Human T lymphocyte subpopulations defined by Fc receptors and monoclonal antibodies. A comparison

Human T cell subpopulations have been defined on the basis of differential expression of either Fc receptors or specfic cell-surface antigens. In this study, we utilized a series of monoclonal antibodies reactive with T cells, monocytes, and Ia antigens to characterize isolated subpopulations of T cells bearing receptors for the Fc portion of IgG (Tγ) and subpopulations of T cells bearing receptors for the Fc portion of IgM Tμ. The results showed that the Tμ population contained both inducer (OKT4 ⁺) and cytotoxic/suppressor (OKT5 ⁺) populations and was similar to the unfractionated T cell population, whereas the Tγ subset contained few T lymphocytes (OKT3 ⁺) and was not enriched for either T cell subset defined by these monoclonal antibodies. Rather, the Tγ population was comprised largely of Ia ^- cells possessing a monocyte antigen (OKM1 ⁺). In reciprocal studies, it was found that both isolated OKT4 ⁺ and OKT5 ⁺T cell subsets contained few Tγ cells, whereas both subsets were mainly comprised of Tμ cells. We conclude that there is little correlation between T cell subsets defined by these monoclonal antibodies and those defined by Fc receptors.