5. CELL RECOGNITION & THE IMMUNE SYSTEM Flashcards
Name the four main types of pathogen
Bacteria, virus, fungi and protista
Define what a pathogen is
A disease-causing microorganism
How do bacteria cause disease?
They release toxins
How do viruses cause disease?
They replicate inside cells and damage them
Explain the purpose of the body’s primary defenses
To prevent pathogens from entering the body
Recall the five primary defenses
Skin, stomach acid, lysosomes in tears and genital tract, cilia and mucus
Which two primary defenses utilise lysosomes?
Tears and genital tract
Describe what a phagosome is
A pathogen engulfed in a phagocyte
Describe what a phagolysosome is
When a phagosome fuses with the lysosomes inside a phagocyte
Explain how macrophages become APCs
The pathogen’s antigens are displayed on the phagocyte’s cell surface membrane
Recall the five cells / molecules that would initiate an immune response
Pathogens, toxins, cancer cells, cells invaded by viruses, and cells of adifferent organism of the same species
Identify non-self and altered self-cells
Non-self: pathogens, toxins, cells of a different organism of the same species.
Altered self: cancer cells, cells invaded by viruses
Which type of lymphocytes facilitate cell-mediated immunity, and which facilitate humoural immunity?
Cell-mediated immunity is mediated by T lymphocytes.
Humoural immunity is mediated by B lymphocytes.
Name the three types of T-Lymphocytes and where they mature
T Helper cells, Cytotoxic T cells and T memory cells.
Mature in the Thymus gland.
Which T-Lymphcyte bind to APCs?
T Helper cells
Recall the four actions of T-helper cells
Stimulates the production of antibodiesby plasma cells.
Stimulates the cloning of cytotoxic T cells.
Produce cytokines, which attracts more macrophages, increasing the number of APCs
How do T lymphocytes divide?
Mitosis
Which is the only T-Lymphocyte that destroys pathogens?
Cytotoxic T cells
How do Cytotoxic T Cells destroy pathogens?
They release perforin, which creates small holes in the pathogen’s cell membrane
How to T-Helper cells attract more macrophages to the infected site?
They release cytokines
Name the T lymphocyte that gives you immunity
T memory cells
Name the three B-Lymphocytes and where they mature
B cells, Plasma cells, B memory cells.
Mature in the bone marrow.
Which B lymphocyte produces antibodies?
Plasma cells
Describe what antibody agglutination is
Binding many pathogens together
What is formed when an antibody binds to an antigen?
Antibody-antigen complex
Name the B lymphocyte that gives you immunity
B memory cells
Define what an antibody is
A protein that is specific to an antigen
What two things can antibodies bind to?
Bind to antigens, and bind to toxins
What is the effect of antibodies binding to viruses in particular?
Prevents them entering self cells
What allows many different shapes of antibodies to be made?
They are made from proteins, which can have many different tertiary structures
How many different types of protein are antibodies made from? How many chains of each?
Two heavy chains and two light chains
How many different regions are there on an antibody? How many of each?
Two variable regions and one constant region
Why is there two variable regions on an antibody?
So the antibody can bind to two antigens at once, agglutinating the pathogens
What are the variable regions on an antibody complimentary to?
the antigen or toxin
What does snake antivenom contain?
Antibodieswhich are complimentary to thespecific snake toxins.
What type of immunity is utilised when snake anti venom is used?
Passive
Why are monoclonal antibodies clones?
Because they are all produced from the same plasma cell
Outside the body, what are monoclonal antibodies used for?
Medical testing, e.g. pregnancy tests and the ELISA test
What is special about the antibodies in the reaction zone of a pregnancy test?
They are bound to coloured dyes or enzymes
How is a coloured strip formed in the test zone of a pregnancy test if the test is positive?
The immobilised enzymes bind to the hCG-antibody complex (with dyes attached)
What is the purpose of the control zone?
To prevent false positives or false negatives
How is a coloured strip formed in the control zone of a pregnancy test?
The immobilised enzymes bind to the antibodies with the coloured dye attached
Name the four types of immunity
Natural active, natural passive, artificial active, artificial passive
What is the fundamental difference between active and passive immunity?
In active immunity, the patient makes their own antibodies and therefore memory cells. In passive, they do not.
Which part of the pathogen is in a vaccination?
The antigens
What is herd immunity?
Herd immunity arises when a sufficiently large proportion of thepopulation has been vaccinated to make it difficult for apathogen to spread within that population
Who is herd immunity important for?
Unvaccinated people, e.g. children and the immunosuppressed
How does antigenic variability occur in pathogens?
Mutations occur in the genes that code for the antigens
Which lymphocyte does HIV invade and kill?
T Helper cells
Label a diagram of a HIV, including; phospholipid bilayer, glycoprotein (antigen), capsid, RNA & reverse transcriptase
Why is HIV classed as a retrovirus?
Because it contains RNA as its genetic material, and reverse transcriptase
Why do the glycoproteins in HIV’s phospholipid bilayer act as antigens?
Because they are a different shape to the antigens on the body’s cells
What is a normal TH count in a healthy person?
800-1200cm-3
Estimate a HIV infected person’s TH count
200cm-3
Why might someone not develop AIDS related symptoms until a long time after initial HIV infection?
Because HIV can lay dormant over time
What kinds of infections occur when a patient’s TH count becomes low?
Opportunistic infections
Explain why a low TH count causes opportunistic infections
Less TH cells means less antibodies are produced
When can someone be diagnosed with AIDS?
When their TH cell count has reduced past a point, and they develop AIDS-like symptoms
During HIV replication, what happens to the viral DNA?
It is incorporated into the host DNA
During HIV replication, what happens to the viral DNA once it is incorporated into the host DNA?
It is transcribed and translated
During HIV replication, what happens once the viral proteins have been translated?
They are assembled
During HIV replication, what happens once the viral proteins have been assembled?
The virus buds off and exits the host cell. It then goes to infect another cell.
What is the ELISA test used for?
To detect the presence and amount of proteins.
In the ELISA test, what is attached to the test well?
The antigen / protein
In the ELISA test, what in the patient’s blood will attach to the antigens in the test well?
The complimentary antibodies
In the ELISA test, why is the well washed?
To remove any unbound antibodies
In the ELISA test, what two things are added after the well is washed?
A second antibody, which is complimentary to the first antibody, and has an enzyme attached. Also a solution which changes colour in the presence of the enzyme.
In the ELISA test, what does the amount of colour signify?
The amount of protein present in the patient’s blood
