The role of divalent cations in interactions between lymphokines and macrophages

The divalent cation requirements of lymphokine-mediated alterations in macrophage function (activation and inhibition of migration) were examined. Normal rabbit alveolar macrophages exposed to incubation supernatants of antigen-stimulated sensitized lymphocytes (lymphokine) were activated, manifested by increased adherence and enhanced bactericidal activity, as compared with control cells. This lymphokine-mediated activation was dependent upon the presence of extracellular Mg²⁺ (but not Ca²⁺). Our data from both current and previous studies suggest that Mg²⁺ influx is necessary for initiation or support of the macrophage activation process. The divalent cation requirements for lymphokine (MIF)-induced inhibition of macrophage migration differed from that of the activation phenomenon. Specifically, both Ca²⁺ and Mg²⁺ were required for expression of MIF activity. Adsorption experiments indicate that these cations are needed for binding of MIF to the macrophage surface.