BACKGROUND: Phagocytes (polymorphonuclear cells and monocyte-macrophages)are the first line of defence of the host against infectious microorganisms and other foreign antigens.Agents which participate in activation of phagocytic cells possess a potential immunomodulating action.Thus, search for convenient in vitro test-systems and study of mechanisms of action of these agents areof practical interest.
MATERIAL AND METHODS: Human blood polymorphonuclear (PMN) cells and murine macrophages(line J774.2) were used as cellular test-systems for study of phagocytosis-stimulating action of immunomodulatingagents. Indexes of phagocytic activity were estimated by the phagocyte ingestion of yeast cells. NO-synthaseactivity, nitrite production, and nitroblue tetrazolium test were determined after phagocyte stimulation.
RESULTS: It was revealed that indexes of phagocytic activity can be used as quantitative indicators formeasurement immunomodulating activity. Zymosan A-induced phagocytosis in almost 100% PMN cells and macrophagesand thus can be used as a positive control. Wheat germ agglutinin (WGA, 0.5-1.0 microg/ml) stimulatedphagocytosis in PMN cells 1.8 times after 2-3 h incubation, although in higher concentrations (5-10 microg/ml)it strongly inhibited phagocytosis. TGF-b1 (10 ng/ml) suppressed phagocytosis in WGA-stimulated PMN cells.Mistletoe agglutinin-1 stimulated phagocytosis in PMN cells, although its effect in macrophages was weak,while concanavalin A stimulation of phagocytosis in macrophages was well expressed. Vasodilating peptidebradykinin increased phagocytosis 2.5 times in macrophages. We did not reveal changes in NO-synthaseactivity and nitrite production in macrophages and PMN cells activated by different immunomodulatig agents.Only lipopolysacharide stimulated such activity in macrophages.
CONCLUSIONS: Cultured macrophages andPMN cells can provide reproducible quantitative results in screening phagocytic activity of differentimmunomodulating agents. Both positively and negatively acting immunomodulators might be studied usingthese test cells.

Keywords: human polymorphonuclear cells, murine macrophages, Phagocytosis, Lectins, TGF-b1, bradykinin, Nitric Oxide