Cell recognition & the immune system Flashcards
Define innate immune system (defence)
An immediate and non-specific defence
Define acquired immune system (defence)
A long term and specific defence (defence is individual to each health threat)
how does the body distinguish between self and non self cells
Non self cells have different shaped glycoproteins (sometimes called antigens or just proteins) on their surface. White blood cells can differentiate between these self and non self antigens
what is a major histocompatibility complex
A group of genes found on the surfaces of cells that help the immune system recognize foreign substances
What are phagocytes and what do they do
Antigen presenting cells, highlight non-self antigens to T helper cells that stimulate T cytotoxic cells to destroy foreign antigens
What are B-cells and what is their function
B lymphocytes, are a type of white blood cell that produce plasma cells and B memory cells. They are involved in humoral responses
what do plasma cells do
secrete antibodies
what do B memory cells do
Remain in the blood for years and provide the body with long term protection
what do macrophages and neutrophils do
Engulf and digest pathogens by fusion of the phagosome with lysosomes
what do T helper cells do
- Activate the replication of Tc cells
- produce cytokines
- promote the production of B cells
- produce opsonin’s
what do cytotoxic T cells do
destroy virus-infected cells and cancerous cells
what is perforin
A protein released by killer T cells which destroy cells by making large pores in their membranes
what are antibodies
proteins produced by B lymphocytes that bind to antigens that they are complimentary to due to their shape. They form antigen-antibody complexes
Explain the process of phagocytosis
- The phagocyte recognises the foreign antigen
- Pathogen is engulfed in a phagosome
- Phagosome fuses with lysosome
- lysosome releases lysozymes
- pathogen is hydrolysed
state the process of phagocytosis
- Chemotaxis
- Adherence
- Ingestion
- Digestion
- Exocytosis
explain 2 physical first line defences against disease
- the skin is a barrier to pathogens (organisms that cause disease)
- blood clotting, a scab forms a barrier over the wound
define pathogen
A bacterium, virus or other microorganism that can cause disease
Explain 2 chemical first line defences against disease
- Sebaceous glands in the skin produce sebum, an oily liquid that destroys pathogens
- tear glands produce lysozymes, an enzyme that destroys pathogens
What is a phagocyte
phagocytes are a type of white blood cell that has the ability to ingest and destroy foreign particles.
explain chemotaxis
STEP 1 of PHAGOCYTOSIS
Chemotaxis- The phagocyte moves towards the pathogen along a concentration gradient.
explain adherence
STEP 2 of PHAGOCYTOSIS
Adherence- The phagocyte has several receptors that attach to the, complimentary in shape, antigens on the pathogen.
explain ingestion
STEP 3 of PHAGOCYTOSIS
Ingestion- A phagosome is formed by the engulfing of the pathogen. Lysosomes within the phagocyte migrate towards the phagosome
explain digestion
STEP 4 of PHAGOCYTOSIS
Digestion- The lysosome releases its lysozymes into the phagosome, where they hydrolyse the pathogen
explain exocytosis
STEP 5 of PHAGOCYTOSIS
Exocytosis- The products of the pathogen that was broken down are expelled or absorbed by the phagocyte
what is a primary immune response in relation to vaccinations
(Memory cells) The primary immune response is when a pathogen infects the body for the first time and the initial immune response is slow
what is a secondary immune response in relation to vaccinations
the secondary immune response is a more rapid and vigorous response caused by a second infection by the same pathogen. This is due to the presence of memory cells
What is a vaccination
The introduction of a weakened or dead pathogen into the body to stimulate an immune response and form memory cells
What is herd immunity
when the vaccination of a significant proportion of the population provides protection for individuals who have not developed immunity
Define active immunity
when specific antibodies are produced by the individuals own immune system
define passive immunity
when specific antibodies are introduced to the individual from an outside source
give an example of natural passive immunity
antibodies through breast milk
give an example of natural active immunity
direct contact with pathogen
give an example of artificial active immunity
vaccinations
give an example of artificial passive immunity
injection of antibodies
what do T cells do
cell mediated immunity, only respond to foreign antigens on the surface of other cells
where are T cells and B cells produced
Bone marrow, but T cells mature in the thymus
How do pathogens cause damage
- releasing toxins
2. Kill cells
How do antibodies destroy antigens
The effect of antibodies is indirect. Instead make the destruction of antibodies more likely through:
agglutination, precipitation, markers, neutralisation and lysis
Explain Agglutination
Binding of antigen antibodies complexes making it easier for phagocytes to locate and destroy bacteria
Explain Precipitation
Precipitation of the antigen facilitates phagocytosis
Explain markers
Markers are Immune complexes are signals that stimulate phagocytosis
Explain neutralisation
The neutralisation of toxins
Explain lysis
Lysis is when enzymes bind to antibodies and catalyse reactions which break down bacteria when bound to antibodies
What are monoclonal antibodies used for
diagnosis and treatment
define monoclonal antibodies
A collection of a single type of antibody that is isolated and cloned
define polyclonal antibodies
A collection of many different types of antibodies
How can monoclonal cells be used to treat cancer cells
Cancer cells have tumour markers that aren’t found on normal cells. Monoclonal antibodies can be made to bind to tumour markers so that we can identify the cancer cells. We can attach anti cancer drugs to the monoclonal antibodies that bind with the cancer cells
what is one positive of using monoclonal cells to treat cancer
they have less side effects as they only bind to cancer cells and not other rapidly multiplying cells, eg. hair cells
