Cell Recognition And The Immune System Flashcards
What are the ways the body protects itself from disease in sequence of events?
Skin - physical barrier
Ciliated epithelial cells and mucus - physical
Stomach acid - chemical
Phagocytosis
What are the immediate defences against disease?
Skin Ciliated epithelial cells and mucus Stomach acid Ear wax Tears, saliva and mucus (lysozymes)
What are is the response for t lymphocytes called ?
Cell mediated
What are the two types of defence mechanisms?
Non-specific
Specific
What types of non-specific defence mechanisms are there?
Physical barriers and phagocytosis
What types of specific defence mechanisms are there?
Cell mediated response
Humor al response
What is the difference between non-specific and specific responses?
Non-specific = same for every foreign material and is immediate
Specific =specific to pathogen, takes time, longer lasting
What types of white blood cells are there?
Phagocytes and lymphocytes
What types of phagocytes are there?
What are the differences
Macrophages
Larger, longer lived and antigen presenting
Neutrophils
Lobed nucleus, arrive first at sight of infection, short lived
What is the purpose of a loved nucleus in neutrophils?
Allows flexibility
To squeeze through walls of capillaries
Describe and explain the role of histamine in the immune response
Histamine released by damaged tissue
Caused swelling by making capillary walls leakier allowing more water to move via osmosis
Also allows more phagocytes to reach site of infection
Describe the stages of phagocytosis
Phagocytes migrates to site of infection via blood stream
Pathogen releases cytokines which attracts phagocytes towards it
Phagocyte attaches to pathogen via complementary receptors
Phagocyte engulfs pathogen (pseudopods form)
Forms phagosome (vesicle containing phagocyte)
Lysosomes migrate towards and fuse membranes with phagosome
Lysozymes are emptied into phagosome and hydrolyse pathogen
Soluble products absorbed into cytoplasm and antigens presented
What is pus?
Dead phagocytes and dead pathogens
How do our white blood cells only recognise foreign material?
When T and B cells are created in the bone marrow they are surrounded by only self antigens
In womb there are no outside materials
Any lymphocytes stimulate undergo programmed cell death (apoptosis) or are suppressed
Leaves only lymphocytes against foreign material
What is programmed cell death called?
Apoptosis
What is immunity?
Ability to resist infection
What is an antigen?
A molecule that stimulates an immune response
Protein or glycoprotein in cell membrane of pathogens
Where are T cells produced and matured ?
Produced
Bone marrow
Mature
Thumbs gland
Name the antigen presenting cells
Phagocytes
B cells
Abnormal and body cells
Infected cells
Give examples of what would trigger a cell mediated response
Abnormal (cancer) cells
Phagocytes containing phagosomes
Cells from same species but different organism (transplanted cells)
Infected cells (viral infection)
Toxins
Describe cell mediated immunity
T helper cell with complementary receptors bind to antigens on an antigen presenting cell
T cell is activated and divides by mitosis to produce clones
Clones differentiate to become cytotoxic, memory, helper or suppressor T cells
Cytotoxic release perforin which kills abnormal or infected cells
Memory cells are involved in the secondary immune response
T helper cells stimulated B, T and phagocytic cells
Suppressor cells stop immune reaction after infection
How do cytotoxic T cells kill a pathogen ?
Release protein called perforin which creates holes in cell membrane of abnormal or infected cells making freely permeable
Osmotic lysis
What T cells secrete cytokines?
Helper
What do B cells respond to?
Free antigens in bodily fluids (blood, tissue fluid)
Where are B cells produced and matured?
Produced
Bone marrow
Mature
Bone marrow
What does antigenic variability mean and what does it mean for production of B cells?
Pathogens have various antigens on their surface (which may change over time)
Multiple Types of B cells produced in humoral response to one pathogen
How many antigens will one B cell respond to?
