Breast cancer associated CD169(+) macrophages possess broad immunosuppressive functions but enhance antibody secretion by activated B cells

CD169(+) resident macrophages in lymph nodes of breast cancer patients are for unknown reasons associated with a beneficial prognosis. This contrasts CD169(+) macrophages present in primary breast tumors (CD169(+) TAMs), that correlate with a worse prognosis. We recently showed that these CD169(+) TAMs were associated with tertiary lymphoid structures (TLSs) and T(regs) in breast cancer. Here, we show that CD169(+) TAMs can be monocyte-derived and express a unique mediator profile characterized by type I IFNs, CXCL10, PGE(2) and inhibitory co-receptor expression pattern. The CD169(+) monocyte-derived macrophages (CD169(+) Mo-M) possessed an immunosuppressive function in vitro inhibiting NK, T and B cell proliferation, but enhanced antibody and IL6 secretion in activated B cells. Our findings indicate that CD169(+) Mo-M in the primary breast tumor microenvironment are linked to both immunosuppression and TLS functions, with implications for future targeted Mo-M therapy.