A possible role of PMN in a casein-induced enhancement of PFC response to sheep erythrocytes in mice.

The effect of inflammation induced by sodium caseinate or aluminum hydroxide on the splenic plaque-forming cells (PFC) response to sheep red blood cells (SRBC) was studied in mice. Direct and indirect splenic PFC responses were enhanced when suboptimal SRBC doses (3 x 10(6)) were injected intraperitoneally (i.p.) within 9 hr of i.p. inflammatory stimulation; antigen administration 48 hr or more after such stimulation resulted in a slight suppression of the direct response. The inflammation had no effect on the secondary immune response, nor did intravenous antigen administration enhance the PFC response. Enhancement occurred when early (3 hr), casein-induced peritoneal exudate cells (PEC, consisting mostly of neutrophils) were adoptively transferred at the same time as antigen. Treatment of the 3-hr PEC with anti-Thy-1 and complement did not decrease their PFC-enhancing capability. Late (96-hr) PEC, consisting mostly of macrophages, manifested only a slight enhancing effect. We suggest that enhancement of the splenic PFC response in the presence of an ongoing inflammation, may be partially attributable to neutrophil function.