Chapter 11: Immunity

• This chapter covers the immune response, immunity, vaccination, and autoimmunity
• Immunity


  Protection against diseases
• Immune system


  The body's defense system with mechanisms and cells to defend against diseases
• First line of defense (external)


  • Saliva
  • Tears
  • Skin
  • Mucus
  • Stomach acid
• First line of defense

  • Non-specific mechanisms that act as a barrier between the outside and inside environment
• Second line of defense (internal)

  • Phagocytes
• Second line of defense

  • Non-specific immune response
• Third line of defense

  • Lymphocytes
• Third line of defense

  • Specific immune response targeted at particular pathogens
• Antigens


  Macromolecules that activate an immune response
• Types of antigens


  • Non-self antigens
  • Self antigens (cell markers)
• Immune response


  The body's immune reaction or processes that target non-self antigens
• Types of white blood cells

  • Phagocytes
  • Lymphocytes
• Phagocytes


  • Produced throughout life, function to patrol tissues and blood and remove dead cells and pathogens, undergo phagocytosis, involved in non-specific defense
• Types of phagocytes


  • Neutrophils
  • Monocytes (mature into macrophages)
• Macrophage immune response


  1. Detect non-self antigens

  2. Engulf pathogen via phagocytosis

  3. Fuse with lysosome to digest pathogen

  4. Present pathogen antigens on cell surface

  5. Activate and stimulate lymphocytes
• Lymphocytes


  • Produced in bone marrow, involved in specific immune response, only respond to specific non-self antigens
• Types of lymphocytes


  • B lymphocytes
  • T lymphocytes
• B lymphocytes


  Produced in bone marrow, produce antibodies
• T lymphocytes


  Produced in bone marrow, mature in thymus, do not produce antibodies
• Lymphocytes


  Cells involved in the immune response
• Our body is constantly fighting a war against many different types of pathogens
• Lymphocytes


  • There are millions of different types of B cells and T cells, each specific to a different antigen
  • Lymphocytes are involved in a specific immune response
• B cell receptor


  A specific antibody on the surface of a B cell that binds to a specific antigen
• Maturation of lymphocytes


  1. Stem cells in bone marrow form naive B cells and T cells

  2. B cells mature in the bone marrow

  3. T cells mature in the thymus

  4. Mature lymphocytes can circulate in the blood and lymph
• Antibody


  A glycoprotein produced by plasma cells that can bind to a specific antigen
• Antibody structure


  • Made up of 4 polypeptide chains - 2 heavy chains and 2 light chains
  • Has a variable region that determines antigen binding specificity
  • Has a constant region that determines antibody class
• Activation of B cells

  1. Antigen presenting cell presents antigen to specific B cell

  2. Activated B cell undergoes clonal selection and clonal expansion

  3. Activated B cells differentiate into plasma cells and memory B cells
• Plasma cells


  Short-lived cells that rapidly produce and secrete large amounts of antibodies
• Memory B cells


  Long-lived cells that provide faster antibody response upon re-exposure to the same antigen
• Primary immune response


  Slower, lower antibody production
• Secondary immune response


  Faster, higher antibody production due to memory B cells
• Lymphocytes


  Immune cells made in the bone marrow before birth
• T lymphocytes


  Differ from B lymphocytes in that they mature in the thymus gland
• The thymus can shrink after puberty, which is why the immune system declines with age
• T cell receptor


  Receptor on the surface of T cells that is complementary to a specific antigen
• T cell receptors are not the same as antibody receptors
• Activation of T cells

  1. Pathogen invades

  2. Antigen presentation by macrophage

  3. Specific T cells with complementary receptors are activated

  4. Clonal selection

  5. Clonal expansion
• T helper cells


  Secrete cytokines that stimulate B cells, macrophages, and killer T cells
• Cytotoxic T cells


  Seek out and destroy infected host cells and cancer cells by punching holes and secreting toxins