Background & aims: Inflammatory bowel disease is characterized by a failure to down-regulate the usual self-limited gut inflammatory response, suggesting that one or more of the predisposing genes could be those that determine the level of the immune response along the inflammatory pathway. The aim of this study was to examine potential associations of intercellular adhesion molecule 1 (ICAM-1) gene polymorphisms with inflammatory bowel disease or subsets of inflammatory bowel disease.
Methods: One hundred eighteen patients with ulcerative colitis (UC) and 130 patients with Crohn's disease (CD) as well as 77 ethnically matched controls were tested for antineutrophil cytoplasmic antibodies (ANCAs) and genotyped by polymerase chain reaction and allele-specific oligonucleotide techniques for ICAM-1 polymorphisms at codon 241 (exon 4) and codon 469 (exon 6).
Results: There was no significant difference between all patients with UC, patients with CD, and controls in either polymorphism. However, when stratified by ANCA status, ANCA-negative UC showed a significantly increased frequency of allele R241 compared with ANCA-positive UC (16.0% vs. 6.6%; P = 0.047, Fisher's Exact Test). In contrast, it was ANCA-positive CD that had an increased allele frequency compared with ANCA-negative CD (19.6% vs. 8.4%; P = 0.027, Fisher's Exact Test).
Conclusions: Because the codon 241 polymorphism is in a functionally important domain III of ICAM-1, we may have identified an actual responsible genetic variation for genetically heterogeneous subsets of both UC and CD.