Objective: To determine if, in children with uveitis, antinuclear antibodies (ANA) are associated with antibodies to an uveitogenic peptide of a soluble retinal antigen and to the homologous nuclear antigen, histone 3 (H3). ANA occur in most children with juvenile rheumatoid arthritis (JRA) and associated uveitis. An uveitogenic segment of retinal soluble antigen (S antigen peptide) is homologous with a similarly uveitogenic peptide of H3. We investigated a possible association between ANA positivity, antibodies to H3, and antibodies to the uveitogenic S antigen peptide.
Methods: The sera of 31 children with uveitis (20 of whom had associated JRA) were tested for the presence of ANA by indirect immunofluorescence. Antibodies to H3 and to an uveitogenic peptide of S antigen (an 18 mer segment having the amino acid sequence DTNLASSTIIKEGIDKTV) were measured by enzyme immunoassay.
Results: 19 of 20 children (95%) with JRA and associated uveitis and none of 11 with uveitis not associated with JRA had positive tests for ANA (X2 = 14.97; p < 0.00001). 16 of 19 ANA positive sera from subjects with JRA (84%) displayed reactivity with the chromosomal regions of metaphase cells. 9 of 20 patients with JRA with uveitis (45%) and 2 of 11 patients (18%) with uveitis not associated with JRA had antibodies to H3. Two uveitic patients with JRA (10%) and 2 non-JRA patients with uveitis (18%) reacted with S antigen peptide. Antibodies to H3 occurred significantly more frequently in children with uveitis than in all adult control subjects (X2 = 12.98; p = 0.003) and in adults with uveitis (X2 = 5.62; p = 0.022).
Conclusion: Humoral immune responses to the uveitogenic peptide of S antigen and the homologous H3 antigen appear not to be uniquely important in the immunopathology of uveitis associated with JRA. Antibodies to isolated H3 do not exclusively account for ANA positivity in the uveitic patient with JRA. A unique immunopathogenic mechanism for the development of uveitis associated with JRA is suggested by the observations that (1) children with uveitis associated with JRA are more likely to be ANA positive than children with uveitis not associated with JRA, and (2) children with uveitis associated with JRA are significantly more likely to be ANA positive and to have antibodies to H3 than adults with uveitis.