TNFSF9 and type 2 diabetes mellitus: Previously, we screened islet transcriptomic data from patients with T2D and healthy controls and reported that six immune checkpoint genes, including CD44, CD47, SIRPA, HAVCR2, TNFSF9, and VTCN1, were highly expressed on human diabetic islet cells, although the functions and underlying mechanisms are not clear [13].