Immune response Flashcards
Physical barriers to infection
- Skin which is a tough physical barrier consisting of keratin.
- Stomach acid (hydrochloric acid) which kills bacteria.
- Gut and skin flora – natural bacterial flora competes with pathogens for food and space.
Non-specific responses of the body to infection include:
- Inflammation
- Lysozyme action
- Interferon
Inflammation (Non-specific response)
histamines released by damaged white tissues cause vasodilation which increases the flow of blood to the infected area and increases permeability of blood
vessels. As a result of that antibodies, white blood cells and plasma leak out into the infected tissue and destroy the pathogen.
Lysozyme action
lysozyme are enzymes found in secretions such as tears and mucus which kill bacterial cells by damaging their cell wall.
Interferons
prevent viruses spreading to uninfected cells by stopping protein synthesis in viruses.
Phagocytosis (Non-specific response)
- Phagocyte is attracted to the pathogen by chemical products of the pathogen. It moves towards it on a concentration gradient
- The surface receptors on the phagocyte attach to chemicals on the surface of the pathogen
- Invagination occurs and a phagosome forms
- Lysosomes release lysozymes into the phagosome, hydrolyse the bacteria
- The hydrolysis products of the bacterium are absorbed by the phagocyte
Specific Immune Response
is antigen specific and produces responses specific to one type of pathogen only
What does the Specfic immune response rely on?
B cells & T-cells
Where are B cells/ Plasma cells found
mature in the bone marrow and are involved in the humoral response.
Where are T cells found
s move from the bone marrow to the thymus gland where they mature, and are
involved in cell mediated response.
Memory cells
Cells which replicate themselves when exposed to an invading pathogen and remain in the lymph nodes for decades searching for the same antigen. Results in a faster immune response
B cells
B effector or plasma cells are antibody producing cells.
T helper cells
Stimulate B cells and T killer cells to divide.
T cytotoxic cells
Release toxins that bind to and kill foreign cells and abnormal cells in the body.
Reservoir
The place where the pathogen is usually found.
Suppressor cells
turn off immune response, e.g. turning off antibody production.
Cell-mediated immune response
- Uses T-lymphocytes which are produced in the bone marrow and mature in the thymus gland.
- Once matured T-lymphocytes circulate the body in the blood until it meets an antigen it has the receptor site for.
- It is then stimulated to divide by mitosis many times forming clones.
Describe the process of cell mediated immunity (immunity that does not result in the production of antibodies).
- Phagocytosis of foreign material by phagocyte.
- Foreign antigens from material are presented on phagocyte.
- Specific T-helper lymphocyte (Th) binds to foreign antigen (clonal selection)
- Attachment causes Th cell to undergo mitosis (clonal expansion).
Cloned T cells can:
- become memory cells for rapid future response.to same pathogen.
- stimulate phagocytes to engulf via phagocytosis.
- stimulate B cells to divide and release antibodies (humoural response)
- activate cytotoxic T cells (Tc) cells to kill.
What can the cloned T-lymphocytes do after clonal expansion has taken place in the cell mediated response?
become memory cells for rapid future response.to same pathogen.
stimulate phagocytes to engulf via phagocytosis.
stimulate B cells to divide and release antibodies (humoural response)
activate cytotoxic T cells (Tc) cells to kill.
Which type of immunity are T-lymphocytes mainly involved in?
Cell Mediated Immunity (they are just used to stimulate B-cells in humoural immunity)
Where can non-self antigens be found that T-lymphocytes may bind to?
- The surface of an antigen presenting cell (phagocyte)
- Body cells invaded by a virus may present viral antigens.
- Transplanted cells from organ donors.
- Cancer cells
- Toxins produced by pathogens.
Can T-lymphocytes bind to non-self antigens floating around freely in the blood?
No - they can only bind to foreign antigens that have been presented on an antigen presenting cell e.g. phagocyte.
How do cytotoxic T lymphocytes (Tc) protect against disease?
They kill cells infected by pathogens or cancerous cells.
They produce a protein called perforin.
Perforin creates holes in target cell membranes, which kills the cell.
Where do T-lymphocytes mature?
In the thymus
Where are all lymphocytes produced?
Bone marrow
What is meant by cell mediated immunity?
An immune response that does not involve the production of antibodies.
Results in the production of cytotoxic T cells that can protect against pathogens.
Which molecules can the immune system identify?
- pathogens
- cells from other organisms of the same species
- abnormal body cells
- toxins
What are the characteristics of bacteria?
- Microscopic
- Living cells that can multiply rapidly
- Attack tissues in host and release toxins
- Examples: food poisoning, cholera
What are the characteristics of viruses?
- Ultra microscopic
- Once inside the host, viral DNA replicated itself 1000s of times
- Burst out of host cell into bloodstream, difficult to treat
- Examples: cold, flu, HIV
What do phagocytes do?
Engulf the pathogens
What do lymphocytes do?
Make antibodies which neutralise microbes or make them stick together, destroying them.
What do Neutrophils do?
Neutralise the toxins produced by the microbes.
What are the two types of immunity?
Natural and Artificial
How does natural immunity occur?
- Antibodies passed from mother to child
- Antibodies are made when microbes infect the body
How does Artificial Immunity occur?
