Clinical and immunological characteristics of cats affected by feline infectious peritonitis

A set of 180 hospitalized or outdoor feline patients was examined for the p resence of antibodies to feline coronavirus (FeCoV) and clinical signs of f eline infectious peritonitis (FIP). The numbers of serologically and clinic ally positive cats were 55 (30.6%) and 35, respectively. The effusive and n oneffusive forms of FIP were diagnosed in 24 and 11 animals, respectively. The most apparent signs, irrespective of the form of infection, included an orexia, lethargy, ischemic mucosae, and undernutrition. Hematological and i mmunological profiles of 14 FIP patients were compared with those found in a control group of 36 clinically normal and FeCoV-negative animals. A signi ficant increase in the number of neutrophilic granulocytes was observed in the FIP patients FIV-/FeLV-cats with effusive form) and a significant decre ase in the number of lymphocytes were observed in the FIP patients. Eosinop enia was also found in patients affected by the effusive form. No alteratio n of the phagocytic activity (ingestion of particles, chemiluminiscence) du e to FIP was demonstrable. The blastic transformation test (stimulation wit h Con A, PHA, or PWM) showed a marked decrease in the activity of lymphocyt es in the FLP patients. Concentrations of immunoglobulins and circulating i mmune complexes were increased in the affected animals. The expression of t he lymphocyte surface antigens CD4, CD5, CD8, and CD21 was studied in a sel ected subgroup of the patients using flow cytometry. The results indicate a n impairment of the activity of the immune system due to FIP. Therefore, tr eatment of FIP with immunosuppressive drugs is considered inappropriate.