Changes in immune cell populations during acclimatization to high altitude

Area of Science:

• Physiology
• Immunology
• Altitude Medicine

Background:

• The immune system's role in high-altitude adaptation is crucial but not fully understood.
• Hypoxemia-induced inflammation can worsen altitude pathologies like acute mountain sickness (AMS).
• Mechanisms and adaptive significance of immune cell changes at high altitude remain unclear.

Purpose of the Study:

• To investigate alterations in immune cell subsets during high-altitude acclimatization.
• To determine if hypoxia influences immune cell responses to inflammatory stimuli.
• To explore the relationship between immune changes and AMS.

Main Methods:

• Multiparameter flow cytometry on peripheral blood mononuclear cells (PBMCs) from 20 healthy individuals over 3 days at high altitude.
• In vitro stimulation assays using lipopolysaccharide (LPS) to assess immune cell responses.
• Correlation analysis between immune cell population changes and AMS incidence/severity.

Main Results:

• Significant alterations observed in monocytes, T cells, and B cells at high altitude.
• Some immune cell changes correlated with AMS incidence and severity.
• In vitro, pro-inflammatory cytokine production by PBMCs decreased significantly after 3 days at high altitude compared to 1 day.

Conclusions:

• High-altitude exposure initiates an immune response involving innate immune sensitization.
• Adaptive immune suppression follows acclimatization, indicating a shift in immune function.
• These findings provide insights into the complex immune mechanisms of high-altitude adaptation and AMS.