Increase in γδ T cells in the blood of cattle persistently infected with Bovine Leukemia Virus following administration of recombinant bovine IFN-γ

To examine the effect of recombinant bovine interferon-γ (rbIFN-γ) on cattle persistently infected with bovine leukemia virus (BLV), BLV-infected cattle were inoculated intraperitoneally with IFN-γ. All cattle were febrile after inoculation with IFN-γ and then recovered within 48 h. Flow cytometric analysis showed that the numbers of CD4+ and CD8+ T cells were decreased for 2–3 days and then their numbers were recovered. The number of γδ T cells increased after the fever. In contrast, the number of IgM+ lymphocytes remained low for about 1 week. Moreover, the numbers of syncytia produced by peripheral blood lymphocytes decreased and remained low compared to that before IFN-γ administration. These results suggest that IFN-γ induces the up-regulation of γδ T cells, decreases the number of IgM+ lymphocytes and suppresses the growth of BLV in BLV-infected cattle in vivo.