Interleukin-10 Producing Regulatory B Cells Transformed CD4+CD25- Into Tregs and Enhanced Regulatory T Cells Function in Human Leprosy.

Regulatory B cells (Bregs) are known to exhibit their regulatory functions through interleukin-10 (IL-10) cytokine which suppress inflammation. There are only a few studies explaining the phenotype and functioning of these cells in contribution to host immunity in leprosy. Here, we evaluated the role of IL-10 producing Bregs in the pathogenesis of leprosy and assessed their immunoregulatory effects on Tregs and effector T cells. We found an increased frequency of Bregs and increased expression of their immune modulatory molecules (IL-10, FoxP3, and PDL-1) in leprosy patients. The potential immunoregulatory mechanism of Bregs was also investigated using MACS sorted Teff (CD4+CD25-) and Treg (CD4+CD25+) cells were cocultured with Bregs to elucidate the effects of Bregs on effector T and regulatory T cells. Cell coculture results showed that purified Bregs cells from leprosy patients convert CD4+CD25- cells into CD4+CD25+ cells. Cell coculture experiments also demonstrated that leprosy derived IL-10 producing Bregs enhance FoxP3 and PD-1 expression in Tregs and enhanced Tregs activity. Blocking of IL-10 receptor confirmed that IL-10 producing Breg has immunomodulatory effect on Tregs and effector T cells as effector T cells are not converted into Tregs and enhanced expression of FoxP3 and PD-1 was not observed on Tregs. Collectively, these findings demonstrate that IL-10 producing Breg cells play an important mechanism in controlling the immunopathogenesis of leprosy and have an immunomodulatory effect on Tregs and effector T cells. Our findings may pave way for novel targets of IL-10 producing Bregs for immunotherapy in leprosy patients.

Fate of T Cells and their Secretory Proteins During the Progression of Leprosy.

Leprosy is an infectious disease caused by non-cultivable bacteria Mycobacterium leprae. Ridley and Jopling classified the disease into five polar forms, Tuberculoid (TT) and Lepromatous (LL), in between two forms of the disease Borderline tuberculoid (BT), Borderline (BB) and Borderline lepromatous (BL) are laid. The tuberculoid type (BT/TT) leprosy patients show good recall of cellmediated immune (CMI) response and Th1 type of immune response, while lepromatous leprosy (LL) patients show defect in cell-mediated immunity to the causative agent and Th2 type of immune response. Due to distinct clinical and immunological spectra of the disease, leprosy attracted immunologists to consider an ideal model for the study of deregulations of various immune reactions. Recent studies show that Tregs, Th3 (TGF-ß, IL-10), IL-35 producing Treg immune response associated with the immune suppressive environment, survival of bugs. IL-17 producing Th17 immune response associated with tuberculoid leprosy and play protective role. γδ T cells also increased from tuberculoid to lepromatous pole of leprosy. In this review, we will discuss the role of various subtypes of T-cell and their cytokines in the pathogenesis of leprosy.

IL-12 and IL-23 modulate plasticity of FoxP3+ regulatory T cells in human Leprosy.

Leprosy is a bacterial disease caused by M. leprae. Its clinical spectrum reflects the host's immune response to the M. leprae and provide an ideal model to investigate the host pathogen interaction and immunological dysregulation. Tregs are high in leprosy patients and responsible for immune suppression of the host by producing IL-10 and TGF-ß cytokines. In leprosy, plasticity of Tregs remain unstudied. This is the first study describing the conversion of Tregs into Th1-like and Th17-like cells using in vitro cytokine therapy in leprosy patients. Peripheral blood mononuclear cells from leprosy patients were isolated and stimulated with M. leprae antigen (MLCwA), rIL-12 and rIL-23 for 48h. Expression of FoxP3 in CD4+CD25+ Tregs, intracellular cytokines IFN-γ, TGF-ß, IL-10 and IL-17 in Tregs cells were evaluated by flow cytometry (FACS) after stimulation. rIL-12 treatment increases the levels of pStat4 in Tregs and IFN-γ production. In the presence of rIL-23, pStat3+ and IL-17A+ cells increase. rIL-12 and r-IL-23 treatment downregulated the FoxP3 expression, IL-10 and TGF-ß production by Tregs and enhances the expression of co-stimulatory molecules (CD80, CD86). In conclusion rIL-12 converts Tregs into IFN-γ producing cells through STAT-4 signaling while rIL-23 converts Tregs into IL-17 producing cells through STAT-3 signaling in leprosy patients. This study may helpful to provide a new avenue to overcome the immunosuprression in leprosy patients using in vitro cytokine.

