Early activated Th-1 type and dominantly diverse natural killer T (CD3+CD161+Vα24−) cells in bone marrow among visceral leishmaniasis patients

Characterization of Regulatory T Cells in Patients Infected by Leishmania Infantum

High IL-10 levels are pivotal to parasite survival in visceral leishmaniasis (VL). Antigenic stimuli induce IL-10 expression and release of adenosine by CD39/CD73. Due their intrinsic ability to express IL-10 and produce adenosine from extracellular ATP, we evaluated the IL-10, CD39, and CD73 expression by Regulatory T cells (Treg) correlated with VL pathology. Using flow cytometry, Treg cells was analyzed in peripheral blood samples from VL patients (in the presence and absence of Leishmania infantum soluble antigen (SLA)) and healthy individuals (negative endemic control-NEC group), without any treatment. Additionally, IL-10 levels in leukocytes culture supernatant were measured in all groups by ELISA assay. VL patients presented more Treg frequency than NEC group, independently of stimulation. ELISA results demonstrated that SLA induced higher IL-10 expression in the VL group. However, the NEC group had a higher Treg IL-10⁺ compared to the VL group without stimulation and SLA restored the IL-10 in Treg. Additionally, an increase in Treg CD73⁺ in the VL group independently of stimuli compared to that in the NEC group was observed. We suggest that Treg are not the main source of IL-10, while the CD73 pathway may be an attempt to modulate the exacerbation of immune response in VL disease.

Single-cell analysis reveals innate lymphoid cell lineage infidelity in atopic dermatitis

Background

Although ample knowledge exists about phenotype and function of cutaneous T lymphocytes, much less is known about the lymphocytic components of the skin’s innate immune system.

Objective

To better understand the biologic role of cutaneous innate lymphoid cells (ILCs), we investigated their phenotypic and molecular features under physiologic (normal human skin [NHS]) and pathologic (lesional skin of patients with atopic dermatitis [AD]) conditions.

Methods

Skin punch biopsies and reduction sheets as well as blood specimens were obtained from either patients with AD or healthy individuals. Cell and/or tissue samples were analyzed by flow cytometry, immunohistochemistry, and single-cell RNA sequencing or subjected to in vitro/ex vivo culture.

Results

Notwithstanding substantial quantitative differences between NHS and AD skin, we found that the vast majority of cutaneous ILCs belong to the CRTH2⁺ subset and reside in the upper skin layers. Single-cell RNA sequencing of cutaneous ILC-enriched cell samples confirmed the predominance of biologically heterogeneous group 2 ILCs and, for the first time, demonstrated considerable ILC lineage infidelity (coexpression of genes typical of either type 2 [GATA3 and IL13] or type 3/17 [RORC, IL22, and IL26] immunity within individual cells) in lesional AD skin, and to a much lesser extent, in NHS. Similar events were demonstrated in ILCs from skin explant cultures and in vitro expanded ILCs from the peripheral blood.

Conclusion

These findings support the concept that instead of being a stable entity with well-defined components, the skin immune system consists of a network of highly flexible cellular players that are capable of adjusting their function to the needs and challenges of the environment.

Dual immune effect of iNKT cells considering human cutaneous and visceral leishmaniasis: An example of cell plasticity according to different disease scenarios

Although the semi-invariant natural killer T cells (iNKT) are a small subpopulation of cells in the peripheral blood, they are presumed to play a role in early stages of infection against various pathogens, including protozoa. This work investigates the activation status and cytokine profile of iNKT cells during human Leishmania infantum and Leishmania braziliensis infection. We studied iNKT cells in patients with symptomatic active visceral leishmaniasis (AVL) (n = 8), patients with symptomatic active cutaneous leishmaniasis (ACL) (n = 13), negative endemic controls (NEC) (n = 6) and non-endemic controls (NonEC) (n = 6), with and without total Leishmania antigen stimulus (TLA). The number of iNKT cells in the peripheral blood of patients with ACL and AVL unaltered in relation to control groups. Moreover, the iNKT cells from ACL showed a hyperactivation profile compared to patients with AVL. Additionally, TLA induced IFN-gamma production in iNKT cells from patients with ACL, while in iNKT of patients with AVL, TLA induced a decrease in this cytokine. Higher IL-17 and IL-10 production by iNKT cells from patients with ACL were also observed compared to all other groups. There were no changes in iNKT IL-10-producing cells in AVL after TLA stimulation. However, TLA induced increase in IL-10 in iNKT cells in patients with ACL. These findings suggest that, although iNKT cells showed distinct profiles in patients with ACL and AVL, they play a dual role in immune modulation in both Leishmania infections.

Leishmania donovani mediated higher expression of CCL4 induces differential accumulation of CD4+CD56+NKT and CD8+CD56+NKT cells at infection site

Sterile cure from visceralized Leishmania donovani (L. donovani) needs Th1 cell support along with the assistance from innate immune cells, NK cells and NKT cells. NKT cells play as a connecting link between innate and adaptive immune cell and support T helper cell function. Earlier, a categorical function of CD56 positive CD4⁺ or CD8⁺ NKT cells was reported in visceral leishmaniasis (VL). It was observed in in vitro that CD4⁺CD56⁺NKT cells, but not CD8⁺CD56⁺NKT cells, were accumulated at the L. donovani infection site. Therefore, in vitro experiments have been carried out to decipher the mechanism behind preferential accumulation of CD4⁺CD56⁺NKT cells at infection site. In this study, 1.89 fold higher expression of CCL4/MIP-1β was noticed in infected macrophages. The higher expression of CCL4 was correlated with preferential accumulation of CCR5⁺CD4⁺CD56⁺NKT cells and apoptosis of CD8⁺CD56⁺NKT cells at in vitro infection site. The CD4⁺CD56⁺NKT cells were also observed expressing TGF-β dominantly. Interaction of CCL4 chemotaxis was interrupted by blocking, which led to drift back the TGF-β producing CD4⁺CD56⁺NKT cells and promoted CD8⁺CD56⁺NKT cells recruitment in in vitro infection site. CCR5 blockade also reduced CD25 and FoxP3 positive CD4⁺CD56⁺NKT cells in in vitro infection site. Therefore, it was concluded that Leishmania promotes strategic expression of CCL4, which alternately attracts CCR5⁺ cells, mostly expressing regulatory cytokines, at infection site. This reduces the CD8⁺CD56⁺NKT cells at infection site through Smad4 mediated TGF-β expression and activation of caspases. Data indicates that L. donovani induces higher expression of CCL4 in host cell to attract CCR5⁺ cells under its strategic plan to downregulate host immune response.

