Light-dependent antibody labelling of photoreceptors.

Monoclonal antibodies are tools widely used to analyse the structure of the nervous system. Whereas some labelling patterns are highly reproducible, others appear to vary from one preparation to the next, as we noticed in particular for some antibodies with respect to photoreceptor labelling. To establish whether some of this variability can be linked to functional criteria, we tested for light-dependence. We found two antibodies that label photoreceptor outer segments, only when the retina has been illuminated, and a third antibody that has a selective affinity for dark-adapted outer segments. The two antibodies against light-activated sites are primarily directed against the highly phosphorylated neurofilament subunit at relative molecular mass 200,000 (200K). One of them, RT97, recognizes on immunoblots, in addition to neurofilaments, a light-activated epitope on a protein that resembles the photopigment rhodopsin, presumably a phosphorylation-dependent site. Antibodies like those described here may allow the study of physiological processes such as light and dark adaptation using morphological techniques.