He is a member of the Royal Netherlands Academy of Arts and Sciences (since 2003), of which he was vice president and chairman of the division of natural sciences (2006-2012). He is a member of Academia Europaea. Between 2014 and 2016 he was president of European Academies Science Advisory Council (EASAC).[1] He performs research on cytokines and host defence, chronic fatigue syndrome and hyper-immunoglobulinemia D syndrome (HIDS). He is also active in graphic art and makes cartoons, for example for the Dutch science journal Mediator.