Haemolytic plaque formation by mouse peritoneal cells, and the effect on it of Friend virus infection.

Peritoneal cells from non-immunized mice, when incubated with sheep red cells and complement in a film of carboxymethyl-cellulose gum, form plaques of haemolysis after a latent phase of 15–20 hours. Plaques are also produced by the free cells of the pleural cavity but not by lymph node, spleen, thymus and bone marrow cells. Plaques are not produced at room temperature, nor when the complement has been inactivated or the peritoneal cells have been heat-killed. The phenomenon is age-dependent: the peritoneal cells reach the highest activity when the donor mice are about 10 weeks old. By testing purified populations of lymphocytes and macrophages the cell type responsible for plaque production has been identified as the lymphocyte. Plaque formation is suppressed in the presence of an anti-mouse immunoglobulin serum without any detectable effect on cell viability or anticomplementary action. This suppressive effect is destroyed by prior precipitation of the antiserum with normal mouse serum. A technique which facilitates the study of peritoneal cells from individual mice has been developed and applied to peritoneal cells from Friend virus-infected mice. The activity of peritoneal cells 10 days after intravenous or intraperitoneal infection is similar to that of their uninfected counterparts. Peritoneal cells from mice killed 17 days after intravenous infection or 19 days after intraperitoneal infection form significantly reduced numbers of plaques. The reduced activity is accompanied by a decrease in the percentage of lymphocytes present in the peritoneal population of the infected mice.