Effects of oral administration of type I interferon on adjuvant arthritis in rats.

We investigated the effects of oral administration of type I interferon (IFN) on adjuvant arthritis (AA) in rats that was induced by immunization with Mycobacterium tuberculosis (MT). The results showed that the oral administration of IFN before immunization with MT significantly suppressed the development of AA. Both delayed type hypersensitivity and proliferation of lymph node cells to MT in vitro were also downregulated by the cytokine. In contrast, when IFN was orally given after the onset of AA, neither the progression of the disease nor the proliferation of T cells to MT was affected by the material. These data suggest that IFN is active by the oral route and has an inhibitory effect on an early T cell activation event.