Different cell death mechanisms are involved in leprosy pathogenesis.

Leprosy is a chronic granulomatous disease that remains a serious public health problem in developing countries. According to the Madrid classification, leprosy presents in four clinical forms: two immunologically unstable forms (indeterminate and borderline) and two stable polar forms (tuberculoid and lepromatous). In leprosy, the relationship of cell death to clinical disease outcome remains unclear. Therefore, we investigated the extent of autophagy and different cell death mechanisms-such as apoptosis, necroptosis, and pyroptosis-in cutaneous lesions of patients with leprosy, as well as the role of these mechanisms in clinical disease progression. This cross-sectional analytical study included 30 patients with a confirmed diagnosis of leprosy, with 10 patients in each of the following groups: lepromatous (LL), tuberculoid (TT), and indeterminate (II) leprosy groups. For histopathological analysis, skin samples were subjected to haematoxylin-eosin staining and immunostaining for apoptotic and necroptotic markers. The results indicated that FasL expression was much higher in the LL form than in the TT and II forms. Similar results (higher expression in the LL form than in the TT and II forms) were observed for caspase 8, RIP1, and RIP3 expressions. MLKL, BAX, and caspase 3 expression levels were highest in the LL form, especially in globular foamy macrophages. Beclin-1 expression was highest in the TT form but was low in LL and II forms. Caspase 1 expression was highest in the LL form, followed by that in the TT and II forms. In conclusion, our study elucidates the role of different cell death mechanisms in the pathophysiology of various forms of leprosy and suggests measures that may be used to control the host response to infection and disease progression.

IL-37 and leprosy: A novel cytokine involved in the host response to Mycobacterium leprae infection.

Leprosy is a chronic infectious granulomatous disease caused by Mycobacterium leprae, in which the clinical outcome depends on the pattern of the host immune response. Because it is a spectral disease, leprosy is a good model for studying the immunology of the pathogen-host relationship. Although previous studies have characterized the participation of cytokine profiles such as Th1, Th2, Th7, Treg, Th9, and Th22 responses in leprosy, the role of new cytokines such as IL-37 have not yet been described for the spectral model of the disease. Here, we used an immunohistochemical technique to evaluate IL-37 expression in the skin of patients with leprosy. The expression of this cytokine was observed in the keratinocytes, endothelial cells, macrophages, and lymphocytes. Moreover, the IL-37 expression level was increased in patients with the tuberculoid (TT) form when compared to those with the lepromatous leprosy (LL) form in keratinocytes, endotheliocytes, and lymphocytes. However, in the macrophages, the cytokine expression was more intense in the LL form of the disease. These results point to the effective participation of IL-37 in the immunopathogenesis of leprosy, which is expressed in both the epidermal cells and the dermis.

Leprosy As a Complex Infection: Breakdown of the Th1 and Th2 Immune Paradigm in the Immunopathogenesis of the Disease.

Leprosy is a chronic infectious disease whose evolution involves complex immune mechanisms of the host that influence the clinical presentation of the disease. For many years, the main interpretation of the host defense response was based on characterization of the established immune paradigm between T helper (Th) 1 and Th2 lymphocytes. However, with advances in the knowledge of immunology, new approaches have emerged along with the development of new immunological pathways that have changed the interpretation of the long-established paradigm of the polar forms of the disease, especially with the identification of new subtypes of T lymphocytes such as Th9, Th17, Th22, and Tregs. Thus, this review discusses the role of these new subtypes of T helper lymphocytes and how the development of the immune response of these cells modifies the pattern of the Th1/Th2 response in the immunopathogenesis of leprosy.

Response of iNOS and its relationship with IL-22 and STAT3 in macrophage activity in the polar forms of leprosy.

Leprosy is a chronic granulomatous infection that manifests as different clinical forms related to the immunological response. The aim of the study was to evaluated the response of IL-22, STAT3, CD68 and iNOS in leprosy skin lesions. The mean number IL-22 positive cells was 12.12±1.90cells/field in the TT form and 31.31±2.91cells/field in the LL form. STAT3 positive cells was 5.29±1.96 cells/field in the TT form, while this number was 11.13±3.48cells/field in the LL form. The mean number of CD68 positive cells was 25.18±6.21cells/field in the TT form and 62.81±8.13cells/field in the LL form. Quantitative analysis of iNOS revealed a significant difference, with the mean number of cells expressing the enzyme being 30.24±2.88cells/field in the TT form compared to 35.44±4.69cells/field in the LL form. Linear correlations in lesions of TT patients showed a moderate positive correlations between CD68 and iNOS, STAT3 and Inos, IL-22 and STAT3, and IL-22 and iNOS. Our results demonstrate that these factors can act synergistically to induce a microbicidal activity in the population of macrophages in the leprosy lesions.

Transforming growth factor ß and apoptosis in leprosy skin lesions: possible relationship with the control of the tissue immune response in the Mycobacterium leprae infection.

The course of leprosy depends of the host immune response which ranges from the lepromatous pole (LL) to the tuberculoid pole (TT). A comparative study was conducted in 60 patients with the LL and TT. The results showed a mean expression of TGF-ß of 339 ± 99.4 cells/field for TT and of 519.2 ± 68.2 cells/field for LL. Frequency of apoptosis was 6.3 ± 1.8 in TT and 14.0 ± 6.1 in LL. A correlation (p = 0.0251) between TGF-ß and caspase-3 in the LL was found. This finding indicates a role of TGF-ß and apoptosis in the immune response in leprosy.

CD1a and factor XIIIa immunohistochemistry in leprosy: a possible role of dendritic cells in the pathogenesis of Mycobacterium leprae infection.

Leprosy is a curable chronic granulomatous infectious disease caused by the bacillus Mycobacterium leprae. This organism has a high affinity for skin and peripheral nerve cells. In the evolution of infections, the immune status of patients determines the disease expression. Dendritic cells are antigen-presenting cells that phagocytose particles and microorganisms. In skin, dendritic cells are represented by epidermal Langerhans cells and dermal dendrocytes, which can be identified by expression of CD1a and factor XIIIa (FXIIIa). In the present study, 29 skin samples from patients with tuberculoid (13 biopsies) and lepromatous (16 biopsies) leprosy were analyzed by immunohistochemistry using antibodies to CD1a and FXIIIa. Quantitative analysis of labeling pattern showed a clear predominance of dendritic cells in tuberculoid leprosy. Difference between the number of positive cells of immunohistochemistry for the CD1a and FXIIIa staining observed in this study indicates a role for dendritic cells in the cutaneous response to leprosy. Dendritic cells may be a determinant of the course and clinical expression of the disease.