Active rosette forming cells as a possible functional subpopulation of human peripheral T lymphocytes

Spontaneous E rosette forming cells (RFC) and active E rosette forming cells (ARFC) were separated individually by the rosette sedimentation technique. The responses of these cells to phytohemagglutinin (PHA) and concanavalin A (Con A) were studied. RFC exceeded ARFC in their responses to PHA at all concentrations of PHA and the maximum PHA response of RFC was significantly higher than that of ARFC. On the other hand, Con A appeared to stimulate RFC and ARFC equally at the level of an optimal dose. Therefore, the binding affinity for sheep red blood cells (SRBC) by T lymphocytes and their responsiveness to PHA stimulation may be inversely related. It is also suggested that the PHA-sensitive population may be different from the Con A-sensitive one, or that there may be heterogenous populations among human T lymphocytes in their mitogenic responses. Thus, it is possible that ARFC may be a functional subpopulation of human T cells. An additional finding is that spontaneous DNA synthesis of rosetting cells was significantly lower than that of non-rosetting cells.