Immunology III: Inflammation, Phagocytosis & Complement

Immune Cell Communication

  • Soluble molecules (cytokines/chemokines) bind to receptors.
  • Cell surface-bound receptors bind to ligands.
  • Antigen presentation to cell surface receptors.

Antigen

  • Recognized by the immune system.
    • Foreign: From outside (pathogens, transplants).
    • Self: Normally tolerated.

Dendritic Cell Communication with T Cells

  • Activated dendritic cells:
    • Release cytokines.
    • Display surface receptors for T cell ligands.
    • Present antigen to T cell receptors.
  • This activates T cells.

Major Histocompatibility Complex (MHC)

  • MHC presents antigen to T cell receptor (TCR).
  • Types:
    • MHC-I: Presents endogenous antigens; on all nucleated cells.
    • MHC-II: Presents exogenous antigens; on antigen-presenting cells like dendritic cells.

Cytokines and Chemokines

  • Cytokines: Control immune cell growth/activity (e.g., interleukins, interferons).
  • Chemokines: Stimulate cell migration.
  • Produced by innate and adaptive immune cells, and other cells (e.g., epithelial cells).

Helper T Cells and B Cells

  • Helper T cells activate B cells through:
    • Cytokines.
    • Surface-bound receptor interactions.
  • This leads to B cell activation and antibody production.

Complement and B Cells

  • Antibody binding can trigger the classical complement pathway.
  • Complement fragments bound to antigen help activate B cells.

Summary of Immune Response

  1. Pathogens enter the body.
  2. Chemical mediators cause vasodilation/phagocyte entry.
  3. Complement pathway is triggered.
  4. Dendritic cells are activated by pathogen recognition.
  5. Dendritic cells migrate to lymph nodes.
  6. Dendritic cells activate T cells via MHC.
  7. Antigen + T cells + complement activate B cells.
  8. B cells produce antibodies.
  9. Pathogen clearance via complement, phagocytosis, and antibodies.