Immunity Flashcards
Describe the process by which vaccines provide immunity
- contain dead or attenuated pathogens
- MACROPHAGE presents antigen on surface
- specific T cells with complementary receptors bind
- stimulate B cells with complementary antibody on surface to divide by mitosis
- differentiate into plasma cells which produce LARGE AMOUNTS OF antibodies
- plus memory cells are produced
Difference between active and passive immunity
Active
- production of antibodies by plasma cells
- slow acting since it takes time to produce antibodies
- long lasting as memory cells produced
Passive
- antibodies are received from outside source
- fast acting
- short term since antibodies are broken down
Organelles involved in production of viruses
- mitochondria to release energy
- ribosomes to synthesise proteins
Describe how an antibody works
- binding sites are complementary in shape to antigens
- hinges allow arms to spread to allow attachment of antigens at different distances
- cause pathogen to agglutinate by joining together so it is easier for phagocytes to engulf
- neutralise by binding to pathogen and prevent them from reaching and harming cells
- act as markers to stimulate phagocytes
Why are viruses unaffected by antibiotics
- lack a cell wall for them to interfere with
- cannot pass cell membrane to reach them inside cells
Antibiotic effect on bacteria
Inhibit enzymes required for synthesis of normal cell walls so bacteria killed from cell lysis (from osmosis)
Antigen
- FOREIGN protein
- triggers an immune response by lymphocytes / production of ANTIBODY
Why do some vaccines have booster injections
- immunological memory decreases overtime
- more antigens so more memory cells produced
- large amount of antibodies are produced rapidly if person was to become reinfected
How do pathogens cause disease
- produce toxins
- damage/kill cells
Reasons for decrease in vaccinations
- more people aware of harmful side effects / risks
- fewer cases of disease
- insufficient vaccine available/ too expensive to distribute
Herd Immunity
- most people are vaccinated so disease cannot spread
- unvaccinated people less likely to contact infected people
Describe and explain curve for primary immune response
- slow increase in antibody concentration as it takes time for phagocytes to stimulate T cells and produce plasma cells by clonal expansion to make antibodies
- plasma cells die reducing antibody production
Describe and explain curve for secondary immune response
- rapid increase in antibody concentration as memory cells differentiate into plasma cells and produce antibodies
- start with memory cells so a larger amount of antibodies produced
Function of cytotoxic T cells
- secrete cytotoxic chemicals called perforins
- create pores in plasma membrane of infected cells
- cytotoxins enter and destroy pathogen
Phagocytosis
- phagocyte identifies pathogen as a foreign body by antigen
- pathogen engulfed by phagocyte and enclosed in vesicles called phagosome
- lysosomes fuse with wall of phagosome and release lysozymes which hydrolyse the cell wall of pathogen and destroy it
- antigens presented on surface
Pathogen
Microorganism that causes disease
Examples of foreign antigens
Pathogens
Organ transplants
Toxins
Abnormal body cells (cancer)
Clonal Selection
Only lymphocytes specific to a certain antigen are activated
Describe advantage of memory cells
- identify original antigen
- divide rapidly in response to future infection
- produce large quantity of antibodies at a faster rate
Antibody
- protein specific to antigen
- secreted by plasma cells
Describe structure of antibody
Made of four polypeptide chains
- two heavy and two light
- joined by disulphide bridges
Monoclonal antibodies
Antibodies produced by a single clone of cells
Describe humoral response
- complementary ANTIBODY on B cell attaches to foreign antigen
- antigen engulfed and processed by B cell
- B cell presents antigen on its surface
- T cells with complementary receptors attach activating clonal expansion
- Memory cells and plasma cells produced
Uses and advantages of monoclonal antibodies
Attached to cancer drugs
- target cells so cheaper since smaller doses needed
- non toxic and few side effects
Medical diagnosis
Reasons vaccination may not eliminate disease
- antigen variability
- many strains of pathogen
- pathogens hide from immune system so fail to induce immunity
- unable to achieve herd immunity as people object on religious, medical and ethical grounds
ELISA test
- apply sample to a surface to which all antigens in sample will attach
- wash sample to remove any unattached antigens
- add antibody specific to antigen being detected for and leave to bind
- wash to remove any unattached antibodies
- add second antibody with enzyme attached which binds to first antibody
- add colourless substrate so enzyme acts on it to cause colour change
- intensity of colour is relative to amount of antigen present
