The participation of thymus-derived and of bone marrow-derived lymphocytes of sensitized mice, in the proliferative response to specific antigen, in vitro

Spleen cells of mice primed with sheep red cells (SRC) responded with increased thymidine uptake when stimulated with SRC in vitro. Depletion of bone marrow-derived (B) cells by filtering the spleen cells through columns of plastic beads coated with anti-mouse immunoglobulin serum resulted in a drastic loss of the proliferative response. A similar loss occurred on depleting the thymus-derived (T) cells by treatment with anti-Θ serum and complement. Addition of peritoneal exudate cells failed to restore the reactivity of the purified T cells to SRC. The proliferative response could be restored to a level exceeding the sum of the individual responses, by mixing the purified T with the purified B cells. A synergistic interaction between T and B cells is suggested.