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. |