SLC6A2 and irritable bowel syndrome: However, they provide a roadmap by comparing risk factors for PI-IBS and sporadic IBS in which toll-like receptor 9, cadherin-1, and interleukin 6 appeared to be involved in PI-IBS, while for sporadic IBS, genetic risk factors were represented by a deregulation of serotoninergic pathway of serotonin receptor 2A and solute carrier family 6 (neurotransmitter transporter, serotonin), member 4 and the secretion of interleukin 10.