ANTIBODIES TO RECOVERIN INDUCE APOPTOSIS OF PHOTORECEPTOR AND BIPOLARCELLS IN-VIVO

Autoantibodies against recoverin are found in the sera of patients wit h cancer-associated retinopathy (CAR) syndrome. In these studies we ex amined the effect of anti-recoverin antibodies from the sera of patien ts with CAR and rat monoclonal antibody on the retinas of Lewis rats. Anti-recoverin autoantibodies penetrated into the photoreceptor and bi polar cell layers following intravitreal injection. Their presence in the retina could be detected by immunofluorescence 24 h after injectio n. At the same time, individual cells undergoing apoptosis were identi fied throughout photoreceptor and bipolar cell layers using terminal t ransferase-mediated dUTP nick-end labeling (TUNEL) and electron micros copy. Normal antibodies used in control experiments did not produce TU NEL labeling. At 24 h, DNA fragmentation was confirmed by DNA ladder e lectrophoresis. At the electron microscopic level, there was clear evi dence of cells undergoing apoptotic cell, death in the retinas treated with anti-recoverin antibodies,At 24 and 96 h, nuclear chromatin cond ensation and increased vacuolization of photoreceptor outer segments w ere observed. An examination of retinas from animals receiving anti-re tinal antibodies revealed a loss of 1-2 rows of nuclei in the outer an d inner nuclear layers whereas all controls (sham, normal IgG, phospha te buffered saline) showed an unchanged number of nuclei rows. In addi tion, there was an increase in spacing between the rows of nuclei of t he outer nuclear layer in retinas treated with anti-recoverin antibodi es, indicating additional cell loss. These studies provide clear evide nce that anti-recoverin antibodies are capable of penetrating photorec eptor and bipolar cells, the normal site of recoverin expression in th e retina, and that anti-recoverin antibodies produce apoptotic cell de ath. A similar mechanism may occur in patients with CAR, which may lea d to visual loss and blindness. (C) 1998 Academic Press