TRAIL expression and apoptosis in bats in vivo . Tissue samples were obtained from a previous unpublished HeV infection of P. alecto bats (Australian black flying fox). The expression of CD40 and TRAIL mRNA was compared in (A) kidney and (B) lung and from bats infected with HeV for 36 and 60 hpi compared to uninfected bats. TUNEL staining was also performed on spleen and kidney sections from the experimentally infected and control bats. TUNEL staining of the (C) spleen and (D) kidney of a representative control bat. Arrows highlight TUNEL-positive cells in the spleen. TUNEL staining from a representative HeV-infected bat (60 hpi) showed no increase in the number of TUNEL-positive cells in the (E) spleen and/or (F) kidney compared to the control. Scale bar is 100 μm in all panels.