Fig 2.

Associations between CD4⁺ T cells and macrophages. T-helper (Th) 1 cells secrete interferon-γ (IFN-γ) to induce M1 macrophages. M1 macrophages secrete IFN-γ and tumor necrosis factor-α (TNF-α) to promote inflammation. Th2 cells secrete IL-4 to induce M2a macrophages. Regulatory T cells (Treg) secrete interleukin (IL)-10 and transforming growth factor-β (TGF-β) to induce M2a, M2c and M2d macrophages. M2a and M2c macrophages secrete IL-10 and TGF-β to contribute to anti-inflammation, wound healing, and tissue remodeling. M2d secrete vascular endothelial growth factor (VEGF) to promote angiogenesis.