Arthritis & Rheumatism, Volume 60,
October 2009 Abstract Supplement

The 2009 ACR/ARHP Annual Scientific Meeting
Philadelphia October 16-21, 2009.


Reciprocal Regulation of FOXP3 and IL-17 Expression in Human CD4 T Cells by 1,25(OH)2 Vitamin D3

Kang1,  Seong Wook, Kim2,  Sang-Hyun, Lee2,  Won-Woo, Hwang2,  Kyung-A, Lee2,  Seung-Hyun, Kang2,  Insoo

Yale University School of Medicine and Chungnam National University. Daejeon, South Korea
Yale University School of Medicine, New Haven, CT

Purpose:

A body of evidence supports the role for regulatory T cells (Treg) and T helper 17 (Th17) cells in developing autoimmunity and inflammatory diseases. While FOXP3+ Tregs are generated in the thymus (nTreg), FOXP3+ Treg can also be induced from non-Treg CD4+ T cells (iTreg). 1,25-dihyroxyvitamin D3 (1,25(OH)2VD3) exerts an inhibitory effect on immune cells and low circulatory levels of 25(OH)VD3 are reported in patients with autoimmune diseases. However, it is unknown whether 1,25(OH)2VD3 can directly alter FOXP3 and IL-17 expression in human CD4+ T cells.

Method:

Human naïve and memory CD25CD4+ T cells were stimulated with anti-CD3/CD28 antibodies in the presence of cytokines and/or 1,25(OH)2VD3. The expression of FOXP3 and IL-17 was measured by flow cytometry and RT-PCR. IL-17 in culture supernatants was analyzed by ELISA. In order to measure the inhibitory effect of 1,25(OH)2VD3 induced FOXP+ cells, stimulated cells were cocultured with autologous CD25-CD4+ T cells (target cells). For reporter gene assay, the promoter and enhancers of the FOXP3 gene were cloned and transfected into human CD4+ T cells using electroporation.

Results:

1,25(OH)2VD3 promoted FOXP3 expression by CD25-CD4+ T cells in a dose-dependent manner with TCR triggering and IL-2. This effect was more prominent in memory CD4+ T cells, which could be secondary to higher levels of vitamin D receptor (VDR) expression in these cells compared to naive CD4+ T cells. Also, 1,25(OH)2VD3-treated cells had increased FOXP3 mRNA expression. To determined whether 1,25(OH)2VD3-induced FOXP3+CD4+ T cells (VDiTreg) had inhibitory function, we co-cultured 1,25(OH)2VD3-treated cells with target CD25-CD4+ T cells. VDiTreg suppressed proliferation of target CD25-CD4+ T cells in a cell number-dependent manner. Such suppression was largely dependent on cell contact and FOXP3 expression as separating the two populations during cell culture or knockdown of FOXP3 expression in VDiTreg blocked the inhibitory effect of VDiTreg. The direct effect of 1,25(OH)2VD3 on the FOXP3 gene expression was further demonstrated by the reporter gene assay showing an enhanced promoter activity of the FOXP3 gene in the presence of this vitamin. 1,25(OH)2VD3 suppressed IL-17 production from human naïve and memory CD4+ T cells, suggesting a reciprocal regulation of FOXP3 and IL-17 expression by1,25(OH)2VD3.

Conclusion:

1,25(OH)2VD3 promotes FOXP3 expression in CD25-CD4+ T cells, more profoundly in memory cells, with TCR triggering and IL-2 and such cells have potent inhibitory function dependently of FOXP3 and cell contact. Our findings suggest that 1,25(OH)2VD3 regulates immune responses by altering IL-17 production and FOXP3 expression in CD4+ T cells in humans.

To cite this abstract, please use the following information:
Kang, Seong Wook, Kim, Sang-Hyun, Lee, Won-Woo, Hwang, Kyung-A, Lee, Seung-Hyun, Kang, Insoo; Reciprocal Regulation of FOXP3 and IL-17 Expression in Human CD4 T Cells by 1,25(OH)2 Vitamin D3 [abstract]. Arthritis Rheum 2009;60 Suppl 10 :1082
DOI: 10.1002/art.26158

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