Immunological nature of the inhibition of BLV-induced early polykaryocytosis by bovine sera.

A quantitative in vitro assay (EPI) was developed for the serological detection of bovine leukemia virus (BLV) infection in cattle. Positive sera inhibit early polykaryocytosis (EP) induced by BLV. We report herein experiments which demonstrate that BLV-induced antibodies are responsible for this inhibition. Serum fractionation by gel filtration and affinity chromatography indicate that EP-inhibiting activity is mediated only by immunoglobulins of the IgG class. Furthermore, on the basis of their ion-exchange chromatographic behaviour, these antibodies were classified as IgG1. We also ruled out the participation in the EP inhibition reaction of the other compounds such as polypeptides, including serum complement and interferon or DNA and RNA. These results demonstrate that EP inhibition by bovine sera is specific to BLV-induced antibodies.