Background & Aims: Genetic studies of the serum expression of antibodies to microbial antigens may yield important clues to the pathogenesis of Crohn's disease. Our aim was to conduct a linkage study using expression of anti-CBir1, anti-I2, anti-OmpC, and ASCA as quantitative traits.
Methods: Expression of antibodies to microbial antigens was measured by ELISA and a standard ~10cM whole genome microsatellite study was conducted. SNP genotyping was performed using either Illumina or TaqMan MGB technology. NFKB1 activation in cells from EBV-transformed cell lines was assessed using EMSA and protein was measured using ELISA and Western blotting.
Results: Evidence for linkage to anti-CBir1 expression was detected on human chromosome 4 (LOD 1.82 at 91cM). We therefore directly proceeded to test the association of haplotypes in NFKB1, a candidate gene. One haplotype, H1, was associated with anti-CBir1 (P = 0.003) and another, H3, was associated with ASCA (P = 0.023). Using cell lines from CD patients with either H1 or H3, NF-κB activation and NFKB1 p105 and p50 production were significantly lower for patients with H1 compared to patients with H3.
Conclusions: These results suggest that NFKB1 haplotypes induce dysregulation of innate immune responses by altering NFKB1 expression. The results also show the use of EBV-transformed lymphoblastoid cell lines to conduct phenotypic studies of genetic variation.