Lymphokine-induced macrophage aggregation: studies on the involvement of Mg2+.

The divalent cation requirements of lymphokine (LK)-induced macrophage aggregation have been investigated using a quantitative assay. It has been shown that LK-induced aggregation is dependent on exogenous Mg2+ but not Ca2+. By contrast, aggregation induced ty the ionophore A23187 is dependent on exogenous Ca2+ and Mg2+. Furthermore, exogenous Mg2+, at 0.5-5.0 mmol, both mimics the aggregation effects of LK and stimulates LK-induced aggregation. Additionally, both chlorpromazine and trifluoperazine inhibited aggregation indiced by LK, A23187, and exogenous Mg2+. Similarly, prostaglandin (PG)E2 inhibited, and indomethacin (10 micro M) stimulated, aggregation induced by these three agents. These results are discussed in the context of the mode of action of macrophage aggregating factor (MAgF).