Cell-mediated immunity against human retinal extract, S-antigen, and interphotoreceptor retinoid binding protein in onchocercal chorioretinopathy.

Autoimmune mechanisms are thought to be involved in the pathogenesis of onchocercal chorioretinopathy. Cell-mediated immune responses to human retinal S-antigen, interphotoreceptor retinoid binding protein (IRBP), and crude retinal extract were investigated in patients with onchocerciasis from Sierra Leone, West Africa using a two-step migration-inhibition factor assay. Patients were subdivided into three groups: (1) without ocular involvement (n = 10), (2) with ocular onchocerciasis limited to the anterior segment (n = 19), and (3) with onchocercal chorioretinopathy (n = 21). A group of endemic controls (n = 25) from Sierra Leone were also studied. The cellular immune response to concanavalin A (Con A) was measured to assess the general capacity of lymphocytes to respond to a mitogen. Four of 50 (8%) patients with onchocerciasis and four of 25 (16%) endemic controls reacted with at least one retinal antigen. From the patients with onchocercal chorioretinopathy two of 21 (10%) showed a positive cellular response. The general mitogen response tested with Con A was positive in all these individuals. A role for an antiretinal autoimmune mechanism in the pathogenesis of onchocercal chorioretinopathy, as studied with human S-antigen, IRBP, or crude retinal extract, could not be shown because the cellular response to these antigens did not differ in patients with or without onchocercal chorioretinopathy or in endemic controls.