Biochemical identification of rat ART-1 and Ly-1 alloantigens

The results of this study indicate that the ART-1 and Ly-1 rat alloantigens are synonymous with each other and also with the leukocyte-common (L-C) antigen which has been previously identified as a major glycoprotein of rat thymocytes and T and B lymphocytes. This conclusion is supported by the following observations: (i) when labeling of rat lymphoid cells was studied with a fluorescence-activated cell sorter, the profiles obtained were similar for labeling with ART-1 and Ly-1 alloantibodies and a monoclonal antibody to L-C antigen: (ii) this labeling was almost completely inhibited by purified L-C antigen: (iii) preincubation with L-C antigen completely inhibited binding of the alloantibodies in a cellular radioimmunoassay; (iv) the cytotoxic effect of the alloantibodies was completely abolished by preincubation with purified L-C antigen; (v) the strain distribution of the ART-1 and Ly-1 alloantigens was identical for 11 rat strains and in linkage analysis the ART-1 and Ly-1 alloantigens were found to cosegregate. Genetic linkage studies have shown that the L-C antigen locus is unlinked to the major histocompatibility antigen (RT1), the immunoglobulin light chain (1k) and to the coat color gene (C) loci.