How do pregnancy tests work
if hCG is present
- Urine sample is applied to the bottom of the stick
- any hCG present bind to the antibodies at the reaction zone
- The antibodies contain enzymes that will cause a colour change at the test zone and control zone
- Then at the test zone the antibodies with hCG attached bind to immobilized antibodies
- The hCG is now sandwiched between two antibodies
- After the binding occurs at the test zone the enzymes are released and cause a colour change
- The antibodies (with attached hCG) continue along the test until they reach the control site where another colour change occurs
- if the colour change does not occur at the control site then the test is faulty
Explain monoclonal antibody production (mice)
- Immunization of mouse to stimulate antibody production
- Anti body forming cell isolated
- Antibody forming cell fused with cultivated tumour cell to form hybridomas
- Hybridomas screened for antibody production
- Antibody producing hybridomas cloned
- Monoclonal antibodies isolated for cultivation
What does ELISA stand for
Enzyme linked immunosorbent assay
What is the purpose of an ELISA test
To see if a person has the specific antibodies to an antigen or the antigen for specific antibodies
What are the uses for ELISA test
Diagnosis of pathogenic infections eg, HIV or allergies
What indicates a positive result on an ELISA test
A colour change, the colour changes can be quantitative eg, darker colour change stronger the infection
What does a direct ELISA test look for
Specific antigens
What does an indirect ELISA test look for
Specific antibodies
Describe the method for an Indirect ELISA test
- Add patients blood containing antibodies to the antigens
- Wash excess unbound antibodies
- add detection antibodies
- Wash out excess unbound detection antibodies
- Add substrate to the enzyme linked detection antibody
- look for colour change
Describe the method for direct ELISA tests
- Add antigens from patient
- add detection antibodies
- Wash out excess unbound antibodies
- Add substrate to the enzyme linked to the antibody
- Look for colour change
explain how B-lymphocytes respond when they are stimulated by anitgens
- form clones by mitosis
- produce plasma cells
- plasma cells produce antibodies
- form memory cells
How do pathogens cause diseases
- kill cells
2. release toxins
Explain how substances with high sugar concentrations (honey) kill bacteria, think water potential
- water potential in bacterial cells is higher than in honey
- so water potential leaves bacteria cells by osmosis
What are features of an effective vaccination programme
For an effective vaccination programme at least 80% of people must be vaccinated.
What are some ethical issues with vaccinations
- Animal testing, vaccinations must pass animal trials before moving onto human trials
- Human testing, may suffer symptoms of the disease (side effects)
3.
What are some ethical issues with monoclonal antibodies
- Animals that the antibodies are taken from must die
- Risk of organ failure
- removal of spleen in humans compromises the immune system
Describe the structure of an antigen-antibody complex
An antibody bound to a complimentary antigen.
Name the structures that make up an antibody
- heavy chain
- light chain
- variable region
- antigen binding site
name 3 types of pathogen
- fungi
- bacteria
- virus
What does HIV infect (specifically)
T helper cells
What are the treatments for HIV
- HIV cant be treated by antibiotics
- Antiretroviral drugs stop the virus replicating
- Treatments do not destroy the virus but keeps it to a low level
Why cant HIV be treated by antibiotics
antibiotics perforate cell walls using perforin but HIV does not have a cell wall
How does Antiretroviral drugs stop replication of HIV
Antiretroviral binds to reverse transcriptase so stops the virus copying itself
What are the components that make up a HIV virus cell
- RNA
- Glycoproteins
- capsid
- Reverse transcriptase
What is reverse transcriptase
An enzyme that catalyses the formation of DNA from RNA, in reverse transcription.
What do antigens allow the immune system to identify
4 things
- pathogens
- abnormal body cells
- toxins
- cells from other organisms (organ transplant)
What feature enables phagocytes to engulf pathogens
The flexibility of the cell-surface membrane enable the phagocyte to engulf pathogens such as bacteria and viruses
Why are phagocytes attracted to pathogens
Chemicals released by pathogens attract phagocytes to them because it forms a concentration gradient down which phagocytes move
What can HIV lead to and how
- AIDS
2. HIV destroys T helper cells meaning that the immune system destroys the causes of diseases less effectively
what are opsonin’s
opsonin’s are proteins that cover antigens making it easier for phagocytes to recognise and target antigens
What do Tc cells do
killer T cells destroy virus-infected cells and cancerous cells
How do Tc respond to a virus-infected body cell
- Bind to virus antigen on the surface of the virus infected cell
- perforin and granzymes are proteins produced by Tc cells and secreted by exocytosis
How does perforin destroy virus infected cells
perforin molecules bind to the cell surface membrane of the target cell and perforate the membrane
How does granzyme (A & B) destroy virus infected cells
- Granzyme A, catalyses reaction that poisons the target cell
2 Granzyme B, catalyses reaction that destroys the target cell
How do B cells respond to antigens and phagocytosis
- produce clones (clonal expansion)
- produce plasma cells that produce antibodies
- Antibodies bind to antigens on the surface of bacterial cell membranes
- these complexes allow agglutination (clumping together of cells) to occur which helps phagocytes destroy bacteria
Why are memory cells ineffective against an influenza virus
Frequent mutation
- Antigenic Drift, minor changes that produce new strains of the virus
- Antigenic Shift, major changes that result in new types of virus
Are vaccines effective against influenza viruses
No, because the antigens on each variant are different from those on the previous variant
Define hybridoma
Two different cells fused together
