The combination of type I IFN, TNF-α, and cell surface receptor engagement with dendritic cells enables NK cells to overcome immune evasion by dengue virus.

Clinical studies have suggested the importance of the NK cell response against dengue virus (DenV), an arboviral infection that afflicts >50 million individuals each year. However, a comprehensive understanding of the NK cell response against dengue-infected cells is lacking. To characterize cell-contact mechanisms and soluble factors that contribute to the antidengue response, primary human NK cells were cocultured with autologous DenV-infected monocyte-derived dendritic cells (DC). NK cells responded by cytokine production and the lysis of target cells. Notably, in the absence of significant monokine production by DenV-infected DC, it was the combination of type I IFNs and TNF-α produced by DenV-infected DC that was important for stimulating the IFN-γ and cytotoxic responses of NK cells. Cell-bound factors enhanced NK cell IFN-γ production. In particular, reduced HLA class I expression was observed on DenV-infected DC, and IFN-γ production was enhanced in licensed/educated NK cell subsets. NK-DC cell contact was also identified as a requirement for a cytotoxic response, and there was evidence for both perforin/granzyme as well as Fas/Fas ligand-dependent pathways of killing by NK cells. In summary, our results have uncovered a previously unappreciated role for the combined effect of type I IFNs, TNF-α, and cell surface receptor-ligand interactions in triggering the antidengue response of primary human NK cells.

Persistent Helicobacter pylori specific Th17 responses in patients with past H. pylori infection are associated with elevated gastric mucosal IL-1ß.

BACKGROUND: Ongoing Helicobacter pylori (HP) infection triggers a chronic active gastritis. Eradicating HP reduces gastric inflammation, but does not eliminate it. We sought to characterize this persistent gastritis, and demonstrate the persistence of HP-specific Th17 responses in individuals previously infected with HP but who no longer had evidence of ongoing infection. METHODOLOGY/PRINCIPAL FINDINGS: Study subjects were divided into 3 groups 55 individuals had active HP infection (group A), 41 were diagnosed with previous HP infection (group P), and 59 were naïve to HP (group N). Blood and gastric tissue were obtained with written informed consent from all subjects, and immune responses were evaluated using flow cytometry, semi-quantitative real time PCR, immunofluorescent staining, ELISA, and multiplex cytometric bead array for cytokine quantification. Elevated IL-17A responses were observed in patients from group A compared to group N. Interestingly, IL-17A responses remained persistently elevated in the blood and gastric mucosa of individuals from group P, despite the absence of ongoing HP infection. Using purified CD4(+) T cells as effectors and antibodies that blocked antigen presentation by MHC Class II, we showed that these persistent IL-17A responses were mediated primarily by HP-specific Th17 cells, rather than other immune cells that have also been described to secrete IL-17A. Gastric mucosal IL-1ß levels were also persistently elevated in group P, and neutralisation of IL-1ß reduced the HP-specific IL-17A response of purified CD4(+) T cells to autologous HP-pulsed antigen presenting cells in vitro, suggesting a functional association between IL-1ß and the persistent Th17 response in group P patients. CONCLUSIONS/SIGNIFICANCE: Despite lack of ongoing HP infection, HP-specific Th17 cells persist in the blood and gastric mucosa of individuals with past HP infection. We speculate that this persistent inflammation might contribute to gastric mucosal pathology, for example, persistent increased gastric cancer risk despite eradication of HP.

Dexamethasone alters bronchoalveolar lavage fluid proteome in a mouse asthma model.

BACKGROUND: Glucocorticoid is the most effective anti-inflammatory agent for asthma. The spectrum of protein targets that can be regulated by glucocorticoid in asthma is not fully understood. The present study tried to identify novel protein targets of dexamethasone in allergic airway inflammation by analyzing the proteome of mouse bronchoalveolar lavage (BAL) fluid. METHODS: BALB/c mice sensitized and challenged with ovalbumin (OVA) showed increased pulmonary inflammatory cell infiltration, airway mucus production and serum OVA-specific IgE level. Dexamethasone inhibited all these allergic airway inflammation endpoints. BAL fluid proteins were resolved by two-dimensional gel electrophoresis and identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. RESULTS: The levels of 26 BAL fluid proteins were found to be markedly altered by dexamethasone. A family of chitinases (Ym1, Ym2 and acidic mammalian chitinase, AMCase), lungkine, gob-5, surfactant protein D and polymeric immunoglobulin receptor have been found for the first time to be downregulated by dexamethasone in allergic airways. The downregulatory effects were confirmed by immunoblotting and RT-PCR analyses. Dexamethasone was also shown to significantly inhibit lavage fluid chitinase bioactivity. In addition, dexamethasone promoted airway expression of vitamin D-binding protein, heptoglobin and alpha(1)-antitrypsin. CONCLUSIONS: Among all these newly identified protein targets of dexamethasone, AMCase and gob-5 have been shown to be pro-inflammatory in asthma. Downregulation of AMCase and gob-5 may be considered as two novel anti-inflammatory actions of glucocorticoid in asthma.