Changes in B cell and T cell subsets in bovine leukaemia virus-infected cattle

Direct immunofluorescence and fluorescence-activated cell sorter techniques were used for the detection of surface immunoglobulin positive (SIg) cells in peripheral blood lymphocytes (PBL's) of bovine leukaemia virus (BLV) infected cattle with or without persistent lymphocytosis (PL, PL) and in BLV-free cattle. The percentage of SIg cells was more than twice as high in BLVPL cattle than in BLV-free and BLVPL cattle. Bovine T cells, and T cell subsets were identified indirectly by the same techniques using three monoclonal antibodies (MAb's) specific for all T cells (IL-A43), T helper (BoT4) cells (IL-A12) and T cytotoxic (BoT8) cells (IL-A17). The major histocompatibility complex (MHC) determinants of both class II (BoT4) and class I (BoT8) as well as all T cells were significantly reduced in BLVPL compared to BLV-free cattle. The actual decrease in the BoT8 cell subset or the dilution effect that would change effector: target cell ratio suggests that a resultant decrease in cytotoxic activity in BLVPL cattle may play an important role in the progress of BLV infection in cattle