Dextran-triggered T cells heighten T- and B-cell reactions to mitogens.

Dextran administered to mice of six strains has been found to cause enhanced responses of spleen cells to the mitogens Con A and LPS. When added to cultures of spleen cells in vitro in a wide range of concentrations dextran, alone, was neither mitogenic nor toxic. The enhancement is mediated through T cells since it was absent in spleen cells from dextrantreated athymic mice. Furthermore, for the enhanced response to LPS, T cells from dextran-treated mice apparently must be in close association with B cells for longer than 2 h. The enhancement is accomplished through a humoral factor(s) produced by splenic T cells. The T cell-derived enhancing factor(s) has been shown to affect allogeneic as well as isogeneic T and B cells.