Modulation by gamma interferon of antiviral cell-mediated immune responses in vivo.

Mice were infected with lymphocytic choriomeningitis virus and injected once 24 h later with a monoclonal antibody directed against gamma interferon. In comparison with controls, the increase of numbers of CD8+ T cells and the generation of virus-specific cytotoxic T lymphocytes in spleens and virus clearance from organs were diminished, as was the ability of spleen cells to transmit adoptive immunity to infected recipients. The same treatment slightly but consistently lessened rather than augmented the virus titers early in infection, which was also observed in thymusless nu/nu mice. Injection into infected mice of the lymphokine itself in quantities probably higher than are produced endogenously resulted in lower virus titers in spleens but higher titers in livers. The adoptive immunity in infected mice achieved by infusion of immune spleen cells was not altered by treating the recipients with gamma interferon monoclonal antibody. Such treatment did not measurably affect the production of antiviral serum antibodies. We conclude that in lymphocytic choriomeningitis virus-infected mice, gamma interferon is needed for the generation of antivirally active CD8+ T lymphocytes, and furthermore that in this experimental model, direct antiviral effects of the lymphokine elude detection.