Immune System Flashcards
Define antigen
Proteins on the surface of cells that cause an immune response
Explain phagocytosis
- Phagocyte recognises foreign antigen
- Cytoplasm moves around pathogen engulfing if
- Pathogen contained in phagocytic vacuole
- Lysosome fuses with phagocytic vacuole
- Lysozymes break down pathogen
- Phagocyte présents antigens on it’s surface
Why do phagocytes present antigen on their surface
Activates T cells
How are T cells activated
Receptor proteins on the T cell bind to complementary antigens on the phagocyte
Function of t helper cells
Release chemical signals that activate tc cells, B cells and phagocytes
Function of tc cells
Kill cells
What forms when antibodies bind with complementary antigens
Antigen-antibody complex
What is clonal selection
Antibody binds with complementary antigen
Chemicals released from B cell
Activate the B cell
B cell divides into plasma cells
What are plasma cells
Clones of B cells (have the same antibody on its surface)
Why does an antibody having 2 binding sites useful
Can bind to 2 antigens at the same time
Pathogens are clumped together = agglutination
Phagocytes can bind to antibodies and engulf many pathogens at once
Why does every antigen have a specific antibody
The variable regions have a specific tertiary structure
What is the cellular response
Phagocytes and T cells
What is the humoral response
B cells
Plasma cells
Clonal selection
Monoclonal antibodies
What is the primary immune response
Antigen enters body for the first time
Why is the primary response slow
Not many B cells with specific antibody needed to bind to the antigen
What is produced at the end of the primary response
Memory t and B cells
What do Tm cells remember
The antigen
What do Bm cells remember
The antibody
What is the secondary immune response
Same pathogen renters body
Why is the secondary response quicker
Clonal selection happens faster = b cells are activated quickly to divide into the correct plasma cell that produce the right antibody
T cells activate quickly = divide into the correct type to kill the antigen
Why do you have no symptoms on the secondary response
Kills pathogen before you can show symptoms
What do vaccines contain
Free/attatched or dead/attenuated antigens
Why are vaccines useful
Body produces memory cells against a pathogen without causing the disease. So if reinfected the body has a fast secondary response
What are 2 disadvantages of taking a vaccine orally
Broken down by enzymes in the digestive system
Molecules are too large to pass into blood stream in small intestines
Why are booster vaccines made
To make sure memory cells are produced
What is antigenic variation
Genes in pathogens mutate
Change in antigens on their surface
Why is antigenic variation bad
The memory cells produced from the first infection don’t recognise antigens. So the immune system goes back through the primary response and you get ill again
Hard to develop vaccines against
How would you describe 2 different strains of the Same pathogen
Immunologically distinct
How do gouvernements choose what strain a vaccine is made for
The one that is most effective against the recent strain
What is active immunity
When your immune system makes its own antibodies stimulated by an antigen
What is an example of natural active immunity
Catch disease
What is an example of artificial active immunity
Vaccine
What is passive immunity
Given antibodies given by different organisms
Immune system doesn’t produces its own antibodies
What is an example of natural passive immunity
Baby gets antibodies from mothers placenta and breast milk
What is an example of artificial passive immunity
Injected with antibodies from someone else
What are the difference between passive and active immunity
Active = Needs antigen exposure Takes time to develop immunity Memory cells produced Long t’en protection
Passive = No exposure to antigen Immediate protection No memory cells Short term protection (antibodies are broken down)
What are monoclonal antibodies
Antibodies produces from a single group of genetically identical B cells (plasma cells)
How are monoclonal antibodies used in cancer treatment
Cancer cells have specific antigens (tumour markers) not found on normal body cells
Monoclonal antibodies can bind to tumour markers and be attached to an anti cancer drug
Why is ther low side effects when using monoclonal antibodies in cancer treatment
Anti cancer drug will only accumulate around the cancer cells (highly specific)
How are monoclonal antibodies used in pregnancy testing
- Application area = antibodies for hCG bound to blue bead
- hCG binds to antibody forming antigen-antibody complex
- Urine carries hCG and blue Beads up to test strip
- Test strip = immobilised antibodies
- hCG binds to immobilised antibodies
- Concentrating the hCG-antibody complex with the blue beads
= test strip turns blue
If there’s no hcg why does test strip stay colourless
Blue beads will pass through test area without binding to the immobilised antibodies
What is the difference between indirect and direct Elisa testing
Direct = 1 antibody Indirect = 2 antibodies
Describe the method for indirect Elisa testing for HIV
- HIV antigen bound to bottom of well in well plate
- Px blood plasma added to well
- HIV specific antibodies will bind to hiv antigens at bottom of well
- Wash out well = remove unbound antibodies
- Secondary antibody with enzyme added to the well
- Secondary antibodies bind to primary
- No primary the secondary can’t bind to anything
- Wash out well = remove unbound antibodies
- Solution containing substrate to enzyme on secondary is added to the well.
- If the secondary antibody is there the enzyme will react forming a coloured solution = showing there was hiv antibodies
Why is it important to wash out the well
Remove unbound antibodies
Make sure to not give false positives
Why would the solution stay colourless if there’s no primary antibodies
No hiv specific antibodies for the secondary antibodies with the enzyme to attach to
What are the ethical issues surrounding vaccines
Animal testing
Aminal products used in the vaccine
Human testing
People at unnecessary risk because they think they are fully protected
Side effects
People don’t take it so rely on herd immunity which is unfair
Rush to receive vaccine In pandemic
Ethical issue of monoclonal antibodies
Animals are used to produce the B cells
More side effects than expected
What is AIDS
Immune system fails and susceptible to other infections
The Th cell level drops below a critical level
What is the host cell of hiv
T helper cells
What is inside the core of hiv
RNA and reverse transcriptase
Draw a viral cell
Capsid Genetic info Reverse transcriptase Envelope Attachment proteins
Why can’t viruses replicate on its own
Doesn’t contain its own ribosomes or enzymes
Describe how hiv replicates
- Attachment proteins bind to receptor proteins on t helper cell
- Capsid released into cell
- Capsid releases rna into t helper cell cytoplasm
- Reverse transcriptase makes complementary strand of dna using viral rna template
- Dna inserted into human dna
- T helper cell enzymes make viral proteins at ribosomes
- New viruses bud from t helper cell or burst from cell (lysis)
What is the latency period in hiv
HIV replication slows in rate after initial first infection
What is progression of aids
The infections become more serious as less t helper cells to fight them off
What effects survival time of aids
Existing infections
Strain of hiv
Age
Access to health care
What type of cell do antibiotics kill and why
Bacteria
Target specific bacterial enzymes and ribosomes that are different to human cells
Why don’t antibiotics damage human cells
Designed to only target bacterial enzymes and ribosomes not human
Why don’t antibiotics work on viruses
Viruses don’t have their own ribosomes or enzymes because they hijack the human ones
What are antiviral drugs designed against
Target the virus specific enzymes
Eg, reverse transcriptase
How to reduce spread of hiv
Don’t share needles
Use protection
Why is hiv testing unreliable on babies under 18 months
The baby might have hiv antibodies from the mothers placenta or breast milk without having the disease
