IL15 and infection: The stimulating factors affected adaptive immune cells (Th1, Th2, Th17, Tgd17, and CD8 T cells) to secrete IL-4, IL-5, IL-15, TNF-α, and chemokine CXCL8 (IL-8), which influenced neutrophils, macrophages (M1 and M2), and other granulocytes to fight against extracellular bacteria, tumors, viruses or extracellular parasites involved in immunologic processes of infection resistance, autoimmunity and allergic disease.