Immune System

• Immunity

  • ability to destroy pathogens
  • ability to prevent further cases of certain infectious diseases
• Types of Immune system

  • innate/natural immunity (non-specific responses)
  • adaptive/acquired immunity (specific responses)
• 1st line of defense

  • skin
  • mucous membranes and secretions
  • normal flora
• 2nd line of defense

  • innate immune cells
  • inflammation
  • complement
  • antimicrobial substances
• 3rd line of defense

  specialized lymphocytes

  • b cells
  • t cells: helper t cells, killer t cells
• Phagocytic cells

  • ingest and destroy foreign substances
• Natural killer cells

  • destroys irreversibly stressed and abnormal cells such as virus infected and tumor cells
• Dendritic cells

  • aka interdigitating dendritic cells
  • most important antigen-presenting cells for initiating T cells responses against protein antigens
• Fever

  • increase metabolic rate
  • inhibits microbial multiplication
  • inactivates enzymes
• Chemical Mediators

  • protein produced by cells infected with viruses and by t cells
  • types of interferon: gamma, alpha, beta
• Interferon

  • stimulates cell to turn on genes for antiviral proteins
• Complement

  • group of more than 20 plasma proteins that circulate in the blood until activated
• Chemical Mediator

  • involved in the lysis of cellular antigens and labeling of non cellular antigens
• Classical pathway

  • depends on the binding of antibodies
• Alternative pathway

  • triggered by the interaction of several protein factors
• Opsonization

  • enhancement of phagocytosis by coating with C3b
• Cytolysis

  • loss of cellular contents through transmembrane channel formed by membrane attack complex C5-C9
• Inflammation

  • increase of blood vessel permeability and chemotactic attraction of phagocytes
• Adaptive immunity

  • specific immunity or acquired immunity
• 2 types of adaptive immunity

  • humoral immunity
  • cellular immunity
• Humoral immunity

  • provided by b lymphocytes which produce antibodies
  • provides immunity to extracellular bacteria, viruses and toxins
  • involved body fluids
• Cellular Immunity

  • provided by T lymphocytes
  • provides immunity to intracellular bacteria, viruses, fungi and protozoa
• Antibodies

  • produced by plasma cells
  • aka gamma globulins, immunoglobulins
  • proteins produced in response to antigen
• Antibodies attaches to multiple cells, making a clump
• Role of antibodies

  • neutralization
  • agglutination
  • opsonization
  • complement activation
  • enhanced NK cell activity
• Immunoglobulin G

  • complement activation, agglutination, opsonization and neutralization
  • crosses placenta to protect fetus
• Immunoglobulin M

  • complement activation, agglutination, and neutralization
• Immunoglobulin A

  • agglutination and neutralization
• Immunoglobulin E

  • triggers release of histamines from basophils and mast cells
• Immunoglobulin D

  • has an unknown function
• Types of T cells

  • killer T cells
  • helper T cells
  • memory T cells
  • suppressor T cells
• Killer T cells

  • t cell that destroys virus infected cell
• Helper T cell

  • t cell that boosts immune response by activating killer t cells and stimulating antibody production by b cells
• Memory T cell

  • t cell that persists in bloodstream to protect against future infections
• Suppressor T cells

  • t cell that protects healthy cells
• T cells mature in thymus gland
• B cells mature in bone marrow
• Active immunity

  • involves the production of antibodies by the body itself and the subsequent development of memory cells
• Passive immunity

  • results from the acquisition of antibodies from another source and hence memory cells are not developed
• Natural mechanism of active immunity

  • producing antibodies in response to exposure to a pathogenic infection