1. From the Program in Cellular and Molecular Medicine (J.I.B., A.B., T.A.F., A.S.S., M.G., K.M., D.D.W.) and Division of Hematology/Oncology (D.D.W.), Boston Children’s Hospital, Boston, MA; Department of Pediatrics (J.I.B., A.B., T.A.F., A.S.S., D.D.W.) and Immunology Graduate Program, Division of Medical Sciences (K.M.), Harvard Medical School, Boston, MA; Laboratory for Clinical Thrombosis and Hemostasis, Department of Internal Medicine (J.I.B., H.t.C.), Department of Cardiology (I.A.J., M.O.V., H...