Identification of an S-antigen-like molecule in human choroid plexus and cerebrospinal fluid.

Sensitisation to retinal S-antigen has been implicated in the pathogenesis of several clinical forms of posterior uveitis. S-antigen-like molecules have recently been demonstrated in the brain and choroid plexus of experimental animals. We used a panel of four monoclonal antibodies (MAbs), MAbF4-C1, MAbC10-C10, MAbA2-G5 and MAbA9-C6, which define specific epitopes in the amino, mid and carboxyl terminal portions of S-antigen in order to identify an S-antigen-like molecule in human choroid plexus and cerebrospinal fluid (CSF). Three MAbs, MAbF4-C1, MAbC10-C10 and MAbA9-C6, localised an S-antigen-like molecule to the cytoplasm of the epithelial cells of the human choroid plexus. Polymerase chain reaction of cDNA from choroid plexus verified the presence of S-antigen homologues in the choroid plexus. The presence of an S-antigen-like molecule in the CSF was demonstrated by western blots in seven CSF samples from patients with a variety of neuropathological disorders. It is proposed that immunological cross-reactivity and biochemical similarity between retinal S-antigen and an S-antigen-like molecule in human choroid plexus and CSF could form a basis for neurological manifestations observed in certain clinical forms of uveitides.