TNF and inflammatory bowel disease: Among these, the polymorphisms TNFα −308 A/G, −238 A/G, and −857 C/T have been studied extensively to determine their association with the response to TNFα blockers in different SpA subgroups (including for AS, IBD/ CD, and PsA/Ps)12, 13, 14, 15, 16, 17, 18, 19, 20, 21.