CD274 and atherosclerosis: While depletion of all B2 cells reduces atherosclerosis,2–4 we have recently discovered that selective depletion of MZB cells promotes atherosclerosis.5 In response to a high-fat/high-cholesterol (HF/HC) diet, MZB cells activate an atheroprotective programme, limiting T follicular helper (Tfh) cell motility in a PDL1 (programmed death ligand-1)-dependent manner.5