Autoimmune disease and interconnections with vitamin D

Area of Science:

• Immunology
• Endocrinology
• Nutritional Science

Background:

• Vitamin D, a secosteroid, influences calcium homeostasis and bone metabolism.
• Emerging research highlights vitamin D's broader role in human health, particularly in immune function.
• The vitamin D system, including the vitamin D receptor (VDR) and 1α-hydroxylase, is active in immune cells like macrophages, dendritic cells, and T cells.

Purpose of the Study:

• To review the mechanistic basis of vitamin D's immunomodulatory effects.
• To detail how vitamin D deficiency impacts immune cell function.
• To explore the link between low vitamin D and increased risk of inflammatory autoimmune diseases.

Main Methods:

• Review of existing literature on vitamin D, VDR, and immune cell interactions.
• Analysis of association studies correlating serum 25-hydroxyvitamin D (25D) levels with immune disorders.
• Exploration of intracrine and paracrine functions of 1,25-dihydroxyvitamin D (1,25D) in immune responses.

Main Results:

• Immune cells can convert 25D to 1,25D, which interacts with VDR to modulate immune responses.
• 1,25D promotes antibacterial/antiviral innate immunity and attenuates inflammatory adaptive immunity.
• Low serum 25D is associated with increased risk and severity of autoimmune diseases like IBD, MS, type 1 diabetes, and rheumatoid arthritis.

Conclusions:

• Vitamin D deficiency impairs innate immunity and promotes over-exuberant inflammatory adaptive immunity.
• Dysregulation of macrophage, dendritic cell, and T cell function due to low vitamin D may increase autoimmune disease risk.
• Understanding vitamin D's immunomodulatory role is crucial for managing immune disorders.