(5)Cell recognition and the immune system Flashcards
define a pathogen
a microorganism that causes disease
what is immunity
the way in which the bodys defences are better prepared for a second infection from the same pathogen and so can kill it before it causes any harm
what is a T cell or T lymphocyte
a type of WBC that has receptor proteins on its surface that bind to complementary antigens presented to it by phagocytes
what is the difference between Tc cells and Th cells
Th cells (helper T cells) release chemical signals that activate and stimulate phagocytes and cytotoxic T cells (Tc cells) which kill abnormal and foreign cells
Th cells also activate B cells which secrete antibodies
what are B cells/ B lymphocytes
a type of white blood cell that’s covered in antibodies . each B cell has a different shaped antibody on its membrane so different ones bind to different shaped antibodies
what happens when a B cell antibody meets a complimentary antigen
they bind together, the B cell is activated because of substances released from helper T cells. The activated B cell divides into plasma cells
what are plasma cells
identical to the b cell they secrete loads of antibodies specific to the antigen (called monoclonal antibodies)
what is agglutination
an antibody has 2 binding sites so can bind 2 pathogens at the same time meaning pathogens become clumped together
what are antibodies
proteins with a variable region that has a unique tertiary structure due to different amino acid sequences
what are the 2 parts of the immune response
cellular- T cells and other immune system cells they interact with
humoral- B cells, clonal selection and the production of monoclonal antibodies
what is the difference between memory B cells and memory T cells
memory T cells remember the specific antigen and will recognise it a second time round. memory b cells record the specific antibodies needed to bind the antigen
what do memory B cells and memory T cells do during the secondary immune response
memory b cells are activated and divide into plasma cells that produce the right antibody to the antigen
memory t cells are activated and divide into the correct type of t cell to kill the cell carrying the antigen
what is a vaccine
something that contains antigens that cause your body to produce memory cells against a particular pathogen without the pathogen causing disease so you become immune without having symptoms
what is active immunity
the type of immunity where your immune system makes its own antibodies after being stimulated by an antigen. Natural: when you become immune after catching a disease
artificial : when you become immune after being given a vaccination
what is passive immunity
the type of immunity you get from being given antibodies made by a different organism
natural: when a baby become immune due to antibodies it receives from mother from placenta and breast milk
artificial: when you become immune after being injected with antibodies from someone else
what are moniclonal antibodies
antibodies produced from a single group of genetically identical B cells (plasma cells) so they’re identical in structure
what does ELISA stand for
enzyme-linked immunosorbent assay
what is the ELISA test used for
to see if a patient has any antibodies to a certain antigen or any antigen for a certain antibody. used to test for allergies or pathogenic infections
what is the difference between direct ELISA and indirect ELISA
direct ELISA uses a single antibody that is complementary to the antigen that you’re testing for but indirect ELISA uses 2 different antibodies
describe how monoclonal antibodies can be used to target a drug to cancer cells (4 marks)
1) monoclonal antibodies are made against antigens specific to cancer cells/ tumour markers
2) an anti cancer drug is attached to the antibodies
3) the antibodies bind to the antigens/tumour markers on cancer cells as their binding sites are complementary
4) This delivers the anti cancer drug to the cells
what are 4 ethical issues surrounding vaccines
1) tested on animals and some animal based substances may be used to produce a vaccine
2) testing on humans - may be put at an unnecessary risk of contracting the disease if the vaccine didn’t work
3) some don’t take the vaccine because of side effects but are still protected because of herd immunity- may be seen as unfair
4) if there is an epidemic of a new disease there would be a rush to be vaccinated- difficult to decide who gets it first
what is one ethical issue with monoclonal antibodies
animals are used to produce the cells from which the monoclonal antibodies are produced. Some disagree with this
what is HIV and AIDS
HIV is a virus that affects the immune system and eventually leads to AIDS
AIDS is a condition where the immune system deteriorates and eventually fails so they are more vulnerable to other infections
what does HIV do inside the body
infects and eventually kills helper T cells which act as host cells for the virus but helper T cells allow the immune system to effectively respond to infections as they send chemical signals that activate phagocytes, cytotoxic T cells and B cells
