ABCB1 and inflammatory bowel disease: Among the polymorphisms identified in MDR1 gene, the most widely investigated in IBD association studies as well as in other diseases are the 1236C>T (exon 12; rs1128503, Gly412Gly), 2677G>T/A (exon 21; rs2032582, Ala893Ser/Thr), and 3435C>T (exon 26; rs1045642, Ile1145Ile) with conflicting results in different populations around the world [9–11].