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 CD14(hi) 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.
Keywords: cancer; inflammation; myeloid subsets; polarization.
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