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. 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. 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. 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.

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.

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.

CD14+CD16+ monocytes are an important cellular target for HIV-1 entry and expand in the peripheral blood of HIV-infected individuals. Because CD14+CD16+ monocytes are a heterogeneous population and consist of CD14highCD16+ and CD14lowCD16+ subsets, we evaluated the effects of HIV infection on distinct subsets of CD16+ monocytes. Untreated HIV-infected patients were recruited to investigate the relationship between the proportions of monocyte subsets with plasma viral loads and CD4+ T-cell counts. Patients receiving highly active antiretroviral therapy (HAART) were followed up in a cross-sectional and a longitudinal study. Compared with CD14lowCD16+, CD14highCD16+ monocytes showed higher levels of CD64 and HLA-DR antigens, which imply that these 2 distinct subsets have different immunoregulatory phenotypes. In HAART-naive patients, elevated proportions of CD14highCD16+ monocytes were correlated with increased viral loads and decreased CD4+ T-cell counts, whereas CD14lowCD16+ monocytes did not show such correlation with disease progression. Of importance, HAART recovered the proportion of CD14highCD16+ monocytes, whereas CD14lowCD16+ monocytes did not decrease during 1 year of antiviral therapy. Taken together, our observations elucidate distinct immune responses of monocyte subsets during HIV infection and antiviral therapy and provide new insight into the roles of innate immunity in HIV-related pathogenesis.

Background: It has been widely accepted that monocytes are one of the central mediators contributing to inflammaging. However, it remains unclear whether aged monocytes, similar to aged T cells, have characteristics of hyperactivation and increased expression of co-inhibitory molecules. Methods: Peripheral blood mononuclear cells (PBMCs) were isolated from young (21–40 years old), middle-aged (41–60 years old), and older human subjects (> 60 years old). Flow cytometry was used to monitor changes in the expression of surface molecules of monocyte subsets and cytokine-producing capacity. Results: We observed increased tumor necrosis factor-α: TNF-α and decreased interleukin-6 (IL-6) production in monocytes from older adults compared with young and middle-aged adults. Older adults had a greater percentage of intermediate and non-classical monocyte subsets, along with increased levels of the immune activation markers human leukocyte antigen-DR (HLA-DR), and adhesion molecules cluster of differentiation molecule 11b (CD11b) and L-selectin (CD62L). Furthermore, we observed increased C–C motif chemokine receptor 2 (CCR2) expression on classical monocytes and decreased C-X3-C motif chemokine receptor 1 (CX3CR1) expression on non-classical monocytes in older adult subjects. The expression of co-inhibitory receptors was reduced on monocyte subsets in older adults. Conclusions: Circulating monocytes in older adults exhibit increased expression of activation, adhesion, and migration markers, but decreased expression of co-inhibitory molecules.