Homogenates of bovine iris were fractionated by gel filtration chromatography, and the column-eluted proteins were probed with pooled sera obtained from patients with pauciarticular juvenile rheumatoid arthritis (JRA). The serum pool prepared from patients with pauciarticular JRA and a history of anterior uveitis, but not from those without the eye disease, contained IgG antibodies which bound a low molecular weight iris antigen (LMW-IA) as measured by a modified ELISA. LMW-IA was protease-sensitive and contained at least four proteins of approximate molecular weights of 16, 13, 9 and 6.5 kD with no uronic acid or carbohydrate. Analysis of individual patient sera for IgG anti-LMW-IA antibody demonstrated that 1/20 (5) pediatric non-rheumatic disease controls (NRDC), 1/19 (5.3) non-uveitic pauciarticular JRA patients and 6/21 (28.6) uveitic pauciarticular JRA patients were positive by ELISA. Levels of anti-LMW-IA antibody did not correlate with serum IgG concentration, the presence of IgG antibody to soluble retinal S antigen (S antigen) or reactivity to the low molecular weight fraction of bovine choroid (LMW-C). Ten of 21 (47.6) children with pauciarticular JRA and uveitis had serum antibody that reacted with LMW-IA and/or retinal S antigen as compared to 1/20 (5) NRDC patients and 3/19 (15.8) patients with pauciarticular JRA uncomplicated by uveitis. Analysis of patient immunoreactivity to proteins of the anterior uveal tract may provide a greater understanding of pathogenic features related to arthritis-associated eye disease.
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