cell recognition and the immune system

Created by

kaiya

Cards (45)

Phagocytes - specific or non-specific?
non-specific
Lymphocytes - specific or non-specific? 
specific
what is a phagocyte?
a macrophage (type of white blood cell) that carries out phagocytosis
Describe how phagocytic white blood cells destroy pathogens (4 marks)
1. phagocyte detects chemicals given off by pathogen and moves towards it
2. pathogen is ingested by phagocyte = phagosome
3. phagosome + lysosome = phago-lysosome - contains enzymes to digest the microbes
4. enzymes separate microbes into useful + non useful parts - non-useful parts are discharged
where are all lymphocytes made?
bone marrow
where to T cells mature?
thymus
what is an antigen presenting cell? Give 3 examples 
Any cell that presents a non-self antigen on their surface
E.g. infected body cells, cells of transplanted organ, cancer cells
describe the process of cell mediated response
1. pathogen is ENGULFED and DESTROYED by a phagocyte, ANTIGENS are positioned on the CELL SURFACE - now APC's

2. HELPER T CELLS have RECEPTORS on their surface which can BIND to antigens on APC's

3. once ATTACHED helper T cells are ACTIVATED and DIVIDE by mitosis to make CLONES

4. cloned helper T cells can DIFFERENTIATE
- some remain as helper T cells and activate B lymphocytes
- some stimulate macrophages to perform phagocytosis
- some become memory cells for that antigen
-some become cytotoxic T cells
What is the role of cytotoxic T cells?
- destroy abnormal/infected cells
- release a protein (perforin) - embeds cell surface membrane and makes a pore so substances can enter/leave cells
- CELL DEATH
where do B cells mature?
bone marrow
what does the humoral response involve
involves B-cells + antibodies
How are B cells activated?
- antigens collide with complimentary antibody on a B cell
->B cell takes in antigen (endocytosis) + presents it
- B-cell collides with helper T cell receptor, activating the B-cell to undergo clonal expansion and selection
- B-cells undergo mitosis - makes lost of cells to differentiate
what process involves memory B-cells?
active immunity
Define an antigen 
a toxin or other foreign substance which induces an immune response in the body, especially the production of antibodies.
explain the effect of antigen variability on disease and disease prevention
- reduces the effectiveness of vaccines
- antibodies are no longer complimentary to antigens = don't bind
define an antibody 
a blood protein produced in response to and counteracting a specific antigen
describe and explain the structure of an antibody
- Y shaped structure
-> 4 polypeptides - 2 heavy, 2 light chains
- structure allows antigen binding and biological activity mediation
what is agglutination? what does it do?
antibodies bind to multiple antigens and clump together
it makes it easier phagocytes to locate
explain how antibodies work
By Four mechanisms of attack against antigens: neutralization, complement fixation, agglutination and precipitation
explain the roles of plasma cells and memory cells in producing primary responses
PLASMA:
- after clonal expansion and selection, the B-lymphocytes that have become B-plasma cells secrete antibodies
- the cells are short-lived but the antibodies stay in the blood for a long time

Memory:
- after clonal expansion and selection, the B-lymphocytes that have become B-memory cells remain in the blood for a long time
explain the roles of plasma cells and memory cells in producing secondary responses 
- if the same antigen is found in the body a second time, the memory cells recognise it, divide quickly and differentiate into lots of plasma cells
- this response is very rapid
how do vaccines work?
- small amount of dead/weakened pathogen
- activates B cell to undergo clonal expansion + selection, producing B-plasma and B-memory cells
- memory B cells able to trigger a rapid secondary immune response
what is herd immunity?
When a majority of a population are vaccinated against a disease.
This means that even people who have not been vaccinated are less likely to get it because there are fewer people to catch it from.
compare active and passive immunity
Active - requires exposure to the antigen, to produce own antibodies
Passive - introduces antibodies from another person/animal
Active - memory B-cells are produced so body is prepared for a secondary immune response
Passive- no memory B-cells
Active - immunity takes time to develop
passive- immunity acquired immediately
what is the difference between natural active and artificial active immunity?
natural active: arises from being exposed to the antigen/ getting the disease
artificial active: acquired through vaccinations which stimulate the immune response
what is the difference between natural passive and artificial passive immunity? 
natural passive: antibodies passed from mother to foetus across the placenta + breast milk
artificial passive: antibodies are injected into the body
suggest four things the success of a vaccination programme depends on
- cost of the vaccine
- severity of side effects
- ease of production, transportation and administration
- number of people who need to be vaccinated for herd immunity
suggest three problems with vaccinations
- different 'strains' with different antigens - formed by mutations
- pathogens may attack immune cells
- pathogens can be evasive and remain protected inside cells by self-antigens
describe the structure of HIV
● Genetic material (2 x RNA) & viral enzyme (reverse transcriptase) surrounded by capsid.
● Surrounded by lipid envelope
● attachment proteins on surface.
describe how HIV replicates in helper T cells
1. HIV binds to protein CD4 - found on helper T cells
2. capsid fuses with cell-surface membrane
3. RNA and reverse transcriptase enter the cell
4. reverse transcriptase converts RNA to DNA which moves into the nucleus of cell
5. DNA joins to hosts DNA/chromosome
6. cell now has instructions to produce viral HIV components
explain how HIV causes symptoms of AIDS
- HIV attacks T helper cells
= low number of T helper cells
= B cells + cytotoxic T cells not stimulated
= antibodies not produced/infected cells can't be killed
- memory cells destroyed
= body susceptible to other infections + cancers
explain why antibiotics are ineffective to viruses
- antibiotics work by preventing bacteria from making cell walls, so they can't control movement of water and burst
- viruses don't have a cell wall and reproduce within host cells
how are monoclonal antibodies used for immunoassay
1. mcab will have an indicator attached
2. if drug/hormones are present, antibody attaches to antigen and triggers colour change of indicator
give some examples for what monoclonal antibodies are used to detect
chlamydia, HIV, pregnancy, cancer cells, covid-19
give some examples for what monoclonal antibodies are used to treat
breast cancer, autoimmune therapies, melanoma, rabies, prevention of blood clots
describe the use of antibodies in the ELISA test
1. antigen added to a well
2. add specific antibody to be measured
3. add enzyme-conjugated secondary antibody
4. add substrate and measure colour
5. rinse well after steps 1-3 to remove any excess
Suggest some ethical issues surrounding the use of vaccines.
- production and testing may be done on animals
- risks of vaccine need to be balanced with benefits
- vaccine must be tested on humans first to determine toxicity
- vaccinations are expensive
Suggest some ethical issues surrounding the use of monoclonal antibodies
- inducing cancer on the mice
- making mice produce antibodies
- deaths associated with use - patients must give informed consent
-drug testing presents some dangers
what is the role of a disulfide bridge in forming the quaternary structure of an antibody?
joins two polypeptides
describe the role of macrophages in stimulating B lymphocytes
macrophages present antigens which the specific B lymphocytes can bind to