This study was done in an attempt to elucidate some of the properties of bovine IFNs. Maximum levels of both fibroblast and leukocyte IFNs occurred prior to 24 h whereas maximum levels of immune IFN were not reached until after 72 h. The latter species of IFN was unstable at either pH 2 or 56 degrees C whereas both the fibroblast and leukocyte IFNs were more stable under these conditions. Studies of cross-species protection between fibroblast and leukocyte IFNs indicate that the former was more protective for other species than the latter.

Partially purified murine immune interferon (IFNγ) was found to be equivalent to IFNα/β in its ability to enhance the production of IFNα/β by L-929 cells. While crude preparations were also able to prime, it was apparent that such preparations of IFN contained ‘blocking factors’ that reduced the priming efficiency of IFN. Exposing IFNγ to heat, low pH or its specific antibody readily destroyed its ability to prime, providing evidence that IFNγ itself was responsible for priming.

Five murine interferon preparations were compared for their antiviral action on 10 heterologous cell types. Immune interferon preparations induced by either BCG/old tuberculin in vivo or concanavalin A in vitro exhibited some protection on porcine, monkey and rat cells. This was also noted with interferon induced by polyriboinosinic acid: polyribocytidylic acid (poly I:C) in spleen cells. Interferons induced by poly I:C in vivo or in L-929 cells did not protect these three cell types. All three preparations induced by poly I:C showed some activity on guinea pig cells, but this was not the case with either immune interferon preparation. None of the five preparations exhibited any measurable activity on human, bovine, chick, or rabbit cells.

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