Objective      To determine the differential expression levels of acute phase proteins (APPs) in peripheral blood mononuclear cells (PBMCs) from patients with ankylosing spondylitis (AS)

and to investigate their role in the pathogenesis of AS.       Methods      PBMCs were isolated from 9 health controls and 10 AS patients by using Ficoll-Paque plus solution. The proteins of PBMCs were extracted using cell lysate

and iTRAQ coupled with multiple chromatographic fractionation and tandem mass spectrometry were used to screen the APPs in the obtained PBMCs. Mascot software (Matrix Science) was applied to identify and quantify the proteins

and Western blotting were used to further validate the expression levels of haptoglobin (Hp) and ceruloplasmin (Cp).       Results      Initial mass spectrometry-based proteomic analysis revealed that the expression levels of 19 APPs were obviously increased in the PBMCs from AS patients (P0.05)

mainly including complement C3

isoform 1 of fibronectin

plasminogen

serotransferrin

Hp and Cp. Moreover

Western blotting indicated that the expression levels of Hp and Cp had a similar trend with iTRAQ results.       Conclusion      The differential expression of APPs might be associated with the pathologenesis and development of AS

and can be used as clinical biomarkers of AS.