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Title: Human Physiology Immune System (SL and HL)


1
Human PhysiologyImmune System (SL and HL)
2
Pathogens and Disease (SL)
  • Bacteria vs. Viruses

3
What is a pathogen?
  • Any living organism, that is foreign to a body,
    that causes disease or sickness
  • Examples of pathogens are viruses, bacteria,
    protozoa, fungi, flatworms and ringworms

4
When is a living organism not a living organism?
  • When it is a virus.

5
Viruses vs. Bacteria
6
Viruses
  • Are tiny bundles of genetic material either DNA
    or RNA, carried in a shell called the viral coat
    or capsid.
  • The capsid is made of bits of protein called
    capsomeres. Some viruses have and additional
    layer called an envelope.

7
A typical Virus
8
There are thousands of different viruses that
come in a variety of shapes.
  • Polyhedral
  • Spiky ovals
  • Like bricks with rounded corners
  • Skinny sticks
  • Looped strings
  • Some look like lunar landing pods

9
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10
Viruses continued
  • Viruses are found on or in just about every
    living material.
  • Viruses are found anywhere there are cells to
    infect
  • They have evolved to infect humans right down to
    bacteria

11
Viruses and the Mechanism of Reproduction
  • Viruses tend to be picky about the the type of
    cells they will infect.
  • Viruses exist for one purpose to reproduce.

12
  • Unlike human cells or bacteria, viruses do not
    contain the enzymes needed to carry out the
    biochemical reactions for reproduction.
  • Viruses only have one or two enzymes that decode
    their genetic instructions.
  • Viruses must have a host cell in which to live
    and make more copies (reproduce)

13
  • Outside of a host cell, viruses cannot function.
    For this reason, viruses tread the fine line that
    separates living things from non-living things.
    Most scientists agree that viruses are alive
    because of what happens when they infect a host
    cell.

14
Viral Reproduction
  • The Lytic and Lysogenic Cycles

15
Reproduction of Viruses
  • Viruses lie around in our environment, waiting
    for a host cell to come along. They enter
    through nose, mouth or breaks in the skin.
  • Once inside, they find a host cell to infect.

16
For example
  • Influenza will attack cells that line the
    respiratory of digestive tract.
  • HIV, which causes AIDS, attacks the T-cells of
    the Immune System. (What we are studying.
  • Then it goes through something called the Lytic
    Cycle.

17
  • The Lytic Cycle

18
The Lytic Cycle
  • Upon landing on an appropriate host cell, a virus
    gets its genetic material inside the cell two
    ways.
  • By tricking the host cell to pull it inside, like
    it would a nutrient molecule.
  • By fusing its viral coat, or injecting its genes
    into the host.

19
  • The steps are known as the lytic cycle.
  • A virus particle attaches to the host cell.
  • The particle releases its genetic material into
    the host cell.
  • The injected material recruits the host cells
    enzymes. It then transcribes its DNA or RNA,
    using the host DNA, and then translates it.
  • The new mRNA assembles new virus particles.
  • New virus break free from the host cell.

20
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21
  • If a virus is a DNA virus, its genetic material
    is inserted into the host cells DNA and
    reproduced.
  • If the virus is an RNA virus, it turns its RNA
    into DNA using reverse transcriptase, before
    inserting into the host DNA.
  • The genes are then copied many times, to
    reproduce many viruses.

22
  • Once free, they go to attack other host cells
  • One virus can reproduce thousands of new viruses
    and infection can quickly spread, overwhelming
    the Immune System.

23
Lysogenic Cycle
  • Some viruses, like HIV and Herpes, do not
    reproduce right away.
  • Instead, they mix their genetic material into the
    host cells genetic material.
  • As the host cell reproduces, the viral material
    is copied along with the new cells.

24
  • The host cell may undergo many rounds of
    reproduction, and then some environmental or
    predetermined genetic signal will stir the
    sleeping viral instructions.
  • The viral genetic instructions take over and the
    virus uses the Lytic Cycle to reproduce.

25
  • The virus can live for years or longer without
    being identified, because it does not carry any
    biochemical reactions on its own.

26
Problems for Mankind?
  • Antibiotics do not work on Viruses.
  • Viruses reproduce so quickly and so often, they
    can change slightly.
  • Mistakes creep into the genetic instructions, and
    mutate. The vaccine for that virus is useless.

27
The Good News
  • There are people who appreciate science (called
    scientists) who are working day and night on
    vaccines.
  • Most vaccines for todays viruses and the
    methodology for implementing the vaccine still
    work.

