Alterations in lymphocyte subpopulations in peripheral blood of sheep persistently infected with border disease virus.

Fourteen sheep persistently infected with border disease virus were investigated to examine the effects of persistent viraemia on lymphocyte subpopulations in peripheral blood and their responses to the mitogen phytohaemagglutinin (PHA) in vitro. Persistently infected sheep had significantly more CD8+ (cytotoxic-suppressor) T-lymphocytes than uninfected sheep of the same age (P less than 0.001). The total number of CD4+ (helper) T-lymphocytes were not significantly different but there were more T-lymphocytes (CD5+) which were CD4- and CD8- in normal sheep than persistently infected sheep (P less than 0.001). Peripheral lymphocytes obtained from persistently infected sheep showed significantly reduced blastogenesis induced by PHA than those obtained from normal sheep (P less than 0.001).