title: Towards understanding the pathology of erythema nodosum leprosum.
abstract: Erythema nodosum leprosum (ENL) is an immune-mediated complication of leprosy presenting with inflammatory skin nodules and involvement of multiple organ systems, often running a protracted course. Immune complex production and deposition as well as complement activation have long been regarded as the principal aetiology of ENL. However, new data show that cell-mediated immunity is also important. We have performed a critical analysis of studies on the pathology of ENL. Our main findings are as follows. ENL is characterised by an inflammatory infiltrate of neutrophils with vasculitis and/or panniculitis. There is deposition of immune complexes and complement together with Mycobacterium leprae antigens in the skin. Changes in serum levels of Igs indicate a transient, localised immune response. The major T-cell subtype in ENL is the CD4 cell, in contrast to lepromatous leprosy where CD8 cells predominate. The cytokines TNFalpha and IL-6 are consistently found whilst IL-4 is low or absent in ENL lesions, indicating a T(H)1 type response. Keratinocyte 1a and intercellular adhesion molecule-1 (ICAM-1) have been shown to be present in the epidermis in ENL, which is evidence of a cell-mediated immune response. Co-stimulatory molecules such as B7-1 have also been studied but further work is needed to draw strong conclusions. We also highlight potential areas for future research.
authors.affiliation: Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK. indira.kahawita@gmail.com
authors.forename: I P
authors.initials: IP
authors.lastname: Kahawita
authors.forename: D N J
authors.initials: DN
authors.lastname: Lockwood
mesh_terms: D000936:Antigen-Antibody Complex / Q000032:analysis; D016207:Cytokines / Q000032:analysis; D004893:Erythema Nodosum / Q000276:immunology / Q000473:pathology*; D006801:Humans; D007111:Immunity, Cellular; D015440:Leprosy, Lepromatous / Q000276:immunology / Q000473:pathology*; D012307:Risk Factors; D012867:Skin / Q000276:immunology
chemical_list: D000936:Antigen-Antibody Complex; D016207:Cytokines