Junyan Han

Imbalance between subpopulations of regulatory T cells in COPD

Background Recent evidence indicates that human regulatory T cells (Tregs) are composed of three distinct subpopulations: CD25++ CD45RA+ resting Tregs (rTregs), CD25+++ CD45RA− activated Tregs (aTregs), which are suppressive, and CD25++ CD45RA− cytokine-secreting (Fr III) cells with pro-inflammatory capacity. Objectives To evaluate the dynamic changes in circulating and pulmonary Treg subpopulations in smokers and patients with chronic obstructive pulmonary disease (COPD), and to explore their potential roles in COPD pathogenesis. Methods Blood samples were obtained from 57 never-smokers, 32 smokers with normal lung function and 66 patients with COPD. Bronchoalveolar lavage (BAL) samples were taken from 12 never-smokers, 12 smokers and 18 patients with COPD. The proportions of Treg subpopulations and activated CD8 T cells were evaluated using flow cytometry. Results In peripheral blood, increased proportions of rTregs, aTregs and Fr III cells were found in smokers compared with never-smokers, whereas patients with COPD showed decreased rTregs and aTregs, and significantly increased Fr III cells compared with smokers. The changes in Treg subpopulations, with an overall decrease in the (aTreg+rTreg):(Fr III) ratio, indicated that immune homeostasis favoured inflammation and correlated with enhanced CD8 T-cell activation (r=−0.399, p<0.001) and forced expiratory volume in 1 s (FEV1) % predicted value (r=0.435, p<0.001).The BAL (aTreg+rTreg):(Fr III) ratios displayed more robust correlations with FEV1% predicted value (r=0.741, p<0.01) and activation of effector T cells (r=−0.763, p<0.001). Conclusions The imbalance between the anti-inflammatory subsets (aTreg+rTreg) and the pro-inflammatory subset (Fr III) of Tregs may play an important role in COPD progression.

Imbalance between circulating CD4+ regulatory T and conventional T lymphocytes in patients with HBV-related acute-on-chronic liver failure

The important pathophysiological role of immune dysfunction, especially innate immune dysfunction in patients with acute‐on‐chronic liver failure (ACLF), has been investigated in recent years, but dysregulation of adaptive immunity remains poorly elucidated. The aim of this study was to (i) determine the CD3+ T‐lymphocyte count and the balance between CD4+ regulatory T (Tregs) and conventional T cells (Tconv) in hepatitis B virus (HBV)‐related ACLF patients; (ii) analyse the frequencies of Tregs subpopulations; and (iii) assess the suppressive potency of CD4+ Tregs and each fraction.

High Level of Neutrophil Extracellular Traps Correlates With Poor Prognosis of Severe Influenza A Infection

Background Most patients with severe infection with influenza A virus (IAV) progress to acute respiratory distress syndrome and even multiple organ dysfunction syndrome (MODS). Neutrophil extracellular traps (NETs) can be induced by pathogens and are responsible for immune tissue damage. We conducted a prospective study on the production and effects of NETs in H7N9 and H1N1 patients. Methods We investigated NET production in plasma and supernatant of cultured neutrophils by measuring cell-free deoxyribonucleic acid (DNA) and myeloperoxidase (MPO)-DNA complexes with PicoGreen dye and enzyme-linked immunosorbent assay methods, respectively. We also observed NET structure by immunofluorescence staining. Results We found that patients with severe influenza showed elevated plasma NET level on the day of admission. Neutrophils from these patients showed higher capacity to release MPO-DNA complex in response to interleukin-8 or lipopolysaccharide stimulation. We also found that NETs from H7N9 and H1N1 patients increased the permeability of alveolar epithelial cells, and, consequently, NET production was positively correlated with acute physiology and chronic health evaluation (APACHE) II score and MODS. Conclusions These data indicate that high level of NETs contributes to lung injury and is correlated with severity of disease. Thus, NETs might be a key factor to predict the poor prognosis in IAV patients.

Immature monocytes contribute to cardiopulmonary bypass-induced acute lung injury by generating inflammatory descendants

Background As immune regulatory and effector cells, monocytes play an important role in the blood–extracorporeal circuit contact-related acute lung injury in patients undergoing cardiopulmonary bypass (CPB). However, circulating monocytes are phenotypically and functionally heterogeneous, so we characterised how immature monocytes affect acute lung injury induced by CPB. Methods The identification and dynamic changes in monocyte subsets were monitored by flow cytometry in patients undergoing CPB and in a rat model of CPB. The differentiation and migration of monocyte subsets were explored by in vitro cultures and adoptive transfer in the CPB rat model. Results We observed a dramatic increase of two monocyte subsets in the peripheral blood of patients undergoing CPB, involving tumour necrosis factor (TNF)-α-producing, mature intermediate CD14highCD16+ monocytes and a novel immature CD14lowCD16− subset. The immature CD14lowCD16− monocytes possessed limited ability for TNF-α production, and failed to suppress T-cell proliferation mediated by T-cell receptor signalling. However, these immature cells were highly proliferative and could differentiate into TNF-α producing, mature CD14highCD16+ monocytes. In the rat model of CPB, we further demonstrated that CPB induced migration of immature monocytes into the lungs, either from the bone marrow or from the spleen. Moreover, we confirmed the hypothesis that immature subsets could contribute to CPB-induced acute lung injury by giving rise to TNF-α producing descendants. Conclusions The immature CD14lowCD16− monocytes might contribute to blood-circuit contact-induced acute lung injury by generating TNF-α-producing, mature monocytes. New strategies based on monocyte manipulation could be a promising therapeutic approach for minimising CPB-related lung injury.

