mucosal immune response

Definition

Target type: biologicalprocess

An immune response taking place in mucosal tissues, including those of the intestinal tract, nasal and upper respiratory tract, and genital tract. [GO_REF:0000022, GOC:jal, ISBN:0781735149]

Mucosal surfaces, such as those lining the gastrointestinal, respiratory, and genitourinary tracts, are constantly exposed to a vast array of foreign antigens, including pathogens, commensal bacteria, and food antigens. The mucosal immune system, a specialized component of the immune system, is strategically positioned to protect these vulnerable surfaces from infection and maintain homeostasis with the environment.

The mucosal immune response is characterized by a complex interplay of innate and adaptive immune mechanisms, orchestrated to rapidly detect and neutralize threats while simultaneously promoting tolerance to harmless antigens.

**Innate Immune Response:**
- **Epithelial Barrier:** The mucosal epithelium serves as the first line of defense, acting as a physical barrier and producing antimicrobial peptides and mucus to prevent pathogen entry.
- **Pattern Recognition Receptors (PRRs):** Cells of the innate immune system, such as epithelial cells and macrophages, express PRRs that recognize conserved pathogen-associated molecular patterns (PAMPs). This recognition triggers the release of pro-inflammatory cytokines, chemokines, and antimicrobial molecules, activating downstream signaling pathways.
- **Dendritic Cells (DCs):** DCs reside in the mucosal tissues and capture antigens through their PRRs or by phagocytosis. Upon activation, DCs migrate to lymph nodes, where they present antigens to T cells, initiating the adaptive immune response.

**Adaptive Immune Response:**
- **T Cell Activation:** DCs present antigens to T cells in lymph nodes. Naive T cells differentiate into effector T cells, including T helper (Th) cells and cytotoxic T lymphocytes (CTLs), depending on the antigen and the cytokine environment.
- **Th Cell Subsets:**
- **Th1 cells** produce interferon-gamma (IFN-γ), which activates macrophages to kill intracellular pathogens.
- **Th2 cells** produce interleukin-4 (IL-4), IL-5, and IL-13, which promote IgE production and eosinophil recruitment, important in combating parasitic infections.
- **Th17 cells** produce IL-17, which recruits neutrophils and contributes to inflammation, particularly in response to bacterial infections.
- **B Cell Activation:** Antigen-specific B cells are activated by helper T cells and produce antibodies that neutralize pathogens. In the mucosal immune system, IgA is the predominant antibody isotype, providing a crucial barrier against pathogens.
- **Mucosal Memory:** Repeated exposure to the same antigen leads to the generation of memory cells, which rapidly mount an effective response upon re-exposure, contributing to long-term immunity.

**Immune Regulation:**
- **Tolerance:** The mucosal immune system must discriminate between harmful pathogens and harmless commensal bacteria and food antigens. Regulatory T cells (Tregs) play a crucial role in maintaining tolerance by suppressing excessive immune responses.
- **Homeostasis:** The mucosal immune system is tightly regulated to prevent excessive inflammation and tissue damage. This involves a balance of pro-inflammatory and anti-inflammatory cytokines and the suppression of immune responses by Tregs.

In summary, the mucosal immune response is a complex and finely tuned system that protects mucosal surfaces from infection and maintains homeostasis with the environment. It involves a dynamic interplay of innate and adaptive immune mechanisms, including the activation of epithelial barriers, PRRs, DCs, T cells, B cells, and Tregs, all working together to maintain a delicate balance of immune activation and tolerance.'
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Proteins (2)

Compounds (7)