Disease and Immunity

Disease and Immunity

1. Disease

   • Causes
     • Infections caused by pathogens e.g bacteria and viruses. For example common cold, food poisoning and chest infections
     • Non infectious disease- caused by malfunctioning of the body e.g cancer
   • Lifestyle
     • Coronary Heart Disease (CHD): -Poor diet (high in saturated fat or salt) -Smoking -lack of exercise
       • All lead to high BP, which can damage the heart and blood vessels, increasing risk of CHD
     • Cancer, result of uncontrolled cell division: -Smoking (mouth, throat and lung cancer) -Excessive exposure to sunlight; skin cancer -Excessive alcohol intake; liver cancer
   • Risk Factor= anything that increases the chance of getting a disease

2. Pathogens

   • Organism that can cause disease
   • Types of Pathogen
     • Viruses
       • HIV-Aids + Influenza
     • Bacteria
       • Myobacterium Tuberculosis
     • Entry into the body
       • Gas Exchange System
         • Mucus trap pathogens, cilia beat and move mucus up trachea and out of the mouth
       • The Skin
         • Blood clots and dries to form a scab
       • Digestive System
         • Most pathogens killed by acidic conditions of the stomach
   • How they cause disease
     • 1. Production of Toxins
     • 2. Cell Damage- kill host cells
       • i). rupture host cell to release nutrients
         • ii) Break down nutrients for own use, this starves the cell
           • iii) cell dies, pathogens replicate inside cells and eventually they burst

3. The Immune Response

   • 1. Phagocytosis
     • 1. Phagocyte recognises antigens on surface
     • 2. Cytoplasm of phagocyte moves around the pathogen, engulfing it
     • 3. The pathogen is now in a phagocytic vacuole
     • 4. A lysosome fuses with the phagocytic vacuole, the lysosomal enzymes break down the pathogen
     • 5. Phagocyte then presents the pathogens antigens on its own surface in order to activate other immune system cells
   • 2. T-Cell Activation (Cellular Response)
     • Type of white blood cell, has proteins on its surface that bind to antigens on phagocytes
       • Some T-cells release substances to activate B cells. Others attach to antigens on the pathogen and kill the cell.
   • 3. B-Cell Activation& Plasma cell production (Humoral Response)
     • B Cells= Type of white blood cell
       • Covered with antibodies (proteins that bind antigens to form an antigen-antibody complex)
       • Each B cell has a diff shaped antibody on its membrane
         • Meets complimentary antigen+ binds. This, together with substances released from T-Cells activate the B-Cells and cause them to divide (Plasma cells)
   • 4. Antibody Production
     • Plasma cells are identical to B cells (clones) so they secrete loads of antibodies specific to the antigen
       • Antibody Functions:
         • Coating pathogen so the phagocyte can easily engulf it
           • Binding to and neutralising toxins produced by pathogen
   • Antibody Structure
     • Proteins- made of chains of AA monomers, linked by peptide bonds
       • Each antibody has a diff shaped variable region due to diff amino acid sequences
   • Primary Response

4. Vaccines

   • Helps avoid a disease

5. Antigenic Variation

6. Monoclonal Antibodies

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