Relation of cytosolic calcium to the microbicidal activation of blood monocytes by recombinant gamma interferon.

Oxygen metabolism and calcium ion (Ca++) handling in blood monocytes were greatly affected by treatment with recombinant gamma interferon (rIFN-gamma). Incubating the monocytes with rIFN-gamma resulted in increased basal production of superoxide anion, as well as a significantly enhanced respiratory burst in response to concanavalin A (Con A). A concomitant increase in microbicidal activity against Listeria monocytogenes was observed, and cell membrane permeability to Ca++ was enhanced by treatment with rIFN-gamma. Con A stimulation was also associated with acute rises in cytosolic-free calcium, and these calcium transients were greatly augmented in cells pretreated with rIFN-gamma. The enhanced respiratory burst and the increased calcium transients were completely neutralized by a monoclonal antibody to rIFN-gamma. Furthermore, enhancement of the respiratory burst and calcium transients occurred in a parallel dose-response range for rIFN-gamma. Blocking the intracellular release of calcium into cytosol by TMB-8 abrogated the capacity of rIFN-gamma to enhance the monocyte respiratory burst. Thus, not only was rIFN-gamma treatment of monocytes associated with altered calcium metabolism, but calcium from intracellular pools was essential to the expression of this activated state during Con A stimulation.