Allotransplantation of rabbit retinal pigment epithelial cells double-labelled with 5-bromodeoxyuridine (BrdU) and natural pigment.

To facilitate identification of transplanted retinal pigment epithelial (RPE) cells, we sought to double-label the cells with 5-bromodeoxyuridine (BrdU) and with natural pigment. The BrdU is not lost during cell division but does require immunohistochemical methods for visualization; the pigment, on the other hand, allows immediate, obvious identification, but is gradually lost with cell division. Together they provide a convenient, long-term double label. Herein we report the successful allotransplantation of double-labelled RPE cells onto Bruch's membrane of albino rabbits. The labelled cells were localized by anti-BrdU antibody and the avidin biotin-alkaline phosphatase complex (ABC-AP) method, and by visible inclusions of pigment. Using this double-label method, allotransplanted RPE cells could be readily and reliably identified on the recipient Bruch's membrane eight months after transplantation. The cells had distinct basal and apical morphology, and were in close contact with the photoreceptor outer segments of the host. This successful allotransplantation raises the possibility that the subretinal space of the rabbit might enjoy some degree of immunologic privilege.