Only one
Describe the humoral response
Pathogen circulates in blood along with free antigens
B cell engulfs antigens via endocytosis and presents them on its membrane
Activated T helper cell with complementary receptors will bind to antigen
Activates B cell to undergo mitosis and produce clones which differentiate into plasma and memory cells
Plasma cells produce antibodies
Describe the ultra structure of a plasma cell compared to a B cell
More Golgi apparatus (modify and secrete proteins) and mitochondria (ATP production)
How long do plasma cells live?
Few days
What is the function of plasma cells?
Produce antibodies and release them into blood stream
What is the function of memory cells?
The produce a secondary immune response
Reactivated to divide into more plasma and memory cells
What are antibodies?
Y shaped protein with a quaternary structure
What is an antigen?
A molecule in the surface of a pathogen or cell that triggers an immune response (protein, glycoprotein or lipoprotein)
What types of polypeptide chains are antibodies made of ?
Heavey (long) and light (short) chains
Name the two regions of an antibody
Constant and variable regions
Where does the antigen bind to the antibody?
Variable region
What hold the heavey and light chains together?
Disulphide bridges
What is formed when an antibody binds to an antigen?
Antigen-antibody complex
How do antibodies lead to the destruction of a pathogen?
Cause agglutination
Mark pathogens so more easily detected by phagocytes
Round up pathogens so that they are less spread out (engulf many at once)
What does agglutination mean?
A network of antibodies and molecules contain complementary antigens bound together
What are monoclonal antibodies?
Identical antibodies produced by clones of the same plasma cell
What are polyclonal antibodies?
Different antibodies produced by a variety of different plasma cells
What is the difference between poly and mono clonal antibodies?
Poly= antibodies to different specific antigens
Mono= antigens to specific antigen
What are the main uses for monoclonal antibodies?
Medical diagnosis
Pregnancy test
Direct monoclonal antibody therapy
What is direct monoclonal antibody therapy?
Antibodies to specific antigen found on cancer cells is produced
Antibodies only bind to cancer cells and block chemical signals that stimulate uncontrolled cell growth
What is the difference between direct and indirect monoclonal antibody therapy?
Direct = just antibodies
Indirect= antibodies bound to cytotoxic or radioactive drug (antibodies act as vessel)
Why are monoclonal antibodies better than conventional drugs?
Use less (£)
Produce less side effects
No damage to healthy cells
How are monoclonal antibodies used in medical diagnosis ?
Why is it used?
Elisa test
Qualitative and quantitative data
More rapid and easier to carry out
How do pregnancy test work?
HCG produced by placenta and present in urine
Antibodies to HCG are mobile on urine strip but immobile on test strip
What does HCG stand for?
Human chorionic
Gonadatrophin
What ethical concerns are there over the use of monoclonal antibodies?
Animal rights (índice cancer in mice)
Who should they be tested on (trials can go wrong)
Some save lives and some kill (MS)
What are the two types of immunity ?
Passive
Receive antibodies from external source (no memory or plasma cells), short lived
Active
produce own plasma and memory cells which produce own antibodies
What are the two types of active immunity?
Natural
Infected with pathogen and get symptoms
artificial
Exposed to attenuated pathogen, no symptoms
What is a vaccination?
A preparation (inject or swallow) containing attenuated pathogen or antigens
What does attenuated mean and how is this achieved?
Weakened
Killed in a way to retain antigens
Produce toxoids from toxins
Weaken pathogen
GM yeast with same antigen
What is herd immunity?
When most of the population is vaccinated against a particular pathogen and so the most vulnerable are protected
Why is herd immunity best achieved when the vaccine is given to everyone at the same time?
So that few people are susceptible to the diesease at once preventing spread
Why might a vaccine not eliminate disease ?
Antigenic variability
People opt out of getting vaccine
Vaccine is ineffective in some
Individual have disease before vaccination
Pathogen hides from immune system
What are the features of a successful vaccination programme?