Increased IL-35 producing Tregs and CD19+IL-35+ cells are associated with disease progression in leprosy patients.

BACKGROUND: The clinical forms of leprosy consist of a spectrum that reflects the host's immune response to the M. leprae; it provides an ideal model to study the host pathogen interaction and immunological dysregulation in humans. IL-10 and TGF-ß producing Tregs are high in leprosy patients and responsible for immune suppression and M. leprae specific T cells anergy. In leprosy, involvement of IL-35 producing Tregs and Bregs remain unstudied. OBJECTIVE: To study the role of IL-35 producing Tregs and Bregs in the human leprosy. METHODS: Peripheral blood mononuclear cells from leprosy patients were isolated and stimulated with M. leprae antigen (MLCwA) for 48h. Intracellular cytokine IL-35 was evaluated in CD4+CD25+ Tregs, CD19+ cells by FACS. Expression of PD-1 on CD4+CD25+ Tregs, CD19+ cells and its ligand (PD-L1) on B cells, CD11c cells were evaluated by flow cytometry (FACS). Serum IL-35 level was estimated by ELISA. RESULTS: The frequency of IL-35 producing Tregs and Bregs cells were found to be high in leprosy patients (p<0.0001) as compared to healthy controls. These cells produced suppressive cytokine IL-35 which showed positive correlation with bacteriological index (BI) and TGF-ß producing Tregs, indicating its suppressive nature. We found higher expression of PD-1 on Tregs, B cell and its ligand (PD-L1) on antigen presenting cells in leprosy patients. CONCLUSION: This study point out a shift in our understanding of the immunological features that mediate and regulate the immune suppression and the disease progression in leprosy patients with a new paradigm (IL-35 producing Tregs and Bregs) that is beyond TGF-ß and IL-10 producing Treg cells.

Association of TNF-α-(308(GG)), IL-10(-819(TT)), IL-10(-1082(GG)) and IL-1R1(+1970(CC)) genotypes with the susceptibility and progression of leprosy in North Indian population.

Leprosy is an infectious disease caused by M. leprae. We analyzed 48 cytokine polymorphisms in 13 (pro as well as anti-inflammatory) cytokine genes using PCR-SSP assay in 102 leprosy patients and 120 healthy controls with intent to find out a link between cytokine polymorphisms and disease susceptibility. TNF-α (-308) GG, IL-10 (-819) TT, IL-10 (-1082) GG and IL1R (+1970) CC genotypes are found to be predominant (p=0.01, p=0.02, p=0.0001 and p=0.001, respectively) in both tuberculoid as well as lepromatous leprosy patients. This observation suggests these genotypes as play the central role(s) in the progression of disease. CBA assay demonstrates the varied serum concentration of these cytokines with respect to their genotypes. The above genotypes appeared as high producer genotypes in our study. Even in presence of high produce genotypes, TNF-α level are found to be affected/masked by the presence of IL-10 in leprosy patients. Expressional masking of TNF-α is associated with the expression of IL-10 in these patients. This is one the negative impact of SNP-SNP interaction in leprosy patients. Therefore, we can conclude that cytokine gene polymorphisms determine the predisposition to the leprosy progression.

FoxP3 provides competitive fitness to CD4⁺CD25⁺ T cells in leprosy patients via transcriptional regulation.

Leprosy is a chronic infectious disease caused by Mycobacterium leprae. FoxP3 have been shown to have important implications in various diseases. The present study describes the mechanism of action of FoxP3 in CD4⁺CD25⁺ T cells derived from leprosy patients. Increased molecular interactions of FoxP3 with histone deacetylases 7/9 in the nucleus of CD4⁺CD25⁺ T cells derived from borderline lepromatous leprosy/lepromatous leprosy (BL/LL) patients were found to be responsible for FoxP3-driven immune suppression activities during the progression of leprosy. Further, downregulation of CTLA-4 and CD25 genes in siFoxP3-treated PBMCs derived from BL/LL patients elucidated the transcription-activating nature of FoxP3. This observation was supported by direct binding of FoxP3 to the promoter region of the CTLA-4 and CD25 genes, and FoxP3's molecular interaction with histone acetyl transferases. The study also revealed that the increased expression of miR155 in CD4⁺CD25⁺ cells from BL/LL governs the competitive fitness of these cells. Again, reduced Annexin V & propidium iodide staining and Nur77 expression, and concomitantly increased Ki-67 positivity suggested that CD4⁺CD25⁺ cells derived from BL/LL patients are more competitively fit than those from borderline tuberculoid leprosy/tuberculoid leprosy and healthy controls. Taken together, the study shows the orchestration of FoxP3 leading to competitive fitness of Treg cells in leprosy.

