TNF and mastitis: It has been reported that cytokines, such as tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, IL-6, IL-8, and granulocyte-macrophage colony-stimulating factor (GM-CSF) [11], and chemokines, such as chemokine CC motif ligand (CCL)2, CCL3, CCL5, CCL20, chemokine CXC motif ligand (CXCL)1, and CXCL2, play important roles in the pathogenesis of mastitis [12].