Reduction of epidermal cell proliferation in skin lesions in lepromatous leprosy is greater than in indeterminate and tuberculoid leprosy lesions.

We have compared epidermal cell proliferation in skin biopsies from areas with lesions to contralateral areas without lesions in patients with indeterminate, tuberculoid and lepromatous leprosy. Cell proliferation was determined as the percentage of labeled cells in the basal and suprabasal epidermal layers, using autoradiographic preparations of skin biopsies taken 1 hr after a 3H-thymidine intradermal injection. We have found a significant reduction in epidermal cell proliferation in areas with lesions in the three groups of patients. The greatest reduction occurred in lepromatous patients. In lesions of patients with indeterminate or tuberculoid leprosy, the reduction was the same, and in both groups it was smaller than in lepromatous patients. In the areas without lesions, the index of labeled cells was similar to that of "normal" skin of nonleprosy patients. In the contralateral unaffected areas from leprosy patients and in "normal" skin from nonleprosy patients, as well as in affected areas from patients with indeterminate leprosy, epidermal cell labeling was greater in the suprabasal layer than in the basal layer. In lesions of lepromatous patients, cell labeling was greater in the basal layer than in the suprabasal layer. Our findings suggest that the reduction of epidermal cell proliferation in leprosy patients is restricted to the cell-mediated immune response, more intense in lepromatous leprosy. It does not seem to be related to denervation, which is greater in tuberculoid leprosy.