IL-5 has been supplemented by tcellreplacing factor (trf), and it has been found that human il-5 has no obvious stimulating effect on b cells; its main function is to stimulate eosinophil proliferation, differentiation and activation. Il-5 not only increases the number of eosinophils, but also enhances its function. Eosinophilia in worm infections and allergic diseases is mainly caused by il-5. Human il-5 also promotes the release of inflammatory mediators such as histamine and leukotrienes from basophils, thereby increasing the activity of basophils.