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6.4 11.1 Immunity PPT

6.4 11.1 Immunity PPT






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    6.4 11.1 Immunity PPT 6.4 11.1 Immunity PPT Presentation Transcript

    • 6.3 Defense against infectious disease
      IB Biology
    • Pathogens
      Any biological agent that can cause a disease
      Examples: bacteria, viruses, fungi, protists, worms
      Ebola virus
      Plasmodium falciparum
      Rust caused by a fungus
    • Pathogens
      Immune system cells patrol the body (blood and tissues)
      Immune system detects foreign particles + cells
      Additional responses: proteins blocking viruses from entering cells or punching holes in bacterial cell wall / membranes
      Immune system must be able to distinguish non-self from self
      Macrophage engulfing a yeast cell
    • How do antibiotics work?
      Bacteria have a metabolism + cell wall (prokaryotic cell)
      Antibiotics block metabolic pathways found in bacteria
      Eukaryotic cells are unaffected
      Viruses are not cells
      Viruses = protein capsid + nucleic acid -> they don’t have the machinery necessary to reproduce on their own
    • How do viruses work?
    • First line of defense
      Goal = to stop pathogens from entering the body
      • Epidermis: dead layer superficial / contains keratin = impermeable
      • Dermis: thicker / contains dermal cells, glands, hairs, capillaries, sensory receptors
    • Additional barriers
      • Respiratory tract produces chemical secretions (mucus) that trap or kill microbes
      • Lysozymes present in mucus, tears, saliva, breast milk = anti-bacterial
      • Cilia sweep the mucus back to the throat = germs go to stomach and acid environment destroys them
    • Second Line of Defense (Once pathogens get within the body...)
      FIRST: non-specific response
      Phagocytosis: ingestion + digestion of bacteria and other foreign substances
      Phagocytic leucocytes (aka macrophages): large white blood cells that engulf pathogens
    • Local inflammatory response
      Activated macrophages and mast cells at the injury site release chemical signals (like histamines) that act on nearby capillaries.
      Capillaries widen and become more permeable allowing fluid containing antimicrobial peptides to enter the tissue. Signals also attract additional phagocytic cells.
      Phagocytic cells digest pathogens and cell debris at the site, and the tissue heals.
    • Antigens
      Molecule recognized by the immune system = triggers a response (ex: production of antibodies)
      All cells have antigens – part of membrane/cell wall (protein, glycoprotein, lipoprotein or polysaccharide)
      Purpose = cell communication
      Cells from different individuals have different antigens
      Antigens are genetically controlled, so close relative have more similar antigens than unrelated individuals.
      Example: blood antigens
    • Antibodies (or Ig = immunoglobulin)
      Proteins made of 4 polypeptide chains
      Produced by lymphocytes B (plasma cells)
      Bind to specific antigens in areas called epitopes
      Antibodies help identify / neutralize pathogens
      Part of acquired immunity (vertebrates are unique – most animals have only innate immunity)
    • Antibody Production
      Specific immune response
      Pathogen enters the body
      Macrophage engulfs pathogen
      Pieces of pathogen become part of macrophage’s membrane
      Antigen presentation = lymphocytes T recognize pieces = become activated
      T cells activate specific B cells – they divide (cloning) and form:
      Plasma cells = secrete antibodies that bind to antigens
      Memory cells = stay in circulation
      B cells = mature in the bone marrow
      T cells = mature in the thymus
    • The Lymphatic System
    • HIV
      Isolated in 1983 by Robert Gallo of the United States and French scientist Luc Montagnier.
      AIDS = AcquiredImmunodeficiency Syndrome
      Transmission: body fluids – mostly blood, semen and vaginal fluid
      Atypical virus = retrovirus (RNA)
      Enzyme known as reverse transcriptase, allows HIV to produce DNA from RNA (whereas most cells carry out the opposite process, transcribing the genetic material of DNA into RNA)
      The activity of the enzyme enables the genetic information of HIV to become integrated permanently into the genome (chromosomes) of a host cell.
    • HIV infection
      HIV infects helper T cells
      T cells = activate and direct other leukocytes
      HIV attaches to CD4 receptors and injects its content inside the cell
      T cell is disabled
      RNA is reverse-transcribed, producing DNA which integrates to the cell’s genome
      Cell starts producing new viral particles
      Immune response is compromised
      High mutation rate because reverse transcription does not allow for correction of errors in nucleotide incorporation = great antigenic variation
      Latency period = inactive DNA
      Decline of T cells = HIV eventually causes AIDS
      A CD4 count of less than approximately 200 cells per microliter of blood may be accompanied by a variety of opportunistic infections and is considered the final stage of infection. The persistent barrage of such infections is what typically leads to the death of AIDS patients.
    • Issues involving HIV
      Difficult to develop medication = high mutation rate
      HIV associated with drug use and sexual activity = hard to allocate research money in the past
      Blood for transfusions was not tested in the past
      AIDS was labeled as a disease affecting homosexuals and drug abusers = discrimination
      HIV positive individuals = problems with employment, insurance, education access, etc...
      Some countries = inadequate medical care