The Journal of Immunology Dendritic Cell-Specific ICAM-3–Grabbing Nonintegrin Expression on M2-Polarized and Tumor-Associated Macrophages Is Macrophage-CSF Dependent and Enhanced by Tumor-Derived IL-6 and IL-10 Angeles Domı ´nguez-Soto,* Elena Sierra-Filardi,* Amaya Puig-Kro ¨ger, † Blanca Pe ´rez-Maceda,* Fernando Go ´mez-Aguado, ‡ Marı ´a Teresa Corcuera, ‡ Paloma Sa ´nchez-Mateos, † and Angel L. Corbı ´* Dendritic cell-specific ICAM-3–grabbing nonintegrin (DC-SIGN; CD209) is a human pathogen-attachment C-type lectin with no obvious murine ortholog and for which ligation leads to enhanced anti-inflammatory cytokine release and altered proinflamma- tory cytokine production. Although induced by IL-4 in monocytes and considered as a DC marker, DC-SIGN expression on human APCs under homeostatic conditions is so far unexplained. We report in this study that M-CSF enhances DC-SIGN expression on in vitro derived anti-inflammatory macrophages and that M-CSF mediates the induction of DC-SIGN by fibroblast- and tumor cell-conditioned media. The M-CSF–inducible DC-SIGN expression along monocyte-to-macrophage differentiation is dependent on JNK and STAT3 activation, potentiated by STAT3-activating cytokines (IL-6, IL-10), and abrogated by the M1- polarizing cytokine GM-CSF. In pathological settings, DC-SIGN expression is detected in tumor tissues and on ex vivo-isolated CD14 + CD163 + IL-10–producing tumor-associated macrophages. Importantly, DC-SIGN Abs reduced the release of IL-10 from macrophages exposed to Lewis x -expressing SKBR3 tumor cells. These results indicate that DC-SIGN is expressed on both wound- healing (IL-4–dependent) and regulatory (M-CSF–dependent) alternative (M2) macrophages and that DC-SIGN expression on tumor-associated macrophages might help tumor progression by contributing to the maintenance of an immunosuppressive environment. The Journal of Immunology, 2011, 186: 2192–2200. C irculating monocytes emigrate into tissue and replenish macrophage-resident populations in response to homeo- static or inflammatory stimuli (1, 2). Macrophages are phenotypic and functionally heterogeneous both under homeo- static conditions and in response to cytokine and microbial pro- ducts (1, 3, 4). Macrophage activation can generate a continuum of functional states and is an extremely plastic and reversible pro- cess that allows macrophages to participate in the initiation and resolution of inflammatory processes (5–7). Polarized macro- phages have been broadly classified into M1 and M2 (3) as a means to distinguish macrophages with proinflammatory, cyto- toxic, and microbicidal activities (M1) from those contributing to wound healing, tissue repair, and resolution of inflammation (M2) (1, 8). The plasticity of the macrophage activation process is best exemplified by the shift in effector functions that takes place along tumor progression. Tumors alter myeloid cell differentiation (9) and shape the effector functions of associated macrophages (10). In the early phases of carcinogenesis, macrophages exhibit pro- inflammatory and antitumor activities, but shift toward an M2- skewed phenotype during tumor progression (11), thus contri- buting to tumor growth, survival, and spread via promotion of angiogenesis and matrix remodeling (11–13). Among the tumor- derived factors that modulate myeloid cell polarization (9), M-CSF is known to promote macrophage recruitment and survival and to enhance tumor growth and aggressiveness by stimulating protumor activities of tumor-associated macrophages (TAM) (11, 14). In fact, M-CSF is commonly overexpressed by tumors of the reproductive system, and its increased levels correlate with poor prognosis (15). Although GM-CSF and M-CSF contribute to ma- crophage development and differentiation (16), each cytokine promotes the acquisition of distinct morphology, pathogen sus- ceptibility, and inflammatory functions (16–18). GM-CSF–derived macrophages (M1) are proinflammatory and potentiate Th1 responses, whereas M-CSF–driven macrophages (M2) secrete IL- 10 in response to pathogens and do not activate Th1 responses. GM-CSF expression usually requires cell stimulation (16), whereas M-CSF is present in serum and appears elevated under immunosuppressive conditions (15, 19). *Centro de Investigaciones Biolo ´gicas, Consejo Superior de Investigaciones Cientı ´f- icas, Madrid, Spain; † Hospital General Universitario Gregorio Maran ˜o ´n, Madrid, Spain; and ‡ Servicio de Anatomı ´a Patolo ´gica, Hospital Carlos III, Madrid, Spain Received for publication February 25, 2010. Accepted for publication December 10, 2010. This work was supported by the Ministerio de Educacio ´ n y Ciencia (Grant BFU2008- 01493-BMC), Ministerio de Sanidad y Consumo, Instituto de Salud Carlos III (Span- ish Network for the Research in Infectious Diseases, REIPI RD06/0008, and Red de Investigacio ´n en SIDA, RIS RD06/0006/1016), Fundacio ´n para la Investigacio ´n y Prevencio ´n del SIDA (FIPSE 36663/07), and Fundacio ´n Mutua Madrilen ˜a (to A.L.C.), Grants SAF2006-08615 from Ministerio de Educacio ´n y Ciencia and Fundacio ´n Ramo ´n Areces (XIV Concurso Nacional, 2007) (to P.S.-M.), and Grant PI08/1208 from Instituto de Salud Carlos III (to A.P.-K.). A.P.-K. is supported by Ministerio de Sanidad y Consumo (CP06/00199). Address correspondence and reprint requests to Dr. Angeles Domı ´nguez-Soto, Centro de Investigaciones Biolo ´gicas, Consejo Superior de Investigaciones Cientı ´ficas, Ram- iro de Maeztu, 9, 28040 Madrid, Spain. E-mail address: ads@cib.csic.es The online version of this article contains supplemental material. Abbreviations used in this article: DC-SIGN, dendritic cell-specific ICAM-3–grab- bing nonintegrin; MDM, monocyte-derived macrophage; MFI, mean fluorescence intensity; MKK, MAPK kinase; qRT-PCR, quantitative real-time PCR; TAM, tumor-associated macrophage. Copyright Ó 2011 by The American Association of Immunologists, Inc. 0022-1767/11/$16.00 www.jimmunol.org/cgi/doi/10.4049/jimmunol.1000475