Evidence for accessory cell function by class II MHC antigen-expressing airway epithelial cells

Area of Science:

• Immunology
• Cell Biology
• Respiratory Medicine

Background:

• Major histocompatibility complex (MHC) class II antigen expression is crucial for accessory cell function in antigen presentation.
• Previous studies suggested the presence of MHC class II antigens on human bronchial epithelial cells.

Purpose of the Study:

• To investigate whether human airway epithelial cells express functional MHC class II molecules capable of interacting with T lymphocytes.
• To determine the role of airway epithelial cells as accessory cells in immune responses.

Main Methods:

• Immunohistochemical staining of human airway epithelial cells for HLA-DR.
• Mixed lymphocyte cultures (MLR) using isolated airway epithelial cells and allogeneic T lymphocytes.
• Depletion of conventional accessory cells from epithelial isolates.
• Inhibition assays using anti-class II monoclonal antibodies.

Main Results:

• Immunohistochemistry confirmed HLA-DR expression on human airway epithelial cells from the bronchus and nasal turbinates.
• Airway epithelial cells, even after depletion of conventional accessory cells, stimulated allogeneic T lymphocytes in MLR.
• The stimulatory capacity of epithelial cells was completely inhibited by an anti-class II monoclonal antibody.
• Both CD4+ and CD8+ T lymphocytes proliferated in response to airway epithelial cell stimulation.

Conclusions:

• Human airway epithelial cells express functional MHC class II molecules.
• Airway epithelial cells can act as accessory cells, presenting antigens and stimulating T lymphocytes.
• These findings highlight a potential role for airway epithelial cells in local immune responses within the respiratory tract.