HUMAN POST-THYMIC PRECURSOR CELLS IN HEALTH AND DISEASE .1. CHARACTERIZATION OF THE AUTOLOGOUS ROSETTE-FORMING T-CELLS AS POST-THYMIC PRECURSORS

Abstract

Human autologous-rosette-forming T cells (Tar cells) have many of the characteristics of post-thymic precursor cells. Thus, they bind to sheep erythrocytes but have neither receptors for the Fc portion of IgG nor for that of IgM. They include a subpopulation that binds peanut agglutinin which suggests that they are immature and, as opposed to T cells, with either receptors for the FC portion of IgM (T.mu.) or of IgG (T.gamma.). Tar cells adhere to nylon wool, another indicator of immaturity, as is their extreme sensitivity to hydrocortisone both in vitro and in vivo. There are more Tar cells in cord blood than in the peripheral blood of young adults and there are more Tar cells in the peripheral blood of young adults than in the peripheral blood of elderly subjects. By co-culturing T.mu. and B cells, or T.mu., or Tar and B cells in the presence of pokeweed mitogen (PWM), it was determined that these cells cause feedback inhibition, a function considered characteristic of post-thymic precursors. In co-cultures in which mononuclear cells (MNC) or MNC plus Tar cells, or MNC depleted of Tar cells or MNC depleted of TAR cells plus Tar cells stimulated with PWM were placed, it was determined that Tar cells play a role in suppression generation, thereby confirming that human Tar cells are precursor cells. Tar cells proliferated and generated T.gamma. and T.mu. cells both spontaneously and in greater numbers, under the effect of serum thymic factor.