CD163L1 and CLEC5A discriminate subsets of human resident and inflammatory macrophages in vivo

Abstract Macrophages (Mφ) can be differentiated and polarized in vitro from human CD14+ monocytes under the influence of GM-CSF (GM-Mφ) and M-CSF (M-Mφ). GM-Mφs are proinflammatory and M-Mφs have an anti-inflammatory phenotype. We found selective expression of the lectin C-type lectin domain family 5 member A (CLEC5A) transcripts in GM-Mφs and the scavenger receptor CD163 molecule-like 1 (CD163L1) in M-Mφs by microarray assay. In vitro, CD163L1 expression was induced by IL-10 and M-CSF and CLEC5A by inflammatory cytokines and cell adherence. In secondary lymphoid organs, their respective expression was restricted to CD68+/CD163+ Mφs that preferentially produced either TNF (CLEC5A+) or IL-10 (CD163L1+). Mφs from healthy liver and colon tissue were mostly CD163L1+, and CLEC5A+ cells were scarce. In contrast, CLEC5A+ Mφs were abundant in the intestinal lamina propria from patients with inflammatory bowel disease (IBD), with higher numbers of CLEC5A+CD163L1+ found compared with those in secondary lymphoid organs. CLEC5A+ cells were CD14+CD209−CD11b+CD11c+TNF+IL-10+, and single positive CD163L1+ cells were CD14−CD209+CD11b−CD11c−TNF−IL-10+ in healthy donors and had lost the ability to produce IL-10 and to express CD209 in those with IBD. In melanomas, CLEC5A+ tumor-associated Mφs (TAMs) were not detected in 42% of the cases evaluated, but CD163L1+ TAMs were found in 100%. Similar to IBD, CD163L1+ TAMs expressed high levels of CD209 and produced significant amounts of IL-10, and CLEC5A+ TAMs were CD14hi and produced enhanced levels of TNF in metastases. Overall, these results suggest that CD163L1 expression is associated with tissue-resident Mφs with an anti-inflammatory or anergic phenotype and that CLEC5A+ Mφs exhibit TNF-producing ability and might display a proinflammatory effect.