conditions of isolation for analysis on polyacrylamide gel electrophoresis (PAGE) in sodium dodecyl sulfate (SDS). Taken together these findings strongly support the hypothesis that TLA comprise a family of chemically similar antigens belonging to a structurally and genetically related group that includes H-2D, H-2K, and Qa-2,3.