Cytokines

🧬 Cytokines – Definition

Cytokines are small proteins secreted by immune cells that act as chemical messengers to regulate immunity, inflammation, and hematopoiesis.
They act in autocrine, paracrine, or endocrine fashion.

📌 Major Types of Cytokines and Their Functions

Cytokine Type

Examples

Main Functions

Interleukins (ILs)

IL-1 to IL-37

- Communication between WBCs - Regulate growth, activation, and differentiation of immune cells

Interferons (IFNs)

IFN-α, IFN-β, IFN-γ

- Antiviral activity - Activate macrophages and NK cells - Increase MHC expression

Tumor Necrosis Factors (TNFs)

TNF-α, TNF-β

- Induce inflammation and apoptosis - Involved in immune cell recruitment

Colony-Stimulating Factors (CSFs)

G-CSF, GM-CSF, M-CSF

- Stimulate production of blood cells in bone marrow

Chemokines

CXCL8 (IL-8), CCL2

- Attract immune cells (chemotaxis) to infection/injury sites

Transforming Growth Factor (TGF-β)

TGF-β

- Immune suppression - Promotes tissue repair and Treg development

🧠 General Functions of Cytokines

  1. Immune Cell Activation – Stimulate T cells, B cells, macrophages, NK cells, etc.

  2. Inflammation – Promote or suppress inflammation (e.g., TNF-α, IL-6).

  3. Cell Proliferation & Differentiation – Help immune cells mature and specialize.

  4. Antiviral Defense – IFNs help fight viral infections.

  5. Cell Migration (Chemotaxis) – Direct immune cells to the site of infection.

  6. Wound Healing & Tissue Repair – Promote tissue regeneration (e.g., TGF-β).

  7. Apoptosis – Regulate cell death in immune and target cells.

🔁 Cytokines Can Act As:

  • Pro-inflammatory (e.g., IL-1, IL-6, TNF-α)

  • Anti-inflammatory (e.g., IL-10, TGF-β)

🧪 Examples in Context:

  • IL-2: Promotes T cell growth (used in cancer therapy)

  • IFN-γ: Activates macrophages

  • IL-10: Suppresses inflammatory responses

  • TNF-α: Key mediator of septic shock and inflammation