Interleukin 1 alpha mRNA-expressing cells on the local inflammatory response in feline infectious peritonitis

By in situ hybridization with biotinylated human interleukin 1 alpha (IL-1 alpha) cDNA probe, distribution of feline IL-1 alpha mRNA-expressing cells was examined in the tissues from 49 cases diagnosed as feline infectious peritonitis (FIP) by pathological examination. IL-1 alpha mRNA-expressing cells were found in visceral peritoneum, lymphoid organs, liver, kidney, pancreas, digestive tract, lung, pleura, brain, palpebral conjunctiva, and bone marrow. Hybridization signals for IL-1 alpha mRNA were mostly located in the local inflammatory lesions on the serosal surface of various organs and omentum, which were frequently involved in the lesions of FIP (27.8 +/- 5.1 cells/mm2). Morphological examination suggested that they were infiltrated macrophages. However, few IL-1 alpha mRNA-expressing macrophages were in the lesions of other organs. These data suggested that IL-1 alpha produced from macrophages in the local inflammatory sites might participate in the initiation and development of the lesions on the visceral peritoneum in FIP.