Background and Objective 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.

Methods and Results Tregs were isolated by magnetic cell sorting-column and analysed by fl ow cytometry. Macrophages were cultured with or without Tregs in the presence of oxidised 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.

Conclusions Tregs can inhibit the proinflammatory properties of macrophages and steer macrophage differentiation toward an anti-infl amatory 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-beta (TGF-beta) are the key factors for these suppressive functions.