Dendritic cells (DC) play important roles in balancing immunity and tolerance, in which β-catenin signaling plays an important role, yet the underlying mechanisms remain elusive. In this study, we investigated the functions of the tumor suppressor adenomatous polyposis coli (APC), also a key component of the β-catenin upstream destruction complex in DC. APC depletion in DC does not alter DC and T cell homeostasis under resting conditions. However, APC deficiency in DC leads to attenuated antitumor immunity in mice, which exhibit fewer CD8+ T cells and more Foxp3+ regulatory T cells in tumor and draining lymph nodes. Loss of APC in DC does not affect the expression levels of costimulatory molecules. However, APC-deficient DC produce more IL-10 and exhibit a higher ability of inducing regulatory T cells but a lower ability of priming CD8+ T cells, both of which can be reversed by IL-10 inhibition. Lastly, β-catenin depletion in APC-deficient DC rescues their antitumor immunity and reverses elevated IL-10 production. Taken together, our results identify that APC drives DC tolerance via the β-catenin/IL-10 axis.
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