Increase in TGF-β Secreting CD4+CD25+ FOXP3+ T Regulatory Cells in Anergic Lepromatous Leprosy Patients

Abstract

BackgroundLepromatous leprosy caused by Mycobacterium leprae is associated with antigen specific T cell unresponsiveness/anergy whose underlying mechanisms are not fully defined. We investigated the role of CD25+FOXP3+ regulatory T cells in both skin lesions and M.leprae stimulated PBMC cultures of 28 each of freshly diagnosed patients with borderline tuberculoid (BT) and lepromatous leprosy (LL) as well as 7 healthy household contacts of leprosy patients and 4 normal skin samples.Methodology/Principle FindingsQuantitative reverse transcribed PCR (qPCR), immuno-histochemistry/flowcytometry and ELISA were used respectively for gene expression, phenotype characterization and cytokine levels in PBMC culture supernatants. Both skin lesions as well as in vitro antigen stimulated PBMC showed increased percentage/mean fluorescence intensity of cells and higher gene expression for FOXP3+, TGF-β in lepromatous (p<0.01) as compared to tuberculoid leprosy patients. CD4+CD25+FOXP3+ T cells (Tregs) were increased in unstimulated basal cultures (p<0.0003) and showed further increase in in vitro antigen but not mitogen (phytohemaglutinin) stimulated PBMC (iTreg) in lepromatous as compared to tuberculoid leprosy patients (p<0.002). iTregs of lepromatous patients showed intracellular TGF-β which was further confirmed by increase in TGF-β in culture supernatants (p<0.003). Furthermore, TGF-β in iTreg cells was associated with phosphorylation of STAT5A. TGF-β was seen in CD25+ cells of the CD4+ but not that of CD8+ T cell lineage in leprosy patients. iTregs did not show intracellular IFN-γ or IL-17 in lepromatous leprosy patients.Conclusions/SignificanceOur results indicate that FOXP3+ iTregs with TGF-β may down regulate T cell responses leading to the antigen specific anergy associated with lepromatous leprosy.

Expansion of T regulatory Cells in Lepromatous Leprosy is Mediated by Phenolic Glycolipid-1

“…High frequency of T regulatory cells in lepromatous leprosy patients has also been reported by Maria et al in 2012 [16]. A recent study has also reported increased percentage of FoxP3+ T regulatory cells in blood and skin biopsies of lepromatous leprosy patients [17]. In contrast to these two studies and present study higher frequency of T regulatory cells in blood of tuberculoid leprosy patients as compared to lepromatous leprosy patients and healthy controls has been reported by Attia et al [15].…”

“…Regulatory T cells suppress the activation and proliferation of other CD4+ and CD8+ T cells [4,5]. Increased frequency of T regulatory cells has been reported in blood and site of infection of leprosy patients [15][16][17]. To confirm that the increased frequency of T regulatory cells in leprosy patients is due to the exposure of M. leprae or M. leprae antigens mediated expansion of T regulatory cells; for the first time we studied the frequency of CD3+CD4+CD25+FoxP3+ T regulatory cells in untreated and treated leprosy patients to correlate these cells with immunosuppression seen in leprosy.…”

“…In human tuberculosis various studies have also shown the increase number of T regulatory cells in blood and at site of infection during the active disease [12][13][14]. However, there are three reports on increased number of T regulatory cells in leprosy patients [15][16][17], two of them reported increased T regulatory cells in lepromatous leprosy patients and one reported increased T regulatory cells in tuberculoid leprosy patients. PGL-1 is M. leprae specific lipid which has been reported to be immunosuppressive [18] and highest rate of leprosy cases was detected in PGL-1 seropositive BCG unvaccinated contacts [19], therefore, we designed the present study to evaluate the percentage of T regulatory cells in different categories of leprosy patients and healthy controls to delineate their role in T cell suppression in leprosy.…”

T-Cell Regulation in Lepromatous Leprosy

“…showed, elevated frequencies of circulating T reg cells (CD4 + CD25 high FoxP3 + ) in TT patients [35] whereas Palermo et al , showed that PBMC stimulated with M. leprae antigen for 6 days in culture had significantly higher number of T reg cells (CD4 + CD25 + FoxP3 + ) in LL patients [23]. Recently, Saini et al , further confirmed the importance of T regs in LL non-responsiveness by measuring TGF- β producing CD4 + CD25 + FoxP3 + cells in stimulated PBMC culture [45]. In this study, we analysed the frequency of T reg cells in PBMC briefly activated with PMA/ionomycin.…”

Apoptotic Cell-induced Tolerogenic Dendritic Cells Facilitate Development of CD4+ and CD8+ Regulatory T cell Subsets

“…CD4 + regulatory T cells play an important role in induction of peripheral tolerance. Multiple sub-populations of CD4 + regulatory T cells such as CD4 + CD25 + FoxP3 + T regs , CD4 + CD127 + Tregs and CD4 + GITR + T regs have been found [9][10][11]. CD4 + T regs produce anti-inflammatory cytokines such as IL-10 to inhibit effector T cellmediated inflammatory responses [12].…”