In situ T regulatory cells and Th17 cytokines in paired samples of leprosy type 1 and type 2 reactions.

Leprosy is a complex chronic, infectious dermato-neurological disease that affects the skin and peripheral nerves especially during immuno-inflammatory episodes known as type 1/T1R and type 2/T2R reactions. This study investigated the in situ expression of CD25+Foxp3+ Treg cells and TGF-β1, IFN-γ, IL-17 in leprosy T1R and T2R. Tregs were evaluated in 114 skin biopsies from 74 leprosy patients: 56 T1R (28-paired reaction-free/reactional biopsies, 28 unpaired T1R), 18 T2R (12 paired reaction-free/reactional biopsies, 6 unpaired T2R). Double CD25+Foxp3+immunostained Treg cells obtained by automated platform (Ventana BenchMark XT, Roche, Mannheim, Germany) were counted (Nikon Eclipse E400 2mm2). Cytokine expression was evaluated by immunostaining in 96 biopsies (48 paired reaction-free/reactional lesions, 24 T1R, 24 T2R) using rabbit polyclonal anti human TGF-β1, IFN-γ, IL-17 antibodies (Santa Cruz Biotechnology CA, USA). Treg cell counts in leprosy reactional lesions were higher compared to reaction-free (p = 0.002). Treg numbers were higher in T1R compared to paired unreactional T1R lesions (p = 0.001). Similar frequency of Treg was seen in paired reactional versus unreactional T2R lesions. Higher expression of TGF-β, IFN-γ and IL-17 was seen in T2R lesions compared to T1R and reaction-free lesions. The increase in Treg cells during T1R suggests a suppressive role to control the exacerbated cellular immune response during T1R that can cause tissue and nerve damage. Evidences of upregulated Treg cells in TR1, which usually occurs in patients with Th1-Th17 immunity and the indications of the expression of Th17/IL-17 in T2R, which develops in patients with Th2-Treg profile, suggest plasticity of Treg-Th17 cells populations and a potential role for these cell populations in the immunopathogenesis of leprosy reactions.