Structure of HIV
Lipid envelope
Attachment proteins
Capsid containing RNA
Reverse transcriptase catalyses production of DNA from RNA
Describe how HIV works
- binds to specific protein on T helper cells
- protein capsid fuses with cell-surface membrane
- RNA and enzymes enter T helper cell
- reverse transcriptase converts viral RNA to DNA
- HIV DNA transcribed into mRNA which is translated by ribosomes to form new HIV viruses
- new HIV break away from T helper cell by budding (cell-surface membrane forms their lipid envelope)
How does HIV create symptoms
- kills T helper cells by replicating inside them
- no T cells to stimulate B cells to produce antibodies
- no cytotoxic T cells to destroy infected cells
- body succumbs to opportunities infections
Suggest what is meant by an attenuated pathogen
- modified
- by heat / chemical treatment
- reduced reproduction rate
Suggest reasons why an attenuated pathogen is better to use in a vaccine compared to a dead pathogen
- more closely resembles real infection
- dead pathogen may have modified antigens
Give reasons why doctors should not over prescribe antibiotics
- constant exposure favours selection of resistant strains of bacteria formed by genetic mutations
- reduces effectiveness of antibiotics / puts patients at risk
- expensive
Give reasons why it is important to finish a course of antibiotics
- surviving bacteria could develop resistance
- surviving bacteria could cause reinfection
- some antibiotics inhibit growth of bacteria for body’s own immune response so might not allow sufficient time
Explain differences between antibiotic reaching infected tissue by intravenous injection and by mouth
Intravenous injection
- provides high concentrations of antibiotic
- travels through capillaries to infected tissue directly
- not long lasting
Tablet by mouth
- lower concentrations since diluted by gut contents
- digested before entering blood stream so slower acting
- long lasting
Explain how malarial parasite avoids immune response
- infects red blood cells
- reproduces inside liver cells
- antigens are hidden / changes antigenic groups
Suggest when passive immunity is necessary
- short term protection
- pathogen divides / spreads rapidly
- body could succumb to infection before body produces immune response
Describe how monoclonal antibodies are produced on a large scale
- mouse infected with pathogen containing foreign antigen
- B cells specific to antigen produced and extracted from spleen
- tumour harvested from culture and fused with B cells
- hybridoma cells are screened for antibody production and cultured
- antibodies are extracted from culture
Why does influenza virus require annual vaccinations but other infections do not
- high rate of mutation
- mutation changes antigens
- antibodies do not recognise new antigens so new memory cells must be produced
Suggest why blood group O is a universal donor despite containing antibodies A and B
- will not cause agglutination
- greatly diluted over large blood volume
Which part of the antibody is the variable position
top section including binding site
Suggest why clonal expansion occurs
- sufficient lymphocytes to destroy/disable pathogen
- all genetically identical so have receptors which are recognise antigen
What is the difference between humoral and cell-mediated immune response
- humoral involves antigens and pathogens that have not entered cells
- humoral involves detection by antibodies on B cell
- cell-mediated involves cells invaded by pathogens (or macrophages), transplant and tumour cells
Suggest why B cells are fused with cancer cells in manufacture of antibodies
- B cells have a limited life span and will eventually die
- fusing them with cancer cells = immortal so can be cultured
Suggest why a logarithmic scale is used
- allows a large range of values to be displayed
- without small values being compressed at bottom of graph
- so small values can be meaningfully interpreted
- straight line graph
Outline how binding of antigen to antibody on plasma membrane of B cell leads to raised antibody levels
- B cell engulfs antigen and presents antigen on its surface
- antigen recognised by specific T cell
- stimulates B cells to divide by mitosis
- form genetically identical cells
- B cells differentiate into plasma cells to produce antibodies
Explain why antibodies only affect specific foreign cells/pathogens
- antibodies have a specific tertiary structure
- complementary in shape to antigen
- antigens ONLY found on specific cell
- bind to antigen to form complex
Difference between primary and secondary defence and what is phagocytosis considered
- primary refers to mucus/ciliates epithelium/skin/stomach acid
- secondary phagocytosis
Suggest ways in which plants can protect themselves against infection by pathogens
- produce callous
- leaf drop or plant tissue death to prevent spread
- produce toxic chemical to kill pathogen
