In vitro phagocytosis and catabolism of opsonized erythrocytes by human monocytes.

Mononuclear phagocytes play a role in immunologic phenomena as well as in the defense reactions of the organism. Therefore, clinicians should have at their disposal methods of evaluating their function. A simple and reproducible method was set up to evaluate mononuclear phagocytosis and catabolism. The test described in this paper is performed using peripheral monocytes. Mononuclear phagocytes were incubated with opsonized Cr51-labelled sheep erythrocytes. The mononuclear cells phagocytosed the opsonized erythrocytes, and any remaining red cells were lysed. The degree of phagocytosis was determined by the intensity of radioactivity within the monocytes. Catabolism was determined by measuring the amount of radioactive waste excreted by the phagocyte after 18 hours incubation. Thus, this method evaluates the afferent limb of the immune response, as well as the capacity of mononuclear phagocytes to remove and destroy foreign material. Levels of phagocyte catabolism, measured in 30 normal subjects, did not vary appreciably neither in the autologous or homologous serum, nor in the presence or absence of complement.