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SUMMARY In a group of 46 patients with retinitis pigmentosa (RP) we studied the presence of circulating immune complexes (CIC) and the alterations in the complement system. Our results showed the presence of CIC in 43.5% of the patients studied, reduced levels of the complement components C3 and C4 (p<0-001), and of the haemolytic activity CH50 (p<0-001) when compared with a control group consisting of a 100 healthy subjects. We found a statistically significant correlation between the values of C3 and CIC (p<0-01), C4 and CIC (p<0.01), and between CH50 and CIC (p<0-001). These findings indicate that the CIC may play a role in the pathogenesis of primary retinitis pigmentosa.

SUMMARYAdenosine deaminase (ADA) expression on the surface of mitogen-stimulated lymphocytes was studied by flow cytometry. The gate for lymphocytes was located by cell size (forward scatter), cytoplasmic complexity (side scatter) and by expression of the markers CD2, CD4, CD8 and CD 19. After mitogenic proliferation two populations appeared, one corresponding to non-stimulated cells, and the other consisting of larger cells which showed relatively high expression of adenosine deaminase on their surface. The increase was similar to that observed for CD71 expression, and paralleled the increase in 3H-thymidine incorporation. There was a correlation between ADA and CD71 expression (r = 0-92 for phytohaemagglutinin (PHA) and 0 97 for pokeweed mitogen (PWM)). These results suggest a role for ecto-adenosine deaminase in lymphocyte proliferation and/or triggering.

SUMMARY A group of 54 patients with primary retinitis pigmentosa were studied and the following findings are described: response of lymphocytes to stimulation by phytohaemagglutinin (PHA); response of lymphocytes to stimulation by xenogenic retinal extract; distribution of T and T-active lymphoid populations; total suppressor activity induced by concanavalin-A (con-A). The results obtained showed a reduction in the response to PHA (p<005), a positive response of 26/45 (p