An in vitro assay for the quantitation of phagocytic cells of different anatomic origin.

The survival of peritoneal exudate macrophages after 3 to 10 days in culture was examined by measuring the numbers of phagocytes per culture. This was determined by letting the cultured cells phagocytize Latex particles. The number of Latex particle-containing cells was taken as a measure of the survival of phagocytes. It was found that one tenth of the cells judged by light microscopy as macrophage-like survived the culture period. Thus, the calculated plating factor of 9.3 was used to estimate the actual number of macrophages in suspensions of spleen, lymph node or thymus cells by culturing these cells and subsequently counting Latex particle-containing cells. In addition, the acridine orange technique was used to determine actual numbers of macrophages in freshly prepared cell suspensions of lymphoid organs. Latex studies on spleen and thymus cells gave results correlating well with data obtained by the acridine orange technique. By contrast, many more acridine orange positive cells than phagocytizing cells were found when lymph node cells were cultured.