28
Entry into the Body
  • Airborne
  • Water-borne
  • Food-borne
  • Insect-borne or animal-borne
  • Sexually Transmitted
  • Direct contact
  • Need to get through the bodys defenses

29
Antibiotics
  • Only effective on bacteria (prokaryotic cells)
  • Not effective on viruses, because they infect
    eukaryotic cells
  • Antibiotics interfere with bacterial metabolic
    processes such as
  • DNA replication, transcription, translation,
    ribosome function and cell wall formation.

30
Pathogen Prevention Lines of Defense
  • Immunity
  • The ability to resist infection by a disease is
    termed.
  • The initial defense mechanisms are called
    Non-specific immunity allows the body to resist
    infection by a wide range of pathogens. An
    example is the skin.

31
Pathogen Prevention Lines of Defense
  • First Line of Defense
  • Skin
  • Mucous
  • Other acidity of fluids, egestion, urination

32
Pathogen Prevention Lines of Defense
  • Second Line of Defense Cell Mediated Response
    (CMI)
  • Last line of Defense Antibody Mediated Response
    (AMI)

33
Response to Entry of Pathogens
  • Cell Mediated Response
  • Phagocytic leucocytes (white blood cells, called
    macrophages)
  • Roam around body, engulfing foreign substances
    caught in the mucous
  • Recognizes by the surface proteins on pathogen,
    as not self

34
Response to Entry of Pathogens
  • Antibody Mediated Response
  • Antigen
  • molecule or particle recognized as foreign by the
    immune system, that can trigger an immune
    response.
  • Antibody
  • Immunoglobulin - a globular protein that
    recognizes an antigen

35
Response to Entry of Pathogens
  • Antibodies are produced by B-cells, specialized
    white blood cells
  • Antibodies recognize the pathogen, latch on to it
  • Other cells involved
  • Helper T cells
  • Cytotoxic T-Cells
  • Suppressor T-Cells
  • Memory B- Cells and T-Cells.

36
Response to Entry of Pathogens
  • Outcomes of binding of antibody to antigen
  • Making the pathogen more recognizable to
    phagocytes so that they are more readily
    engulfed.
  • Preventing viruses from docking to host cells so
    that they cannot be taken up by host cells

37
  • Causing sticking together or agglutination of
    pathogens so that they are prevented from
    entering cells and are easier for the phagocytes
    to ingest.

38
Immune Response (HL)
  • Antibody Mediated Immunity
  • Blood Clotting
  • Blood Typing (not in curriculum, but needed, for
    later)

39
Antibody Mediated Immunity
  • Process of the body to make antibodies and
    respond to infection is
  • T-Cells are inactive. When an antigen enters the
    body, they are off, in response to excess blood
    flow to the area, and influx of macrophages
  • When the pathogen is found, the T-Cell acts like
    a macrophage

40
  • The T-Cell pushes parts of the cell wall from the
    pathogen, which has the markers, to the outside
    of their own cell membrane.
  • As a result, the T-Cell now becomes a Antigen
    Presenting Cell (APC), and forms the Major
    Histocompatibility Complex (MHC) proteins found
    on the macrophage.
  • T-Cell receptors do not respond to antigens
    unless the antigens are associated with MHC
    proteins.

41
  • The T-Cell, now an APC, travels to the lymph node
  • The antigen it has is presented and read by a
    Helper T-Cell. It has matching receptors for the
    antigen. Helper T-Cells are like the general and
    coordinate the response
  • This is known as clonal selection. The Helper
    T-Cells divide by mitosis, forming clones of
    themselves, and Memory T-Cells.

42
  • The Helper T-Cells clones release a chemical
    (IL2) that activates B-Cells
  • B-cells have surface receptors complimentary to
    the antigen. The B-Cells also produce clones, by
    a process called Clonal Expansion. ( B-Cells
    differentiate into plasma cells and memory cells.
    )
  • The plasma cells make large amounts of
    antibodies, and the memory cells serve to
    remember the antigen, as the infection
    progresses.

43
  • The antibodies are released into the blood stream
    and flow to the site of the infection, and attach
    to the pathogen.
  • Macrophages identify and engulf the pathogen,
    destroying it.
  • If a viral infected cell, cytotoxic T-Cells,
    identify the infected body cells from the
    antibodies, and destroy them
  • Suppressor Cells take care of the extra white
    blood cells, when the infection is under control

44
  • Most of the B and T-Cells used to fight the
    infection die.
  • Memory B and some T-Cells remain, containing the
    information on the shape of the antigen, and
    corresponding antibody.
  • If the antigen gets into the body again, the
    second response is faster than the first and the
    pathogen is removed (more on this in Immunity)

45
Blood Clotting
  • Need to close the opening to make sure pathogens
    cannot get in
  • Process
  • Blood will react with the air and substances from
    the damaged cells.
  • Damaged cells release chemicals which stimulate
    platelets to adhere to the damaged area.

