Monoclonal antibodies which recognize endoplasmic reticulum in the retinal pigment epithelium

Balb/c mice were immunized with dissociated chick retinal pigment epithelial cells and monoclonal antibodies prepared. Retinas of chick, bovine, rabbit, rat and mouse were examined with the monoclonal antibodies by immunofluorescence microscopy. Among the antibodies obtained, two (S5D8 and S5H8) stained the cytoplasm of epithelial cells of the animals examined in finely granular pattern and recognized a 63-kDa protein in retinal pigment epithelial cells. These antibodies, however, did not react with the rest of the chick eye (cornea, iris, ciliary body, lens and sclera) nor with extraocular tissues (liver, kidney, intestine, brain, testis, adrenal gland, heart, gizzard and skeletal muscle). Immunoelectron microscopy revealed that the antigen was localized in the endoplasmic reticulum of retinal pigment epithelial cells.