cell recognition and the immune system Flashcards
phagocytosis , cell mediated immunity, humeral immunity, antibodies, vaccines and HIV
outline steps of phagocytosis (non specific response)
1) pathogen releases chemicals and debris that are attracted to the phagocyte so they move towards it
2) the chemicals or antigens bind to the phagocyte using the binding site regions on its surface
3) the phagocyte changes shape and engulfs the pathogen forming a phagosome vesicle
4) a lysosome within the phagocyte fuses with the phagosome
5) the lysosome releases a lytic enzyme called lysozyme that hydrolyses the pathogen
6) soluble products absorbed by phagocyte and used by it
outline steps of cell mediated response (specific response)
1) once pathogen has been engulfed and destroyed, antigens position themselves on the surface forming an antigen presenting cell
2) helper T cells have receptors on their surface which allow them to bind to the APC
3) once attached this activates the helper T cells to divide by mitosis to replicate and form large amounts of clones
4) these cloned helper T cells differentiate into different cells
- some remain as T cells and activate B lymphocytes
- some stimulate phagocytes to perform phagocytosis
- some become memory cells incase antigen encountered again
- some become cytotoxic T cells (killer T cells)
what’s is the role of cytotoxic T cells and how do they perform their role?
- they destroy abnormal or infected T cells by releasing a protein called perforin
- perforin embeds itself into the cell surface membrane of cell and creates a pore (hole)
- this leads to any substance being able to move in and out of cell eg water causing cell death
give an example of when cytotoxic T cells perform their role
cytotoxic T cell action is most common in viral infections as viruses infect body cells. infected body cells are killed to prevent further viral replication. (sore throat during cold)
outline the steps of B cell activation (humoral response and immunity)
1) antigens collide with B cells which take them in by endocytosis and position them on their cell surface membrane (antigen presenting cell)
2) B cells antigen binds with helper T cell and activates B cell to undergo clonal selection
3) B cell rapidly divides by mitosis and cells differentiate into plasma cells or memory B cells
- plasma cells produce antibodies
- memory B cells live for decades in body and rapidly divide into plasma cells when reinfected with same pathogen to produce antibodies (active immunity)
what is the role of antibodies in immunity?
antibodies are flexible so bind to multiple antigens marking them for phagocytosis but also causing them to agglutinate (clump together) making it easier for phagocytes to locate antigen and perform phagocytosis
what is passive immunity?
antibodies introduced to body so plasma or memory cells aren’t produced so immunity isn’t long term eg antibodies pass to fetus through placenta or breastmilk
what is active immunity?
immunity created by your own immune system through exposure of pathogen or antigen so long term
what are the types of active immunity?
natural - following infection and the production of plasma and memory B cells
artificial - introduction of weakened pathogen or antigen via vaccine
outline the steps of HIV replication? (the lytic cycle)
1) attachment proteins attach to CD4 receptor on helper T cell
2) this leads to capsid being released into cell and uncoating releasing all the genetic material into cytoplasm
3) inside cell reverse transcriptase enzyme used to form a complementary strand of DNA from the viral RNA
4) this forms a double stranded DNA which is inserted into human DNA
5) host cell enzymes are used to make viral proteins from viral DNA in human DN
6) viral protein assembled into new virus which bud off host cell and infect other cells
what is a monoclonal antibody?
a monoclonal antibody is a single type of antibody that can be isolated and cloned
what are the uses of monoclonal antibodies?
- medical treatment
- medical diagnosis
- pregnancy testing