46
  • Traumatized tissue, releases a tissue protein
    called thromboplastin, which initiates the
    formation of prothrombinase, along with
    coagulation factor VII and X.
  • Once factor X is activated, it combines with Ca2
    ion and factor V. This will change the
    prothrombinase (or prothrombin) to thrombin.

47
  • Thrombin will hydrolyse soluable fibrinogen to
    insoluable fibrin molecules. These form a
    network to catch the erythrocytes and form a
    clot.
  • The epithelial tissue can grow under the build up
    of clot tissue and repair the area.

48
Blood Clotting Process
  • Hemostasis

49
Blood Typing
  • Type A
  • A antigens on surface of red blood cells
    (erythrocytes)
  • B antibodies in blood plasma

50
Blood Typing
  • Type B
  • B antigens on surface of red blood cells
    (erythrocytes)
  • A antibodies in blood plasma

51
Blood Typing
  • Type AB
  • Both A and B antigens on surface of red blood
    cells (erythrocytes)
  • No antibodies in blood plasma

52
Blood Typing
  • Type 0 (Null)
  • No antigens on surface of red blood cells
    (erythrocytes)
  • Both A and B antibodies in blood plasma

53
Blood Typing
  • How do we determine blood type?
  • What is Rh?
  • Blood transfusions What is given?

54
Immunity and Vaccination
  • First time you get an infection Primary
    Infection
  • The response is called Polyclonal Response
  • For any infection, the following principles are
    followed
  • Challenge and Response
  • Clonal Selection
  • Memory Cells

55
Immunity and Vaccination
  • With memory cells, immunity is achieved
  • Types of Immunity
  • Active Immunity
  • Passive Immunity

56
Active Immunity
  • Immunity due to the production of antibodies by
    the organism itself after the bodys defence
    mechanisms have been stimulated by the invasion
    of pathogens. Due to the Memory B and T-Cells,
    people who have had the disease (strains of cold,
    flu, chicken pox, measles) are not likely to
    become reinfected.

57
Passive Immunity
  • Immunity due to acquisition of antibodies from
    another organism, in which active immunity has
    been stimulated. Included in this are antibodies
    received via the placenta or colostrum from the
    mother. This means the person is immediately
    protected from the disease.

58
  • These two types of immunities can also be
    classified in two different ways Natural and
    Artificial immunity
  • Natural Active antibodies as a result of
    infection.
  •  
  • Natural Passive made antibodies from the
    placenta and passed on to the fetus or through
    the colostrum
  • Artificial passive obtained from another
    organism through biotechnology
  • Artificial active vaccination

59
Immune Response
60
Vaccination
  • Vaccines
  • viruses, weakened or a similar vaccine (cowpox
    for smallpox) that is injected into the body.
  • T-Cells go through the whole process and develop
    Memory cells to make antibodies in the case of
    infection.
  • When someone is vaccinated, the second response
    is faster and stronger than the first.

61
Vaccination
  • Purpose of Vaccinations
  • Develop Herd Immunity
  • Eradicate diseases
  • Prevent Epidemics from spreading

62
Vaccination
  • Pros
  • Cons
  • Develop Herd Immunity
  • Eradicate diseases
  • Prevent Epidemics from spreading
  • Side Effects
  • Allergic Reactions
  • Weakened immune systems can develop the disease
  • Mutations of pathogens

63
ApplicationsMonoclonal Antibodies
  • Purified antibodies that are man-made
  • Used for
  • Drug Tests
  • Pregnancy Tests
  • Treatments of anthrax, and possibly cancer

64
Process of producing Monoclonal Antibodies
65
HIV and AIDS
  • HIV
  • Human Immunodeficiency Virus
  • Attacks the Helper T-Cells of the immune system
  • Uses the Lysogenic Cycle to reproduce
  • Can hide and some event causes the outbreak of
    the virus
  • At this time, the infected person has AIDS

66
HIV and AIDS
  • AIDS
  • Acquired Immune Deficiency Syndrome
  • Immune system is depressed
  • Common cold can kill person
  • Treatment almost like Chemotherapy
  • Develop types of skin cancers, called Karposis
    sarcoma
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