The differential requirement for vitamin D and vitamin D receptor in iNKT cell development

Open Access
Author:
YU, SANHONG
Graduate Program:
Immunology and Infectious Diseases
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
August 10, 2009
Committee Members:
  • Margherita Teresa Anna Cantorna, Dissertation Advisor
  • Margherita Teresa Anna Cantorna, Committee Chair
  • Avery August, Committee Member
  • Robert Paulson, Committee Member
  • Na Xiong, Committee Member
  • Terryl Johnson Hartman, Committee Member
Keywords:
  • vitamin D
  • vitamin D receptor
  • iNKT cells
Abstract:
CD1d-reactive natural killer T (NKT) cells with an invariant T cell receptor V14 rearrangement are a unique subset of lymphocytes, which play important roles in immune regulation, tumor surveillance and host defense against pathogens. Vitamin D is a nutrient/hormone that has been shown to regulate conventional T cell responses, but it remains unclear whether it regulates iNKT cell development and function. Here we determined the effect of both the vitamin D receptor (VDR) and the vitamin D ligand (1,25(OH)2D3) on iNKT cell development. The data show that expression of the vitamin D receptor (VDR) as well as vitamin D is required for normal development while only the VDR is required for normal function of iNKT cells. Moreover, the receptor and ligand regulate iNKT cell development by different mechanisms. The iNKT cells from VDR KO mice are intrinsically defective and lack T-bet expression. VDR KO iNKT cells fail to express NK1.1 although they express normal levels of CD122. Extrinsic factors that impact iNKT cell development and function in the VDR KO mice included a failure of the liver to support homeostatic proliferation and reduced thymic expression of CD1d and other factors important for optimal antigen presentation in the thymus. In addition, VDR KO iNKT cells were intrinsically defective even when wild type antigen presenting cells were used to stimulate them. Similar to what was shown in VDR KO mice, fewer iNKT cells were identified in the 1,25(OH)2D3-deficient mice. However, 1,25(OH)2D3-deficiency did not affect the function of the remaining iNKT cells. In addition, 1,25(OH)2D3-deficiency did not affect the development of iNKT cells in the thymus, while VDR KO iNKT cells were blocked at the CD44+/NK1.1- stage of development. The 1alpha-hydroxylase (encoded by Cyp27B1) is an enzyme required for production of 1,25(OH)2D3. Cyp27B1 KO mice are 1,25(OH)2D3 deficient because they cannot convert vitamin D to the active form. Cyp27B1 ko/+ breeders were fed vitamin D deficient diets. At three weeks of age WT and Cyp27B1 KO littermates were weaned and fed diets that are vitamin D-deficient for the next 5 weeks. Analysis of iNKT cells from these mice showed that both the WT and Cyp27B1 KO littermates had very few iNKT cells. In fact the percentage of iNKT cells in the liver of vitamin D deficient mice was very low 1.2-1.8% and lower than in the VDR KO mice (6%). Early exposure to vitamin D in utero is required for iNKT cell development and iNKT cells failed to recover in either WT or Cyp27B1 KO littermates that were 1,25(OH)2D3 fed from the age of 3-8 wks. Taken together, the data indicate that both the VDR and vitamin D are required for iNKT cell development. Furthermore, there are differences in the role of the VDR and the vitamin D ligand in iNKT cell development. In addition, the data suggest a critical role for vitamin D early during neonatal development or the first 3 weeks post-birth in inducing iNKT cells.