chapter 5 - cell recognition and the immune system Flashcards
What is an antigen
An antigen is a spike protein on the cell surface membrane of a cell it causes phagocytosis (immune response)
What cells are involved in the humoral response
B cells/B lymphocytes are involved in the humoral response B cells make antibodies present in the bodily fluids
Which cells are involved in the cell mediated response
T cells are involved in the cell mediated response. This happens in the body cell/own cell/self cell/ host cell
What do B lymphocytes/B cells do
B cells produce antibodies
What do T cells do
T cells have receptors on the cell membrane which are specific to an antigen. When the T-cell binds to an antigen it will neutralise the pathogen
What do B cells differentiate to
B cells differentiate to plasma B cells and memory B cells
memory B cells stay in the body for decades, however they can’t divide by mitosis
plasma B cells produce more antibodies
What do T cells differentiate to
helper T cells - help B cells in antibody production
memory T cells - stay in the body for decades
surpressor T cells - acts as an ‘off switch’ and stops expansion when specific antigens have been set with
Killer T cells - combine with an antigen and perforate it, Meaning the cell can’t grow and therefore the pathogen is killed
Define clonal selection and clonal expansion
clonal selection-B/T cell binds to the antigen. In direct contact it would bind directly to the pathogen. In indirect contact the B/T cell would bind to the phagocyte/antigen Presenting cell
Clonal expansion- after clonal selection, A macrophage or neutrophil will produce interleukins, these will bind to a specific lymphocytes and this will cause the lymphocyte to divide by mitosis this produces clones (clonal expansion)
What is the definition of cancer
When control mechanisms (tumour suppressor genes/Proto Oncegens) breakdown cells undergo repeated Uncontrollable cell division
What is a benign tumour
A benign tumour is where the cells remain at the position they are formed up, as the Cheema grows it will compress tissues that are surrounding it. As they are localised tumours can be removed by surgery or radiation
what is a malignant tumour
A malignant tumour does not remain in the position that they were formed at. They travel in the blood and to other parts of the body where they can cause a new tumours. The migration of cancer cells to form new tumours in the body is called METASTASIS. Malignant tumours are more difficult to treat then benign tumours because cancer cells spread in the blood or to the lymph to other areas of the body
How can you detect cancer cells
You can detect cancer cells under a microscope this is called a biopsy
what are oncogenes
oncogenes are a type of gene that can cause cells to divide into tumour cells. They are a mutated type of Porto-oncogenes (Which stimulate cells to divide normally)
What are tumour suppressor genes
tumour suppressor genes slow down cell division, they repair mistakes in DNA and program cells to die. If a tumour suppressor gene has become mutated or damaged this will cause cell division to spiral out of control.
What is Tamoxifen
Tamoxifen is a drug used to treat breast cancer. Tamoxifen fits onto oestrogen receptors and stops oestrogen from reaching cancer cells so cancerous cells don’t divide.
what is the definition of a pathogen
A pathogen is an organism that causes disease
Describe the process of phagocytosis
1-detection of antigens, foreign antigen is bind to receptors on the cell surface membrane of phagocytes.
2-phagocyte moves towards the pathogen and the cytoplasm of the phagocytes surrounds the pathogen and engulfs it. When the pathogen is engulfed it is sealed into a phagosome. (vacuole inside the cytoplasm)
3-Digestion of the pathogen, phagocytes have many lysosomes that contain protelytic digestive enzymes(lysozymes). enzymes break down the pathogen.
4-The pathogen is antigens are transported to the phagocyte cell membrane and are presented on the soul surface. This is an antigen presenting cell (APC). The antigens can activate other cells in the immune response
How are phagocytes specialised for their function and structure
They have a well-developed cytoskeleton to help them change shape to engulf the pathogen
They have mitochondria to release energy for cell movement
They contain lots of ribosomes to synthesise lysozyme enzymes
They have a lobed nucleus to help them squeeze through narrow gaps between cells and tissues
What is specific immunity
Cell mediated response (T cells)
Humoral response (B cells)
What is non-specific immunity
Physical barrier
Phagocytosis
How is a vaccine made harmless
The pathogen is killed by its antigens remain unaffected, purified antigens are used to make a vaccine, using the toxin that the pathogen makes and in activating it.
