Experimental granulomatous uveitis: an electron microscopic study of pigment containing giant cells.

An experimental granulomatous uveitis in the Brown Norway rat is characterized by large numbers of giant cells and epithelioid cells containing uveal pigment. Ultrastructurally, the epithelioid cells and the giant cells exhibited melanosomes and individual melanin granules in the absence of phagocytic membranes and compound pigment granules. These observations support the view that the pigment containing giant cells may develop from uveal melanocytes.