IDENTIFICATION OF MONONUCLEAR PHAGOCYTES BY INGESTION OF PARTICULATE MATERIALS, SUCH AS ERYTHROCYTES, CARBON, ZYMOSAN, OR LATEX

This chapter discusses the identification of mononuclear phagocytes by the ingestion of participate materials, such as erythrocytes, carbon, zymosan, or latex. Mononuclear phagocytes are generally less avidly phagocytic when in suspension, especially if particles do not bind strongly to their surfaces. In addition to increasing the efficiency with which uptake occurs, by forming a monolayer, one enriches for mononuclear phagocytes and other adherent cells, eliminates loss of adherent cells from suspensions during incubation steps, and facilitates the removal of uningested particles after incubation has been completed. The principal problem with carbon particles centers on their tendency to obscure the cells with which they are associated. Neutrophils engulf this material and, when engorged with it, can be indistinguishable from mononuclear phagocytes that are similarly filled. If neutrophils contaminate the monolayer, it is essential that the result with carbon be interpreted as indicative of the total number of phagocytic cells in the monolayer.