Monoclonal antibodies to RT7 and LCA antigens in the rat: cell distribution and segregation analysis.

Fluorescein-conjugated monoclonal antibodies (mAb) have been used to examine the cellular distribution and genetic relationship of the RT7 and the leukocyte common antigen (L-CA) in the rat. We demonstrate here that the RT7.1 alloantigen, recognized by the mAb BC84, is present on B lymphocytes as well as T lymphocytes, although at markedly different apparent concentrations; T cells binding approximately 4 times more BC84 than do B cells. In contrast, the polymorphic L-CA recognized by the NDS58 mAb and the non-polymorphic L-CA recognized by the OX1 mAb appear to be expressed in equal concentrations on T and B cells and differ in their tissue distribution from the RT7.1 alloantigen. We have also tested a new mAb termed 8G6.1, that is reactive with RT7b rat strains and has a cell, tissue and strain distribution profile resembling that of a polymorphic L-CA. Segregation analysis of the RT7 and polymorphic L-CA antigenic systems using a single backcross model demonstrate that the alloantigens recognized by BC84 and NDS58 cosegregate and that both are allelic with respect to 8G6.1. The L-CA antigenic determinant defined by OX1 was non-polymorphic and thus was not allelic with any of the antigenic systems tested. These results suggest that there is a close genetic relationship between the expression of RT7 and L-CA in the rat.