Immunity Flashcards
Define antigen
A protein which can generate an immune response
Define pathogen
Organisms that cause disease
Describe the process of phagocytosis
- phagocyte attracted to chemicals produced by foreign pathogen
- Phagocyte engulfs pathogen
- Lysosome fuses with ingested pathogen forming a phagosome
- Lysosome inject Lysozymes into pathogen to hydrolysis it
- Phagocyte then presents pathogens antigens on cell surface to be activate immune response
Phagocyte is now an antigen presenting cell
What activates a t helper cel
When it’s receptor proteins bind to complementary antigen ps presented on phagocytes
What are the 4 things a t helper cell does?
Stimulate cytotoxic t-cells which produce perforin which makes holes in cell membrane of foreign cells killing them
Activate B cells (humoral)
Activate production of memory cells
Tigger phagocytes to perform phagocytosis
Describe the process of cell mediated immunity
- Phagocytosis takes place and phagocyte becomes antigen presenting cell
- T(h) cell that has complementary receptor binds to antigen which activates T cell to divide by mitosis by clonal selection
- T helper cells specialise into memory cells, stimulate phagocytes, stimulate B cells or active cytotoxic T cells
Describe process of humoral response
- B cell covered in antibodies which bind to antigen on antigen presenting cell forming antigen-antibody complex
- Happens as antibody has complementary shape
- When T cell activates B cell then B cell will divide by mitosis Process is clonal selection
- Divide into plasma cells or memory cells
- Plasma cells secrete antibodies specific to antigen- monoclonal antibodies
- Pathogens become clumped together called agglutination
On an antibody what is the variable region?
On the very tip of the antibody they determine the the specificity of antibodies as that is where antigens bind
What is the primary response?
When pathogen enters body for the first time.
Specific B cell antibody that is complement to invading pathogen antigen is activate and plasma cells secrete antibodies into blood which leads to destruction
Memory cells remain in blood
What is secondary response
When you encounter the same pathogen, memory cells divide rapidly developing into plasma cells which then secret more antibodies at a quicker pace. Leads to destruction of antibody much quicker before can feel the harmful effects.
Define active immunity
Immunity you get when immune system makes its own antibodies after being stimulated by an antigen
Natural-immune after catching disease
Artificial- immune from vaccine with antigens
Define passive immunity
Immunity you get after been given antibodies made by a different organism don’t produce antibodies of your own
Natural-baby becomes immune due to antibodies in breast milk
Artificial-immune after being injected with someone else’s antibodies
Compare active vs passive immunity
AI requires exposure to antigen whereas PI doesn’t require exposure to antigen
AI takes a while for protection to develop whereas PI protection is immediate
AI memory cells are produced in PI memory cells aren’t produced
AI protection is long term whereas PI protection is short term as antibodies are broken down
Define vaccine
A vaccine contains antigens that cause your body to produce memory cells against a specific pathogen without the pathogen causing disease
Define herd immunity
Vaccines protect individuals that have the vaccine and don’t because they are less likely to catch the disease as there are fewer people to catch it from
What can vaccines contain
- dead or weakened pathogen antigens which induce a immune response
- memory cells then produced
- future infections by same pathogen produces greater more immediate response
What are the ethical issues surrounding vaccines?
- tested on animals
- testing vaccine on humans may cause them to be less careful when not contracting disease
- side effects
Define antigenic variation
Different antigens are formed due to changes in genes of a pathogen
Define monoclonal antibodies
Antibodies produced from a single group of genetically identical plasma cells
Why do antibodies have to be so specific
Their binding sites have to be complementary to antigen which has a specific tertiary structure
Describe monoclonal antibodies use in targeted medication?
Can be used in cancer treatments eg. Direct monoclonal antibody therapy -herceptin or
Indirect therapy where cytotoxic drugs can be attached to monoclonal antibodies
How does HIV cause AIDS?
HIV infects and kills helper T cells which act as host cells. Without any helper T cells the body is unable to produce an immune response and cannot fight off even the simplest of infections.
When does HIV become AIDS?
When the no of H T cells reach a low enough level
Describe the structure of HIV
- it’s core has genetic material (rna) an some enzymes eg. Reverse transcriptase
- outer coating layer called a capsid and an extra outer layer called an envelope (envelope is made from stolen membrane from previous host)
- sticking out of envelope are attachment proteins
Describe process of HIV replication
- Attachment protein attaches to receptor molecule on cell membrane of host T cell
- Capsid is released into cell where it uncoats and releases genetic material into cytoplasm
- Inside cell, reverse transcriptase used to make a complementary strand of dna from viral rna template
- From this, double stranded dna made and inserted into humans dna
- Host cell enzymes used to make viral proteins from viral dna found within the human dna
- Viral proteins assembled into new viruses which go on to infect other cells
