The Cutaneous Infiltrates of Leprosy

TLDR

The study reports on the cellular characteristics of cutaneous lesions and blood in 21 leprosy patients spanning lepromatous, tuberculoid, and intermediate forms. The authors examined skin lesion infiltrates and peripheral blood samples to characterize macrophage and T‑cell populations. Lepromatous lesions are dominated by heavily parasitized macrophages and suppressor T cells, whereas tuberculoid lesions contain organized granulomas with helper T cells; both lesion types express HLA‑DR, blood T‑cell phenotypes are unchanged, indicating that T‑cell subset differences may affect macrophage microbicidal activity.

Abstract

We report on the characteristics of cells in the cutaneous lesions and blood of 21 patients with lepromatous, tuberculoid, and intermediate forms of leprosy. A large proportion of the infiltrates in lepromatous lesions consist of macrophages heavily parasitized with Mycobacterium leprae. The T cells in the lesions are devoid of OKT4/Leu 3a-positive ("helper") cells and consist almost exclusively of OKT8/Leu 2a-positive ("suppressor") populations. In contrast, the tuberculoid infiltrates contain well-organized epithelioid and giant-cell granulomas and only remnants of bacilli, and the predominant T cell is from the OKT4/Leu 3a-positive subset. In both tuberculoid and lepromatous infiltrates, T cells and macrophages expressed HLA-DR antigen. No marked alteration in the distribution of blood T-cell phenotypes was noted. We conclude that there is a marked difference between T-cell subsets in lepromatous and tuberculoid infiltrates, which may influence the microbicidal activity of macrophages in the lesions.