Macrophage infiltration and activation in myocardium are hallmarks of acute cardiac inflammatory response to high blood pressure. However, the underlying mechanisms remain elusive. In this article, we report that CD8+ T cells are required for cardiac recruitment and activation of macrophages. First, mice with CD8 gene-targeted (CD8 knockout) or CD8+ T cells depleted by Ab showed significantly reduced cardiac inflammatory response to the elevation of blood pressure after angiotensin II (Ang II) infusion, whereas CD8 knockout mice reconstituted with CD8+ T cells restored the sensitivity to Ang II. More importantly, CD8+ T cells were required for macrophage infiltration in myocardium and subsequent activation to express proinflammatory cytokines and chemokines. Furthermore, macrophage activation required direct contact with activated CD8+ T cells, but with TCR dispensable. TCR-independent activation of macrophages was further confirmed in MHC class I-restricted OVA-specific TCR transgenic mice, which showed a CD8+ T cell activation and cardiac proinflammatory response to Ang II similar to that of wild-type mice. Finally, only myocardium-infiltrated, but not peripheral, CD8+ T cells were specifically activated by Ang II, possibly by the cardiac IFN-γ that drove IFN-γR+ CD8+ T cell infiltration and activation. Thus, this work identified a TCRindependent innate nature of CD8+ T cells that was critical in initiating the sterile immune response to acute elevation of blood pressure. The Journal of Immunology, 2014, 192: 3365-3373.
ASJC Scopus subject areas
- Immunology and Allergy