Abstract
The interaction of Pneumocystis carinii purified from rat lungs with rat peritoneal macrophages and human circulating polymorphonuclear leucocytes was studied by amplified chemiluminescence and examination of stained cytospin preparations. A polyclonal rat antiserum to P. carinii was opsonic with both types of phagocyte. Complement had no opsonic properties alone but produced a synergic effect in combination with antibody.