Cytokines in leprosy, I. Serum cytokine profile in leprosy

Background Leprosy is a chronic infectious disease characterized by a broad spectrum of clinical forms depending on the patient's immune response, in particular cell-mediated immune response. Methods Cytokines can play a role in the cell-mediated immune response. Serum levels of interferon-gamma (IFN-γ), interleukin-2 (IL-2), interleukin-2 receptor (IL-2R), interleukin-10 (IL-10), tumor necrosis factor-alpha (TNF-α), and interleukin-1beta (IL-1β) were measured by enzyme-linked immunosorbent assay (ELISA) in 55 untreated leprosy patients and 35 reactional leprosy patients, in addition to 20 age- and sex-matched healthy controls. Results Leprosy patients showed significantly higher serum levels of the studied cytokines (except IL-2) compared with healthy controls. When the two poles were compared, tuberculoid leprosy (TT) patients showed significantly higher levels of IFN-γ and TNF-α with significant negative correlations with the bacterial index (BI), whereas lepromatous leprosy (LL) patients showed significantly higher serum levels of IL-2R, IL-10, and IL-1β with significant positive correlations with the BI. Both type I and type II reactional patients showed significantly higher serum IFN-γ, IL-2R, and IL-1β, in addition to IL-10 in type II reactional patients, compared with nonreactional leprosy patients. When compared with each other, type I reactional patients showed increased levels of IFN-γ, whereas type II reactional patients showed increased levels of IL-10. Conclusions In leprosy patients, both IFN-γ and TNF-α are immunoprotective, whereas IL-2R, IL-10, and IL-1β are immunosuppressive. Our results indicate that type I reaction, with increased levels of IFN-γ, is a cell-mediated immune response, whereas type II reaction, with increased levels of IL-10, is essentially an immune complex disease.