What is passive immunity
It is produced by the introduction of antibodies into individuals From an outside source. the immunity is generally short lived.
eg
antibodies from placenta/breast milk - natural
immunity via injection - artificial
What is active immunity
Active immunity is produced by stimulating the production of antibodies by the individuals own immune system it is generally longer lasting.
eg
antibodies from infection, phagocytosis- natural
immunity provided by antibodies from a vaccination - artificial
Features of a successful vaccination program
There must be very few side-effects from any vaccination
It has to be available in sufficient quantities to immunise the vulnerable population
Means of transporting/ storing the vaccine must be available
There must be a means of administration of the vaccine properly at appropriate times, this involves training stuff with appropriate skill sets
What is herd immunity
If a large number of the population of the people in the community is vaccinated it is harder for the pathogen to pass between those who are not vaccinated and cause disease. When most of the population is it Manises so it provides some protection for those who have not been vaccinated
what are monoclonal antibodies
A single type of antibody which has been isolated and cloned. They are specific to only one antigen and are made from a single clone of B-lymphocyte cells. They have a number of Useful functions (cancer treatment, transplant surgery, separation of a chemical from a mixture, and the ELIZA test)
What are the ethical issues with monoclonal antibodies
Some vaccines are developed and tested on animals, all monoclonal antibody is are produced in a lab with animals. In some remote parts of the world people may not know/be suspicious of a vaccine and may not volunteer. vaccines aren’t 100% effective.
What is agglutination
When antibodies stick the pathogens together by binding the antigens and clumping them together, This makes it easier for the phagocyte to engulf and digests them and it prevents the virus from interacting cells
What is the structure of an antibody
Made up of four polypeptide chains (2 heavy, 2 light)
They have a variable region which allows the antibody to attack a complimentary antigen
Disulphide bridges strengthen the bonds between the light and heavy chains making the molecule more sturdy
Constant regions bind to the phagocytes/ Bacteria
The hinge region binds to more than one antigen
Describe the primary response
This involves the production of antibodies from plasma cells, and memory cells.
Explain the secondary immune response
memory cells live for decades and circulate in the blood and tissue fluid, memory cells are responsible for the secondary immune response. When they encounter the same antigen later on they divide rapidly by mitosis into more plasma memory cells. Memory cells continue to circulate around the body providing long-term immunity against the original pathogen.
Explain why there is a delay between the first infection by pathogen and the parents of the antibodies in the blood (primary and secondary immune response)
Because it takes time for B cells to bind to the antigens and it takes time for clonal expansion to take place via mitosis which produces memory B-cells and plasma B cells
What is antigenic variability
This means that they frequently change the antigens on there cell surface membrane/receptors. This happens due to mutations producing new antigen is on the pathogen, the new answer gyms are no longer complimentary to the previously produced memory cells. So new vaccinations which are complimentary to the mutated antigen have to be made and rolled out
Explain and describe the structure of a HIV particle
There are two strands of RNA in the centre, and there is a protein attached to the RNA and this protein is called a reverse transcriptase enzyme.
There is a nucleocapsid which surrounds the RNA and protects it
There is a protein coat (CAPSID) which surrounds and encloses the RNA
There is a lipid envelope (coat)
On the very outside there is a spherical envelope of a lipid bilayer with glycoproteins
how does HIV spread
Spreads from an infected person to another person when bodily fluids mix
How does HIV cause disease
It’s infects and destroys T-helper cells, it’s only affects T-helper cells as they have receptors on the cell surface membrane that the protein of HIV is complimentary to.
Why are T-helper cells important in the immune system
T-helper cells are needed to stimulate Antibody production by B cells. Without T cells be cells will not be activated I know antibodies will be produced
How does HIV infect T-helper cells
1-HIV enters the bloodstream and it’s glycoproteins will attach to receptors on a T helper cell. The viral RNA will enter the cell.
2-The reverse transcriptase enzyme makes a DNA copy of the virus RNA.
3-This DNA copy is inserted into the DNA of the T-helper cell, this T cell will divide, And copy the viral DNA as well.
4-The virus DNA becomes active (could be many years later) and the T-helper cell makes new viruses.
5-This causes the T-helper cell to die therefore releasing thousands of new viruses from the cell this infects new T-helper cells.
How HIV can cause AIDS
AIDS Occurs in the final stage of infection, when the virus is destroyed the immune system by destroying T-helper cells as a result B cells cannot function. This leads to the person becoming severely immuno compromised
What is the ELIZA test (enzyme linked Immunoabsorbent assay)
biochemical technique used in immunology, To detect the presence of a specific Antibody
Describe and explain the direct ELIZA test
The antigen are Immobilised onto the plastic surface of a well. Then a primary antibody conjugated with an enzyme is added to the well. the Well is washed out to remove any antibodies that have not found to the antigen to prevent a false positive. Then a substrate is added to the well and if this substrate binds to the antibody a colour change will occur
Describe and explain the indirect ELIZA test
The antigen is imobilised To the plastic surface of a well. Then a primary antibody is added on the well is rinsed out. Then a secondary Antibody conjugated with an enzyme is added to the well And once again the well is washed out. Then a substrate is added and a colour change will develop
What are the benefits of the indirect ELIZA test
There is a better analysis for the total antibody concentration in a sample
