OKT6+ epidermal Langerhans' cell numbers in DNCB reactions among leprosy patients.

A study was made on the Langerhans' cells at the sites of contact sensitivity skin reactions in 45 untreated leprosy patients. The skin reaction was induced by 2,4-dinitrochlorobenzene (DNCB). Langerhans' cells were quantitated using OKT6 monoclonal antibody and indirect immunofluorescence. Clinically, the skin reaction in the tuberculoid patients was positive at 4, 24, and 48 hr, while the lepromatous patients failed to respond at any of the time intervals. Sequential histological analysis of the skin reaction showed predominantly mononuclear cell infiltrates around the blood vessels and neurovascular bundles in both the tuberculoid and lepromatous patients. Time kinetic assessment showed no difference in the numbers and distribution of OKT6+ epidermal Langerhans' cells at the site of the DNCB skin reactions among the tuberculoid and lepromatous patients. This, therefore, suggests that either there is a functional defect in Langerhans' cells or some other mechanism(s) such as a T-cell abnormality is responsible for the lack of clinical reaction in lepromatous patients.