Detection of different macrophage‐activating factor and interferon activities in supernatants of chicken lymphocyte cultures1

Chicken spleen lymphocytes were cultivated under various conditions in order to produce and characterise functionally avian lymphokines. Biological properties of lymphokine-containing culture supernatants were evaluated with regard to their antiviral activity and their effects on cultured bone marrow-derived chicken macrophages, including induction of cytostatic activity, enhancement of phagocytic activity towards vital Candida albicans, and giant cell formation. Optimal doses of concanavalin A (ConA) for stimulation of lymphocytes varied between 2.5 and 40 microg/ml, depending on the cell concentration and presence or absence of serum. Lymphokine production occurred even without exogenous mitogen stimulation when cells were cultured at sufficiently high concentrations (1 to 2 x 10(7) cells/ml). Cytostasis-inducing capacity of lymphokine preparations against lymphoblastoid MDCC-RP1 cells was always combined with the presence of antiviral activity. Experimental results suggested that these two activities had to be attributed to at least two distinct lymphokines, i.e. macrophage-activating factor and interferon (IFN). ConA stimulation of lymphocytes from a single donor appeared to be the appropriate signal for production of IFN-gamma. Endogenous stimulation in mixed lymphocyte cultures more appropriately triggered production of IFN-alpha or IFN-ss, although production of IFN-gamma was not completely suppressed. Phagocytic activity of macrophages could also be increased by a cytokine present in conditioned media from confluent cultures of chicken embryo fibroblasts, chicken kidney cells, or bone marrow-derived chicken macrophages. In lymphokine preparations, this mediator may-even be a cofactor necessary for induction of multinucleated giant cell formation of cultured macrophages.