γδ T cells are associated with inflammation and immunopathogenesis of leprosy reactions.

BACKGROUND: Leprosy reactions appear episodically in leprosy patients, which lead to high inflammation, morbidity and peripheral nerve damage. The role of Th17 cell has been well studied in leprosy reactions but the role of γδ or unconventional T cells which is an other major source of IL-17 in many diseases, not studied in leprosy reactional episodes. OBJECTIVE: The aim of the present study to elucidate the role of γδ T cells in leprosy reactions. METHODOLOGY: A total of 40 untreated non-reaction and reactions patients were recruited. PBMCs were isolated and stimulated with M. leprae sonicated antigen (MLSA) for 48 h and immuno-phenotyping was done using flow cytometry. Moreover, γδ T cells were isolated by Magnetic beads technology and mRNA expression of IL-17, IFN-γ, TGF-ß and FOXP3 were analyzed by real-time PCR (qPCR) and cytokine was estimated in the culture supernatant by ELISA. RESULTS: γδ T cells were significantly increased in both Reversal reaction (RR) and Erythema nodosum leprosum (ENL) reaction patients. These cells produced significant amount of IL-17 and IFN-γ. Furthermore, CD3+TCRγδ+ T cells expressed transient FOXP3 with a low amount of TGF-ß in both reactions as compared to stable patients. Moreover, low TGF-ß producing TCR-γδ cells were associated with low phosphorylation of STAT5A. CONCLUSION: This study will add to our understanding of the immunological features that mediate and regulate the pathogenesis of leprosy and may helpful to reduce the immuno-pathogenesis of leprosy reaction by targeting these cells.

Langerhans cells utilize CD1a and langerin to efficiently present nonpeptide antigens to T cells.

Langerhans cells (LCs) constitute a subset of DCs that initiate immune responses in skin. Using leprosy as a model, we investigated whether expression of CD1a and langerin, an LC-specific C-type lectin, imparts a specific functional role to LCs. LC-like DCs and freshly isolated epidermal LCs presented nonpeptide antigens of Mycobacterium leprae to T cell clones derived from a leprosy patient in a CD1a-restricted and langerin-dependent manner. LC-like DCs were more efficient at CD1a-restricted antigen presentation than monocyte-derived DCs. LCs in leprosy lesions coexpress CD1a and langerin, placing LCs in position to efficiently present a subset of antigens to T cells as part of the host response to human infectious disease.

Identification of a 68 kd surface antigen of Mycobacterium avium that binds to human macrophages.

Infection caused by Mycobacterium avium is the major cause of bacteremia in patients with AIDS. A critical event in the initiation of a variety of bacterial infections is the adherence of bacteria to host cell surfaces, which is often brought about by the interaction of specific molecules on the bacterial surface with host cell surface receptors. In the present study, a sonicate of M. avium was used to isolate monocyte-binding proteins by affinity chromatography with CNBr-Sepharose-4B coupled to extracts of monocytes. A 68 kd protein present on the surface of M. avium was identified as one of nine monocyte-binding proteins. This protein was isolated and further characterized. The N-terminal amino acid sequence (22 residues) of the protein was determined and was found to exhibit strong homology with the 65 kd heat shock proteins of M. tuberculosis, M. leprae, and M. bovis. However, a previously characterized monoclonal antibody directed against a 66 kd antigen of M. avium was found to cross-react with the 68 kd protein from M. avium but not with the 65 kd proteins from M. leprae and M. bovis, suggesting that the 68 kd antigen may differ from the 65 kd proteins of M. leprae and M. bovis with respect to certain epitopes. In an in vitro inhibition assay, the 68 kd protein was found to compete with the attachment of intact fluorescein isothiocyanate-labeled M. avium to monocyte-derived macrophages, inhibiting this attachment in a dose-dependent manner up to 42%. The 65 kd proteins of M. leprae and M. bovis, on the other hand, did not appear to inhibit this attachment substantially (13.9% and 14.6%, respectively). These results suggest that the 68 kd protein of M. avium may be involved in binding to receptors on macrophages and help in the attachment of the organism to its host cell.

Expression of adhesion molecules in leprosy lesions.

Leprosy presents as a clinical spectrum that is precisely paralleled by a spectrum of immunological reactivity. The disease provides a useful and accessible model, in this case in the skin, in which to study the dynamics of cellular immune responses to an infectious pathogen, including the role of adhesion molecules in those responses. In lesions characterized by strong delayed-type hypersensitivity against Mycobacterium leprae (tuberculoid, reversal reaction, and Mitsuda reaction), the overlying epidermis exhibited pronounced keratinocyte intracellular adhesion molecule 1 (ICAM-1) expression and contained lymphocytes expressing the ICAM-1 ligand, LFA-1. Conversely, in lesions in which delayed-type hypersensitivity was lacking (lepromatous), keratinocyte ICAM-1 expression was low and LFA-1+ lymphocytes were rare. Expression of these adhesion molecules on the cells within the dermal granulomas was equivalent throughout the spectrum of leprosy. The percentage of lymphocytes in these granulomas containing mRNA coding for gamma interferon and tumor necrosis factor alpha, synergistic regulators of ICAM-1 expression, paralleled epidermal ICAM-1 expression. In lesions of erythema nodosum leprosum, a reactional state of lepromatous leprosy thought to be due to immune complex deposition, keratinocyte ICAM-1 expression and gamma interferon mRNA+ cells were both prominent. Antibodies to LFA-1 and ICAM-1 blocked the response of both alpha beta and gamma delta T-cell clones in vitro to mycobacteria. Overall, the expression of adhesion molecules by immunocompetent epidermal cells, as well as the cytokines which regulate such expression, correlates with the outcome of the host response to infection.