FOXP3 and neoplasm: Le Mercier et al. reported that VISTA acts as a negative checkpoint regulator to suppress T cell activation and induce Foxp3 expression and is highly expressed within the tumor microenvironment.24 In addition, Ceeraz et al. reported that in VISTA-deficient mice, surface expression of the C5a receptor was reduced on monocytes, neutrophils, and cultured macrophages, suggesting that VISTA supports optimal responses to C5a and modulates macrophage responses to immune complexes.25