TFF1(Trefoil factor 1), also known as pS2, is a protein that in humans is encoded by the TFF1 gene. Members of the trefoil family are characterized by having at least one copy of the trefoil motif, a 40-amino acid domain that contains three conserved disulfides. They are stable secretory proteins expressed in gastrointestinal mucosa. Their functions are not defined, but they may protect the mucosa from insults, stabilize the mucus layer, and affect healing of the epithelium. It is found that TFF1 in normal human urine inhibited the growth of calcium oxalate crystals. Urinary TFF1 showed an inhibitory potency similar to that of nephrocalcin, and inhibition was dose dependent and inhibited by TFF1 antisera, particularly by antisera directed to the TFF1 C terminus. Concentrations and relative amounts of TFF1 in the urine of patients with idiopathic calcium oxalate kidney stones were significantly less than those found in controls.This gene, which is expressed in the gastric mucosa, has also been studied because of its expression in human tumors. This gene and two other related trefoil family member genes are found in a cluster on chromosome 21.