The role of CD4+CD25+ regulatory T cells in macrophage-derived foam-cell formation

Cluster of differentiation (CD)4+CD25+ regulatory T cells (Tregs) exert a suppressive activity on atherosclerosis, but the underlying mechanism remains unclear. Here, we investigated whether and how Tregs affect macrophages foam-cell formation. Tregs were isolated by magnetic cell sorting-column and analyzed by flow cytometry. Macrophages were cultured with or without Tregs in the presence of oxidized LDL (oxLDL) for 48 h to transform foam cells. After co-culture with Tregs, macrophages showed a decrease in lipid accumulation, which was accompanied by a significantly downregulated expression of CD36 and SRA but no obvious difference in ABCA1 expression. Tregs can inhibit the proinflammatory properties of macrophages and steer macrophage differentiation toward an anti-inflammatory cytokine producing phenotype. Mechanistic studies reveal that both cell-to-cell contact and soluble factors are required for Treg-mediated suppression on macrophage foam-cell formation. Cytokines, interleukin-10 (IL-10), and transforming growth factor-β (TGF-β) are the key factors for these suppressive functions.