key term - Langerhans Cells

Definition

Langerhans cells are a type of dendritic cell found in the epidermis, the outermost layer of the skin. They play a crucial role in the skin's immune defense system and are considered part of the physical defenses against pathogens.

5 Must Know Facts For Your Next Test

1. Langerhans cells are derived from bone marrow and migrate to the epidermis during development.
2. Langerhans cells express MHC class II molecules, allowing them to present antigens to T cells and initiate adaptive immune responses.
3. Langerhans cells are capable of phagocytosing and processing pathogens, then migrating to lymph nodes to present the antigens to T cells.
4. The presence of Langerhans cells in the epidermis is a key component of the skin's physical defenses against invading microorganisms.
5. Langerhans cells play a role in the development of contact dermatitis, a type of allergic skin reaction, by presenting allergens to T cells.

Review Questions

• Explain the role of Langerhans cells in the skin's physical defenses.
  • Langerhans cells are a critical component of the skin's physical defenses against pathogens. Located in the epidermis, they act as sentinels, constantly surveying the skin for any foreign invaders. When Langerhans cells encounter a pathogen, they phagocytose and process the antigen, then migrate to the lymph nodes to present the antigen to T cells. This initiates an adaptive immune response, mobilizing the body's defenses to eliminate the threat. The presence of Langerhans cells in the epidermis is a key part of the skin's multilayered physical barrier against infection.
• Describe the relationship between Langerhans cells and the normal microbiota of the skin.
  • Langerhans cells play a crucial role in maintaining the delicate balance between the skin's normal microbiota and the immune system. While Langerhans cells are primed to detect and respond to pathogenic microorganisms, they must also tolerate the presence of the beneficial commensal bacteria that reside on the skin's surface. This balance is essential for preventing excessive inflammation and autoimmune reactions, while still allowing the immune system to mount a response against true threats. Langerhans cells achieve this by selectively presenting antigens from pathogens to T cells, while ignoring harmless commensal bacteria, thus preserving the skin's normal microbiota.
• Analyze the potential implications of Langerhans cell dysfunction in the development of skin disorders.
  • Disruptions in Langerhans cell function can have significant consequences for the health and integrity of the skin. For example, in contact dermatitis, Langerhans cells inappropriately present harmless environmental allergens to T cells, triggering an inflammatory immune response and skin irritation. In autoimmune skin conditions, Langerhans cells may break tolerance and present self-antigens, leading to the activation of autoreactive T cells and the development of lesions. Conversely, impaired Langerhans cell migration or antigen presentation could compromise the skin's ability to mount effective defenses against pathogens, increasing the risk of infection. Understanding the critical role of Langerhans cells in maintaining the delicate balance between immunity and tolerance is essential for developing targeted therapies for a variety of skin disorders.

Related terms

Dendritic Cells:

Dendritic cells are specialized antigen-presenting cells that play a central role in the immune system by initiating and regulating immune responses.

Epidermis:

The epidermis is the outermost layer of the skin, providing a protective barrier against environmental factors and pathogens.

Antigen Presentation:

Antigen presentation is the process by which specialized cells, such as dendritic cells, display foreign antigens on their surface to be recognized by T cells, initiating an immune response.