Copy Number Variations of Complement Component C4 Are Associated With Behçet's Disease but Not With Ankylosing Spondylitis Associated With Acute Anterior Uveitis
Article first published online: 28 OCT 2013
Copyright © 2013 by the American College of Rheumatology
Arthritis & Rheumatism
Volume 65, Issue 11, pages 2963–2970, November 2013
How to Cite
Hou, S., Qi, J., Liao, D., Zhang, Q., Fang, J., Zhou, Y., Liu, Y., Bai, L., Zhang, M., Kijlstra, A. and Yang, P. (2013), Copy Number Variations of Complement Component C4 Are Associated With Behçet's Disease but Not With Ankylosing Spondylitis Associated With Acute Anterior Uveitis. Arthritis & Rheumatism, 65: 2963–2970. doi: 10.1002/art.38116
- Issue published online: 28 OCT 2013
- Article first published online: 28 OCT 2013
- Accepted manuscript online: 5 AUG 2013 03:16PM EST
- Manuscript Accepted: 30 JUL 2013
- Manuscript Received: 30 MAY 2013
- Natural Science Foundation Major International (Regional) Joint Research Project. Grant Number: 81320108009
- Key Project of the Natural Science Foundation. Grant Number: 81130019
- National Basic Research Program of China (973 Program)
- National Natural Science Foundation Project. Grant Numbers: 31370893, 81070723, 81270990
- Clinic Key Project of the Ministry of Health, Basic Research program of Chongqing. Grant Number: cstc2013jcyjC0001
- Chongqing Key Laboratory of Ophthalmology. Grant Number: CSTC, 2008CA5003
- Key Project of the Health Bureau of Chongqing. Grant Number: 2012-1-003
- Fund for PAR-EU Scholars Program
Complement component C4 copy number variations are associated with various inflammatory diseases. This study was undertaken to investigate whether copy number variations of C4 are also involved in the pathogenesis of Behçet's disease (BD).
Gene expression was examined by enzyme-linked immunosorbent assay (ELISA) or real-time polymerase chain reaction (PCR). Copy number variations of C4 isotypes (C4A and C4B) were detected by real-time PCR in 905 patients with BD, 205 patients with ankylosing spondylitis (AS) and acute anterior uveitis, and 1,238 controls. The activation of CD4+ T cells was analyzed by flow cytometry, and cytokine production was detected by ELISA.
Protein expression of total C4 in serum was significantly increased in patients with active BD compared with those with inactive BD or controls (Bonferroni corrected P [Pcorr] = 1.64 × 10−4 and Pcorr = 0.037, respectively), but not in patients with AS and acute anterior uveitis. Copy number variation analysis identified a significantly increased frequency of more than 2 copies of C4A in BD patients (P = 1.65 × 10−7, odds ratio [OR] 2.84). HLA–B51, which is located on the same chromosome as C4, showed a strong association with BD in the Han Chinese population (P = 8.90 × 10−65, OR 5.05), but logistic regression showed that C4A copy number variation was an independent risk factor for BD. A significantly increased expression of C4A was observed in the high copy number groups (>2 copies or 2 copies) versus the low copy number group (Pcorr = 0.019 and Pcorr = 0.044, respectively). Increased production of interleukin-6 (IL-6) was also observed in the high C4A copy number group (Pcorr = 0.037). No effect of C4 copy number variation on the expression of T cell activation markers was detected.
Our findings indicate that a high copy number of C4A confers risk for BD by modulating the expression of C4A and enhancing IL-6 production.