Ability to store, transport and administer vaccine safely
Enough of suitable vaccine economically available
Few side effects
Able to produce herd immunity
What are the ethical worried around vaccines?
Who should we test vaccines on? (Animals, people most susceptible to disease (will gain most of successful) )
Should it be compulsory
Should money be spent on expensive vaccines if disease is nearly eradicated ?
Does individual health risk outweigh benefit to whole population?
Side effects (long term)
Why was the MMR vaccine created and what concerns are there around it?
Cheaper
Thought to cause autism (small sample size and not reproducible)
Describe the difference in antibody production between the first and second immune response
Second produces more antibodies a lot faster
How do vaccines protect against disease?
Stimulate formation of memory cells so more antibodies can be produced at a faster rate if pathogen is encountered
Describe and explain the structure of a HIV particle
Attachment proteins (allow particle to bind to T helper cell for membranes to fuse)
Lipid envelope (allow membranes to fuse, structural support)
Matrix (protein layer under lipid envelope, structural support)
Capsid (made of capsimeres/proteins, contains RNA and enzymes)
RNA (contains genetic info for reproduction)
Reverse transcriptase (catalyse synthesis DNA from RNA)
Describe how HIV replicates
HIV particles circulate in blood
Attach to T helper cell receptors
Membranes fuse, capsid enters cell and disintergrates
Reverse transcriptase catalyses DNA synthesis
Viral DNA diffuses into nucleus via nuclear pore
Viral DNA inserted into host DNA and is dormant for years
viral DNA activated and mRNA produced which diffuses our if nucleus via nuclear pore
Viral components synthesised using cells protein synthesis mechanisms
Components assemble and bud off of cell taking part of cell membrane with them
Occurs continually until cell dies
Why does the HIV DNA remain dormant for years?
Allows for more T helper cells to contain viral DNA
divide by mitosis to produce genetically identical daughter cells
What happens to T concentration as more HIV particles are produced?
Decline
How does HIV cause disease ?
Damages T helper cells
Less B, T and phagocytes stimulated
Opportunistic infections occur which cause damage to cells
What does AIDS stand for and what is it?
Acquired immune deficiency syndrome
Less than 200 T helper cells per mm3 of blood
What does ELISA stand for?
Enzyme linked immnosorbant assay
What can the ELISA test be used for?
The identify and quantify the amount and type of antibody or antigen present
What substances can you identify using an ELISA test?
Drugs
Hormones
Allergens
Describe the ELISA test (to test for the presence of HIV)
Add blood sample to microtitre containing HIV antigens stuck to the base
Wash out and add solution containing antibodies to HIV antibodies attached to an enzyme
Wash out and add solution containing substrate
If Individual is HIV+ then solution will change colour
How is the ELISA test quantitative ?
The intensity of colour indicates concentration of substance
Why is it important to wash the microtitre during the ELISA test?
The remove excess uncomplimentary antibodies and unbound antibody attaches to enzyme
Prevents false positive
How is HIV spread (examples)
Via bodily fluids
Unprotected sex
Sharing needles
Blood transfusions
Via placenta (rare)
How can HIV transmission be reduced?
Use of condoms
Use of clean needles
Screening blood before transfusion
What type of virus is HIV ?
Why?
Antiretroviral
Synthesises DNA from RNA (usually other way around)
What treatment is there for HIV?
Use of antiretroviral drugs
Inhibit reverse transcriptase and protease production
How do antibiotics work?
Inhibit enzymes required for the synthesis and assembly of murein cell walls (weakens cell wall causing osmotic lysis)
Interfere with protein synthesis and metabolic pathways via enzyme inhibition
Prevent replication (inhibit DNA helicase and polymerase)
Why don’t antibiotics work on viruses?
No cell structures (cell walls) or metabolic pathways to interfere with
Hide within cells
Why don’t vaccines work on viruses?
Antigenic variability
Hide in cells
No memory or plasma cells
