Hypothesis:Abnormal Vitamin D (Vit D) level could have consequences on the immuno-inflammatory processes in Ankylosing Spondylitis (AS).

Aim:The purpose of this study was to analyze the role of Vitamin D in the interplay between immune and inflammation effectors in AS associated-Acute Anterior Uveitis (AAU).

Methods and Results:25-hydroxyvitamin D (Vit D), LL-37 peptide, IL-8 and Serum Amyloid A (SAA) were identified and quantified in the serum/ plasma of thirty-four AS patients [eleven AS patients presenting AAU (AAU AS patients) and twenty-three AS patients without AAU (wAAU AS patients)] and eighteen healthy individuals (Control) using enzyme-linked immunosorbent assay. Acute-phase SAA level was significantly higher in AS patients compared to Controls. Contrary with wAAU AS patients, significantly elevated levels of IL-8, and diminished levels of Vit D characterized AAU AS patients. Regarding LL-37, its level decreased concomitantly with the level of Vit D. When AS patients were subgrouped based on AAU presence or on Vit D level, important associations between immuno-inflammatory assessed markers and AS features were noticed. Generally, Vit D levels were associated indirectly with leukocytes/ neutrophils number or with ESR, CRP, and Fibrinogen levels. The levels of SAA and IL-8 associated directly with AAU or with AAU relapses, especially in AS patients with Vit D insufficiency, while SAA associated directly with infection/ inflammatory markers and with disease activity indexes or with the degree of functional limitation.

Discussion:Altered levels of Vit D affect the balance between LL-37, IL-8 and SAA, suggesting an association with AAU, an extra-articular manifestation of AS.

Abbreviations:Vit D = Vitamin D, AS = Ankylosing Spondylitis, AAU = Acute Anterior Uveitis, AAU AS = AS patients with AAU, wAAU AS = AS patients without AAU, SSZ = Sulphasalazine, Leu = Leukocytes, Neu = Neutrophils.