Positive selection of T-cell subsets. I. Proliferative responses of Lyt 2 separated thymocytes and splenic T cells.

Flow microfluorometry analysis of peanut lectin non-agglutinable (PNA-) thymocytes (ThC) reveals the existence of 30%-50% Lyt 1,2,3+ and 50%-70% Lyt 1+,2,3- subpopulations. Using positive selection on anti-immunoglobulin-coated (Mage) plates, we selected PNA- Lyt 2+ and PNA- Lyt 2- ThC as well as their peripheral counterparts in the spleen. These populations were tested in parallel for their ability to respond to concanavalin A (Con A) and phytohaemagglutinin (PHA), to respond to allogeneic stimulation in the mixed lymphocyte reaction (MLR); ThC subpopulations were also tested for their ability to provide synergy with lymph node cells (LNC) in the MLR. It was found that (a) Lyt 2- cells of both thymic and splenic origin responded to all doses of Con A or PHA; (b) PNA- Lyt 2+ ThC were unresponsive to Con A or PHA, whereas splenic Lyt 2+ T cells responded to low doses of mitogens; and (c) PNA- ThC of both Lyt phenotypes responded in a MLR and provided synergy with LNC in the MLR. These data support the notion that Lyt 2+ cells of either PNA- or PNA+ subpopulations must undergo post-thymic maturation before becoming responsive to low doses of T-cell mitogens.