Cytokines and Chemokines

Summary

This script delves into the intricate communication between immune cells via cytokines and chemokines. It outlines the roles of Th1, Th2, Th17, and regulatory T cells in immune responses, detailing their respective cytokines and their functions in fighting pathogens, promoting tissue repair, and regulating immune reactions. The script also explains chemokine families and their crucial role in guiding immune cell migration and positioning within lymphoid tissues.

Takeaways

• 📚 Cytokines and chemokines are small proteins that play a crucial role in immune cell communication and movement.
• 🔍 Cytokines are grouped into families based on structure and are named with prefixes or suffixes, like IFN- for interferons and TNF- for tumor necrosis factors.
• 🌐 Chemokines guide immune cell migration and localization, and are named based on the arrangement of cysteine residues, with CC and CXC being the two major families.
• 💊 Th1 cytokines, driven by Type 1 T helper cells, promote cellular immunity against intracellular pathogens like viruses.
• 🧬 Th2 cytokines, controlled by Type 2 helper T cells, activate humoral immunity and are characterized by eosinophils, basophils, and mast cells.
• 🌱 Th17 cytokines, secreted by Th17 cells, are effective against fungi and extracellular bacteria by recruiting neutrophils.
• 🛡️ Regulatory T cells, or Tregs, release cytokines like IL-10 and TGF-β to dampen immune responses and prevent autoimmunity.
• 🔄 Chemokines are involved in cell adhesion, motility, and chemotaxis, playing a key role in the organization of lymph nodes.
• 🔑 CC chemokines like CCL2 (MCP-1) promote Th2 immunity, while CXC chemokines like CXCL8 (IL-8) recruit neutrophils to infection sites.
• 📈 The interplay of cytokines and chemokines allows for a nuanced immune response tailored to the specific threat posed by different pathogens.

Q & A

What are cytokines and chemokines?

Cytokines are small proteins used by immune cells to communicate with each other, while chemokines guide the migration and localization of immune cells.

How are cytokines named and what are some major families?

Cytokines are grouped into structurally similar families and named with a prefix or suffix indicating their family, along with an identifier like a number or Greek character. Major families include interferons (IFN-), tumor necrosis factor (TNF-), and colony stimulating factors (-CSF).

What is the role of interleukins in the immune system?

Interleukins are a large family of cytokines that facilitate communication between leukocytes, or white blood cells. Despite the term 'interleukin' not being entirely accurate as non-immune cells also release them, it is still widely used.

What is a Th1 immune response and which cytokines are involved?

A Th1 immune response is driven by Type 1 T helper cells and is geared towards cellular immunity against intracellular pathogens. Cytokines involved include IL-2, IL-12, TNF-α, LT-α, and IFN-γ.

How does the Th2 immune response differ from the Th1 response?

The Th2 immune response is controlled by Type 2 helper T cells and activates humoral immunity, dominated by antibody actions from B cells. It is characterized by the presence of eosinophils, basophils, and mast cells.

What are the functions of IL-4 and IL-5 in a Th2 response?

IL-4 is critical for polarizing helper T cells to a Type 2 phenotype, promotes mast cell growth, stimulates eosinophils, and activates B cells. IL-5 drives eosinophil development in the bone marrow.

What is the primary role of Th17 cytokines?

Th17 cytokines are involved in the Th17 response, which is particularly effective against fungi and extracellular bacteria due to their ability to recruit a strong neutrophil response.

How do regulatory T cells (Tregs) contribute to immune responses?

Tregs work to dampen the immune response to prevent excessive tissue damage and the risk of autoimmunity. They do this by producing regulatory cytokines such as IL-10 and TGF-β.

What is the significance of chemokines in the immune system?

Chemokines regulate cell movement and migration, promote changes in cell adhesion and motility, cause cytoskeleton rearrangement, and guide cell movement towards certain stimuli in a process called chemotaxis.

How are chemokines categorized and what are the two major families?

Chemokines are categorized into two major families: CC and CXC, based on the arrangement of cysteine amino acid residues near the amino terminus. CC chemokines have two adjacent cysteine residues, while CXC chemokines have them separated by a variable amino acid.

What are some specific functions of chemokines in lymphoid tissues?

Chemokines are crucial for directing lymphocytes to their proper locations within lymphoid tissues. For example, CCL21 recruits dendritic cells, while CCL18 and CCL19 recruit T and B cells to the lymph node.