Studies on the functional heterogeneity of rat T cells using monoclonal antibodies

A new monoclonal antibody against rat lymphocytes is described. This antibody, designated MRC-OX22, recognises an antigen found on all peripheral B cells, all suppressor/cytotoxic lymphocytes, but only on some helper cells, as defined by the W3/25 antibody. The antigen is found on a significant number of bone marrow cells, but only on 3% of thymocytes, which were located by immunoperoxidase staining at the cortico-medullary junction. The phenotypic division of the W3/25+ peripheral T cells, is mirrored functionally. By using the popliteal lymph node assay, and the induction of lethal graft-versus-host disease as indicators of alloreactivity, it is found that the alloreactive T cells have the phenotype MRC-OX22+ ,W3/25+. In contrast, using an adoptive transfer system to assess T cell help for B cell antibody production, the phenotype of the Thelper for B cells is shown to have the phenotype MRC-OX22-, W3/25+. Evidence is also presented that the phenotype of the Thelper cell for B cells is stable after priming and boosting. The phenotype of the memory B cell is shown to be MRC-OX22+, and the cell responsible for allogeneic suppression is also shown to be MRC-OX22+, using the adoptive transfer system for antibody formation. The significance of the functional heterogeneity of the W3/25+ subset is discussed, and the biochemical nature of the antigen recognised by MRC-OX22 is reviewed, and compared with possible homologues in mouse and man.