Abstract
Further evidence is presented of the coordinate production and similar properties of two mediators, migration inhibitory factor (MIF) and interferon, in the circulation of BCG-infected mice inoculated with specific antigen (Old Tuberculin, OT). In addition, the interferon elicited by OT in BCG-infected mice is shown to be a distinct molecular species of viral inhibitor and is designated “Type II interferon.” The designation “Type I interferon” is used to describe the viral inhibitor produced in BCG-infected or control mice given nonspecific stimuli such as bacterial lipopolysaccharide (LPS) or Newcastle disease virus (NDV). Although Type II interferon possesses the biologic attributes required to classify a viral inhibitor as “interferon,” it, as well as MIF, differs markedly from Type I interferon in stability at pH 2 and at 56°C, range of species specificity, and antigenicity. Antibodies against highly purified L cell interferon induced by NDV (anti-Type I interferon antibodies) neutralize the activity of interferons elicited in mice by nonspecific stimuli such as LPS or NDV. In contrast, the antiviral activity of Type II interferon and the macrophage-inhibitory activity of MIF, elicited by specific antigen in mice with delayed hypersensitivity, are not affected by high concentrations of antibody against Type I interferon. Evidence is presented which emphasizes the striking similarities in properties of MIF and Type II interferon, although it is not possible to determine whether the two mediators are the same or different protein molecules.
