Factors inhibiting IFN activity.

Several factors may inhibit the activity of IFNs. Some of these occur naturally, others are therapy-induced or artificial. Naturally occurring antibodies appear to have a much broader reactivity than therapy-induced antibodies. Naturally induced antibodies are reported in patients suffering from chronic graft-versus-host disease after bone marrow transplantation. Differences in the reported immunogenicity between interferons may not be due to the minor variation in amino acid sequence. The clinical significance of therapy-induced antibodies has been unclear. In patients treated for chronic hepatitis C, antibody formation is closely related to relapse. In animal studies the efficacy of treatments targeting the IFN receptor interaction has been shown. Soluble IFN-gamma receptor inhibits the development of autoimmune diseases in mice. Monoclonal antibodies to the IFN-alpha receptor protects against allograft rejections in monkeys. Two naturally occurring inhibitors of IFN action were reported. The clinical significance and structure of these inhibitors remain elusive.