• To study T lymphocytes in erythema nodosum leprosum (ENL), monoclonal antibodies were used to identify T-lymphocyte subpopulations in the blood and skin lesions of patients with ENL and patients with nonreactional lepromatous leprosy. The blood of nonreactional lepromatous patients had a lymphopenia and a proportionate reduction in pan T cells, helper-inducer, and suppressor-cytotoxic subsets, but a normal helper-suppressor ratio, as compared with controls. Patients with ENL did not differ significantly from the controls. In skin lesions, an admixture of helper and suppressor phenotypes among foamy histiocytes was found. The ENL tissue had more numerous cells of the helper-inducer phenotype and fewer of the suppressor-cytotoxic phenotype, as compared with nonreaction lepromatous tissues. In 22 patients with simultaneous examination of tissue and blood T-cell subsets, there was no correlation between tissue and blood helper-suppressor ratios, indicating that some sort of selection process brings lymphocytes into tissues from peripheral blood.
(Arch Dermatol 1985;121:216-219)