M cells

Definition

M cells, or microfold cells, are specialized epithelial cells located in the mucosal tissues of the intestine that play a crucial role in the immune response by sampling antigens from the gut lumen and delivering them to underlying immune cells. They are essential for maintaining immune surveillance in the gut and facilitate the interaction between the microbiome and the host's immune system. By doing so, M cells help bridge the innate and adaptive immune responses.

5 Must Know Facts For Your Next Test

1. M cells are strategically located above Peyer's patches, allowing them to efficiently transport antigens to immune cells located in these lymphoid structures.
2. These cells have a unique morphology with a folded membrane that increases surface area for antigen uptake, facilitating their function.
3. M cells play a critical role in distinguishing between harmless and harmful antigens, which is essential for maintaining tolerance to commensal bacteria.
4. The interaction of M cells with the microbiome can influence systemic immune responses and contribute to either health or disease states.
5. In addition to their role in antigen transport, M cells can also secrete factors that modulate local immune responses.

Review Questions

• How do M cells contribute to the immune surveillance of the gut?
  • M cells play a vital role in gut immune surveillance by sampling antigens from the intestinal lumen and transporting them to underlying immune cells. This process helps initiate both innate and adaptive immune responses, allowing for an effective reaction against pathogens while maintaining tolerance to beneficial microbes. By facilitating communication between the gut microbiome and the immune system, M cells ensure that the body's defenses remain vigilant yet balanced.
• Discuss how M cells interact with Peyer's patches and the implications of this interaction on immune responses.
  • M cells are positioned directly above Peyer's patches, enabling them to effectively deliver sampled antigens to dendritic cells and other immune cells within these lymphoid structures. This interaction is crucial for activating T and B cells, which leads to an adaptive immune response tailored to specific antigens. Furthermore, this process helps to educate the immune system about commensal bacteria versus pathogens, influencing overall gut health and tolerance.
• Evaluate the potential impact of dysfunctional M cell activity on health and disease outcomes.
  • Dysfunctional M cell activity can lead to inadequate antigen sampling or misidentification of harmless microbes as threats, contributing to various health issues such as inflammatory bowel disease or allergies. When M cells fail to maintain proper immune balance, it can result in overactive immune responses against benign microbes or insufficient responses against harmful pathogens. This dysregulation highlights the importance of M cell function in sustaining gut homeostasis and preventing disease.

Related terms

Dendritic Cells: A type of antigen-presenting cell that processes and presents antigens to T cells, playing a key role in initiating adaptive immune responses.

Peyer’s Patches: Lymphoid follicles found in the small intestine that contain a high concentration of immune cells and are involved in the immune response to intestinal pathogens.

Innate Immunity: The first line of defense against pathogens that provides immediate but non-specific responses, including physical barriers and immune cells.