Induction of cyclo-oxygenase-2 by acute liver allograft rejection and cytomegalovirus infection in the rat.

Cytomegalovirus (CMV) infection has been shown to increase inflammation in rat liver allografts. In-vitro CMV has been shown to transactivate cyclo-oxygenase-2 (COX-2), while COX-2 plays a role in the CMV replication cycle. Our aim was to investigate the expression of COX-2 in liver allograft rejection and concomitant CMV infection. Expression of COX-2 was studied immunohistologically in rat liver allografts with or without rat CMV infection, in isografts, and in normal rat liver. There were small amounts of COX-2-positive mononuclear inflammatory cells in the normal liver and isografts. Acute rejection increased the amount of COX-2-expressing cells in the portal areas only, whereas concomitant CMV infection did this also in the sinusoid area. COX-2 may play a role in CMV infection in vivo as well. The possible role of COX-2 in the association between CMV infection and allograft rejection warrants further study.