Decrease in the Frequency of Circulating CD56+CD161+ NK Cells in Human Visceral Leishmaniasis

BACKGROUND

Natural Killer (NK) cell plays an important role in the innate immune system and is known to produce IFN-γ at an early stage of infection that is essential to eliminate intracellular infection like Leishmania spp. It is already established that Leishmania parasite inhibits the activity of NK cells, avoiding the encounter with the early innate immune response. This, in turn, favors establishment and further dissemination of the infection.

METHODS

In the present study, we have tried to measure the frequency of different phenotypic subsets of NK cells among visceral leishmaniasis (VL) patients.

RESULTS

We have phenotyped three distinct three distinct subsets (CD56^-CD161⁺, CD56⁺CD161^-, and CD56⁺CD161⁺) of NK (CD3^-) cell using their specific markers CD161 and CD56.

CONCLUSION

Interestingly, we observed selective loss of CD56⁺CD161⁺ subset of circulating NK (CD3^-) cells. Importantly, the other subsets (i.e., CD56^-CD161⁺ and CD56⁺CD161^-) of circulating NK cells remain unaffected as compared with healthy subjects.

Effects of Invariant NKT Cells on Parasite Infections and Hygiene Hypothesis

Invariant natural killer T (iNKT) cells are unique subset of innate-like T cells recognizing glycolipids. iNKT cells can rapidly produce copious amounts of cytokines upon antigen stimulation and exert potent immunomodulatory activities for a wide variety of immune responses and diseases. We have revealed the regulatory effect of iNKT cells on autoimmunity with a serial of publications. On the other hand, the role of iNKT cells in parasitic infections, especially in recently attractive topic “hygiene hypothesis,” has not been clearly defined yet. Bacterial and parasitic cell wall is a cellular structure highly enriched in a variety of glycolipids and lipoproteins, some of which may serve as natural ligands of iNKT cells. In this review, we mainly summarized the recent findings on the roles and underlying mechanisms of iNKT cells in parasite infections and their cross-talk with Th1, Th2, Th17, Treg, and innate lymphoid cells. In most cases, iNKT cells exert regulatory or direct cytotoxic roles to protect hosts against parasite infections. We put particular emphasis as well on the identification of the natural ligands from parasites and the involvement of iNKT cells in the hygiene hypothesis.

Invariant NKT cells drive hepatic cytokinic microenvironment favoring efficient granuloma formation and early control of Leishmania donovani infection

The development of inflammatory granulomas around infected Kupffer cells is necessary for hepatic parasite clearance during visceral leishmaniasis. Invariant NKT (iNKT) cells are predominant T cells in the mouse liver and can synthesize large quantities of IL-4 and IFN-γ, two cytokines involved in granuloma formation. This study analyzed the role of iNKT cells in the hepatic immune response during Leishmania donovani infection, using a murine model of wild-type (WT) and iNKT cell-deficient (Jα18^-/-) C57BL/6 mice sacrificed 15, 30 or 60 days post-infection. We recorded hepatic parasite loads, cytokine expression, and analyzed granulomatous response by immunohistochemistry and hepatic immune cell infiltration by flow cytometry. Whereas WT animals rapidly controlled the infection and developed an inflammatory response associated with a massive influx of iNKT cells observed by flow cytometry, Jα18^-/- mice had significantly higher parasitic loads on all time points. This lack of control of parasite burden was associated with a delay in granuloma maturation (28.1% of large granulomas at day 60 versus 50.7% in WT). Cytokine transcriptome analysis showed that mRNA of 90/101 genes encoding chemokines, cytokines and their receptors, was underexpressed in Jα18^-/- mice. Detection of IL-4 and TNF-α by ELISA in liver extracts was also significantly lower in Jα18^-/- mice. Consistent with flow cytometry analysis, cytokinome profile in WT mice showed a bias of expression towards T cell-chemoattractant chemokines on D15, and displayed a switch towards expression of granulocytes and/or monocytes -chemoattractant chemokines on D60. In Jα18^-/- mice, the significantly lower expression of CXCL5, MIP-2 and CCL2 mRNA was correlated with a defect in myeloperoxidase positive-cell attraction observed by immunohistochemistry and with a lower granulocyte and monocyte infiltration in the liver, as shown by flow cytometry. These data indicate that iNKT cells play a role in early and sustained pro-inflammatory cytokine response warranting efficient organization of hepatic granulomas and parasite clearance.

Enrichment of invariant natural killer T cells in the bone marrow of visceral leishmaniasis patients

Lipid antigens of Leishmania donovani like lipophosphoglycans are shown as a potent ligand for the activation of invariant natural killer T (iNKT) cells. It is reported that activation of iNKT cells augments the disease pathology in experimental visceral leishmaniasis (VL). In this study, we demonstrate the enrichment of iNKT cells in the bone marrow, one of the disease sites among patients with VL.