Immunity

• Antigens

  Any molecule which illicits an immune response; surface proteins, making them identifiable
• Active immunity

  Stimulates production of antibodies by an individual’s own immune system.

  • Direct contact with a pathogen and its antigen
• Passive immunity

  Antibodies are introduced by an outside source

  • No contact between pathogens/antigens
  • No memory cells are created; no antibodies produced.
• Antibodies

  Proteins with specific binding sites complementary to an antigen.

  • Produced by plasma cell in response to the presence of the appropriate antigen.
• Agglutination

  Antibodies attach to antigens on two pathogens

  • Two binding sites, bind to two pathogens
  • Compact structure, all pathogens brought together in one small area.
• Agglutination of bacterial cells act as marker for phagocytes.
• Variability

  When pathogens mutate frequently

  • All previous immunity is lost; hard to vaccinate against.
• Vaccinations must be:

  • Economical
  • Few side effects
  • Storable
  • Administerable
• Chemicals released by pathogens attract the pathagocyte

  • Moves towards pathogen along a concentration gradient.
• Phagocytosis

  1. Phagocytes have receptors which attach to the pathogens
  2. Engulf pathogen via endocytosis
  3. Forms phagosome, lysosomes fuse with it
  4. Release hydrolytic enzymes (lysozymes) into phagosome
  5. Hydrolyses ingested pathogen
  6. Soluble products from pathogen breakdown are absorbed into the phagocyte’s cytoplasm.
• T-lymphocytes: Cellular Response

  • Involves body cells
• B lymphocytes: Humoral response

  • Involved with antibodies in bodily fluids.
• Cell Mediated response

  1. Phagocytosis; Macrophase presents processed antigens on cell surface membrane, becoming an antigen processing cell.
  2. Helper T-cell with complementary receptor
  3. Binds to Macrophage, activating helper T-cells
  4. Helper T-cells divide by mitosis
  5. Memory T cells and Cytotoxic Killer T-cells form.
• Memory T-cells

  Wait for next infection

  • Matures in Thymus gland
  • Travels via lymphatic and blood stream.
• Cytotoxic Killer T-cells

  Target Infected cells

  • Causes cell apoptosis
  • Releases perforin
  • Bursts cell walls and membranes
  • Osmotic effect
• T cells will only respond to antigens present on a body cell

  • receptors only respond to a single antigen.
• B-cell response

  1. B-lymphocyte takes in pathogen via endocytosis
  2. Displays processed antigens on cell-surface membrane
  3. Complementary T-helper cell has complementary receptor binds to processed antigen,
  4. Binding activates B-cell
  5. Divides via mitosis
  6. Forms Memory B-cells and plasma cells.
• Memory B-cells

  Mature in bone marrow

  • Travels through lymphatic system and blood stream
• Plasma cells

  Releases antibodies complementary to original antigen.
• Humoral immunity includes antibodies
• Clonal selection are cloned B cells that produces the specific antibody
• Monoclonal Antibodies

  Antibodies produced from the clone of a B-lymphocyte
• Antibodies only prepare antigens for destruction; does not destroy directly

  1. Forms antigen-antibody complex
  2. Leads to destruction
• Agglutination

  1. Antibodies attach to antigens on pathogens
  2. Two binding sites, bind to antigens on two pathogens
  3. Forms compact structure; all pathogens in concentrated area.
  4. Act as marker
  5. Pathgocytes engulf them; phagocytosis
• Vaccines

  Introduces antigen into body

  • Stimulates immune response; produces memory cells.
• Herd Immunity

  Enough people have been vaccinated to significantly reduce the spread of pathogen through the population by reducing the change of an infected person meeting someone who is not vaccinated.
• HIV life cycle.

  1. Attachment proteins attach to T-helper cell receptors
  2. HIV RNA enters cell
  3. Reverse transcriptase converts RNA to DNA; inserted into cell DNA in the nucleus
  4. Viral protein are produced
  5. Virus is assembled and released from cell.
• Monoclonal Antibody

  1. Antibodies with the same tertiary structure
  2. Antibodies produced from identical/cloned B-cells
• Monoclonal antibodies in medical treatment

  • Targeted drugs
  • Block antigens/receptors on cells
• ELISA test

  1. First antibodies are complementary in shape to the antigen, binding to them
  2. Wash off excess antibodies with water
  3. Second antibodies with enzymes attached to them bind to first antibodies
  4. Wash off excess antibodies with water
  5. Substrate complementary to enzyme is added, causing a colour change in positive results
• Antibodies

  1. Bind to antigens; acting as markers
  2. Cause clumping/agglutination; attracts phagocytes.