Lymphokines. II. Use of horse monocytes as indicator cells for human MIF

Peritoneal exudate macrophages in guinea pigs and peripheral blood monocytes in man are the most readily available cells sensitive to the migration-inhibiting factor(s) (MIF) induced by tuberculin or insoluble concanavalin A in supernatants of stimulated lymphocyte cultures. The scarcity of MIF-sensitive cells is probably the main reason for the unsatisfactory results obtained with direct and indirect MIF tests when using white blood cells as indicator cells. Isolated horse monocytes represent an alternative sensitive source of indicator cells for human MIF assays, whereas guinea pig peritoneal exudate macrophages appear to be less sensitive and to show large individual variations in sensitivity to human MIF. The species specificity of MIF from various origins shows various patterns and is briefly discussed.