TAP gene transporter polymorphism in inflammatory bowel diseases

Area of Science:

• Immunogenetics
• Gastroenterology
• Molecular Biology

Background:

• Genetic factors are implicated in inflammatory bowel diseases (IBD), including ulcerative colitis (UC) and Crohn's disease (CD).
• Major histocompatibility complex (MHC) and transporter associated with antigen processing (TAP) genes are potential susceptibility loci.
• Previous studies show limited data, possibly due to ethnic variations, clinical heterogeneity, or involvement of additional genes like TAP.

Purpose of the Study:

• To investigate the polymorphism of TAP genes (TAP1 and TAP2) in patients with UC and CD.
• To determine if TAP gene variations are associated with genetic susceptibility or clinical features of IBD.

Main Methods:

• Analyzed TAP1 and TAP2 gene dimorphisms in 101 UC patients, 148 CD patients, and 173 healthy controls.
• Utilized sequence-specific oligonucleotide typing for allele analysis.
• Compared genotype frequencies between patient groups and controls, and within CD patients based on steroid responsiveness.

Main Results:

• No significant differences in TAP gene polymorphisms were observed between overall UC/CD patient groups and healthy controls.
• A significantly lower frequency of the TAP2 AA (*0101/*0101) genotype was found in CD patients unresponsive to steroid therapy (22.9%) compared to steroid responders (43.7%).
• This association was independent of HLA DRB1*01 or DRB1*03 alleles, despite linkage disequilibrium with TAP2A.

Conclusions:

• The TAP2 gene, or other genes on chromosome 6, may contribute to the genetic heterogeneity observed in Crohn's disease.
• While not a primary susceptibility factor, TAP2 variations might influence disease phenotype or treatment response in CD.