HuiQing Xiao

Identification of a novel cytokine, ML-1, and its expression in subjects with asthma.

A novel gene, designated ML-1, was identified from a human genomic DNA clone and human T cell cDNA sequences. The second exon of ML-1 gene shares significant sequence identity with the gene encoding IL-17 (IL-17). ML-1 gene expression was up-regulated in activated PBMCs, CD4+ T cells, allergen-specific Th0, Th1, and Th2 clones, activated basophils, and mast cells. Increased expression of the ML-1 gene, but not IL-17, was seen following allergen challenge in four asthmatic subjects, suggesting its role in allergic inflammatory responses. ML-1 from transiently transfected COS-7 cells was able to induce gene expression and protein production for IL-6 and IL-8 (at 10 ng/ml of ML-1: for IL-6, 599.6 ± 19.1 pg/ml; for IL-8, 1724.2 ± 132.9 pg/ml; and at 100 ng/ml of ML-1: for IL-6, 1005.3 ± 55.6 pg/ml; for IL-8, 4371.4 ± 280.5 pg/ml; p < 0.05 for both doses vs baseline) in primary bronchial epithelial (PBE) cells. Furthermore, increased expression of ICAM-1 was found in ML-1-stimulated PBE cells (mean fluorescence intensity (MFI) = 31.42 ± 4.39 vs baseline, MFI = 12.26 ± 1.77, p < 0.05), a functional feature distinct from IL-17 (MFI = 11.07 ± 1.22). This effect was not inhibited by a saturating amount of IL-17. These findings demonstrate that ML-1 is a novel cytokine with a distinct function, and suggest a different receptor for ML-1 on PBE cells.

TLR9- and FcεRI-Mediated Responses Oppose One Another in Plasmacytoid Dendritic Cells by Down-Regulating Receptor Expression

Plasmacytoid dendritic cells (pDC) express not only TLR9 molecules through which ligation with CpG DNA favors Th1 responses but also possess IgE receptors (FcεRI) implicated in allergen presentation and induction of Th2 responses. This dichotomy prompted an investigation to determine whether TLR9- and IgE receptor-mediated responses oppose one another in pDC by affecting receptor expression and associated functional responses. Results showed that IgE cross-linking reduced TLR9 in pDC and inhibited the capacity of these cells to secrete IFN-α when stimulated with the CpG oligodeoxynucleotide (ODN)-2216. In contrast, an ∼15-fold reduction in FcεRIα mRNA and a loss in surface protein were seen in pDC first exposed to TLR9 ligation with ODN-2216. Results indicated that type I IFNs partly mediated this effect, as rIFN-α also caused a significant ∼4-fold reduction in FcεRIα mRNA. Finally, this reduction in FcεRIα mediated by ODN-2216 correlated with a selective suppression of allergen-induced CD4+ T cell proliferation, but not of responses resulting from tetanus toxoid. Overall, these results imply mechanisms by which specific innate and IgE-dependent immune responses counterregulate one another at the dendritic cell level and may have significant impact on whether an ensuing response is either of Th1 or Th2 in nature.

Lysophosphatidic acid is detectable in human bronchoalveolar lavage fluids at baseline and increased after segmental allergen challenge

Background Lysophosphatidic acid (LPA) is a biologically active lysophospholipid and a component of normal plasma. LPA binds to receptors expressed on circulating and structural lung cells and affects cell growth and activation. Whether LPA is present in the lung has not been previously reported.

Decreases in human dendritic cell–dependent TH2-like responses after acute in vivo IgE neutralization

BACKGROUND Dendritic cells (DCs) and other professional antigen-presenting cells express a variant of the high-affinity IgE receptor known as alphagamma(2), which, on the basis of in vitro findings, has long been implicated to function in facilitating allergen uptake and presentation to T(H) cells. OBJECTIVES To use omalizumab as an in vivo tool to neutralize IgE binding to circulating dendritic cells and to assess whether this results in altered DC-dependent T-cell responsiveness to allergen ex vivo. METHODS Subjects with cat allergy were enrolled in a 3.5-month, double blind, randomized (3.5:1), placebo-controlled trial of omalizumab using standard dosing for allergic asthma. Blood plasmacytoid and myeloid DCs were assessed at baseline and posttreatment for expression of surface IgE, FcepsilonRIalpha, and induction of CD4(+)T-cell proliferation and cytokine responses to cat allergen. RESULTS IgE expression on plasmacytoid and myeloid DCs from omalizumab-treated subjects (n = 12) decreased by > or =95% posttreatment (P = .0005), whereas FcepsilonRIalpha expression decreased by 66% and 48%, respectively (P = .0005). Cat allergen-induced proliferation in DC/T-cell cocultures observed at baseline was suppressed approximately 20% to 40% postomalizumab treatment (P = .001). Multiplexing for cytokines in plasmacytoid DC/T-cell cocultures also showed decreases in IL-5, IL-13, and IL-10 (P < .05), whereas IL-2 and IFN-gamma were unaltered or slightly increased. These changes were not evident in placebo-control subjects (n = 4). CONCLUSION IgE likely facilitates allergen presentation by dendritic cells in vivo and is also important in regulating DC-dependent T-cell cytokines during effector phases of allergic disease.

