Objective: To identify differentially expressed genes in peripheral blood mononuclear cells (PBMCs) from patients with ankylosing spondylitis (AS) compared to healthy individuals.
Methods: RNA was extracted from PBMCs collected from 18 AS patients with active disease and 18 gender- and age-matched controls. Expression profiles of these cells were determined using microarray. Candidate genes with differential expressions were confirmed in the same samples using quantitative reverse transcription-polymerase chain reaction (qRT-PCR). These genes were then validated in a different sample cohort of 35 AS and 18 patients by qRT-PCR.
Results: Microarray analysis identified 452 genes detected with 485 probes which were expressed at significantly different levels (p<0.006) between AS patients and controls. Under-expression of NR4A2, TNFAIP3, and CD69 was confirmed. These genes were further validated in a different sample group where the AS patients had a wider range of disease activity. Predictive algorithms were also developed from the expression data using Receiver-Operator Characteristic (ROC) curves, which demonstrated that the 3 candidate genes have ~80% power to predict AS according to their expression levels.
Conclusions: Our findings showed differences in global gene expression patterns between AS patients and controls suggesting an immunosuppressive phenotype in AS patients. Furthermore, we confirmed downregulated expression of 3 immune-related genes. These candidate genes were also shown to be strong predictive markers for AS.