The main findings of the present work can be summarized as follows: (1) Treg cells are decreased in CHF patients and CRT seems not to be able to restore their normal levels; (2) responders to CRT presented a higher frequency of Tc cells producing IL-2 at baseline than non-responders and a higher percentage of Tc cells expressing TNF-α and IFN-γ after CRT than healthy individuals. Here, IL2 is linked to congestive heart failure.