Erythema Nodosum Leprosum Neutrophil Subset Expressing IL-10R1 Transmigrates into Skin Lesions and Responds to IL-10.

Erythema nodosum leprosum (ENL) is an inflammatory complication in leprosy. Yet, the involvement of ENL neutrophils in the inflammatory response against Mycobacterium leprae remains poorly explored. Our primary aim was to investigate the utility of the surface expression of neutrophil IL-10R1 as an ENL biomarker and, secondarily, to evaluate whether leprosy or healthy M. leprae-stimulated neutrophils produce cytokines and are able to respond to IL-10. We, in this study, describe a subpopulation of circulating neutrophils of ENL patients that exclusively expressed IL-10R1, providing evidence that IL-10R1+ neutrophils are present in ENL lesions. It was also found that ENL neutrophils, but not those of nonreactional leprosy controls, were able to secret detectable levels of TNF ex vivo and the addition of IL-10 blocked TNF release. It was likewise observed that M. leprae-stimulated, healthy neutrophils expressed IL-10R1 in vitro, and ENL-linked cytokines were released by M. leprae-cultured neutrophils in vitro. Moreover, consistent with the presence of a fully functional IL-10R, the addition of IL-10 prevented the release of M. leprae-induced cytokines. Most importantly, dead M. leprae revealed its superior capacity to induce CCL4 and IL-8 in primary neutrophils over live Mycobacterium, suggesting that M. leprae may hamper the inflammatory machinery as an immune escape mechanism.

Expression of CD64 on Circulating Neutrophils Favoring Systemic Inflammatory Status in Erythema Nodosum Leprosum.

Erythema Nodosum Leprosum (ENL) is an immune reaction in leprosy that aggravates the patient´s clinical condition. ENL presents systemic symptoms of an acute infectious syndrome with high leukocytosis and intense malaise clinically similar to sepsis. The treatment of ENL patients requires immunosuppression and thus needs to be early and efficient to prevent both disabilities and permanent nerve damage. Some patients experience multiple episodes of ENL and prolonged use of immunosuppressive drugs may lead to serious adverse effects. Thalidomide treatment is extremely effective at ameliorating ENL symptoms. Several mechanisms have been proposed to explain the efficacy of thalidomide in ENL, including the inhibition of TNF production. Given its teratogenicity, thalidomide is prohibitive for women of childbearing age. A rational search for molecular targets during ENL episodes is essential to better understand the disease mechanisms involved, which may also lead to the discovery of new drugs and diagnostic tests. Previous studies have demonstrated that IFN-γ and GM-CSF, involved in the induction of CD64 expression, increase during ENL. The aim of the present study was to investigate CD64 expression during ENL and whether thalidomide treatment modulated its expression. Leprosy patients were allocated to one of five groups: (1) Lepromatous leprosy, (2) Borderline leprosy, (3) Reversal reaction, (4) ENL, and (5) ENL 7 days after thalidomide treatment. The present study demonstrated that CD64 mRNA and protein were expressed in ENL lesions and that thalidomide treatment reduced CD64 expression and neutrophil infiltrates-a hallmark of ENL. We also showed that ENL blood neutrophils exclusively expressed CD64 on the cell surface and that thalidomide diminished overall expression. Patient classification based on clinical symptoms found that severe ENL presented high levels of neutrophil CD64. Collectively, these data revealed that ENL neutrophils express CD64, presumably contributing to the immunopathogenesis of the disease.