Mitogenic Responsiveness of Human T-Lymphocyte Subpopulations: Regulation by Suppressive Fc-Receptor-bearing T Cells and Influence of Fractionation Procedures

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Abstract
The proliferative response induced by leucoagglutinin (La) in different subpopulations of human I lymphocytes was studied Subpopulations enriched in cells with either high- or low-avidity receptors for sheep erythrocytes (SRBC) (EH.+, Et+) were prepared by sequential E-rosetting. In addition, T lymphocytes prepared by E-rosetting under optimal conditions (E+ror) were fractionated on wheat germ agglutin (WGA)-Sepharose columns, rendering fraction enriched in lymphocytes with either low- or high-avidity receptors for WGA. The T lymphocytes were found to comprise at least three functionally distinct subpopulations, differing with respect to mitogen responsiveness. Cell characterized by high-avidity receptors for WGA and SRBC were highly responsive to La simulation, regardless of the method used for purification. In contrasts cell with low-avidity receptors for WGA and probably also for SRBC hut lacking Fe receptors for IgG responded only marginally but were conditioned to respond when subjected to E-rosetting under optimal conditions. This response was suppressed by lymphocytes with Fc receptors for IgG, which probably also had low-avidity receptors for WGA and SRBC. The lymphocytes with high-avidity receptors for WGA and SRBC did not appear to be susceptible to suppression by Fcγ+ cells.