Immunology

• Endemic:

  A disease occurring frequently, at a predictable rate, in a specific location or population
• Epidemic:

  The rapid spread of infectious disease to a large number of people within a short period of time
• Toxin:

  A small molecule, e.g. a peptide made in cells or organisms that causes disease following contact or absorption. Toxins often affect macromolecules e.g. enzymes, cell surface receptors
• Pandemic:

  An epidemic over a very wide area, crossing international boundaries, affecting a very large number of people
• Carrier:

  An infected person, or other organism, showing no symptoms but able to infect others
• Antigen:

  A molecule that causes the immune system to produce antibodies against it. Antigens include individual molecules and those on viruses, bacteria, spores or pollen grains. They may be formed inside the body.
• Disease reservoir:

  The long-term host of a pathogen, with few or no symptoms always a potential source of disease outbreak
• Vector:

  A person, animal, or microbe that carriers and transmits an infectious pathogen into another living organism
• Infection:

  A transmissible disease often acquired by inhalation, ingestion, or physical contact
• Antigenic type:

  Different individuals of the same pathogenic species with different surface proteins, generating different antibodies
• Cholera:

  • The bacteria releases a toxin resulting in watery diarrhoea and dehydration
  • Consume contaminated food or water
  • By giving clean waters and electrolytes, and antibiotics
  • Better sewage and water treatment, safe handling of food, washing hands, and a vaccine
• Tuberculosis:

  • Cells in lungs become damaged, present with chest pain, blood in sputum, and a fever
  • Inhalation of water droplets
  • Long course of antibiotics, a vaccine
• Smallpox:

  • Fever, pain, rash, fluid-filled blisters
  • Infection enters small blood vessels in the skin and mouth
  • Pain killers and fluid replacement therapy, antibiotics, and a vaccine
• Influenza:

  • Attacks the mucus membrane in the upper respiratory tract
  • Fever, sore throat, and cough
  • Droplets
  • Washing of hands, using tissues, isolating patients, vaccines
• Malaria:

  • Recurring fevers
  • Female mosquito feeds on blood which it ingests the plasmodium parasite which migrates to the liver where they develop before being released to infect red blood cells causing them to burst
  • Antimalarial drugs, mosquito repellants, bed nets, insecticides, draining of stagnant water, sterile male mosquito
• Virus pathogenicity and reproduction:

  • The cell bursts allowing virus particles to emerge and infect other cells, which causes many of the symptoms seen
  • Viruses produce many different toxic substances
  • Cell transformation can occur, the viral DNA integrates into the host chromosome
  • Immune suppression results from some viruses
• Control of bacterial infection:

  • Sterilisation results in all microorganisms and spores being killed
  • Disinfection with antiseptics or disinfectants will remove the majority of microorganisms
  • Bactericidal antibiotics
  • Bacteriostatic antibiotics
• Bacterial cell wall:

  • Penicillin prevents the synthesis of the cross-links in peptidoglycan as transpeptidase enzyme are inhibited by penicillin. This weakens the cell and water enters so the cell bursts
  • Tetracycline and chloramphenicol stop protein synthesis within the bacterial cell
  • Tetracycline works by binding to the 30s subunit if the bacterial ribosome in the second position which blocked further tRNA attachment
• Antibiotic resistance:

  • The ability of a microorganism to withstand the effects of an antibiotic
  • It evolves naturally as bacteria have a high mutation rate and divide rapidly
  • Resistance has risen due to the over use of antibiotics for viral infections and prevention of infection in farmed animals
• Immune response:

  • Skin - a physical barrier, slightly acidic pH
  • Skin flora - compete with pathogenic bacteria
  • Lysozymes - hydrolyse bacterial cell walls
  • Stomach acid - kills bacteria
  • Cilia and mucus - trap and remove particles and microbes from the airway
  • Blood clotting - seal wounds
  • Inflammatory response - increases blood flow to site of injury
• Lymphocytes:

  • B lymphocytes mature in the spleen and lymph nodes
  • T lymphocytes are activated in the thymus gland
• T lymphocytes:

  • Killer T cells which bind to foreign cells with complementary antigens and destroy them
  • Helper T cells that stimulate phagocytosis and antibody production and activate T killer cells
  • T memory cells which remain in the blood and respond quickly in case the same infection in encountered again
• Humoral immune response:

  • The production of antibodies by b lymphocytes
  • When a b lymphocytes recognises its specific antigen it divides rapidly and produces plasma cells, which secrete antibodies, and memory cells
  • The variable region on the antibody is specific to each antigen and acts as antigen binding site, allowing each antibody to bind to two antigen molecules
  • Microbes with antigens on their surface clump together making it more difficult for them to infect other cells and more easy for macrophages to engulf them
• Cell-mediated response:

  • Involves attacking foreign material inside cells
  • B lymphocytes and t lymphocytes are all activated
  • T lymphocytes respond to specific antigens on the surface of cells and divide rapidly by mitosis to form clones
  • T helper cells which cooperate with b lymphocytes to initiate antibody response, they release chemicals including cytokines which stimulate phagocyte
  • T killer cells which engulf and lyse target cells
  • T memory cells which remain in the blood in case of infection
• Primary response:

  • Antigen presenting cells carry out phagocytosis and incorporate foreign antigen into their cell membranes
  • T helper cells detect these antigens and secrete cytokines, which stimulate b cells and macrophages
  • B cells are activated and undergo clonal expansion to produce plasma cells and memory cells
  • Plasma cells secrete antibodies
  • Memory cells remain in the blood to protect against reinfection
• Secondary response

  • Memory cells are stimulated to clone themselves and produce plasma cells which produce antibodies
  • This response is much more rapid than the primary response and produces a larger concentration of antibodies
• Passive immunity:

  • Occurs when the body receives antibodies, either naturally or artificially from an injection
  • The advantage is that the body receives immediate protection
  • The disadvantage is that the protection is short-lived as the body has not produced memory cells
• Active immunity:

  • Occurs when the body produces its own antibodies in response to antigens being present
  • This protects against reinfection where the antigens on the invading microorganism are the same
  • Antigen-specific memory cells are produced and some antibodies remain in the blood to protect against reinfection
  • Can be natural or artificial from a vaccine