TNFSF18 and atherosclerosis: B cell–restricted overexpression of another costimulatory ligand, GITRL, in transgenic hCD19-mGITRL Ldlr–/– BM chimeras also reduced early atherosclerosis.75 Although the mechanism is unclear, the authors attributed this to B-cell GITRL directly or indirectly inducing TREG expansion possibly through elevated IL-2 only detected in the thymus and aortas.