Ulcerative colitis (UC) is a chronic relapsing-remitting inflammatory disorder of the large intestine. CTLA-4 is a member of the immunoglobulin superfamily, which binds B7-1 and B7-2 on APCs, and induces an inhibitory signal to T cells. The aim of this study was to investigate the effect of vitamin D on CTLA-4 gene expression in UC patients.

In this double-blind randomized placebo-controlled trial 90 mild to moderate UC patients were randomized to receive either a single injection of 7.5 mg vitamin D3 or 1 ml normal saline as placebo. Three months following the intervention fold changes in CTLA-4 mRNA expression were determined and statistical comparisons between the two groups were performed.

Forty patients in the placebo group and 46 patients in the vitamin D group completed the study. Three months after the intervention, serum vitamin D raised significantly only in the vitamin D group. Fold changes in the vitamin D group were significantly higher than the placebo group (Median ± IQR: 1.21 ± 2.3 vs. 1.00 ± 1.5 respectively; p= 0.007).

The results of this study revealed that vitamin D administration in UC patients enhances the CTLA-4 gene expression.