Immunological functions of macrophages and their regulation by interferons.

Important progress has been recently made on the identification, physico-chemical properties, purification and production by recombinant technology of a series of immunoregulatory mediators, including interferons (IFNs). It is now possible to appreciate which part play IFNs in the regulation and activation of monocyte-macrophage (MO) functions. The present review discusses old concepts, such as Macrophage-Activating Factor (MAF) activity, at the light of recent data on the effects of IFN alpha, beta and gamma on four main immunological properties of MO, namely intracellular killing of microorganisms, non specific lysis of tumor cells, antigen presentation and secretion of soluble immunoregulatories molecules such as interleukin 1. All three IFN species enhance such functions, whereas enhancement of membrane class II major histocompatibility complex antigens is a unique property of IFN gamma. The role of IFNs, especially IFN gamma, as major MAF in vitro and in vivo is discussed.