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To the Editor.—
We are grateful to Dr. Okun for his detailed consideration of dopa and tyrosine oxidases. In our study of lichen planus we observed a striking reduction of dopa-positive melanocytes in the basal region of the epidermis where the lichen planus was active. In the dermal infiltrate we observed a few weekly dopa-positive cells, but we were unconvinced that any of these represented dendritic melanocytes. We did not have the opportunity of preincubating our sections with sodium diethyldithiocarbamate and adding catalase to the incubation medium to distinguish a peroxidase-dependent dopa reaction from a tyrosinase-dependent reaction. We certainly in no way wished to imply any "commitment to the unproven and highly questionable hypothesis that mammalian melanogenesis is based on the catalysis of a single aerobic oxidase" as Dr. Okun has suggested.
Black MM, Jones EW. Dopa and Oxidases. Arch Dermatol. 1972;106(3):422. doi:10.1001/archderm.1972.01620120096035