Use of serum-free, compositionally defined medium for analysis of macrophage differentiation in vitro

Macrophage differentiation is mediated by the action of a variety of environmental signals, such as cytokines and endotoxin. For in vitro analysis of macrophage differentiation, most studies utilize a basal tissue culture medium supplemented with fetal calf serum (FCS). As the composition of specific components within FCS varies enormously from lot to lot, one can never be certain that the differentiative effects observed in vitro are attributable solely to the exogenous signals provided to the cultures. In this study, primary macrophages were cultured in a basal medium supplemented either with FCS or a compositionally defined supplement, HL-1, and a spectrum of differentiative functions (i.e., induction of antiviral activity, Fc receptor-mediated phagocytosis, Ia antigen expression, and tumoricidal activity) were measured following stimulation with exogenous signals. The results indicate that the use of serum-free, defined media may provide an important approach to dissect and characterize the differentiative signals which are operative in macrophage activation.