Vitamin A, infection, and immune function.

Area of Science:

• Nutrition and Immunology
• Public Health

Background:

• Vitamin A deficiency is a significant public health issue in regions with low dietary vitamin A intake.
• Infectious diseases exacerbate vitamin A deficiency through reduced intake, absorption, and increased excretion.
• The acute-phase response during infection can falsely lower serum retinol, complicating status assessment.

Purpose of the Study:

• To elucidate the multifaceted impact of vitamin A deficiency on immune function.
• To understand how infectious diseases interact with vitamin A status.
• To explain the increased mortality associated with vitamin A deficiency in specific populations.

Main Methods:

• Review of existing literature on vitamin A metabolism and immune responses.
• Analysis of the effects of infection on vitamin A status and utilization.
• Examination of vitamin A's role in innate and adaptive immunity.

Main Results:

• Vitamin A deficiency impairs mucosal barrier regeneration and the function of key immune cells (neutrophils, macrophages, NK cells).
• Vitamin A is crucial for adaptive immunity, affecting T-helper (Th) and B-cell development.
• Deficiency particularly impacts Th2-mediated antibody responses and also affects Th1 responses.

Conclusions:

• Vitamin A deficiency severely compromises both innate and adaptive immunity.
• Impaired immune function due to vitamin A deficiency contributes to increased mortality in infants, young children, and pregnant women.
• Addressing vitamin A deficiency is critical for improving infectious disease outcomes and reducing mortality.