Immunohistochemical studies on meningoencephalitis in feline infectious peritonitis (FIP)

WANG, Huanan; HIRABAYASHI, Miyuki; CHAMBERS, James K.; UCHIDA, Kazuyuki; NAKAYAMA, Hiroyuki

In three cases (Case Nos. 1 to 3), the majority of inflammatory cells was CD204-and/or Iba1-positive macrophages and a moderate number of CD20-positive B lymphocytes accumulated around the glia limitans adjacent to the inflammatory foci. On the contrary, in Case No. 4, the majority of the inflammatory cells was CD20-positive B lymphocytes and moderate to severe diffuse GFAP-positive astrogliosis in the subventricular lesions was also observed adjacent to inflammatory foci. Similar astrocytic response together with microglial reaction have been reported also in previous FIP cases [12] . In a previous study on FIP, it was reported that viral antigens were detected in macrophage dominant lesions, and B lymphocytes and plasma cells which were positive for coronavirus-specific antibodies were observed as bands around or the basal side of the lesion. On the other hand, viral antigens were rarely detected in B lymphocytes and plasma cells dominant lesions. B lymphocytes and plasma cells are considered to induce FIP virus-specific immune responses and be replaced by macrophages [8, 9] .