Type 3 immunity is a specific arm of the immune system characterized by its unique cellular components and cytokine production. It plays a crucial role in defending the body, particularly at barrier surfaces like the skin and gut.
Components of Type 3 Immunity
Type 3 immunity is primarily composed of the following cell types:
- RORγt (RORC)+CD4+TH17 cells: These are a subset of CD4+ T helper cells that express the transcription factor RORγt (RORC).
- CD8+ TC17 cells: These are cytotoxic CD8+ T cells that also express RORγt.
- ILC3s (Innate Lymphoid cells type 3): These are a group of innate immune cells that do not express antigen-specific receptors but contribute to type 3 responses.
Key Cytokines in Type 3 Immunity
These cells produce specific cytokines that drive the immune response:
- IL-17: This cytokine is crucial for recruiting neutrophils and other immune cells to the site of infection, particularly in response to extracellular pathogens.
- IL-22: This cytokine is important for maintaining barrier integrity and promoting tissue repair. Some cells may produce both IL-17 and IL-22.
Functions of Type 3 Immunity
Type 3 immunity is essential for:
- Protection against extracellular bacteria and fungi: These responses are essential for clearing pathogens at mucosal sites.
- Maintaining barrier integrity: IL-22 and other factors secreted by type 3 immune cells help keep the gut and skin healthy.
- Tissue repair: Type 3 immunity plays a role in repairing damaged tissues.
- Immune Homeostasis: It plays a role in the balance between pro- and anti-inflammatory processes at barrier surfaces.
Summary
In essence, type 3 immunity is a specialized branch of the immune system reliant on specific immune cells like RORγt+CD4+TH17 cells, CD8+ TC17 cells, and ILC3s, producing cytokines like IL-17 and IL-22. These responses are crucial for defense against extracellular pathogens and for maintaining barrier integrity.
| Cell Type | Transcription Factor | Key Cytokine(s) | Function |
|---|---|---|---|
| RORγt+CD4+TH17 cells | RORγt (RORC) | IL-17, IL-22 | Pathogen Clearance, Inflammation, Barrier Integrity, Tissue Repair |
| CD8+ TC17 cells | RORγt (RORC) | IL-17 | Cytotoxicity, Pathogen Clearance, Inflammation |
| ILC3s | (Various) | IL-17, IL-22 | Innate immunity against pathogens, Barrier Integrity, Tissue Repair, Homeostasis |
