5. Cell Recognition and immune system Flashcards
How does the body detect pathogens?
Body can recognise ‘non self’ protiens on the set face of the cell
What is an antigen
(Macromolecule) markers that allow cell to cell recognition. Can either be self or non self
How do pathogens avoid causing a specific immune response?
Antigen variability, antigen change due to genetic mutations.
Memory cells can no longer bind
How does passive immunity happen?
Anti-venoms, fetal immunity (breast milk)
No memory cells are made, immunity is temporary
What is (natural) active immunity?
Organism is infected, triggering numeral immune response
Antibodies made but symptoms of disease may be displayed
What is (artificial) active immunity?
Vaccination, body produces antibodies and memory cells providing long-term immunity
Without experiencing symptoms
Describe process of phagocytosis
- phagocyte is attracted to pathogen by the pathogens chemical products
- pathogen attaches to receptors on phagocyte
- lysosomes migrate to forming phagosome as pathogen gets engulfed
- lysosomes release lysoZYmes into phagosome, these hydrolyse the pathogen
- pathogen absorbs hydrolysis products
[ext] phagocyte ‘present’ pathogens antigens. (Not part of cell phagocytosis)
What are the two types of phagocytes?
Neutrophils
Macrophages
Two examples of specific immune responses?
Cell mediated- T cells
(matured in thymus)
Humeral- B cells
(matured in bone marrow)
Summarise the role of T cells in CELL-MEDIATED immunity
- receptors helper T-cell fit onto antigen presenting cell
- T-cell is activated to divide by mitosis
- cloned T cells can either:
Become memory cell
Stimulate phagocytosis
Stimulate B cell
Activate TC cell
What is a TC cell?
Explain how they carry out function.
Cells that kill infected body cells by releasing the protein perforin. This protein makes holes in membrane
When are b cell produced produced?
At birth, around 10 million of each are present in body.
B cells are not produced in response to pathogen, they only multiply in response to pathogen
When b cells are cloned they can either be…
plasma cells or memory cell.
What cells are involved in primary and secondary responses
Primary - PRODUCTION of antibodies and memory cells
Secondary - memory cells recognise pathogen, providing faster response on later infection
How are monoclonal antibodies used to treat cancer? (indirect and direct)
DIRECT
Antibodies specific to cancer antigen blocks chemicals that stimulate uncontrolled growth.
INDIRECT
Radioactive or cytotoxic material is attached to MA, binding to and killing cancer
How are monoclonal antibodies used in diagnosis
Eg. Prostate cancer causes an increase in PSA antibodies, this is detected and causes concern for further testing
The ELISA test
Give three reasons why monoclonal antibodies raise ethical issues
Mice involved in production
Deaths linked with MA
drug testing (2006 six volunteers had multiple organ failure)
What 5 things are necessary for an effective vaccination program
Economically viable
Few side effects
Viable transport, storage + production
Training of staff to perform vaccination
Majority of population must be vaccinated = herd immunity
6 reasons why vaccination might not work
-will not work on people with defected immune systems
- disease may develop immediately after vaccination, potentially spreading to others
-antigen variability
-variants of the same pathogen
-Some pathogens ‘hide’ in body cells eg HIV
-some may object because of medical or ethical issues
Discuss ethical issues of vaccination
Testing often involves animals
Potentially long lasting side effects
Risks involved in human testing
Should it be compulsory so herd immunity can be achieved?
What do Plasma cells do?
Secrete antibodies into blood plasma. Survive for short amount of time but produce a lot of antibodies
What do memory cells do?
Memory cells live longer, when they ‘recognise’ the same pathogen they divide rapidly and develop into plasma cells.
They provide readiness for future infections
Summarize the humoral response.
B-cell takes up antigens of pathogens and presents them.
Helper T cells attach, activating B cell.
Stimulated to clone into plasma or memory cells.
Draw and label an antibody
go online for images;
- light chain
- heavy chain
- constant region
- variable region
- antigen binding sites
Explain how antigens are destroyed by antibodies.
- agglutination of bacterial cells, clumps of cells are formed (antigens have multiple binding sites) Easier for phagocytes to find.
- act as markers for phagocytes to engulf cells they are attached
Where do T and B cells mature?
T cells, mature in thymus
B cells, mature in bone marrow
Explain how vaccinations work.
- Small amounts of weakened/ dead pathogen injected
- B cells are activated (plasma/memory)
- memory cells remain in the bloodstream
Explain the concept of herd immunity
If enough of the population is vaccinated, pathogens cannot easily spread.
protects those who aren’t vaccinated/ can’t get vaccinated.
Draw the structure of HIV.
- RNA
- Reverse transcriptase
- capsid
- matrix
- attachment proteins
- membrane
Summarize the replication of HIV
HIV is transported in blood until it attaches to a CD4 PROTEIN on a helper T-cell
HIV capsule fuses with the Th-cell, RNA and reverse transcriptase enter.
Th-cell synthesises new viral enzymes and RNA
How do new viral RNA and proteins exit host cell? (HIV)
Move to cell membrane, and is released, New HIV molecules membrane is from Th-cell
What is AIDS?
Replication of viruses via Th-cells interferes with immune response. The host is vulnerable to infections and cancer.
Explain the process of the Enzyme linked immunosorbent assay (ELISA)
7 steps…
- add a test sample to the base of a beaker
- wash to remove any unbound test sample
- add an antibody, complementary in shape of antigen that is being tested for
- wash any unbound antibody
- add a second antibody antibody that is complementary to the first, enzyme attached to it, rinse unbound antibodies
- add substrate for enzyme - colorless in absence of enzyme, coloured in the presence of enzyme
- colour indicates presence of enzyme and therefore antigen. intensity indicates quantity present
Why are antibodies ineffective against viruses?
viruses rely on host cells for metabolic pathways. no mechanisms for antibodies to disrupt.
inside organisms own cells, cant be reached
