Surfactant protein D deficiency influences allergic immune responses

Background: The collectin surfactant protein D (SP-D) confers protection against pulmonary infection and inflammation. Recent data suggest a role for SP-D in the modulation of allergic inflammation. Objective: The aim of this study is to characterize the immune responses of SP-D-deficient (SP-D ^-/-) mice in a kinetic model of allergic inflammation. We determined whether allergic parameters were enhanced in SP-D^-/- mice in vivo. Further, we examined whether functional immune responses in vitro such as lymphocyte proliferation (LP) and cytokine production were modulated in the absence of SP-D. Methods: In vivo, wild-type (WT) and SP-D^-/- mice were sensitized and challenged with the allergen ovalbumin (OVA) and assessed for allergic parameters (bronchoalveolar lavage (BAL) eosinophils, IL-13 production, pulmonary IFN-γ, IL-10 expression) at early time points (1 and 3 days of challenge) in comparison with late time points (7 days of challenge). In vitro, spleen cells from WT and SP-D^-/- mice were stimulated with the mitogen concanavalin A (ConA) and lipid A (LpA) and analysed for LP, IL-13 and IFN-γ production. Toll-like receptor 4 (TLR4), ligand for LpA, was assessed by mRNA expression and immunohistochemistry in vivo. Results: Following allergen exposure in vivo, SP-D^-/- mice expressed higher BAL eosinophils and IL-13 concentrations and lower IFN-γ expression at early time points compared with WT mice. IL-10 expression was increased at early time points in SP-D^-/- compared with WT mice. Allergen-induced TLR4 expression was increased in WT, but not in SP-D^-/- mice. After stimulation with LpA and ConA in vitro LP was increased and IFN-γ concentration was decreased in SP-D^-/- mice. Conclusion: SP-D may be critical for the modulation of early stages of allergic inflammation in vivo.