Cellular targets of anti-alpha-enolase autoantibodies of patients with autoimmune retinopathy.

Autoantibodies against alpha-enolase are often associated with visual loss in patients with autoimmune retinopathy. Anti-recoverin autoantibodies have been the most extensively studied for their pathologic association with cancer-associated retinopathy (CAR). It has been shown that anti-recoverin antibodies penetrate retinal layers corresponding to the cellular location of recoverin and cause the death of photoreceptors and bipolar cells. However, the pathogenic effects of anti-alpha-enolase antibodies have not been studied. In this study, we tested the labeling and apoptotic effects of such autoantibodies on retinal cells. Serum antibodies against alpha-enolase from patients with autoimmune retinopathy were tested ex vivo and in vivo in Sprague-Dawley rats. Autoantibodies to alpha-enolase specifically labeled the retinal ganglion cells and inner nuclear layer cells. Using ex vivo experiments and intravitreal injections, we observed that antibodies were capable of penetrating retinal tissue to target ganglion cell and inner nuclear layers and, consequently, were able to induce cell death through an apoptotic process. The apoptotic nuclei detected by a DNA fragmentation assay and caspase 3-positive cells were co-localized in the ganglion cell layer and inner nuclear layer. The results showed that antibodies against alpha-enolase target antigens in these layers and induce the apoptotic death of sensitive cells. Rat retinal explants and the intravitreal injection of antibodies provide us with a good model to identify antibody pathogenic targets in the retina. Such identification may help explain the complex of clinical symptoms for autoimmune retinopathy mediated by autoantibody and may help guide treatment strategies.