Separation and further characterization of early and late rosette-forming cells.

Human peripheral blood T-lymphocytes (PBL) can be separated into early rosette-forming cells or active T cells (A-RFC) and late rosette forming cells (L-RFC) according to the time required for formation of rosettes with sheep red blood cells (SRBC). Experimental results showed that treatment of the SRBC with neuraminidase was necessary for the formation of stable early rosettes. The optimum proportion of SRBC to lymphocytes for total rosette formation was 64:1, whereas a 16:1 ratio yielded maximal early rosette formation. The proliferative responses of A-RFC to concanavalin A (Con A) or to alloantigens were less than those seen with L-RFC. The percentage of T gamma cells in A-RFC was significantly lower than in L-RFC. Leukocyte inhibitory factors (LIF) released by the A-RFC fraction after treatment with Con A were more effective inhibitors of the migration of polymorphonuclear leukocytes (PMN) than the factors released from the L-RFC fraction. These results suggest that A-RFC represent a subpopulation of T lymphocytes which are more active in certain lymphocyte responses than another subpopulation which forms rosettes more slowly with sheep red blood cells.