Role of vitamin D in COVID-19 and other viral infections

Table 1 Effects of vitamin D supplementation on the immune system and other different conditions[25]

Immune system component	Effect
T cells	↓ Th 1/Th 17 and ↑ Th 2
	↓ IL-8, IFN-γ, IL-12, IL-6, TNF-α, IL-17
	↑ IL-4, IL-5, IL-10
	Recognition of viral dsRNA by TLR - 3
B cells	↑ Apoptosis
Plasma cells	↓ Proliferation and immunoglobulin secretion
Neutrophils, monocyte-macrophages and dendritic cells	Reception to infectious areas, ↑ TLR
	↑ Intracellular killing of Mycobacterium tuberculosis (macrophages)
Infected cells	↑ Autophagy and apoptosis
Antimicrobial peptides (human cathelicidin peptide LL - 37 and β-defensin)	Augmented
Respiratory tract infections	Effect
Acute respiratory infections	↓ Proinflammatory cytokines in the lung through modulation of the activity of both macrophages and T lymphocytes
	↓ Risk of getting sick
VAP	↓ IL-6
	↓ Mortality rate
Autoimmune disease	Effect on disease
Type 1 diabetes	Prevention of onset, ↓ serum antibody levels, delayed β cell destruction in early stages of disease
Multiple sclerosis	Prevention of the onset
Rheumatic joint inflammation	Prevention of onset, reduced disease activity
Systemic lupus erythematosus	Prevention of onset, reduced disease activity
Crohn's disease	Prevention of the onset
Thyroiditis	Prevention of the onset
Psoriasis	Prevention of the onset
Polymyalgia rheumatica	Prevention of the onset
Autoimmune gastritis	Prevention of the onset
Systemic sclerosis	Downregulation of TGF-β/Smad signaling (putative antifibrotic effect in early stages of disease)
Pulmonary fibrosis	Effect
IL-1β	Decreased antagonism of pulmonary fibroblast cell activity in a murine model of bleomycin-induced lung fibrosis
Hydroxyproline, col1a1, col3a1, and α-smooth muscle actin mRNAs	Prevention of bleomycin-induced lung fibrosis in a mouse model

Th: T helper; IL: Interleukin; IFN: Interferon; TNF: Tumor necrosis factor; TLR: Toll-like receptor; VAP: Ventilator associated pneumonia.