Regulatory dendritic cells protect against allergic airway inflammation in a murine asthmatic model

Background: Dendritic cells (DCs) are crucial for the induction of immunity and tolerance. Despite an improved understanding of the DC-mediated control of T(H)1-biased immunity, little is known about how DCs regulate T(H)2-mediated immunity. Objective: The effects of immunostimulatory mature DCs (maDCs) and regulatory DCs (DCregs) on T(H)2-driven allergic immunity involving IgE production were examined. Methods: A murine model of airway hyperresponsiveness; the adoptive transfer of maDCs, DCregs, and T cells; and T-cell function were studied. Results: Antigen-pulsed maDCs inhibited antigen-specific IgE production but enhanced the production of antigen-specific IgG1 and IgG2a. Analysis of Ifng(-/-) mice and Il21r(-/-) mice revealed that the inhibitory effect of antigen-pulsed maDCs on antigen-specific IgE production involved IL-21-producing T follicular helper cells but not IFN-gamma-producing T(H)1 cells. In contrast, antigen-pulsed DCregs impaired the production of antigen-specific IgE, IgG1, and IgG2a. In vivo blockade experiments showed that antigen-specific CD4(+)CD25(+)Foxp3(+) regulatory T cells mainly mediated the suppressive effect of antigen-pulsed DCregs on the production of antigen-specific IgE. Antigen-pulsed maDCs promoted airway inflammation, whereas antigen-pulsed DCregs markedly suppressed the pathogenesis. Conclusion: DCregs abolish T(H)2-mediated IgE production and allergic inflammation based on antigen-specific dominant tolerance, whereas maDCs exacerbate the pathogenesis despite inhibiting the IgE response through the activation of diverse types of T-H cell responses.