[Interferons and their effects]

The interferon system is an integral part of the defense system of the body, mediating a large variety of biologic effects. Presently, three groups of interferons (IFN) are known: IFN alpha, IFN beta and IFN gamma. IFN alpha and IFN beta show homology on the nucleotide level of about 40-50%, and both IFNs bind to a common receptor. IFN alpha and IFN beta are produced after induction by leukocytes and fibroblasts. IFN gamma is, by definition, not only an interferon but also a lymphokine, since it is a product exclusively of lymphocytes. There is no homology on the nucleotide level between IFN gamma and IFN alpha/beta. Furthermore, the receptor of IFN gamma is different from the receptor of IFN alpha/beta. IFNs are defined by their antiviral activity directed against a large number of different viruses. The target of IFN is the cell rather than the virus itself. Through binding on the cell surface and subsequent activation of specific genes IFNs induce an antiviral state which makes cells less permissive for virus replication. The antiviral state consists of various antiviral mechanisms. Among the non-antiviral effects of IFNs are the effects on cellular components of the immune system. Thus, one has postulated a role for interferons as immunoregulatory molecules. Interferons augment the expression of MHC-genes of which IFN alpha/beta only affect the molecules of class I, whereas IFN gamma affects both the molecules of class I and class II. Moreover, all IFNs increase the activity of macrophages and NK cells. Possibly the activation of components of the immune system is in part responsible for the antitumor effects of interferon.(ABSTRACT TRUNCATED AT 250 WORDS)