Innate Immune Responses in Leprosy

Leprosy is an infectious disease that may present different clinical forms depending on host immune response to Mycobacterium leprae. Several studies have clarified the role of various T cell populations in leprosy; however, recent evidences suggest that local innate immune mechanisms are key determinants in driving the disease to its different clinical manifestations. Leprosy is an ideal model to study the immunoregulatory role of innate immune molecules and its interaction with nervous system, which can affect homeostasis and contribute to the development of inflammatory episodes during the course of the disease. Macrophages, dendritic cells, neutrophils, and keratinocytes are the major cell populations studied and the comprehension of the complex networking created by cytokine release, lipid and iron metabolism, as well as antimicrobial effector pathways might provide data that will help in the development of new strategies for leprosy management.

Thalidomide and emergence of Mycobacterium leprae (ML)-specific responses in erythema nodosum leprosum (45.20)

Acute inflammatory lesions are seen in lepromatous leprosy (LL) during reactions, such as ENL. Necrotic ENL as the initial manifestation of LL was diagnosed at the Souza Araujo Outpatient Unit of FIOCRUZ in Rio de Janeiro (female patient, 26 yrs old). Biopsies and peripheral blood mononuclear cells (PBL) were obtained on days 0, 7 and 30 of treatment with thalidomide (negative pregnancy test). At days 7 and 30 progressive healing of the lesions was observed. The quantification of specific mRNAS for IL-6, TNF-α, ninjurin and IL-10 by qPCR detected an initial high level of IL-6, TNF-α and ninjurin mRNAs, and after thalidomide treatment a decrease of the first 3 mRNAs in the lesion, but IL-10 message increase. ML-specific synthetic peptides induced progressively lower levels of IL-6 in the culture supernatants, but high-level IFN-γ, IL-13 and TNF-α in PBL responses after the healing of the lesions (ML 1419c protein; multiplex assay). CD4+, CD8+, CD45-RO+ and γδ T cells were present in the initial biopsy, but were nearly absent in the last one. Activated (CD69+) CD4, CD8 and γδ T cells were observed in short-term ML-stimulated cultures. Taken together these observations suggest that thalidomide may contribute to the emergence of a ML-specific T cell response with a potential role in the healing process of ENL.