Immunity Flashcards
What are 1st physical barriers of the immune system?
Skin, stomach acid, cilia
What is an antigen?
A protein on the cell surface membrane of a molecule that stimulates a immune response by recognizing self/non-self cells.
What is antigenic variability?
The DNA of the antigen mutates causing change in 3’ so immune system will not recognize pathogen and kill it since memory cell no longer complementary. Since so many varieties its harder to develop vaccine.
What is a foreign body?
Toxins, pathogens, abnormal self- cells (cancer), transplant cells.
Describe the non-specific immune response
By phagocytosis. Chemotaxis, endocytosis of pathogen into phagocyte. Forms phagosome around pathogen, lysosome fuses with phagosome and secrets lysozyme.
Hydrolyses pathogen, absorbs products, displays antigen onto cell surface membrane.
What is the function of APC?
The phagocyte becomes APC. Allows recognition of antigen by T- helper cell for cell mediated response.
What are the 2 types of specific immune responses?
Cell mediated- T cells
Humoral- B cells
What is a T- cell?
Lymphocytes that mature in thymus glands and are involved in cell mediated response.
What is a B- cell?
Lymphocyte that matures in the bone marrow and is involved with the humoral response.
Describe cell mediated response
Receptor on complementary T- helper cell attaches to antigen of APC through clonal selection. This stimulates clonal expansion of the right T cell. They then differentiate into
a) T- helper cell: stimulate B cell
b) T- memory cells: incase of re-infection
c) T- killer cells: produce perforin to destroy infected cells
Describe humoral response
B- cell becomes APC and the complementary T- helper cell through clonal selection will bind to receptors which will stimulate clonal expansion of the right B- cell. Then differentiate into
a) B- plasma cell: secretes antibodies
b) B- memory cell: circulates in blood incase of re- infection
What is an antibody?
Proteins made and secreted by B- plasma cells with a specific 4’ binding site. Made of 4 polypeptide chains (2 light/ 2 heavy)
Describe the structure of an antibody
Light chains attached to heavy chains by disulphate bonds.
Variable region: unique for each complementary to antigen by specific 3’
Constant region: same for every antibody
Antigen binding site: on the VR where it recognizes particular antigen
How do antibodies cause pathogens to be destroyed?
a) Agglutination
b) Becomes marker
c) Binds to flagella
What is primary response?
When you are initially exposed to a pathogen for the 1st time. Concentration of antibodies increase as B- cells try to fight off, then concentration decreases when killed pathogen, but symptoms still show. Body produces B- memory cells from this exposure so they remember incase of re-infection.
What is secondary response?
Secondary exposure upon reinfection B- memory cells produce large amount antibodies rapidly. The concentration of antibodies increases more rapidly this time. This will kill pathogen before infection and symptoms show.
Describe a vaccine
Vaccine uses the concept of 1st/2nd response. A dead or inactive pathogen will initiate primary response causing formation of B- memory cells. So upon infection by actual pathogen will stimulate secondary response so antibodies produced at higher rate killing pathogen before symptoms show.
What is herd immunity?
When the majority of the population is vaccinated therefore vulnerable and unvaccinated are unlikely to come into contact with pathogen carrier/ infected person.
What are some ethical issues with vaccines?
a) Use of animals
b) Potentially fatal side-effects
c) Compulsory/ opt out
d) Clinical test on healthy/sick/young/old?
e) Will newly introduced vaccines have long term effect?
What is active immunity?
Results from the production of antibodies by the immune system in response to the presence of an antigen of pathogen.
Give examples of natural/artificial active immunity
Natural: Humoral response
Artificial: Vaccine
What is passive immunity?
Results from the introduction of antibodies
from another person or animal.
Give examples of natural/artificial passive immunity
Natural: Antibodies in breastmilk/ across placenta
Artificial: Anti-venom
Contrast passive/active immunity
PASSIVE: -Short term -Immediate -External source ACTIVE: -Long term -Time lag -Lymphocytes produce own antibodies
Describe structure of HIV
Genetic material (RNA + reverse transcriptase)
all surrounded by capsid
which is surrounded by viral envelope
Glycoproteins on cell surface membrane
How does HIV replicate?
HIV binds to CD4 receptors on T- helper cells. Capsid fuses with cell membrane and releases RNA + reverse transcriptase into T- cell. RT turns RNA into DNA which moves into the nucleus of T- cell. Starts to produce HIV viral proteins to make new HIV. Bud off membrane of T- cell, causing host cell to die.
How does HIV cause AIDS?
T- cells = lowered stimulus of B- cells = decreased immunity = patient vulnerable to even small infections = fatal
Why is anti-biotic ineffective against viruses?
Anti-biotics kill bacteria by damaging murein cell wall which virus don’t have, and virus and bacteria have different structure and replication. Also hard to kill virus without killing host cell.
What is a monoclonal antibody?
Antibodies isolated and produced by same clone of B-cells.
Give uses of monoclonal antibodies
- Pregnancy tests
- ELISA test for diagnostic
- Attach drug to target abnormal cell (cancer)
- Attach tracker to see where abnormal cell is
Describe how the ELISA test works
Monoclonal antibody attached to the bottom of plate. Add sample with antigen and it attaches to antibody. Rinse out. Add antibody with enzyme which binds to antigen. Rinse out. Add substrate for enzyme, color change = positive
Give some ethical issues with monoclonal antibodies
- Production involves mice
- Some drug trail = organ failure
