We found a significant increase of CD157 (encoded by Bst1)-expressing fibroblasts (Fig. 2e and Extended Data Fig. 2d) and significant upregulation of the fibroblast activation molecules NCAM1 (Fig. 2f), SCA-1 (Fig. 2g) and ICAM1 (Fig. 2h) early after onset of myocarditis, supporting the notion that fibroblasts can change swiftly from a homeostatic to an inflammatory phenotype during myocardial inflammation. Here, NCAM1 is linked to myocarditis.