## TNF-α: The Master Cytokine of Chronic Inflammation **Key Point:** TNF-α is the primary pro-inflammatory cytokine and the most important mediator of chronic inflammation. It is produced mainly by activated macrophages and drives the entire inflammatory cascade. ### Role of TNF-α in Chronic Inflammation **High-Yield:** TNF-α functions: 1. **Macrophage activation** — enhances antimicrobial and antitumor activity 2. **Endothelial activation** — increases adhesion molecules (ICAM-1, VCAM-1) 3. **Leukocyte recruitment** — promotes migration of lymphocytes and monocytes 4. **Amplification loop** — induces production of other cytokines (IL-1, IL-6, chemokines) 5. **Systemic effects** — fever, cachexia, shock (at high levels) 6. **Fibrosis** — promotes TGF-β production and tissue remodeling ### Comparison of Key Cytokines in Chronic Inflammation | Cytokine | Primary Source | Main Function | Role in Chronic Inflammation | |----------|----------------|---------------|-----------------------------| | TNF-α | Macrophages, T cells | Master regulator, macrophage activation | **Primary driver** | | IL-1 | Macrophages, endothelium | Co-stimulator, fever, adhesion molecules | Amplifier, synergizes with TNF-α | | IL-6 | Macrophages, fibroblasts | Acute phase response, B cell differentiation | Systemic inflammation marker | | TGF-β | Macrophages, T cells | Anti-inflammatory, fibrosis, tissue repair | Resolution and remodeling phase | **Clinical Pearl:** TNF-α is so central to chronic inflammation that TNF-α inhibitors (infliximab, etanercept, adalimumab) are used therapeutically in rheumatoid arthritis, Crohn's disease, and psoriasis. **Mnemonic:** **TNF = The Notorious Factor** — the master regulator that initiates and perpetuates chronic inflammation.
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