Analysis of the activation profile of dendritic cells derived from the bone marrow of interleukin-12/interleukin-23-deficient mice

摘要

We have previously shown that macrophages from interleukin (IL)-12p40 gene knockout (IL-12/IL-23^−/−) mice have a bias towards the M2 activation profile, spontaneously secreting large quantities of transforming growth factor-β1 (TGF-β1) and producing low levels of nitric oxide (NO) in response to lipopolysaccharide (LPS) and interferon-γ (IFN-γ). To verify whether the activation profile of dendritic cells (DCs) is also influenced by the absence of IL-12/IL-23, bone marrow-derived DCs from IL-12/IL-23^−/− and C57BL/6 mice were evaluated. At first we noticed that ≈ 50% of the C57BL/6 DCs were dead after LPS-induced maturation, whereas the mortality of IL-12/IL-23^−/− DCs was < 10%, a protective effect that diminished when recombinant IL-12 (rIL-12) was added during maturation. Similarly to macrophages, mature IL-12/IL-23^−/− DCs (mDCs) produced higher levels of TGF-β1 and lower levels of NO than C57BL/6 mDCs. NO release was IFN-γ-dependent, as evidenced by the poor response of IFN-γ^−/− and IL-12/IL-23^−/−IFN-γ^−/− mDCs. Nevertheless, IFN-γ deficiency was not the sole reason for the weak NO response observed in the absence of IL-12/IL-23. The high level of TGF-β1 secretion by IL-12/IL-23^−/− mDCs could explain why exogenous IFN-γ partially restored the NO production of IFN-γ^−/− mDCs, while IL-12/IL-23^−/− IFN-γ^−/− mDCs remained unresponsive. We also showed that CD4⁺ T-cell proliferation was inhibited by C57BL/6 mDCs, but not by IL-12/IL-23^−/− mDCs. IFN-γ and NO appear to mediate this antiproliferative effect because this effect was not observed in the presence of mDCs from IFN-γ^−/− or IL-12/IL-23^−/− IFN-γ^−/− mice and it was attenuated by aminoguanidine. We conclude that the presence of IL-12/IL-23 during LPS-induced maturation influences the activation profile of DCs by a mechanism that is, only in part, IFN-γ dependent.