5 Cell recognition and the immune system Flashcards
Describe the cell mediated response
Memory T cells to enable a rapid response to reinfection of the same pathogen.
Cytotoxic T cells kill abnormal cells and infected body cells. They release a protein called perforin which creates pores (holes) in the cell membrane. This allows all substances to move into the cell and causes cell death.
Helper T cells stimulate B cells to divide and secrete antibodies.
T cells also stimulate phagocytosis of pathogens.
Describe the humoral response
Memory cells live for decades in some cases. When they encounter the same antigen they divide rapidly into plasma cells and more memory cells. The memory cells provide long term immunity. This is known as the secondary immune response.
1. The surface antigens of the invading pathogen are taken up by the B cells.
2. The B cells process the antigens and present them on their surface.
3. T helper cells attach to the processed antigens and B cells thereby activating them.
4. The B cells are now activated to divide by mitosis to give a clone of the plasma cells.
5. The cloned plasma cells produce antibodies that exactly fit the antigens on the pathogens surface.
6. The antibodies attach to antigens on the pathogens and destroy them. This is the primary immune response.
7. Some B cells develop into memory cells. These can respond to future infections by the same pathogen by dividing rapidly and developing into plasma cells that produce antibodies. This is the secondary immune response.
Structure of an antibody
Antibodies are proteins that have binding sites complementary in shape to antigens. The binding site is described as the variable region, as the shape changes for each antigen. The rest of the antibody is the constant region. They are made up of four polypeptide chains, two heavy and two light chains. When an antigen binds to an antibody, it is described as an antigen-antibody complex.
Describe active immunity
the immune system has created its own antibodies in response to something.
Describe passive immunity
Antibodies are received from an external source, eg anti-venom/antibodies the baby receives across the placenta
Describe the structure of HIV
two copies of a single-stranded RNA genome within a conical capsid surrounded by a plasma membrane of host-cell origin containing viral envelope proteins.
How are monoclonal antibodies produced?
antibody-producing lymphocytes in mice are fused with human cancer cells to produce large quantities of specific monoclonal antibodies.
How are monoclonal antibodies used in medical diagnosis?
Monoclonal antibodies can be used to detect the presence of antigens. They can also be used in different techniques which include ELISA as well as pregnancy testing.
Describe the events of the ELISA test
An enzyme is attached to antibodies
When this enzyme reacts with a certain substrate, a coloured product is formed, causing the solution in the reaction vessel to change colour
If a colour change occurs, this shows that the antigen or antibody of interest is present in the sample being tested (e.g. blood plasma)
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