les 4

• Pathogens


  Agents that cause disease, such as bacteria, viruses, fungi, or others
• Dedicated cells of the immune system

  • Enable animals to avoid or limit many infections
• First lines of defense

  • Prevent pathogens from gaining entry to the body
• Innate immunity


  Recognition and response rely on traits common to groups of pathogens, using a small set of receptors. Rapid response.

  
• Adaptive immunity


  Recognition of traits specific to particular pathogens, using a vast array of receptors. Slower response.
• Innate immunity of invertebrates

  • Exoskeleton made of chitin forms first barrier, digestive system protected by chitin-based barrier and lysozyme, immune cells produce recognition proteins, major immune cells are hemocytes that ingest and break down microorganisms, hemocytes secrete antimicrobial peptides

  
• Innate immunity of vertebrates

  • Similar to invertebrates (barrier defenses, phagocytosis, antimicrobial peptides), additional defenses unique to vertebrates (natural killer cells, interferons, inflammatory response)

  
• Cellular innate defenses


  Innate immune cells detect, devour, and destroy invading pathogens using TLRs, two main types of phagocytic cells (neutrophils, macrophages), two additional types (dendritic cells, eosinophils), natural killer cells detect abnormal cells and induce cell death

  
• Local inflammatory response


  Molecules released upon injury or infection, mast cells discharge cytokines and histamine, blood vessels dilate and become more permeable, pus and excess fluid taken up as lymph, lymph nodes contain macrophages that engulf pathogens, dendritic cells migrate to lymph nodes and stimulate adaptive immunity

  
• Antimicrobial peptides and proteins

  Pathogen recognition triggers production and release of peptides that attack pathogens or impede their reproduction, interferons inhibit viral replication, complement system consists of proteins in blood plasma that are activated by pathogens and lead to lysis of invading cells

  
• Adaptive immunity


  Enhanced by previous exposure to the pathogen, relies on two types of lymphocytes (T cells, B cells)

  
• Antigen recognition by B cells and antibodies

  B cell receptors bind to specific antigens, antibodies secreted by plasma cells bind to antigens

  
• Antigen recognition by T cells

  T cell receptors bind to peptide fragments of pathogens displayed on MHC molecules

  
• B cell and T cell development

  Lymphocytes mature in the thymus (T cells) and bone marrow (B cells)

  
• Adaptive immune system


  • Immense diversity of lymphocytes and receptors, self-tolerance, B and T cells proliferate after activation, immunological memory

  
• Antigen receptor gene rearrangement


  Functional Ig gene assembled by rearrangement of DNA segments (V, J, C)

  
• Origin of self-tolerance


  Lymphocytes with receptors specific for the body's own molecules are destroyed or rendered nonfunctional during maturation

  
• Proliferation of B cells and T cells

  Clones of lymphocytes specific to a pathogen are formed

  
• Immunological memory


  Responsible for long-term protection against diseases, primary immune response forms a clone of lymphocytes specific to the pathogen, secondary immune response is faster and greater due to memory cells
• Phagocytic cells


  Cells that engulf and destroy pathogens
• Types of phagocytic cells in the mammalian body

  • Neutrophils
  • Macrophages
  • Dendritic cells
  • Eosinophils
• Neutrophils


  • Circulate in the blood
• Macrophages


  • Migrate through the body or reside permanently in organs and tissues
• Dendritic cells


  • Stimulate development of adaptive immunity
• Eosinophils


  • Discharge destructive enzymes against parasites
• natural killer cells


  These circulate through the body and detect abnormal cells • They release chemicals leading to cell death, inhibiting the spread of virally infected or cancerous cells
• lymphocytes


  Lymphocytes that mature in the thymus, above the heart, are called T cells, and those that mature in bone marrow are called B cells
• antigen 


  zit op de patogeen
• antibody


  word gemaakt door het lichaam om het patogeen aan te vallen
• Dendritic cells


  Type of immune cell that processes and presents antigens to immune cells, stimulating the adaptive immune response and memory cell formation