Purpose: To investigate whether antirecoverin antibodies are present in patients with retinitis pigmentosa (RP). Recoverin, a retinal protein, has been implicated as a cause of cancer-associated retinopathy (CAR), which manifests as an RP-like retinal degeneration. The rationale is that the ocular findings in CAR syndrome are similar to those found in many forms of RP, and since 40% of patients with RP have no family history, some patients may have an underlying autoimmune process causing or contributing to their retinopathy. Methods: Serum samples from 521 patients diagnosed with RP were screened for antiretinal proteins activity by Western blot analysis. Fifty-one patients had antibody reactivity against retinal proteins in the range of 23 to 26 kd and underwent dot-blot analysis for antirecoverin antibody, checking IgG and IgM antibodies. Enzymelinked immunosorbent assay (ELISA) was performed to evaluate the titer of antirecoverin antibodies in patients with positive results on dot-blot analysis. Lymphocyte proliferation assays using recoverin were performed on 26 samples. Results: Ten patients were found to have antirecoverin antibody and/or cellular immunoreactivity. Eight patients had positive dot-blot testing: 6 patients had both IgG and IgM antirecoverin activity, and 1 patient each had IgG or IgM activity. In these 8 patients, numerous other antiretinal protein antibodies were present. Three patients had positive recoverin-mediated lymphocyte proliferation, and all patients were positive for antirecoverin antibodies on ELISA testing. Concluslons: Antirecoverin immunoreactivity was found in 10 patients without systemic malignancy but with clinical findings consistent with RP. These results suggest that there are other immunogenic mechanisms occurring in the formation of antirecoverin antibodies in addition to the putative tumor-mediated mechanisms. This survey suggests that there may be rare cases of CAR-like syndrome in the category of simplex RP, or that some patients with RP also have antirecoverin antibodies that may be exacerbating their underlying disease.
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