ALLOTRANSPLANTATION OF RABBIT RETINAL-PIGMENT EPITHELIAL-CELLS DOUBLE-LABELED WITH 5-BROMODEOXYURIDINE (BRDU) AND NATURAL PIGMENT

To facilitate identification of transplanted retinal pigment epithelia l (RPE) cells, we sought to double-label the cells with 5-bromodeoxyur idine (BrdU) and with natural pigment. The BrdU is not lost during cel l division but does require immunohistochemical methods for visualizat ion; the pigment, on the other hand, allows immediate, obvious identif ication, but is gradually lost with cell division. Together they provi de a convenient, long-term double label. Herein we report the successf ul allotransplantation of double-labelled RPE cells onto Bruch's membr ane of albino rabbits. The labelled cells were localized by anti-BrdU antibody and the avidin biotin-alkaline phosphatase complex (ABC-AP) m ethod, and by visible inclusions of pigment. Using this double-label m ethod, allotransplanted RPE cells could be readily and reliably identi fied on the recipient Bruch's membrane eight months after transplantat ion. The cells had distinct basal and apical morphology, and were in c lose contact with the photoreceptor outer segments of the host. This s uccessful allotransplantation raises the possibility that the subretin al space of the rabbit might enjoy some degree of immunologic privileg e.