Proinflammatory cytokines induce lymphocyte apoptosis in acute African swine fever infection

Twenty-one pigs inoculated with a highly virulent isolate (E70) of African swine fever (ASF) virus were killed 1-7 days later; a further three animals served as uninfected controls. An early increase in TNF-α, IL-1α, IL-1β and IL-6 expression was detected in lymphoid organs from infected animals, together with an increase in the serum concentrations of TNF-α and IL-1β. These changes were accompanied by increased apoptosis of lymphocytes, and the presence of infected and uninfected macrophages showing changes indicative of secretory and phagocytic activation. The present study demonstrated an increase in the number of macrophages expressing TNF-α, IL-1 and IL-6 in proximity to lymphocytes undergoing apoptosis, supporting previous suggestions that in acute ASF proinflammatory cytokines induce lymphocyte apoptosis.