Targeting CD206+ macrophages disrupts the establishment of a key antitumor immune axis.

Abstract

CD206 is a common marker of a putative immunosuppressive "M2" state in tumor-associated macrophages (TAMs). We made a novel conditional CD206 (Mrc1) knock-in mouse to specifically visualize and/or deplete CD206+ TAMs. Early depletion of CD206+ macrophages and monocytes (Mono/Macs) led to the indirect loss of conventional type I dendritic cells (cDC1), CD8 T cells, and NK cells in tumors. CD206+ TAMs robustly expressed CXCL9, contrasting with stress-responsive Spp1-expressing TAMs and immature monocytes, which became prominent with early depletion. CD206+ TAMs differentially attracted activated CD8 T cells, and the NK and CD8 T cells in CD206-depleted tumors were deficient in Cxcr3 and cDC1-supportive Xcl1 and Flt3l expressions. Disrupting this key antitumor axis decreased tumor control by antigen-specific T cells in mice. In human cancers, a CD206Replete, but not a CD206Depleted Mono/Mac gene signature correlated robustly with CD8 T cell, cDC1, and NK signatures and was associated with better survival. These findings negate the unqualified classification of CD206+ "M2-like" macrophages as immunosuppressive.