Healing and repair after myocardial infarction: the forgotten but resurgent basophil.

The biphasic wound-healing response in the heart after myocardial infarction involves an initial inflammatory phase followed by a more prolonged period of inflammation resolution, tissue repair, and scar formation. Infiltrating proinflammatory Ly6Chi monocytes and monocyte-derived macrophages are key drivers of the inflammatory phase and are also the source of the locally generated reparative macrophages that promote inflammation resolution. In this issue of the JCI, Sicklinger et al. from the Leuschner laboratory uncover a salutary role for cardiac basophils in this process. The authors demonstrated that basophils promote healing and proper scar formation and also limit late cardiac remodeling by augmenting reparative macrophages in the infarcted heart, in part via basophil-derived enhancement of cardiac IL-4 and IL-13 levels. These findings underscore the potentially disproportionate (relative to cell numbers) yet essential biological effects of immune cells of low abundance on cardiac repair and remodeling, related in part to amplification of downstream macrophage responses via secreted cytokines.