Chloride conductance and intracellular chloride accumulation in mouse Peyer's patch enterocytes

Area of Science:

• Gastrointestinal Physiology
• Epithelial Cell Biology
• Immunology

Background:

• The follicle-associated epithelium (FAE) of Peyer's patches plays a critical role in mucosal immunity and antigen sampling.
• M cells are specialized epithelial cells within the FAE responsible for transporting luminal antigens to underlying lymphoid tissues.
• Understanding the distinct physiological characteristics of M cells, enterocytes, and intraepithelial lymphocytes is essential for elucidating their functions.

Purpose of the Study:

• To characterize the physiological properties, including membrane potential (Vm) and ion activities (Cl-, K+, Na+, H+), of M cells, enterocytes, and intraepithelial lymphocytes in the mouse Peyer's patch FAE.
• To differentiate between distinct enterocyte populations within the FAE based on their electrophysiological properties.
• To explore the relationship between these physiological properties and the proposed function of M cells in antigen uptake.

Main Methods:

• Electrophysiological measurements of membrane potential (Vm) and intracellular ion activities (Cl-, K+, Na+, H+) were performed on isolated cells from the mouse Peyer's patch FAE.
• Cells were identified based on their electrophysiological responses, such as characteristic voltage jumps during impalement.
• Differential responses to varying extracellular chloride concentrations were used to distinguish enterocyte subpopulations.

Main Results:

• Intraepithelial lymphocytes exhibited distinct electrophysiological profiles, including higher K+ and H+ activities and lower Na+ and Cl- activities compared to epithelial cells.
• M cells were identified by a unique Vm profile and an inability to accumulate chloride, with a Vm sensitive to low extracellular chloride concentrations.
• Enterocytes were classified into at least two populations: chloride-sensitive and chloride-insensitive, with the latter exhibiting properties similar to mature villus enterocytes.

Conclusions:

• Distinct physiological properties differentiate M cells, enterocytes, and intraepithelial lymphocytes within the Peyer's patch FAE.
• The electrophysiological characteristics of M cells, including chloride conductance and low membrane potential, may facilitate the endocytosis of macromolecules.
• The identification of distinct enterocyte populations within the FAE provides insights into the cellular heterogeneity and potential origins of M cells.