Dysregulation of peripheral blood B-cells and NK-cells is associated with myocarditis in idiopathic inflammatory myopathies

Myocarditis is estimated to affect up to 50% of IIM patients and is a major cause of adverse outcomes in these patients. Yet, we know very little about the underlying immunologic processes that are driving myocarditis in the context of IIM.

In this study we use single-cell RNA sequencing of peripheral blood mononuclear cells of 12 patients with myositis alone (n=4), myositis plus myocarditis(n=4) and healthy controls(n=4), in order to better understand the immunologic alterations characterizing this manifestation of the disease. We found the most notable changes in B cells and NK cells with myositis plus myocarditis patients B cells having gene expression signatures suggestive of increased DNA replication and repair, somatic hypermutation, and lymphocyte activation, but a smaller proportion of memory B cells, suggesting a greater activation of naive B cells in the periphery.