TNF and autoimmune disease: As a critical pro-inflammatory factor, IL-6 is produced by both immune cells, as well as various types of tissue cells (e.g., fibroblasts, epithelial cells, and keratinocytes) under the stimulation of IL-1, TNF-α, PDGF, virus, double-stranded RNA, and c-AMP, and subsequently promotes the development of inflammatory and autoimmune diseases (54–58).