In 2004 a novel function of the neutrophil was identified: formation of neutrophil extracellular traps (NETs). Apparently, neutrophils are able to extrude part of their cellular contents in the form of DNA, histones and proteases, to form extra cellular NETS that trap and kill bacterial pathogens without the need for phagocytosis. We aim to study if pathological NETs formation could be the underlying pathology among these patients with recurrent infections and a normal screening of the immune system.