CD274 and esophageal squamous cell carcinoma: PD-L1-EVs from esophageal squamous cell carcinoma decrease the ratio of circulating follicular helper T cells to follicular regulatory T cells and upregulate CTLA4 in the former, inhibiting follicular helper T cell differentiation by preventing the binding of CD28 to its ligands, leading to high expression of ICOS and activation of downstream PI3K100,101.