In situ characterization of lymphocytic immunophenotypes and interleukin-2 receptors in cutaneous tuberculosis and leprosy--a comparative evaluation.

The granulomas of lupus vulgaris (LV) were characterized by preponderance of CD4+ lymphocytes and a raised CD4+/CD8+ ratio. In contrast, in scrofuloderma (SF) the CD8+ T-lymphocyte subpopulation predominated and the CD4+/CD8+ ratio was significantly decreased. A higher percentage of lymphocytes expressed interleukin-2 receptor (IL-2R) in LV as compared with SF, indicating an activated cellular immune response in the former. Immunophenotypic changes in tuberculosis verrucosa cutis (TBVC) were intermediate between LV and SF. CD4+ lymphocytes were the main infiltrating T-cell type in borderline tuberculoid leprosy (BT), while CD8+ lymphocytes predominated in the granuloma of lepromatous lepromatous (LL). The CD4+/CD8+ ratio and percentage of lymphocytes expressing IL-2R was significantly higher in BT as compared with LL. These immunophenotypic findings suggest that in both cutaneous tuberculosis and leprosy there is a continuous spectrum with regard to cell-mediated immunity depending on the clinical presentation.