B cell depletion mediated by DT administration reduced cardiac fibrosis and scar size of adult Cd19DTR mice post-MI, which partially attributed to the decreased expression of fibrosis-related genes (such as fibronectin 1 [Fn1] and collagen type I alpha 1 chain [Col1a1]) and the limited myofibroblast proliferation (Supplementary Fig. 2c–e). The gene discussed is FN1; the disease is myocardial infarction.