Regulation of cell-mediated immunity in lepromatous leprosy

Abstract

Patients with lepromatous leprosy demonstrate a selective T cell unresponsiveness to M. leprae and fail to mobilize appreciable numbers of T cells-- particularly of the T4 (helper) phenotype, into their dermal lesions. In the absence of lymphokine production, cutaneous macrophages serve as permissive hosts for the bacilli and extensive intravacuolar replication takes place. For examining the factors leading to T cell and monocyte emigration into the skin and the role of interferon-γ the authors generated delayed hypersensitivity reactions in the dermis of control and lepromatous patients and examined the nature and host-parasite interactions of the cells accumulating at these sites. In addition, they have administered recombinant, human interferon-γ into the skin of patients with lepromatous leprosy. The nature of these reactions at the local and systemic level are discussed.