ELEVATED INTERLEUKIN-6 ACTIVITY IN AQUEOUS-HUMOR OF CATS WITH UVEITIS

The purpose of this study was to assess the role of interleukin 6 (IL- 6) in feline uveitis by measuring IL-6 activity in the serum and aqueo us humor of cats. Serum and aqueous humor was collected from clinicall y normal, random source cats (n = 10); clinically normal, specific-pat hogen free cats experimentally inoculated with Toxoplasma gondii strai n ME49 and sampled sequentially for 20 months (n = 4); and client-owne d cats with uveitis (n = 27). Interleukin 6 activity was measured in e ach sample. Client-owned cats with uveitis were also evaluated for evi dence of present or prior exposure to T. gondii, feline leukemia virus , feline immunodeficiency virus, and feline coronaviruses. Interleukin 6 activity was non-detectable or low in serum from cats of each group . Interleukin 6 activity was not detected in aqueous humor of clinical ly normal cats. Interleukin 6 activity was detected in 22/27 (81.5%) a queous humor samples from cats with uveitis, with a range of 28.9 U ml (-1)-15 702.9 U ml(-1) (mean = 1911.9 U ml(-1), SD = 3946.7 U ml(-1)). Serologic evidence of exposure to T gondii, feline immunodeficiency v irus, feline leukemia virus, or a coronavirus was present in 21/27 (77 .8%) cats with uveitis, Interleukin 6 was detected in the aqueous humo r of 18/21 (85.7%) and 3/6 (50%) of the cats with and without serologi c evidence of exposure to one to the infectious diseases, respectively , Statistically significant increases in mean IL-6 activity in aqueous humor were found for cats with any evidence of infection with T. gond ii, for cats with T. gondii antigen in aqueous humor and for cats with coronavirus antibody titers greater than or equal to 1:100. Aqueous h umor IL-6 activity was greater than corresponding serum IL-6 activity in 21/27 cats. These results show that IL-6 is produced intraocularly in some cats with uveitis and that IL-6 may be a mediator of uveitis i n cats. (C) 1997 Elsevier Science B.V.