Research in the laboratory is focused on the immunobiology of eosinophils. As cells of the innate immune system eosinophils are notable for their content of a single type of intracellular granule. These granules in human eosinophils contain four principal eosinophil cationic proteins as well as multiple diverse pre-formed cytokine proteins and their receptors. These granules may function both intracellularly and when released extracellularly. Intracellular granules participate in a process of selective secretion of their granule-derived proteins termed piecemeal degranulation that is distinct from wholesale exocytosis. Ongoing studies are investigating the mechanisms of selective secretion including the role of the highly abundant and human specific eosinophil protein that forms Charcot-Leyden crystals. In addition by a process of cytolysis, human eosinophils release intact granules extracellularly that remain secretion competent.