The presence of isoenzymes in monocytes and macrophages

The present paper gives a review of enzyme polymorphism found in individual human blood cells with special reference to human blood monocytes. Evidence is presented indicating that not only different blood cells but also their descendants are characterized by certain constellation of isoenzymes. Considering the typical polymorphism of acid phosphatase (EC 3.1.3.2) and acid esterase (EC 3.1.1.6), we could show that a reliable biochemical marker for blood monocytes can be worked out, which is also detectable in peritoneal and alveolar macrophages as well as epithelioid cells. In different examples we could demonstrate that the isoenzyme patterns of blood monocytes can be modified into that of peritoneal and alveolar macrophages by different stimulation procedures in vitro. Studying the enzyme variants in blood monocytes and different tissue macrophages, additional criteria have been collected, which document the monocytic origin and homogeneity of the human mononuclear-phagocytic system.