Vitamin D and Immune System

Question 1

What are two ways vitamin D can enter a cell?

Answer 1

1. Through dietary sources of vitamin D

2. UV activation of 7-dehydrocholesterol in the skin that leads to D3

Question 2

What happens to vitamin D in the blood vessel?

Answer 2

Vitamin D3 binds to VDBP as it is not soluable

Question 3

What happens to vitamin D in the Liver and the Kidney?

Answer 3

• Vitamin D3 enters the liver and is hydroxylated by 25-OHase
• > 25(OH)D
• 25(OH)D enters the kidney and is hydroxylated by 1alpha-OHase
• > 1,25(OH)2D
• This form can enter the target cell

Question 4

What is are the non-genomic actions that 1,25(OH)2D causes when bound to the VDR?

Answer 4

• VDR: Vitamin D receptor
• activates G-protein, IP3/DAG, PLC, PKC and Ion channels
• regulation of Ca2+/Pi metabolism, chloride channels, migration of endothelial cells, cross-talk with genomic vitamin D pathways

Question 5

What are the genomic actions that results from 1,25(OH)2D?

Answer 5

• It binds to a nuclear VDR which is also bound to RXR (retinoic X)
• Binds to a VDRE which results in co-activator gene expression or co-repressor gene repression
• regulation of cell differentiation, proliferation, apoptosis, inflammation, angiogenesis, Ca2+/Pi metabolism

Question 6

What does 1,25(OH)2D have a role in?

Answer 6

• apoptosis
• gene expression regulation (G0/G1 arrest and proliferation)
• stem cells regulation
• mineral metabolism

Question 7

What did recent evidence support about vitamin D?

Answer 7

The concept that it contributes to apoptosis, differentiation and telomere biology
- eg. there is an inverse relationship b/w serum vitamin D and cancer, as well as serum vitamin D and mortality

Question 8

What does vitamin D regulate at a cellular level?

Answer 8

• proliferation, senescence and apoptosis

- through genomic and non-genomic pathways

Question 9

What are the components of the innate (nonspecific) immune system?

Answer 9

• antigen presenting cells (dendritic cells, macrophages)
• cytotoxic cells (NK cells, macrophages)
• proteins

Question 10

What are the two arms of the immune system?

Answer 10

• humoral (B cells)

- cellular (T cells (specific), antigen presenting cells (nonspecific) and cytotoxic cells (nonspecific))

Question 11

When do NK cells attack?

Answer 11

If membrane proteins are expressed that are irregular (including expression level), NK cells can attack the cancer cell.