Immunomodulatory action of double-stranded RNA in unirradiated and irradiated mice.

Double-stranded RNA (ds RNA) stimulates the regional graft-versus-host reaction (GVHR) in mice irradiated with 3 Gy or 5 Gy (but not 7 Gy) of gamma-rays; in control animals GVHR is not influenced. Sensitization of animals to delayed-type hypersensitivity (DTH) reaction is suppressed by ds RNA in both irradiated and unirradiated mice. In the antibody formation to sheep and blood cells (SRBC) ds RNA given before immunization inhibits the switch of IgM to IgG. When injected simultaneously with or after immunization, ds RNA markedly stimulates antibody formation. The differences in the influence of ds RNA on individual immune reactions can be explained by its different action on the regulatory mechanisms.