The Effect of IL-10 on M2-Activated Human Microglia (S12.006)

OBJECTIVE: To investigate the effect of IL-10 on the phenotypic characteristics of M2 polarized human microglia. BACKGROUND: Myeloid cells acquire distinct immunologic phenotypes dependent on their state of ‘polarization’: either ‘M1’ (pro-inflammatory) or ‘M2’ (anti-inflammatory). M2 polarized cells, generated using mCSF/IL-4/IL13, produce increased quantities of anti-inflammatory cytokines and display increased phagocytic activity and expression of scavenger receptors. Previous in vitro studies show that mCSF/IL-4/IL13 treated human microglia express more limited M2 phenotypic and functional properties than blood-derived macrophages. Rodent-based studies have defined distinct subsets (M2a, M2b and M2c) within the overall M2 population that thus far have not been investigated in the human microglia system. Human M2c macrophages induced by treatment with IL-10 in combination with mCSF/IL-4/IL13 (M2a protocol) show enhancement of aforementioned M2-like properties. DESIGN/METHODS: Human microglia were cultured from both fetal and adult brain tissue; these cells were polarized in vitro with exposure to mCSF/IL-4/IL13 ± IL-10 (50ng/ml). Phenotypic markers (cell surface and intra-cellular) were assessed by way of multi-colour flow cytometery and qPCR. In situ expression of markers of M2 polarized myeloid cells was demonstrated by immunohistochemical staining of post-mortem CNS tissue. RESULTS: We were able to demonstrate higher expression of specific M2c markers, CD163 and HMOX-1, in human microglia polarized in the presence of IL-10 compared to M2a conditions alone; M2 markers CD206 and CD209 were comparably expressed. Analysis of a case of Schistosoma mekongi parasitic infection confirmed that CD163 is selectively expressed in situ on myeloid cells in the CNS and its expression is elevated under a pathologic condition that promotes Th2 responses. CONCLUSIONS: Our findings demonstrate that IL-10 induces expression of M2c specific markers in human microglia in vitro, and that pathological conditions associated with increased IL-10 levels are also likely to induce such expression in situ. Disclosure: Dr. Healy has nothing to disclose. Dr. Moore has nothing to disclose. Dr. Touil has nothing to disclose. Dr. Ludwin has nothing to disclose. Dr. Bar-Or has received research support from Amplimmune, EMD Serono, and Novartis. Dr. Antel has received personal compensation for activities with Biogen Idec, Teva Neuroscience, EMD Serono, Genzyme, Sanofi-Aventis, and Novartis.