TGFB1 and HIV infectious disease: It is well documented that Tregs promote collagen deposition and subsequent mucosal fibrosis via the secretion of transforming growth factor β1 (TGF-β1) starting from the acute phases of SIV/HIV infections particularly in mesenteric lymph nodes (MLNs), which drain the small and large intestines (4, 22), and in lower levels in nonpathogenic lentiviral infections such as in African green monkeys (22).