Tumor necrosis factor alpha and its receptors in experimentally bovine leukemia virus-infected sheep

To examine whether tumor necrosis factor alpha (TNF alpha) contributes to t he pathogenesis of bovine leukemia virus (BLV) infection, the mRNA expressi on patterns of TNF alpha and its receptors, type I (TNF RI) and type 2 (TNF R2) were investigated. Sheep inoculated with BLV were divided into two gro ups: one was BLV-positive and the other BLV-negative based on the detection in peripheral blood mononuclear cells (PBMC). Expression of TNF R1 mRNA wa s down-regulated in PBMC from the BLV-positive compared to BLV-negative she ep. No difference was shown in the expression levels of TNF R2 mRNA between the two groups, Furthermore, proliferative responses of PBMC in the presen ce of TNF alpha were observed from the BLV-positive, but not BLV-negative s heep. Membrane-bound TNF alpha (mTNF alpha) is thought to be one of the lig ands, inducing B-cell activation. Flow cytometric analysis demonstrated tha t the number of PBMC that were positive for mTNF alpha expression, was incr eased in the BLV-positive sheep. Thus, the expression of TNF alpha and its receptors may be closely associated with lymphocytosis induced by BLV. (C) 2001 Elsevier Science B.V, All rights reserved.