Immunocytochemical demonstration of rabbit ribonuclease and phospholipase A₂ by the peroxidase-antiperoxidase technique in professional phagocytes (pulmonary alveolar macrophages and granulocytic and mononuclear peritoneal exudate cells) and in glycol methacrylate sections of dermal tuberculous (BCG) lesions

ACID-acting (pH 6-7) (presumably lysosomal) ribonuclease and neutral-acting (pH 7-8) calcium-dependent phospholipase A2 (presumably the enzyme releasing arachidonic acid from membrane phospholipids) were demonstrated by the peroxidase-antiperoxidase (PAP) immunocytochemical technique in rabbit professional phagocytes: pulmonary alveolar macrophages (AM), oil-induced peritoneal exudate macrophages (Mφ) and glycogen-induced peritoneal exudate polymorphonuclear granulocytes (PMN). All three cell types stained positively with antisera to purified rabbit lung RNase and purified rabbit granulocyte phospholipase A₂. The RNase and phospholipase A₂ were also demonstrated by the PAP technique in the activated macrophages and granulocytes present in tissue sections of tuberculous (BCG) lesions. The intensity of staining of these two enzymes in individual macrophages did not change appreciably as the BCG lesions developed and regressed, but there were more macrophages rich in both enzymes when the lesions reached their peak size at 21 days. When the anti-RNase serum was fractionated by immunoabsorbent chromatography, the anti-δ RNase serum fraction stained exudate Mφ and PMN better than AM; and the anti-β RNase fraction stained AM better than Mφ and PMN. Similar to isolated phagocytes, tissue granulocytes stained best with the anti-δ fraction; and activated tissue macrophages stained best with the anti-β fraction. Thus, macrophages and granulocytes contain two types of RNase, β and δ; and the β RNase is associated with macrophage activation.