Autoimmunity plays an important role in the development of uveitis. The uveitis are linked to Th1 or Th2 lymphocyte activation. We studied 41 patients with uveitis, divided into autoimmune uveitis (n = 32) and infectious uveitis (n = 9), 30 normal controls, and 20 asthmatic atopic without ocular diseases. The infectious uveitis patients were separated into bacterial (n = 6) and toxoplasmic (n = 3) retinochoroiditis. We measured IgE and sCD23 serum levels and specific IgG and IgE to retinal S antigen by ELISA tests. The IgE levels were 500 +/- 325 kU/L in autoimmune uveitis, 57 +/- 35 kU/L in bacterial uveitis, 280 +/- 38 kU/L in toxoplasmic retinochoroiditis, 75 +/- 32 kU/L in the controls, and 557 +/- 243 kU/L in atopics (P < 0.0005). The sCD23 levels were 10.4 +/- 5.4 ng/ml in autoimmune uveitis, 3.7 +/- 1.17 ng/ml in bacterial uveitis, 6.76 +/- 1.36 ng/ml in toxoplasmic retinochoroiditis, 3.4 +/- 1 ng/ml in controls, and 8.35 +/- 2.2 ng/ml in atopic patients (P < 0.005). The specific IgG to retinal S antigen was positive in 27 of 32 cases, and the specific IgE to retinal S antigen was positive in 22 of 32 autoimmune uveitis. The bacterial uveitis patients as well as the controls were negative for both autoantibodies to retinal S antigen. The toxoplasmic retinochoroiditis patients presented specific IgG and IgE to retinal S antigen in two of three cases, respectively, one of them with overlap of both antibodies. These results suggest the importance of specific IgG and IgE to retinal S antigen in autoimmune uveitis, which, along with higher IgE and sCD23 levels, reveal Th2 activation.