Dendritic cells

Definition

Dendritic cells are specialized antigen-presenting cells that play a critical role in the immune system by capturing and processing antigens to activate T cells. These cells act as a bridge between innate and adaptive immunity, initiating immune responses to pathogens, including parasites, and helping to shape the nature of that response. They are found in tissues that are in contact with the external environment and migrate to lymph nodes to stimulate T cell responses.

5 Must Know Facts For Your Next Test

1. Dendritic cells are the most effective antigen-presenting cells and are crucial for initiating T cell responses, particularly against parasites.
2. They can capture antigens through various mechanisms like phagocytosis and receptor-mediated endocytosis, making them efficient in recognizing different types of pathogens.
3. Dendritic cells express specific surface markers like CD11c and major histocompatibility complex (MHC) molecules that are essential for presenting antigens to T cells.
4. They are present in various tissues, including the skin, lungs, and gastrointestinal tract, which allows them to monitor for pathogens entering the body.
5. Once activated by pathogens, dendritic cells migrate to lymph nodes where they interact with T cells, promoting the differentiation of naive T cells into effector T cells.

Review Questions

• How do dendritic cells link innate and adaptive immunity?
  • Dendritic cells serve as a critical link between innate and adaptive immunity by capturing and processing antigens from pathogens. Once they detect a pathogen, they migrate to lymph nodes where they present these antigens on their surface using major histocompatibility complex (MHC) molecules. This interaction with naive T cells activates them, leading to an adaptive immune response tailored specifically against the identified pathogen.
• Discuss the mechanisms by which dendritic cells capture antigens and the implications for immune activation.
  • Dendritic cells capture antigens through several mechanisms such as phagocytosis, pinocytosis, and receptor-mediated endocytosis. This ability allows them to efficiently recognize and internalize various forms of pathogens. Once the antigens are processed, dendritic cells present peptide fragments on MHC molecules to T cells, which is crucial for activating the adaptive immune response. The nature of the antigens captured can influence whether the response is more Th1 or Th2 polarized, affecting how the body fights off infections.
• Evaluate the role of dendritic cells in shaping immune responses to parasitic infections compared to other types of immune responses.
  • Dendritic cells play a pivotal role in shaping immune responses specifically tailored for parasitic infections by determining how T cell populations respond. They can influence whether the immune system mounts a Th1 response associated with cellular immunity or a Th2 response linked with humoral immunity. This decision is critical since many parasites employ strategies to evade immune detection. By properly activating T cells and influencing their differentiation pathways, dendritic cells ensure that the immune response is both effective against the parasite and appropriately regulated to prevent excessive tissue damage.

Related terms

Antigen-presenting cells (APCs): Cells that capture, process, and present antigens to T cells, including dendritic cells, macrophages, and B cells.

T cells:

A type of white blood cell involved in the adaptive immune response, which can be activated by dendritic cells presenting antigens.

Innate immunity: The body's first line of defense against pathogens, characterized by immediate but non-specific responses, where dendritic cells play a crucial role.