Researchers have found that a specific type of immune cell, the regulatory T lymphocyte plays an important role in hypertension-induced cardiac damage. The injected Treg that they harvested from donor mice into recipient mice were infused with angiotensin II, a blood pressure-raising peptide. The Tregs had no influence on the blood pressure response to angiotensin II. Nonetheless, cardiac enlargement, fibrosis, and inflammation was sharply reduced by Treg treatment.