CD4+CD25+ T regs with acetylated FoxP3 are associated with immune suppression in human leprosy.

Leprosy is a chronic human disease that results from infection of Mycobacterium leprae. T reg cells have been shown to have important implications in various diseases. However, in leprosy, it is still unclear whether T regs can mediate immune suppression during progression of the disease. In the present study, we have proposed the putative mechanism leading to high proportion of T reg cells and investigated its significance in human leprosy. High levels of TGF-ß followed by adaptation of FoxP3(+) naive and memory (CD4(+)CD45RA(+)/RO(+)) T cells were observed as the principal underlying factors leading to higher generation of T reg cells during disease progression. Furthermore, TGF-ß was found to be associated with increased phosphorylation-mediated-nuclear-import of SMAD3 and NFAT towards BL/LL pole to facilitate FoxP3 expression in these cells, the same as justified after using nuclear inhibitors of SMAD3 (SIS3) and NFAT (cyclosporin A) in CD4(+)CD25(+) cells in the presence of TGF-ß and IL-2. Interestingly, low ubiquitination of FoxP3 in T reg cells of BL/LL patients was revealed to be a major driving force in conferring stability to FoxP3 which in turn is linked to suppressive potential of T regs. The present study has also pinpointed the presence of CD4(+)CD25(+)IL-10(+) sub class of T regs (Tr1) in leprosy.

IL-10 production from dendritic cells is associated with DC SIGN in human leprosy.

The defective antigen presenting ability of antigen presenting cells (APCs) modulates host cytokines and co-stimulatory signals that may lead to severity of leprosy. In the present study, we sought to evaluate the phenotypic features of APCs along with whether DC SIGN (DC-specific intercellular adhesion molecule-grabbing nonintegrin) influences IL-10 production while moving from tuberculoid (BT/TT) to lepromatous (BL/LL) pole in leprosy pathogenesis. The study revealed an increased expression of DC SIGN on CD11c⁺ cells from BL/LL patients and an impaired form of CD83 (∼50 kDa). However, the cells after treatment with GM-CSF+IL-4+ManLAM showed an increased expression of similar form of CD83 on DCs. Upon treatment with ManLAM, DCs were found to show increased nuclear presence of NF-κB, thus leading to higher IL-10 production. High IL-10 production from ManLAM treated PBMCs further suggested the role of DC SIGN in subverting the DCs function towards BL/LL pole of leprosy. Anti-DC SIGN treatment resulting in restricted nuclear ingression of NF-κB as well as its acetylation along with enhanced T cell proliferation validated our findings. In conclusion, Mycobacterium leprae component triggers DC SIGN on DCs to induce production of IL-10 by modulating intracellular signalling pathway at the level of transcription factor NF-κB towards BL/LL pole of disease.

Disruption of HLA-DR raft, deregulations of Lck-ZAP-70-Cbl-b cross-talk and miR181a towards T cell hyporesponsiveness in leprosy.

Leprosy, a chronic human disease, results from infection of Mycobacterium leprae. Defective CMI and T cell hyporesponsiveness are the major hallmark of M. leprae pathogenesis. The present study demonstrates immunological-deregulations that eventually lead to T cell anergy/hyporesponsiveness in M. lepare infection. We firstly, evaluated the membrane fluidity and antigen-presenting-lipid-raft (HLA-DR) on macrophages of leprosy patients using fluorescence anisotropy and confocal microscopy, respectively. Increased membrane fluidity and raft-out localizations of over-expressed HLA-DR towards BL/LL pole are pinpointed as major defects, may be leading to defective antigen presentation in leprosy. Furthermore, altered expression and localization of Lck, ZAP-70, etc. and their deregulated cross talks with negative regulators (CD45, Cbl-b and SHP2) turned out to be the major putative reason(s) leading to T cell hyporesponsiveness in leprosy. Deregulations of Lck-ZAP-70 cross-talk in T cells were found to be associated with cholesterol-dependent-dismantling of HLA-DR rafts in macrophages in leprosy progression. Increased molecular interactions between Cbl-b and Lck/ZAP-70 and their subsequent degradation via ubiquitinization pathway, as result of high expression of Cbl-b, were turned out to be one of the principal underlying reason leading to T cell anergy in leprosy patients. Interestingly, overexpression of SHP2 due to gradual losses of miR181a and subsequent dephosphorylation of imperative T cell signaling molecules were emerged out as another important reason associated with prevailing T cell hyporesponsiveness during leprosy progression. Thus, this study for the first time pinpointed overexpression of Cbl-b and expressional losses of miR-181 as important hallmarks of progression of leprosy.