The Journal of immunology : official journal of the American Association of Immunologists
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Influenza viruses remain a critical global health concern. More efficacious vaccines are needed to protect against influenza virus, yet few adjuvants are approved for routine use. Specialized proresolving mediators (SPMs) are powerful endogenous bioactive regulators of inflammation, with great clinical translational properties. ⋯ To our knowledge, this is the first report on the biological effects of ω-3-derived SPMs on the humoral immune response. These findings illustrate a previously unknown biological link between proresolution signals and the adaptive immune system. Furthermore, this work has important implications for the understanding of B cell biology, as well as the development of new potential vaccine adjuvants.
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Conventional dendritic cells (cDC) are necessary and sufficient to drive mixed maladaptive Th2/Th17 immune responses toward aeroallergens in experimental allergy models. Previous studies suggest that the anaphylatoxin C3a promotes, whereas C5a protects from the development of maladaptive immunity during allergen sensitization. However, only limited evidence exists that such effects are directly mediated through anaphylatoxin-receptor signaling in cDCs. ⋯ Furthermore, C3aR(-/-) BMDCs produced less IL-1β. The mechanisms underlying the failure of C5aR1(-/-) BMDCs to induce experimental allergy include a reduced capability to migrate into the lung tissue and a decreased potency to direct pulmonary homing of effector T cells. Thus, we uncovered a crucial role for C5a, but only a minor role for C3a in BMDC-mediated pulmonary allergy, suggesting that BMDCs inappropriately reflect the impact of complement on lung cDC-mediated allergic asthma development.
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Myeloid-derived suppressor cells (MDSCs) are major immunosuppressive cells that lead to T cell defects in cancer. IL-18 is important in inflammatory and immune responses. IL-18 has been reported to have a dual effect on tumor progression, as it not only stimulates host immune responses, but also exerts procancer effects by inducing immune escape and angiogenesis. ⋯ Additionally, we demonstrated that IL-18-induced M-MDSCs have a more potent suppressive effect on T cell responses with lower IFN-γ production than do G-MDSCs, suggesting that the increased suppressive effect observed in our study resulted from M-MDSCs. Furthermore, in vivo administration of IL-18 significantly increased the accumulation of M-MDSCs in the tumor microenvironment. Taken together, our findings indicate that IL-18 specifically enhances the differentiation and function of M-MDSCs, leading to immunosuppression.