Abstract
Purpose::
Autoimmune reactions have been discussed to play a role in the pathogenesis of some types of intraocular inflammation. In a previous study we showed that autoantibodies to lens proteins occur in a high incidence in sera from patients with uveitis. The autoantibodies had reacted in the Western blot predominantly with alpha crystallins. Aim of the study was to achieve information about their immunodominant epitopes.
Methods::
Epitope specificities of alpha A- and alpha B-crystallins were examined by ELISA using overlapping proteins. Ten solid-phase peptides, beginning with peptide no.1 at the N-terminus and ending with peptide no.10 at the C-terminus of alpha A- and alpha B-crystallins, respectively, were separately synthesized on pins. The peptides consisted of 25 amino acid residues, with an overlap of 8 amino acids each. To determine the immunodominant epitopes, the synthetic peptides were tested in ELISA against sera of uveitis patients, healthy controls and patients with other eye diseases, being positive in ELISA to lens crystallins.
Results::
Testing the patients` sera, a restricted number of epitopes of alpha-crystallins were detected. Peptides no.9 and no.10 of both, alpha A- and alpha B-crystallins, located in the C-terminus (alpha A: aa 136-173; alpha B: aa 136-175), were recognized as immunodominant regions by IgG and IgM antibodies. Some patients showed reactivity to peptide no.6 of alpha B-crystallin (aa 85-110) additionally.
Conclusions::
After previous demonstration of antibody formation against alpha A- and alpha B-crystallins, preferentially in uveitis patients, we now have shown that this immune response is directed against aa 136-173 of alpha A- and aa 136-175 of alpha B-crystallins.
Keywords: uveitis-clinical/animal model • autoimmune disease • crystallins