The physiological interferon response. V. Antiviral activity present in rat lymph is neutralized by anti-mouse interferon-gamma antibodies

By neutralization tests using anti-rat and mouse interferon (IFN) antibodies, we tested whether the antiviral activity present in abdominal lymph but absent in plasma of healthy rats, could be ascribed to IFN. Antimouse IFN-gamma antibodies neutralized the inhibitor completely while anti-rat IFN-alpha/beta antibodies did not. We conclude that rat lymph contains traces of IFN-gamma and that the antiviral activity is not due to low-density lipoproteins, immunoglobulins, or to cell-produced viral inhibitors. This finding extends previous observations on rabbit lymph and further supports the existence of a physiological low-level interferon response.