Vitamin D modulates peripheral immunity in patients with Behçet's disease

There is little knowledge about clinical and immunological variables associated with vitamin D insufficiency in inflammatory diseases. We sought to investigate disease variables associated with vitamin D levels in patients with Behçet's disease (BD) and its interaction with inflammatory responses.

One hundred and sixty BD patients (102 patients in active stage) were enrolled in a study assessing the relationship between serum vitamin D concentrations and disease activity. As control diseases we studied 22 Rheumatoid arthritis (RA) and 30 multiple sclerosis (MS) patients. Serum concentrations of vitamin D were assayed with a radioimmunoassay kit. To assess the correlation between inflammatory mediators, immune cell expression and vitamin D, 20 active BD patients and 18 healthy controls were investigated: T-cell subsets and Treg cells were quantified by flow cytometry. Th1/Th2 ratio and Th17 were studied by intracytoplasmic cytokines expression (IFN-γ, IL-4, IL-10 and IL-17).

Decreased levels of vitamin D were observed in active BD patients compared to patients in the inactive stage and to healthy controls (p=0.0246; p=0.0001). A low significant difference was observed between inactive BD and healthy controls (p=0.004). Active BD expressed higher vitamin D levels than RA (p=0.007) and MS (p=0.044) patients (p=0.0238). In active BD, vitamin D levels were correlated with CRP and ESR. Serum levels of vitamin D correlated positively with the number of Treg cells (r=0.640; p=0.0024). The IFN-γ/IL-4 ratio (Th1/Th2) was inversely correlated with serum 25(OH)D levels (r=-0.599; p=0.0053).

Active BD was associated with lower serum Vitamin D levels. Our results showed that low levels of vitamin D were associated with a decrease in Treg cells and a skewing of the Th1/Th2 balance towards Th1. These findings suggest that vitamin D is an important promoter of T cell regulation in vivo in BD patients. As suggested in other inflammatory/autoimmune diseases, vitamin D may modulate inflammatory mediators.