Enhanced B-lymphocyte expression of IL-2R alpha associated with T lymphocytosis in BLV-infected persistently lymphocytotic cows.

Peripheral blood lymphocytes from bovine leukemia virus (BLV)-negative and BLV-infected, aleukemic cows with persistent lymphocytosis were evaluated for expression of B and T lymphocyte subset-specific molecules and co-expression of the interleukin-2 receptor alpha (IL-2R alpha) molecule. Results demonstrate enhanced mitogen-induced expression of the IL-2R alpha molecule on B lymphocytes from BLV-infected, lymphocytotic cows. Lymphocyte subset analyses further demonstrate that BLV-infected, lymphocytotic cows are not only characterized by sustained elevations in CD5+ B lymphocytes, but also show significantly elevated numbers of CD3+, CD4+, and CD8+ T lymphocytes. These results provide evidence suggesting that B lymphocytes from BLV-infected, lymphocytotic cows are more sensitive to activation signals and up-regulation of the IL-2 signaling pathway than lymphocytes from clinically normal BLV-free cows, and that T lymphocytes may be involved in the aberrant regulatory pathways underlying BLV-induced persistent B lymphocytosis.