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OVA-induced Th2-cell response enhanced by HDM-derived chitin is abolished by chitinase treatment. For all panels, wild-type (WT) mice (C57BL/6 background) were sensitized with 75 µg of OVA, 75 µg of OVA+chitinase, 75 µg of OVA+100 µg of HDM-derived chitin, or 75 µg of OVA+100 µg of HDM-derived chitin+chitinase, then challenged with OVA (50 µg) alone, and evaluated 24 hours after last OVA challenge. Data are presented as the mean±SEM (n=5 mice per group) are from a single experiment representative of at least 3 independent experiments. *P<0.05; **P<0.01; ***P<0.001 relative to the OVA group; #P<0.05; ##P<0.01; ###P<0.001. (A) Bronchoalveolar lavage (BAL) cellularity after acute OVA challenge. (B) Lung histologic findings (a, OVA; b, OVA+chitinase; c, OVA+HDM-derived chitin; d, OVA+HDM-derived chitin+chitinase; magnification: 100×, scale bar: 200 µm). (C) Levels of OVA-specific IgE, IgG1, IgG2a in serum after acute challenge. (D) Levels of IL-4, IL-5, eotaxin, TGF-β, IL-10, IL-17, IL-12p70, and IFN-γ in BAL fluid after acute challenge. For panels (E), cells were isolated from lung-draining lymph nodes (LNs) and lung tissues, and incubated with PBS or CD3 and CD28 antibodies for 12 hours. Levels of each cytokine were evaluated in supernatant fraction. (E) Levels of IL-4, IL-10, IL-17, and IFN-γ from lung and lung-draining LN cells.