Abstract 384: Pirfenidone Protects the Heart Through Immune Modulation of Subsets of Cardiac B Lymphocytes

Despite the long-standing recognition that the immune response to acute myocardial injury contributes to adverse left ventricular (LV) remodeling, it has not been possible to effectively target inflammation clinically. Using two different in vivo models of acute myocardial injury, we show that Pirfenidone confers beneficial effects in the murine heart through a new mechanism that depends upon cardiac B lymphocytes. Naïve hearts contained a large novel population of CD19 + CD11b - CD23 - CD21 - IgD + IgM low lymphocytes, and two smaller populations of CD19 + CD11b + B1a and B1b cells. In response to tissue injury, there was an increase in neutrophils, monocytes, macrophages, as well as an increase in CD19 + CD11b - B lymphocytes. Treatment with Pirfenidone had no effect on the number of neutrophils, monocytes, or macrophages, but decreased CD19 + CD11b - lymphocytes. B cell depletion abrogated the beneficial effects of Pirfenidone. In vitro studies demonstrated that stimulation with lipopolysaccharide and extracts from necrotic cells activated CD19 + lymphocytes through a TIRAP dependent pathway. Treatment with Pirfenidone attenuated this activation of B cells. These findings reveal a previously unappreciated complexity of myocardial B lymphocytes within the inflammatory infiltrate triggered by cardiac injury and suggest that Pirfenidone exerts beneficial effects in the heart through a unique mechanism that involves modulation of cardiac B lymphocytes.