- ACTIVE: Vaccine with dead or modified (attenuated) microbes injected causing antibodies to be produced ready for real infection
- PASSIVE: Serum of antibodies are injected directly into a person to fight infection
What is malaria caused by?
Plasmodium
What is phagocytosis?
A process in which pathogens are ingested by a phagocyte (macrophage)
Describe the process of lymphocytosis:
- Lymphocyte approaches bacterium
- Antibodies attach to antigens on the bacterium, neutralising them because they can not replicate
What is cell mediated immunity?
Lymphocytes respond to an organisms own cells that have
What is an antigen-antibody complex?
When a complimentary antibody and antigen join
How many polypeptide chains are there in an antibody molecule?
4, joined by disulphides bridges
What are the 4 duplicated regions of an antibody molecule?
Variable and light regions on the heavy chain, and variable and light regions on the light chain.
What does the generic constant region allow and antibody to do?
Attach to phagocytic cells
What does the variable region allow an antibody to do?
It is specific (complimentary) to a particular antigen, which it binds to, depending on the amino acid sequence
What does the hinge region allow the antibody to do?
Flex in order to bind with more than one antigen (accommodation)
What are specific defence mechanisms?
Where the body produces specific antibodies in response to specific antigens associated with specific pathogens.
Pathogen
organisms that cause disease.
What term is used to describe an organisms that cause disease?
Pathogen
Antigen
Molecules (proteins and glycoproteins) that are present on the cell surface membrane of all cells. Antigens signal to the immune system if the cells are ‘foreign’.
What are the ways that the immune response responds to antigens
- Lysozymes break down the foreign cells.
- Phagocytosis of the foreign cells.
- Production of antibodies that bind to the antigens and inhibit the functioning of the foreign cells.
Where are the complementary receptors to antigens located in immune cells?
Cell surface membrane
What type of response is the action of t-cells
Cellular response
What type of response is the action of B-cells
Humoural response
Simple steps Involed in the immune response
- Phagocytosis
- Activation of T-cells
- Activation of B-cells
- Production of antibodies
The two types of T cells are:
Helper T cells
Cytotoxic T cells
How many antigens do antibodies bind to for agglutination.
Two
How are monoclonal antibodies used:
Targeted medication - Cancer
Medical diagnosis =
Step One of the ELISA Test
1) Fixing the antigens - The antigen for the infection that is being tested for is immobilised to the bottom of a beaker.
Step Two of the ELISA Test
2) Additon of blood - A sample of the blood that is being investigated is added to the beaker.
If the antibodies that are complementary to the disease-causing antigen are present in the blood, they will bind to the antigens at the bottom of the beaker to form many antigen-antibody complexes.
Step Three of the ELISA Test
3) Beaker must be washed so that any antibodies that have not bound to antigens are removed.
Step 4 of the ELISA Test
4) Secondary antibodies
Secondary antibodies are added to the solution.
The secondary antibodies are bound to an enzyme.
If a secondary antibody binds to the other antibodies from the blood sample, the enzyme will change the colour of a solution in the beaker.
Step 5 of the ELISA Test
5) Addition of the solution
The solution that reacts with the enzymes on the secondary antibodies is added.
If the solution changes colour, the secondary antibodies have bound to the antibodies from the blood sample.
This indicates the blood sample is infected by the pathogen.
How does the ELISA test show the blood sample is infected with a specific pathogen?
Colour change
What structure of the antibody binds to specific antigens?
Variable regions
What do T helper cells activate?
- Phagocytes.
- T cytotoxic (TC) cells.
- B cells.
What are cytotoxic t cells active by
T helper cells
What are cytotoxic t cells activeded by
T helper cells
Simple steps of Humoral response
5 STEPS
- Activation of B cells from T helper cells
- Divison of B cells into plasma cells by clonal selection
- Release of monoclonal antibodies from plasma cells
- Binding of antibodies to antigens of pathogen
- Agglutination and phagocytosis of pathogens
What structure is the pathogen sealed into when it is engulfed?
Phagosome
What is the name of the process where B cells divide into identical cells that produce antibodies?
Clonal expansion
ELISA TEST
The enzyme linked immunosorbent assay test uses antibodies to detect the presence and quantity of a protein in a sample. The test can be used to test a person from HIV and other pathogens.
Passive immunity
An individual receives antibodies from an external source. Can be natural or artifical
Active immunity
Active immunity is where the immune system has created its own antibodies. Can be natural or artifical
Natural passive immunity
Antibodies are transferred to a baby from its mother in breast milk
Artifical passive immunity
Antibodies are transferred to an individual by injection
Natural active immunity
Antibodies have been created in response to catching a disease).
Artifical active immunity
Antibodies have been created in response to vaccination of antigens).
What type of immunity is the transfer of antibodies to a baby from its mother in breast milk?
Passive & Natural
How many variable regions does each antibody have?
2
What name do we give the process whereby a pathogen is engulfed by a specialised cell from the immune system?
Phagocytosis
Neutralisation
Antibodies can bind to a site on a pathogen to block the harmful effect of a toxin.
Opsonisation
Antibodies can attract phagocytes to the pathogen by binding strongly to receptors on the phagocyte membrane.
Why does IPV not cause any harm to a paitent anymore?
It is inactivated
