Sex and disease regulate major histocompatibility complex class I expression in human lung epithelial cells

Area of Science:

• Immunology
• Respiratory Medicine
• Cell Biology

Background:

• Major histocompatibility complex class I (MHC I) molecules are crucial for CD8+ T-cell mediated immunosurveillance.
• Lung epithelial cells (LECs) are known to express low levels of MHC I in mice, but this is not well-characterized in humans.
• Chronic respiratory diseases are a major cause of mortality, and understanding immune cell interactions within the lung is vital.

Purpose of the Study:

• To determine if human LECs exhibit low constitutive MHC I expression.
• To investigate whether MHC I expression in human LECs is altered in the context of chronic respiratory diseases.
• To identify potential regulatory factors, including sex-based differences, influencing MHC I levels in human LECs.

Main Methods:

• Analysis of human LECs from parenchymal explants using single-cell RNA sequencing.
• Immunostaining techniques to assess MHC I protein levels.
• Comparative analysis of MHC I expression between healthy individuals and those with chronic respiratory diseases, considering sex as a variable.

Main Results:

• Human LECs demonstrate low basal levels of MHC I expression.
• Significant upregulation of MHC I was observed in LECs from patients with chronic respiratory diseases.
• A notable sexual dimorphism was identified, with males exhibiting higher steady-state MHC I levels, potentially linked to redox balance.
• Differential regulation of MHC I expression in human LECs was observed based on disease state and sex.

Conclusions:

• Human LECs express low levels of MHC I, which are upregulated in chronic respiratory diseases.
• Sex-based differences, possibly related to redox balance, influence MHC I expression in human LECs.
• The findings suggest a complex interplay between MHC I, sex, and respiratory disease pathogenesis, with implications for lung immunopathology.