IL-5 is an interleukin produced by T helper-2 and mast cells. It is known to stimulate B cell growth and increase immunoglobulin secretion through binding to the IL-5 receptor. IL-5 is also known to be a cause of asthma and allergic rhinitis. IL-5 can stimulate growth and differentiation of eosinophils and activation and differentiation of eosinophilic granulocytes.