Cytokine and Chemokine Families Quiz

Cytokine and Chemokine Families

• Cytokines are signaling proteins produced by immune cells and other cells to communicate with each other, regulating immune responses and controlling inflammation.
• Chemokines are a subset of cytokines, guiding immune cell migration and localization.
• Cytokine families are categorized by prefixes or suffixes, reflecting structural similarity (e.g., IFN-, TNF-, -CSF).
• Interleukins are a significant cytokine family, traditionally associated with leukocyte communication.
• Chemokine families are classified as CC and CXC, based on cysteine residue arrangement near the amino terminus.
• CC chemokines have two adjacent cysteine residues.
• CXC chemokines have two cysteine residues separated by one amino acid.
• Ligands are chemokines that bind to receptors.
• Receptors are proteins binding chemokines to initiate signaling pathways.

Immune Response Types and Associated Cytokines

• Th1 response: Driven by Type 1 helper T cells, targeting cellular immunity against intracellular pathogens (viruses, some bacteria).
• Th1 cytokines:
  • IL-2: Crucial for T cell survival, proliferation, and differentiation.
  • IL-12: Activates NK cells, polarizes helper T cells to Th1.
  • TNF-α: Pro-inflammatory, induces cell death.
  • LT-α: Related to TNF-α, signals in soluble or membrane-bound forms. Kills infected cells, activates macrophages, crucial for lymphoid tissue development.
  • IFN-γ: Type II interferon, antiviral activity, enhances killer T cell detection of infected cells, activates macrophages, suppresses Th2 polarization.
• Th2 response: Driven by Type 2 helper T cells, characterized by humoral immunity (antibody-mediated), eosinophils, basophils, and mast cells.
• Th2 cytokines:
  • IL-4: Critical for Th2 cell polarization, mast cell development, eosinophil stimulation, B cell activation.
  • IL-5: Promotes eosinophil development in bone marrow.
  • IL-13: Signals B cells to produce IgE (a hallmark of Th2 responses).
  • IL-25: Amplifies Th2 responses by inducing IL-4, IL-5, and IL-13, activates type 2 innate lymphoid cells.
  • IL-10: Enhances B cell activation, antibody production, suppresses Th1 cytokines.
• Th17 response: Driven by helper T cells, secreting high levels of IL-17, effective against fungi and extracellular bacteria.
• Th17 cytokines:
  • IL-17: Stimulates CXCL8 (IL-8) production, a potent neutrophil chemoattractant.
  • IL-22: Promotes cell proliferation, tissue healing, antimicrobial peptide production in epithelial cells.
  • IL-23: Polarizes helper T cells to the Th17 phenotype.
• Treg response: Regulatory T cells dampen immune responses to prevent excessive damage and autoimmunity.
• Treg cytokines:
  • IL-10: (Already mentioned as a Th2 cytokine)
  • TGF-β: Pleiotropic cytokine promoting tissue repair, wound healing, anti-inflammatory effects via promoting Treg development, inhibiting B cell proliferation and suppressing macrophage activation.
• Follicular helper T cells (Tfh): Subset of CD4 T cells assisting B cell activation in lymphoid tissue.

Chemokines and Their Roles in Cell Migration

• Chemokines regulate cell movement and migration, affecting cell adhesion, motility, cytoskeleton rearrangement, and chemotaxis.
• Chemokines are essential for organizing lymphoid tissues, guiding immune cells to specific areas in lymph nodes.
• CCL2 (MCP-1): Promotes Th2 immunity, histamine release by basophils.
• CCL3 (MIP-1α): Recruits monocytes, macrophages, neutrophils, promotes Th1 immunity.
• CCL4 (MIP-1β): Recruits monocytes and NK cells.
• CCL5 (RANTES): Recruits eosinophils, T cells, basophils to infection sites, activates NK cells.
• CXCL8 (IL-8): Recruits neutrophils to infected tissues.
• CXCL7: Released by activated platelets, activates neutrophils, promotes angiogenesis (tissue repair).
• CXCL1, CXCL2, CXCL3: Promote angiogenesis, activate neutrophils, stimulate fibroblast proliferation, released by endothelial cells, fibroblasts, and monocytes.
• CCL21: Secreted by stromal cells in lymphoid tissues to recruit dendritic cells.
• CCL18 and CCL19: Secreted by dendritic cells, recruit T and B cells to lymph nodes.
• CXCL13: Secreted by follicular dendritic cells in lymph nodes, recruits B cells to the B cell zone.

Summary

• Cytokines and chemokines are vital for coordinating immune responses and regulating cell migration, fundamentally impacting how the immune system manages pathogens and homeostasis.