1. From the Immune Disease Institute (S.F.D.M., D.D.W.) and the Program in Cellular and Molecular Medicine (S.F.D.M., D.D.W.), Children's Hospital Boston, Boston, MA; the Department of Pediatrics (S.F.D.M., D.D.W.), Harvard Medical School, Boston, MA; the Laboratory for Thrombosis Research (S.F.D.M.), KULeuven Campus Kortrijk, Kortrijk, Belgium; and the Department of Neurology (G.S., C.K.), University of Wuerzburg, Wuerzburg, Germany.