ALTERED INTERLEUKIN-2 PRODUCTION BY LYMPHOCYTE POPULATIONS FROM BOVINE LEUKEMIA VIRUS-INFECTED CATTLE

The effects of bovine leukosis virus (BLV) on the phenotypic and funct ional characteristics of peripheral blood mononuclear cells were inves tigated. Whole blood differentials showed that persistently lymphocyto tic (BLV+PL) dairy cattle had more lymphocytes and fewer neutrophils t han the aleukemic seropositive (BLV+AL) or seronegative (BLV-) animals . Flow cytometric analyses of peripheral blood mononuclear cells indic ated that the BLV+PL animals had more B lymphocytes, with a concomitan t decrease in CD2 positive cells when compared with the BLV- group. Mo nonuclear cells from the BLV+AL animals also had fewer CD2 positive ce lls, but no differences in B lymphocytes were observed when compared w ith BLV- cattle. Peripheral blood mononuclear cells were used in blast ogenesis assays to assess the functional ability of lymphocytes. Lymph ocytes from BLV+PL animals had lower proliferative responses to concan avalin A and pokeweed mitogen when compared with cells from the BLV- o r BLV+AL groups. The level of spontaneous blastogenesis in the absence of mitogenic stimulation was high for lymphocytes obtained from BLV+A L cattle. Cultures of lymphocytes obtained from BLV+PL animals produce d greater amounts of interleukin-2 (IL-2) than BLV+AL and BLV- groups, although no differences were observed in the expression of IL-2 recep tors. The development of uncontrolled lymphocytosis in BLV-infected ca ttle may result from an altered responsiveness to IL-2-regulated B-lym phocyte proliferation.