Macrophage-intrinsic and IL-9–dependent arginine metabolism promotes lung tumor growth

Tumor-associated macrophages are an abundant, tumor-infiltrating cell population that supports the evasion of tumor cells from antitumoral immune cell detection by generating an immunosuppressive tumor-immune microenvironment (TIME). The immunosuppressive function of macrophages is dictated by the cytokine environment. IL-9 is a pleiotropic cytokine that can be a positive or negative regulator of tumor growth. Our lab previously identified a protumoral role of IL-9 by expanding lung interstitial