Dendritic cells function in immune system?

By: Prof. Dr. Fazal Rehman | Last updated: February 3, 2024

Question: Dendritic cells function in immune system? Answer:           Antigen Capture:
  • Dendritic cells are specialized in capturing antigens.
  • They have specialized receptors on their surface that allow them to recognize and engulf antigens through a process called phagocytosis.
Antigen Presentation:
  • Dendritic cells are unique in their ability to process and present antigens to other immune cells.
  • After capturing antigens, DCs break them down into smaller fragments and present these fragments on their cell surface using major histocompatibility complex (MHC) molecules.
  • This presentation allows T cells to recognize and respond to the antigens.
Activation of T Cells:
  • When a dendritic cell presents an antigen to a T cell that recognizes the antigen, it triggers the activation and proliferation of T cells.
  • This activation process helps orchestrate the immune response, leading to the elimination of pathogens or foreign substances.
Immune Cell Communication:
  • Dendritic cells communicate with other immune cells, such as B cells and natural killer cells, by secreting chemical signals called cytokines.
  • Cytokines help coordinate and regulate the immune response, promoting inflammation, enhancing antigen presentation, and influencing the activation and differentiation of various immune cells.
Bridge between Innate and Adaptive Immunity:
  • Dendritic cell have pattern recognition receptors (PRRs) that allow them to detect specific molecular patterns associated with pathogens.
  • When dendritic cells detect pathogens, they initiate an innate immune response and, at the same time, capture antigens for presentation to adaptive immune cells.
Function               Description                 Mechanisms
Antigen Capture   ·        Dendritic cells capture pathogens or foreign substances from the surrounding environment. ·        Receptors on the dendritic cell surface recognize and bind to antigens.  
Antigen Processing ·        Dendritic cells process captured antigens into smaller peptide fragments. ·        Antigens are broken down into smaller pieces within the dendritic cells. ·        Enzymes degrade antigens in endosomes and phagosomes. ·        Proteasomes generate antigenic peptides in the cytoplasm.
Antigen Presentation ·        Dendritic cells display processed antigen fragments on their cell surface using major histocompatibility complex (MHC) molecules. ·        Peptide fragments bind to MHC class II molecules (for exogenous antigens) or MHC class I molecules (for endogenous antigens). ·         MHC-antigen complexes are transported to the cell surface.
Activation of T Cells ·        Dendritic cells play a central role in activating T cells. ·        Dendritic cells present antigens to T cells through interaction between MHC-antigen complexes and T cell receptors. ·        Co-stimulatory molecules on dendritic cells, such as CD80 and CD86, provide additional signals to promote T cell activation.
Cytokine Production   ·        Dendritic cells produce cytokines that regulate immune responses.   ·        dendritic cells release cytokines such as interleukin-12 (IL-12), tumor necrosis factor-alpha (TNF-α)  and interferons (IFNs) upon antigen recognition. ·        Cytokines influence the behavior of other immune cells, affecting inflammation, cell differentiation, and immune activation.
Induction of Immune Tolerance ·        Dendritic cells help induce immune tolerance to prevent autoimmune reactions. ·        Dendritic cells present self-antigens to T cells in the absence of co-stimulation, leading to T cell deletion. ·        Regulatory T cells may be induced by dendritic cells to suppress immune responses.
Cross-Presentation ·        Dendritic cells can cross-present antigens to activate T cells of different specificity. ·        Dendritic cells take up antigens from infected cells or dying cells. ·        The antigens are processed and presented using MHC class I molecules.
Modulation of Immune Responses ·        Dendritic cells modulate immune responses by interacting with other immune cells. ·        Dendritic cells interact with B cells, natural killer (NK) cells and macrophages to influence their activity. ·        Dendritic cells can promote or suppress immune responses based on the cytokines and signals they provide.

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