Human peritoneal macrophages show functional characteristics of M‐CSF‐driven anti‐inflammatory type 2 macrophages

Abstract

We have recently shown that in vitro polarized M-CSF-driven anti-inflammatory macrophages (MΦ2) have the unique capacity to preferentially bind and ingest early apoptotic cells. However, these data are based on in vitro polarized cells and it is unclear whether MΦ2-like cells exist in vivo. Here we used CD163 as a cell surface marker to distinguish MΦ2 from the pro-inflammatory MΦ1. We show that human peritoneal MΦ (pMΦ) freshly isolated from patients on peritoneal dialysis have the phenotypical characteristics of MΦ2, including CD163 surface expression and lack of CD16. Like MΦ2, pMΦ have the capacity for endocytosis and macropinocytosis, are able to preferentially bind and ingest early apoptotic cells, and produce large amounts of IL-10 upon stimulation with LPS. Moreover, upon LPS stimulation both pMΦ and MΦ2 down-regulate CD86, resulting in a reduced capacity to stimulate proliferation of allogeneic T cells and an inhibition of Th1 cytokine release of these T cells. Our data provide the evidence for the first time that in vitro polarized MΦ2 exist in vivo, and human pMΦ resemble the anti-inflammatory MΦ2. We propose that pMΦ have the potential to maintain an anti-inflammatory condition in the peritoneal cavity.