Genetic and immunological markers in pouchitis

Previous studies of the interleukin-1 receptor antagonist (IL-1RN) have found an increased frequency of the associated variable number tandem repeat (VNTR) allele 2 for ulcerative colitis (UC) and further evidence has been reported that this allele is associated with increased severity of several other inflammatory conditions. The HLA type of UC patients has also been implicated in the extent of disease as has the presence of perinuclear anti-neutrophil cytoplasmic antibodies (p-ANCA). We therefore decided to test the hypothesis that the p-ANCA, HLA type or the presence of the IL-1RN allele 2 in patients who received a restorative proctocolectomy for UC had an effect on the risk of developing pouchitis.

We determined the genotypes of the IL-1RN and HLA DR beta and DQ beta loci for 28 subjects with previous UC and a pouch with no evidence of pouchitis for a minimum of 2 years after formation of an ileo-anal reservoir (mean 6.3 years; range 2-17 years) and 25 subjects with previous UC and pouchitis confirmed by strict histological examination of pouch mucosal biopsy. The IL-1RN genotypes were also determined for 86 healthy controls and 61 unrelated patients with familial adenomatous polyposis (FAP). The p-ANCA status was determined for all 25 pouchitis subjects but only 23/28 non-pouchitis subjects, with 15 unaffected subjects as a negative control.

The HLA haplotypes of the UC groups were determined by polymerase chain reaction sequence-specific primer (PCR-SSP) typing and the IL-1RN genotypes were determined by PCR and agarose gel electrophoresis. The p-ANCA status was determined by indirect immunofluorescence.

A chi 2 of 5.686 with 1 degree of freedom and a P value of 0.0171 using Yates' correction was obtained by comparing the IL-1RN allele frequencies of the combined UC groups to the FAP controls, and a chi 2 of 6.801 with 1 degree of freedom and a P value of 0.0091 comparing the pouchitis group to the FAP controls. The HLA haplotype frequencies did not vary significantly between groups nor did they correlate with p-ANCA status. There were also no significant associations of the p-ANCA status and pouchitis.

There is an increased frequency of IL-1RN allele 2 in UC, with the majority of the association arising from the pouchitis group, suggesting that the presence of allele 2 in patients with UC affects the disease outcome. However, the HLA frequencies and p-ANCA status do not have any significant associations.