Clonal diversity of IL-4 and IL-13 expression in human allergen-specific T lymphocytes.

The expression of IL-4 and IL-13 was analyzed in a panel of short ragweed allergen (Amb a 1)-specific T-cell clones from an allergic subject and a nonallergic individual. The T cells from the allergic subject showed a predominantly TH0 phenotype. The T cells from the nonallergic individual produced undetectable levels of IL-4 and high level of interferon-gamma, suggesting a TH1 cytokine profile. However, all T-cell clones showed significantly higher levels of IL-13 secretion than IL-4 secretion, and no quantitative correlation could be found between the levels of IL-4 and IL-13 in the clones tested. Furthermore, both cytokines showed similar kinetics of expression in antigen-induced steady-state messenger RNA. Finally, both cytokines were induced by stimulation of the cells with either ionomycin alone or with a combination of ionomycin and phorbol myristate acetate. These results demonstrate that there is a significant clonal diversity and quantitative difference in the levels of IL-4 and IL-13 expression in allergen-specific human T cells.

Local release of B cell–activating factor of the TNF family after segmental allergen challenge of allergic subjects

BACKGROUND Local production of IgA and IgE in the airways has been proposed to be an important event in both immune protection from pathogens and the pathogenesis of airway allergic diseases. OBJECTIVE The objective of this study was to investigate the production of B cell-activating factor of the TNF family (BAFF), an important regulator of B-cell survival and immunoglobulin class-switch recombination, in bronchoalveolar lavage (BAL) fluid after segmental allergen challenge of allergic subjects. METHODS Segmental allergen challenge with saline or allergen was performed in 16 adult allergic subjects. BAL was performed at both saline- and allergen-challenged sites 20 to 24 hours after challenge. Concentrations of B cell-active cytokines, including BAFF, IL-6, and IL-13, were measured by using specific ELISA and cytometric bead array assays. RESULTS Levels of BAFF protein were significantly increased in BAL fluid after allergen challenge (53.8 pg/mL [range, 0-407.4 pg/mL], P = .001) compared with those at saline-challenged sites (0 pg/mL [0-34.7 pg/mL]). In the BAL fluid after allergen challenge, BAFF levels were significantly correlated with absolute numbers of total cells (r = 0.779, P < .001), lymphocytes (r = 0.842, P < .001), neutrophils (r = 0.809, P < .001), and eosinophils (r = 0.621, P = .010) but did not correlate with macrophages. Normalization to albumin indicated that BAFF production occurred locally in the airways. BAFF levels were also significantly correlated with the other B cell-activating cytokines IL-6 (r = 0.875, P < .001) and IL-13 (r = 0.812, P < .001). CONCLUSION The antigen-induced production of BAFF in the airway might contribute to local class-switch recombination and immunoglobulin synthesis by B cells.

Pulmonary allergic responses augment interleukin‐13 secretion by circulating basophils yet suppress interferon‐α from plasmacytoid dendritic cells

Background Allergic inflammatory processes may have the capacity to propagate systemically through the actions of circulating leucocytes. Consequently, basophils from allergic individuals are often ‘primed’, as evidenced by their hyperresponsiveness in vitro. IFN‐α secreted predominantly by plasmacytoid dendritic cells (pDCs), suppresses basophil priming for IL‐13 production in vitro.

Association of vitamin D and antimicrobial peptide production during late-phase allergic responses in the lung

Vitamin D may play important roles in regulating immune responses and in defence against infectious diseases by effects on both innate and adaptive immune responses. Little is known regarding activation of vitamin D within airway tissues and its relationship to inflammation and antimicrobial responses.

Enhanced antigen presenting and T cell functions during late-phase allergic responses in the lung

Allergic inflammation is a common feature of asthma and may contribute to both development and perpetuation of disease. The interaction of antigen‐presenting cells (APC) with sensitized helper T lymphocytes (TC) producing Th2 cytokines may determine the inflammatory response. Recruitment of APC and TC to the lung during allergic responses has been demonstrated, but functional studies in humans have been limited.