If I were still doing sternotomies for CABG surgery I would do a study and look at thymic tissue Old folks have skinny little thymus, children and young adults it is thick, well vascularized and full of good immunogenic cells. My vote is the thymus lymphocytes (T-cells) are the key. Of course with no data except >3000 heart surgeries... but that is more than Fauci ever offered.