cells and the immune system Flashcards
what triggers an immune response
foreign antigens
what are antigens
molecules (usually proteins) found on the surface of cells, used by immune system to identify pathogens, abnormal body cells, toxins or cells from other individuals of the same species
what are pathogens
micro-organisms that cause disease
what are abnormal body cells
cells with abnormal antigens (e.g cancerous or pathogen-infected)
4 stages of immune response
1) phagocyte engulfs pathogen
2) phagocyte activates T-cells
3) T-cells activate B-cells (which divide into plasma cells)
4) plasma cells make more antibodies to specific antigen
phagocytes engulfing pathogens
1) phagocyte recognises foreign antigens a pathogen
2) cytoplasm of phagocyte moves around the pathogen and englufs it
3) pathogen is contained in phagocytic vacuole in phagocyte cytoplasm
4) lysosome fuses with phagocytic vacuole and breaks down the pathogen
5) phagocyte presents pathogens antigens on its surface to active other immune system cells (becomes antigen presenting cell)
what is a phagocyte
type of white blood cell that carries out phagocytosis, found in blood and tissues, first cells to respond to an immune trigger
what is phagocytosis
engulfment of pathogens
phagocytes activating T-cells
the receptor proteins on the T-cell surface bind to the complimentary antigens present on phagocytes
what are T-cells
type of white blood cell (t-lymphocyte)
types of T-cells
helper T-cells, cytotoxic T-cells
helper T-cells
release chemical signals that activate and stimulate phagocytes and cytotoxic T-cells, and activate B-cells
cytotoxic T-cells
kill abnormal and foreign cells
B-cells
type of white blood cell, covered with antibodies (each a different shape so bind to different antigens), secrete antigens, divides into plasma cells
B-cells into plasma cells
1) antibody on surface of B-cell meets a complimentary antigen and binds to it to form an antigen-antibody complex
2) activates the B-cell (colonial selection)
3) activated B-cell divides into plasma cells
plasma cells
secrete antibodies specific to the antigen (monoclonal antibodies) which bind to the antigens on the surface of the pathogen to form antigen-antibody complexes
what are antibodies
proteins that have variable regions, coat pathogens to make them easier to be engulfed
what is agglutination
pathogens that become clumped together (as antibodies have 2 binding sites)
immune responses
cellular or humoral
cellular response
T-cells and other immune system cells that they interact with (e.g phagocytes)
humoral response
B-cells, colonial selection and production of monoclonial antibodies
immune response for antigens
primary and secondary
primary immune response
when antigen first enters body and triggers immune response, slow (as aren’t many B-cells, but eventually will come, until them symptoms are seen), afterwards B-cells produce memory cells
what are memory cells
produced by B-cells, remain in body for a long time, record specific antibodies needed to bind the antigen and produce them quickly
secondary immune response
if same pathogen enters body again, immune system will produce a quicker, stronger immune response (clonal selection), memory B-cells activated and divide into plasma cells that produce the right antibody, memory T-cells are activated and divided into correct T-cells, gets rid of pathogen before symptoms occur
vaccines
dead or inactive forms of the pathogens that cause body to produce memory cells (become immune without symptoms)
what do vaccines do
protect individuals, and create herd immunity
what is herd immunity
people not vaccinated are less likely to catch the disease because there are fewer people to catch it from
how are vaccines given
injected or taken orally
disadvantage of taking orally
could be broken down by enzymes in the gut, or molecules of vaccine may be too large to be absorbed into the blood
booster vaccines
sometimes given to ensure memory cells are produced
antigenic variation
antigen changes shape (makes vaccination difficult), (e.g influenza virus = new strains that are immunologically distinct)
immunity types
active or passive
active immunity
when your immune system makes its own antibodies after being stimulated by an antigen
2 types - natural or artificial, requires exposure, takes a while for protection to develop, memory cells are produced, protection is long term
natural active immunity
when you become an immune after catching a disease
artificial active immunity
when you become immune after being given a vaccination
passive immunity
immunity got from being given antibodies made by a different organism (when your immune system doesn’t produce antibodies of its own)
2 types - natural or artificial, doesn’t require exposure to antigen, protection is immediate, memory cells aren’t produced, protection is short term
natural passive immunity
when a baby becomes immune due to the antibodies it receives from its mother through the placenta and in breast milk
artificial passive immunity
when you become immune after being injected with antibodies from someone else (e.g tetanus can be injected with antibodies against the toxin collected from blood donations)
what are monoclonal antibodies
antibodies produced from a single group of genetically identical B-cells (plasma cells), identical in structure, made to bind to anything
example - cancer cells
1) cancer cells have tumour markers that are not found on normal body cells
2) monoclonal antibodies can be made that will bind to the tumour markers , and anti-cancer drugs can be attatched ti the antibodies
3) when the antibodies come in contact with cancer cells they bind to the tumor markers, so drug will only accumulate in the body where there are cancer cells
4) side effects will be lower (as they accumulate near specific cells)
pregnancy test
detect the hormone human chorionic gondotropin that’s found in urine of pregnant women
ELISA test
medical diagnosis that uses antibodies for things such as pathogenic infections
ELISA test method
an antibody is used which has an enzyme attached to it, and the enzyme can react with a substrate to prduce a coloured product
colour change = antigen is present
types of ELISA test
direct and indirect
direct ELISA test
uses a single antibody that is complimentary to the antigen you’re testing for
indirect ELISA test
uses 2 different antibodies
ELISA test example
for HIV
what is HIV
human immunodeficiency virus, causes AID’s through affecting the immune system, no cure, replicates inside host cells
ELISA test for HIV method
1) HIV antigen is bound to bottom of a well in a well plate
2)sample of patients blood plasma is added to the well
3)if there are any HIV specific antibodies, they will bind to the antigen , then the well is washed out
4)secondary antibody is added to the well, which can bind to the antibody and the well is washed out to remove any un-bound secondary antibody
5)a solution that contains substrate is added to the well which will react to the with the enzyme .
if it changes colour = patient has HIV
MMR
measles, mumps and rubella
MMR scare
caused autism in children (insufficient testing - sample size of 12 children)
herceptin
treat breast cancer - sample size of 1694
ethical issues of vaccines
tested on animals, unnecessary risk for volunteers, side effects, who receives it first in an epidemic
