Are Systematic Screening for Vitamin D Deficiency and Vitamin D Supplementation Currently Feasible for Ankylosing Spondylitis Patients?

Figure 1

Vitamin D immunomodulatory activity influencing ankylosing spondylitis. +: stimulation by vitamin D (Vit D); −: inhibition by Vit D. Vit D can have effect on the naïve T cell, the natural killer (NK) cell, the B cell, and monocyte hence putatively inhibiting ankylosing spondylitis pathogenesis. (I) Vit D may stimulate the naïve T cell’s differentiation into T helper (Th) 2 with raised production of anti-inflammatory cytokines and into the T regulatory (Treg) cell, thus inhibiting the self-reactive T lymphocyte. Besides, Vit D may inhibit differentiation of the naïve T cell into Th1 and Th17 with decreased production of proinflammatory cytokines. (II) Vit D may stimulate the NK cell to inhibit the self-reactive T lymphocyte. (III) Vit D may inhibit differentiation of the B cell into plasmocyte, thus inhibiting the production of cross-reacting antibodies. (IV) Vit D may inhibit monocyte-to-dendritic cell differentiation and monocyte-to-macrophage differentiation, with consequential reduced production of proinflammatory cytokines. IL: interleukin; IFNγ: interferon gamma; TNF-α: tumor necrosis factor alpha.