Haemolytic activity of mouse peritoneal exudate cells in vitro.

Mouse peritoneal exudate cells, and to a lesser degree spleen cells, can cause haemolysis of both syngeneic and allogeneic mouse red blood cells whereas lymph node and tumour cells are ineffective. The reaction was clearly detectable after 0.5–1 hour, and is usually complete after 5–6 hours at 37°. An analogous reaction was found also with sheep red blood cell targets, but haemolysis was weaker and a significant effect was not obtained until 24 hours later. The degree of haemolysis did not increase after the addition of complement. Hemolysis was not potentiated when specifically sensitized cells were employed or when PHA was present. Viability and active metabolism of the PE cell was essential for haemolysis. Only red blood cells were affected by the PE cells, nucleated target tumour cells being resistant. It was concluded that macrophages were responsible for haemolysis, which was not mediated by antibody and complement, but represented an active macrophage reaction unrelated to previously known mechanisms of haemolysis .