3.2.3 immunity Flashcards
what is an antigen
cell surface protein which stimulates an immune response
2 types of immune response
cell mediated + humoral
phagocytosis
- pathogen release chemical attracting phagocytes
- phagocyte binds to pathogen
- phagocyte engulfs the pathogen forming a phagosome
- phagosome fuses with lysosome to form phagolysosome.
- lysozomes/hydrolytic enzymes break down the pathogen
- the pathogens antigens are presented on the surface of the phagocyte
cell mediated response
- T cells bind to the antigen with complementary receptors
- The T cells divide by mitosis to form genetically identical cells.
- Cloned T cells develop into helper T cells and cytotoxic T cells, stimulate b cells and memory cells
role of helper T cells
release chemical signals which stimulate phagocytes and B cells
role of cytotoxic T cells
kill abnormal and foreign cells
role of memory T cells
enable a rapid response to a secondary infection
humoral response
- B-lymphocyte binds to the complementary antigen
- B cell is activated by helper T cell
- B-lymphocyte divides by mitosis ( clonal expansion)
3.producing plasma cells and memory B cells
role of plasma cells
secrete antibodies specific to one antigen
structure of an antibody
quaternary structure
2 heavy chains and 2 light chains
disulfide bridge holding the 2 chains together
variable region which acts as the binding site
constant region
what are monoclonal antibodies
antibodies which have been produced from 1 plasma cell from 1 B cell
what is active immunity
when the bodys immune system makes antibodies after being stimulated by an antigen
what is passive immunity
when the body is given antibodies made by a different organism
example of passive and active immunity
passive - antibodies given to babies via breast milk or
antivenom
active - catching a disease or a vaccination
secondary immune response
stronger and faster than a primary response
memory cells produced in the primary response quickly recognise the pathogen and divide to form plasma cells
how do vaccines prevent infection
vaccines contain antigens of a dead pathogen
the antigen becomes presented on an phagocyte
a T cell will bind to the antigen, then dividing into B cells
B cells will divide into plasma cells and memory B cells
the memory B cells will remain in the body until a second infection, quickly producing antibodies complementary to the pathogen before the person become infected or shows any symptoms
herd immunity
vaccinating large enough proportion of the population reducing carriers of the pathogen
structure of HIV
RNA genetic material and reverse transcriptase
capsid
lipid envelope
attachment proteins on the lipid envelope
how does HIV replicate
- attachment proteins on HIV bind to CD4 receptors on helper T cells
- capsid is released into the cell, releasing the genetic material in the cytoplam
- reverse transcriptase makes complementary strands of DNA from the RNA template
- HIV DNA is converted into double stranded DNA and then inserted into the cells DNA
- viral proteins are mode using the host enzymes
- viral proteins are assembled into new viruses which leave infected other cells
how does HIV lead to AIDS
HIV weakens helper T cells, weakening the immune system. this makes people who show AIDS more susceptible to infection
what is AIDS
when the number of T cells in the body are really low
indirect ELISA
- add sample to plate, if antigen is present it will stick. wash
- add the antibody specific to the antigen. wash
3.add second antibody with an enzyme attached. wash
4.add substrae - if there is a colour change shows the antigen was present in the sample
difference between direct and indirect ELISA
direct - one antibody used
indirect - two antibodies used
ethical issues using vaccines
production may use animals
dangerous side effects
direct ELISA
- monoclonal antibody bins to bottom of plate. wash
2.sample added, if it contains an antigen it will bind to the antibody. wash - mobile antibody with an enzyme attached is added. wash
- substrate added which binds to the enzyme
- colour change means the sample contained the antigen
ethical issues of monoclonal antibodies
production involves animals
