Rhesus macaque (Macaca mulatta) peripheral blood T-lymphocyte subpopulations were assessed for the distribution of helper and suppressor/cytotoxic cells using the T-cell subset specific monoclonal antibodies T4 and T8 respectively. Highly purified T-lymphocytes (> 90% E-rosetted) were separated into subpopulations by rosetting with IgG (Tγ) and Igm (Tμ) sensitized bovine red blood cells, or by adsorption with insolubilized histamine. In this study, rhesus peripheral blood T-lymphocytes were found to express cell-surface determinates recognized by T4 and T8 monoclonal antibodies. Subset frequencies were found to be comparable to that found in humans (50% T4 and 33% T8). The helper subpopulation, Tμ, contained 30% T4 and 2% T8 type cells. These results suggest Tγ helper activity may be due to a selective depletion of suppressor cells, rather than an enrichment of helper T-cells. The suppressor subpopulations, Tγ, contained 9% T4 and 2% T8 type cells. These results suggest Tγ cells may represent either an undifferentiated suppressor cell or, perhaps, a separate suppressor subpopulation which does not express T8 differentiation antigens. The Tγ-subpopulation (depleted of cells with Fc-IgG receptors) was rich in helper T-cells (52% T4) and depleted of suppressor T-cells (6% T8). T-cells depleted of cells expressing IgM or IgG receptors, T-null, contained 47% T4 and 12% T8 type cells. Further, T-cells adsorbed with insolubilized histamine were selectively depleted (70% reduction) of T8 type cells, while the frequency of T4 type cells remained unaffected by histamine absorption. The majority of suppressor/cytotoxic T-cells (T8), therefore, appear to express cell-surface receptors for histamine.
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