Pleiotropic effects of vitamin D on CD4 T lymphocytes mediated by human periodontal ligament cells and inflammatory environment.

Aims: Both, vitamin D and human periodontal ligament cells (hPDLCs) possess immunosuppressive properties, but their combined effect on immune cells has never been investigated. Here, we analysed the impact of vitamin D on the immunosuppressive properties of hPDLCs towards CD4 T lymphocytes.

Material And Methods: Allogenic CD4 T lymphocytes were activated by phytohemagglutinin either in monoculture or co-culture with hPDLCs, in the presence or absence of IFN-γ and 1,25(OH) D . After 5 days, CD4 T-lymphocyte proliferation, CD4 CD25 FoxP3 regulatory T lymphocytes (T ) proportion and IL-10, TGF-β1 and IL-17A production were analysed.

Results: In monoculture, 1,25(OH) D suppressed CD4 T-lymphocyte proliferation, increased the percentage of CD4 FoxP3 CD25 FoxP3 T and enhanced IL-10 and TGF-β1 production. In the presence of IFN-γ treated hPDLCs, 1,25(OH) D significantly increased CD4 T-lymphocyte proliferation and decreased the percentage of CD4 CD25 FoxP3 T . IL-10 and IL-17A expression was significantly diminished by 1,25(OH) D , whereas TGF-β1 was slightly increased. The effects of 1,25(OH) D in co-culture were reversed by inhibition of indoleamine-2,3-dioxygenase-1, prostaglandin-endoperoxide synthase and programmed cell death 1 ligand 1. 1,25(OH) D also suppressed the expression of these proteins in hPDLCs.

Conclusion: Effects of vitamin D on CD4 T lymphocyte are modified by hPDLCs depending on the microenvironment.