Increased activated regulatory T cells proportion correlate with the severity of idiopathic pulmonary fibrosis

BackgroundRegulatory T cells (Tregs) are crucial in maintaining immune tolerance and immune homeostasis, but their role in idiopathic pulmonary fibrosis (IPF) is unclear. This study was designed to explore the role of Tregs in IPF.MethodsPercentages of Tregs and their subpopulations in peripheral blood (PB) and bronchoalveolar lavage (BAL) samples were determined by flow cytometry in 29 patients with IPF, 19 patients with primary Sjögren’s syndrome-related interstitial pneumonia (pSS-IP), and 23 healthy controls (HCs).ResultsIn peripheral blood, no difference was found in CD4+CD25+Foxp3+ Treg percentages among patients with IPF, pSS-IP, or HCs. However, activated Treg (aTreg) fractions among CD4+ T cells increased significantly in IPF compared with pSS-IP or HCs. Being consistent with the result from the PB, aTreg fractions among CD4+ T cells in IPF also increased significantly compared with pSS-IP or HCs, accompanied by increased fraction III compared with HCs in BAL. IPF patients had lower levels of resting Tregs (rTregs) from the thymus than did HCs, whereas aTreg levels originating from the thymus did not significantly differ from HCs. Both rTregs and aTregs proliferated in IPF, with aTregs being more proliferative than rTregs. Both rTregs and aTregs significantly inhibited proliferation of CD4+ T lymphocytes in vitro. The percentage of aTregs was correlated negatively with predicted diffusing capacity values for carbon monoxide and positively with GAP index in IPF.ConclusionsOur study showed the imbalance between subpopulations of Tregs in IPF. Increased aTregs proportion in the peripheral blood correlated inversely with disease severity.

Sepsis-Induced Thymic Atrophy Is Associated with Defects in Early Lymphopoiesis.

Impaired T lymphopoiesis is associated with immunosuppression of the adaptive immune response and plays a role in the morbidity and mortality of patients and animal models of sepsis. Although previous studies examined several intrathymic mechanisms that negatively affect T lymphopoiesis, the extrathymic mechanisms remain poorly understood. Here, we report a dramatic decrease in the percentage of early T lineage progenitors (ETPs) in three models of sepsis in mice (cecal ligation and puncture, lipopolysaccharide continuous injection, and poly I:C continuous injection). However, septic mice did not show a decrease in the number of bone marrow (BM) precursor cells. Instead, the BM progenitors for ETPs expressed reduced mRNA levels of CC chemokine receptor (CCR) 7, CCR9 and P‐selectin glycoprotein ligand 1, and exhibited impaired homing capacity in vitro and in vivo. Furthermore, RNA‐Seq analysis and real‐time PCR showed a marked downregulation of several lymphoid‐related genes in hematopoietic stem and progenitor cells. Hematopoietic stem and progenitor cells differentiated into myeloid cells but failed to generate T lymphocytes in vitro and in vivo. Our results indicate that the depletion of ETPs in septic mice might be a consequence of an impaired migration of BM progenitors to the thymus, as well as a defect in lymphoid lineage commitment. Stem Cells 2016;34:2902–2915

Expansion of activated regulatory T cells by myeloid-specific chemokines via an alternative pathway in CSF of bacterial meningitis patients

Previous studies have demonstrated that activation/expansion by certain cytokines as well as recruitment by specific chemokines is involved in enrichment of regulatory T (Treg) cells in local tissues or organs under pathological conditions. Recent evidence indicates that human Treg cells are a heterogeneous population that comprises three distinct subpopulations: CD25+CD45RA+ resting Treg (rTreg) cells, CD25hiCD45RA− activated Treg (aTreg) cells, which are both suppressive, and CD25+CD45RA− cytokine‐secreting T cells with proinflammatory capacity. Moreover, rTreg cells can proliferate and convert to aTreg cells. Here, we found an increase in aTreg‐cell frequency in the cerebrospinal fluid (CSF) of patients with postneurosurgery bacterial meningitis. We revealed that such an increased aTreg‐cell frequency in the CSF was not due to enhanced chemotaxis. Instead of a classic conversion pathway from rTreg to aTreg cells, we identified an alternative route of Treg‐cell conversion from cytokine‐secreting cells to aTreg cells induced by myeloid‐specific chemokine CXC chemokine receptor (CXCR) ligand 5 via CXCR1 and CXCR2 receptors, or by CSF myeloid cells in a cell–cell contact manner. Our results reveal a different view of how the immune system controls overwhelming local immune responses during infection, and provide evidence of how innate immunity negatively regulates adaptive immunity.

VISTA is highly expressed on MDSCs and mediates an inhibition of T cell response in patients with AML

ABSTRACT Treatment of acute myeloid leukemia (AML) remains challenging. Enhancement of anti-tumor responses by blocking negative immune regulators is a promising strategy for novel effective leukemia therapeutics. V-domain Ig suppressor of T-cell activation (VISTA) is a recently defined negative regulator mediating immune evasion in cancer. To investigate the effect of VISTA on anti-leukemia immune response in AML, we initiated a study using clinical samples collected from AML patients. Here we report that VISTA is highly expressed on myeloid-derived suppressor cells (MDSCs) in the peripheral blood of AML patients. Both the frequency and intensity of VISTA expression on MDSCs are significantly higher in newly diagnosed AML than in healthy controls. Importantly knockdown of VISTA by specific siRNA potently reduced the MDSCs-mediated inhibition of CD8 T cell activity in AML, suggesting a suppressive effect of VISTA on anti-leukemia T cell response. Furthermore, we observed a strong positive association between MDSC expression of VISTA and T cell expression of PD-1 in AML. These results support the strategy of VISTA-targeted treatment for AML and underscore the strong potential for combined blockade of VISTA and PD-1 pathways in effective leukemia control.