cell recognision Flashcards
how do cells tell the difference between self and non self cells
they have different antigens which the body wont recognise which triggers an immune response so will therefore attack it.
what do antigens allow the body to identify
pathogens, abnormal body cells, toxins, cells from other organisms of the same species
what is phagocytosis
the cellular process of engulfing solid particles using the cell membrane carried out.
steps of phagocytosis
- pathogen recognises the foreign antigens. travels towards the pathogen by chemotaxis. pathogen attaches to the phagocyte by receptors.
- the pathogen binds to receptors on the phagocyte cell membrane and is engulfed by the phagocyte and forming a phagosome
- lysosomes fuse to phagosomes to form phagolysosomes and release a digestive enzyme to digest the pathogen.
- harmless products are removed by exocytosis or used by the phagocyte and presents antigens on cell surface membrane
what do antigen presenting cells activate
they activate t helper cells which stimulates and recruits more phagocytes and t cells to carry out an immune response
types of t cells
t helper cells which activate b cells and immune responses and cytotoxic t cells which destroy foreign cells by releasing chemicals such as perforin
two parts to a specific immune response
cell mediated response- specialised white blood cells (T lymphocytes) which target pathogens outside and inside cells.
humoral response- specialised white blood cells (B lymphocytes) which target pathogens by producing antibodies.
cell mediated immune response
APCs can be either phagocytes or cells that have been invaded by the pathogen. T cells respond to the cells which is presenting the antigen. T helper cells respond first as the have receptors that fit exactly to the presented antigen. activates the T cells and begin to differentiate and recruit other T cells and activate B cells.
how do B cells help in immune responses
B cells get the antigen from antigen from pathogens or APCs and presents antigens in its cell surface membrane. T helper cells bind to the antigen to activate the B cells. the b cells begin to divide by mitosis to form plasma cells and memory cells that is known as clonal selection. plasma cells produce antibodies that are complimentary to the antigens.
how does the body prepare for secondary responses
the body has memory cells with stay in the blood stream. if they come into contact with the antigen again the response fast.
differences between primary and secondary responses
in primary responses there aren’t many b cells to make antibodies and they only survive for a few days. in secondary responses they produce antibodies much more quickly and more new memory cells.
structure of antibodies
they are proteins made out of four polypeptide chains, 2 heavy and 2 light chains.
do all antibodies have the same constant region
yes
what does the constant region allow
it allows them to bind to receptors on immune system cells.
what are the 2 variable regions
the antigen binding sites so they will have a unique tertiary structure complementary to an antigen.
what is agglutination
antibodies bind to antigens on pathogens causing them to clump together. clumps are destroyed by phagocytosis. easier for phagocytes to engulf more pathogens.
neutralising toxins
some antibodies work well by neutralising toxins released my pathogens.
how do antibodies prevent viruses from entering the host cells
viruses have spike proteins on their surface which recognise and bind to receptors on the surface of the host cell which allows them entry into the cell. antibodies bind to these viruses and stop them attaching to their host cells.
what is antigenic variation
when pathogens can form different strains which often have different antigens.
what does antigenic variation allow
means that when people have a secondary infection the memory cells will not remember the antigen so no antibodies, so a primary response will happen again.
what do monoclonal antibodies help with medically
pregnancy tests, radioimmunology, ELISA tests
radioimmunology
allows doctors to target radiation to specific sites. links radioactive atoms to monoclonal antibodies that deliver the radioactivity by latching onto proteins found in cancer cells. they use it to find tumours.
pregnancy tests
antibodies complimentary to hCG protein are bound to coloured beads. the protein in the urine binds to antibodies. urine moves up the strip carrying the bead of colour. binds to the first line ‘the blue line’.
ELISA test
antigen is attached to a well in a test dish. sample of blood plasma is added to the well. if antibodies are present, bind to the antigen. the well is washed. secondary antibody with an enzyme attached is added. binds to the antibody. well is washed again. changes colour is enzyme is present.
