Sequence analysis and expression of a mouse homolog of human IkappaBL gene

NFKBIL1 confers resistance to experimental autoimmune arthritis through the regulation of dendritic cell functions

We and others have reported that human NF-κB inhibitor-like-1 (NFKBIL1) was a putative susceptible gene for autoimmune diseases such as rheumatoid arthritis (RA). However, its precise role in the pathogenesis of RA is still largely unknown. In this study, we generated transgenic mice expressing human NFKBIL1 (NFKBIL1-Tg) and examined whether NFKBIL1 plays some role(s) in the development of autoimmune arthritis. In both a collagen-induced arthritis model and a collagen antibody-induced arthritis model, NFKBIL1-Tg mice showed resistance to arthritis compared to control mice, indicating that the gene product of NFKBIL1 was involved in the control of thusly induced arthritis. Total spleen cells of NFKBIL1-Tg mouse showed decreased proliferation to mitogenic stimuli, consistent with its resistance to arthritis. Unexpectedly, purified T cells of NFKBIL1-Tg mouse showed increased proliferation and cytokine production. This apparent discrepancy was accounted for by the impaired functions of antigen-presenting cells of NFKBIL1-Tg mouse; both T/B cell-depleted spleen cells and bone marrow-derived dendritic cells of the Tg mouse induced less prominent proliferation and IL-2 production of T cells. Furthermore, dendritic cells (DCs) derived from NFKBIL1-Tg mouse showed lower expression of co-stimulatory molecules and decreased production of inflammatory cytokines when they were activated by lipopolysaccharide. Taken together, these results indicated that NFKBIL1 affected the pathogenesis of RA at least in part through the regulation of DC functions.

Direct Determination of Single Nucleotide Polymorphism Haplotype of NFKBIL1 Promoter Polymorphism by DNA Conformation Analysis and Its Application to Association Study of Chronic Inflammatory Diseases

We previously revealed that one of the human leukocyte antigen-linked susceptibility genes for Takayasu's arteritis (TA) was mapped between TNFA and MICB loci and that -63T allele of NFKBIL1, which is between TNFA and MICB loci, was associated with rheumatoid arthritis (RA) in the Japanese population. We have developed a novel typing method based on reference strand-mediated conformation analysis for the upstream sequence of the NFKBIL1 gene, where -422 (T)8/(T)9, -325 C/G, -263 A/G, and -63 T/A polymorphisms were found. Upon the analysis of the patients with TA (n = 84), those with RA (n = 120), and healthy control subjects (n = 217), five common haplotypes named IKBLp*01 through IKBLp*05 were found in the Japanese population. The frequency of IKBLp*03 was significantly increased in the patient with TA (57.1% vs 35.0%, giving an odds ratio of 2.47). In addition, the frequency of IKBLp*01, but not that of other -63T-bearing alleles, was increased in the patients with RA (73.3% vs 58.1%, giving an odds ratio of 1.99), suggesting that the susceptibility to RA was conferred not by -63T alone but by combination of single nucleotide polymorphisms in the NFKBIL1 promoter. A higher promoter activity associated with IKBLp*03 and a lower activity associated with IKBLp*01 may contribute to the susceptibility to TA and RA, respectively.