IL-17A is involved in inflammation and defense against infection by inducing fibroblasts, endothelial cells, and epithelial cells to express pro-inflammatory cytokines (TNF, IL-1, IL-6, G-CSF, and GM-CSF), chemokines (CXCL1, CXCL5, IL-8, CCL2, and CCL7), and antimicrobial peptides (defensin and S100 protein) and matrix metalloproteinases (MMP1, MMP3, and MMP13) [11, 34, 35]. The gene discussed is MMP1; the disease is infection.