๐งฌ Cytokines are small proteins released by cells that regulate immune responses, inflammation, and hematopoiesis.
They act in autocrine ๐, paracrine ๐ก, or endocrine ๐ฉธ fashions to influence cell behaviour.
๐ Types of Cytokines
- ๐งช Interleukins (ILs) :
- Produced mainly by leukocytes ๐ฆ โ act on other leukocytes.
- Roles: activation, proliferation, differentiation, migration.
- Examples:
- ๐ฅ IL-1: Promotes inflammation & fever.
- ๐ช IL-2: Stimulates T-cell proliferation.
- ๐ฉธ IL-6: Inflammation + hematopoiesis.
- ๐ IL-10: Anti-inflammatory regulator.
- ๐ฅ Tumour Necrosis Factors (TNFs) :
- Produced by macrophages + T cells.
- Key in inflammation + apoptosis โ ๏ธ.
- Examples:
- ๐ฅ TNF-ฮฑ: Drives inflammation & apoptosis.
- ๐งฉ TNF-ฮฒ: Immune regulation & lymphoid development.
- ๐ก๏ธ Interferons (IFNs) :
- Produced in response to viral infections ๐ฆ .
- Antiviral, antitumour, immunomodulatory.
- Examples:
- ๐ฆ IFN-ฮฑ & IFN-ฮฒ: Antiviral defence.
- โ๏ธ IFN-ฮณ: Activates macrophages + boosts antigen presentation.
- ๐งญ Chemokines :
- Guide immune cell migration ๐ถโโ๏ธ.
- Examples:
- ๐ฏ CCL2 (MCP-1): Recruits monocytes + T cells.
- ๐ CXCL8 (IL-8): Attracts neutrophils.
- ๐ฉธ Colony-Stimulating Factors (CSFs) :
- Stimulate hematopoiesis in bone marrow.
- Examples:
- ๐ต G-CSF: Granulocytes (esp. neutrophils).
- ๐ GM-CSF: Granulocytes + macrophages.
- ๐ฑ Growth Factors :
- Control cell growth & repair.
- Examples:
- ๐ ๏ธ TGF-ฮฒ: Immune regulation + tissue repair.
- ๐ฟ EGF: Stimulates cell proliferation.
โ๏ธ Functions of Cytokines
- ๐งฉ Immune regulation: balance between humoral & cell-mediated immunity.
- ๐ฅ Inflammation: recruit leukocytes; IL-1 & TNF-ฮฑ vs. IL-10.
- ๐ฉธ Hematopoiesis: CSFs drive blood cell production.
- ๐ฑ Cell growth & differentiation: guided by growth factors.
- ๐ฆ Antiviral defence: IFNs inhibit viral replication.
- โ ๏ธ Apoptosis: TNF induces programmed cell death.
๐ฅ Clinical Relevance
- โป๏ธ Autoimmunity: e.g., RA, MS, SLE โ cytokine imbalance; TNF inhibitors used therapeutically.
- ๐ฅ Chronic inflammation: e.g., IBD, psoriasis.
- โ ๏ธ Infections: Cytokine storms in sepsis, COVID-19.
- ๐๏ธ Cancer: IL-2 & IFN-ฮฑ used as immunotherapy agents.
- ๐คง Allergy & asthma: IL-4, IL-5 drive IgE + eosinophil activation.
๐ Summary
๐งฌ Cytokines are essential signalling proteins that coordinate immunity, inflammation, blood cell production, and tissue repair.
โ๏ธ They act in complex networks, and dysregulation underlies many diseases โ making them key drug targets in modern medicine.
