Expression of tumor necrosis factor-α in IgM+ B-cells from bovine leukemia virus-infected lymphocytotic sheep

Tumor necrosis factor (TNF)-α is thought to be one of the cytokines that account for bovine leukemia virus (BLV)-induced B-cell lymphoproliferative disorder, however, information on TNF-α expression in B-cells is limited. In this study, the expression of TNF-α in IgM+ B-cells from BLV-infected sheep with or without lymphocytosis was determined. Freshly isolated IgM+ B-cells from three sheep with lymphocytosis constitutively transcribed TNF-α mRNA. Although TNF-α mRNA expression in IgM+ B-cells was transiently up-regulated after cell culture, TNF-α mRNA expression was markedly higher in lymphocytotic sheep when compared to that of non-lymphocytotic sheep or uninfected sheep. Expression of membrane-bound TNF-α on IgM+ B-cells was also augmented in lymphocytotic sheep. TNF-α expression in lymphocytotic sheep may support the proliferation of B-cells.