Human Physiology Immune System (SL and HL)

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Human PhysiologyImmune System (SL and HL)
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Pathogens and Disease (SL)

• Bacteria vs. Viruses

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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

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When is a living organism not a living organism?

• When it is a virus.

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Viruses vs. Bacteria
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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.

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A typical Virus
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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

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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

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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.

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• 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)

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• 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.

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Viral Reproduction

• The Lytic and Lysogenic Cycles

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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.

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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.

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• The Lytic Cycle

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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.

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• 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.

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• 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.

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• 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.

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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.

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• 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.

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

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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.

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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.

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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

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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.

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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.

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Pathogen Prevention Lines of Defense

• First Line of Defense
• Skin
• Mucous
• Other acidity of fluids, egestion, urination

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Pathogen Prevention Lines of Defense

• Second Line of Defense Cell Mediated Response
  (CMI)
• Last line of Defense Antibody Mediated Response
  (AMI)

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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

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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

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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.

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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

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

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Immune Response (HL)

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

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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

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• 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.

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• 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.

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• 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.

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• 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

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• 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)

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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.

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• 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.

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• 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.

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Blood Clotting Process

• Hemostasis

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Blood Typing

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

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Blood Typing

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

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Blood Typing

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

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Blood Typing

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

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Blood Typing

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

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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

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Immunity and Vaccination

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

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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.

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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.

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• 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.
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• 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

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Immune Response
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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.

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Vaccination

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

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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

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ApplicationsMonoclonal Antibodies

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

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Process of producing Monoclonal Antibodies
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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

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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