Suppression of the plaque-forming cell response by macrophages present in the normal rat spleen

Depletion of phagocytic and/or adherent cells from normal rat spleen cell preparations permitted the generation of PFC to SRBC in vitro. Suppressive activity was associated with the presence of macrophages in the normal rat spleen, since irradiated unfractionated or irradiated adherent cells suppressed the PFC response of macrophage-depleted cells. Whereas depletion of macrophages from normal rat spleen cells permitted the PFC response to SRBC to occur, comparable treatment of mouse spleen cells eliminated the PFC response. These results are discussed in relation to the requirement for macrophages in the generation of PFC with rat cells in vitro.