Role of thymus-dependent lymphocytes and antibodies in feline infectious peritonitis after oral infection.

Sero-negative kittens were inoculated intragastrically with feline infectious peritonitis (FIP) virus after thymectomy and/or treating with immune serum or immune ascites against FIP virus. At necropsy performed 10 days postinoculation, thymectomized kittens showed severer intestinal lesions than did non-treated controls. The kittens that had received high-titered serum or ascites with or without thymectomy were found to have fibrinous peritonitis. Peritonitis was severer in the thymectomized and antibody-treated kittens. The results suggest that the virus caused damage to the thymus-dependent lymphocytes and that the humoral antibody played some role in inducing serositis as well as parenchymatous organ lesions.