In inflammatory bowel disease, which cytokine is predominantly elevated in Crohn's disease and is the target of anti-TNF-α monoclonal antibody therapy?

Explanation

## Cytokine Profile in Crohn's Disease **Key Point:** TNF-α is the primary pro-inflammatory cytokine in Crohn's disease pathogenesis and is the most important therapeutic target in IBD management. ### Th1/Th17-Mediated Inflammation in Crohn's Disease **High-Yield:** Crohn's disease is characterized by a Th1 and Th17 immune response, with TNF-α as the central pro-inflammatory mediator. ### Cytokine Roles in IBD | Cytokine | Source | Role in IBD | Therapeutic Target | | --- | --- | --- | --- | | **TNF-α** | Macrophages, T cells | Pro-inflammatory; activates endothelium; increases intestinal permeability | Yes (anti-TNF agents) | | **IL-10** | Regulatory T cells | Anti-inflammatory; protective | No (supplementation failed) | | **TGF-β** | Regulatory T cells | Anti-inflammatory; promotes wound healing | No (not primary target) | | **IL-4** | Th2 cells | Anti-inflammatory; Th2 response | No (Crohn's is Th1/Th17) | ### Anti-TNF-α Therapeutic Agents 1. **Infliximab** (chimeric monoclonal antibody) 2. **Adalimumab** (fully human monoclonal antibody) 3. **Certolizumab pegol** (pegylated Fab fragment) 4. **Golimumab** (human monoclonal antibody) **Mnemonic:** **ICAG** — Infliximab, Certolizumab, Adalimumab, Golimumab (anti-TNF agents) **Clinical Pearl:** TNF-α blockade is effective in both induction and maintenance of remission in moderate-to-severe Crohn's disease and is the first-line biologic therapy. **Warning:** Anti-TNF agents increase risk of tuberculosis reactivation, opportunistic infections, and lymphoma — TB screening is mandatory before initiation. [cite:Harrison 21e Ch 297]