Cell Recognition Flashcards
Describe the process of lymphocyte selection within a feotus
Huge number
Some collide with self material
These are will apotose - die
What is an autoimmune disease?
Where the immune system targets self cells
Describe phagocytosis
Chemicals from pathogen attract phagocyte
Phagocyte engulfs the pathogen due to its flexible membrane
Forms a phagosome ( pathogen inside vescile in the phagocyte)
Lyosomes fuse to phagosome
Release hydrolytic enzymes
Hydrolyse bacteria
Products absorbed into cytoplasm
Which type of phagocyte undergoes antigen presentation
Macrophage
Give three ways an antigen can be picked up by a T lymphocytes
Macrophage presentation
Infected cells
Pathogen itself
Describe the cell mediated response to infection
T helper cell (specific to pathogen antigen)
Finds pathogen
Clonal selection of these lymphocytes
Lymphocytes undergo clonal expansion
Cells differentiate into memory cells, cause further phagocytosis, stimulate b cells to make plasma cells
Activate cytotoxic t cells
What do cytotoxic t cells do?
Produce perforin
Makes holes in the cell
Membrane becomes permeable
Describe humoral immunity
Clonal selection produces specific B cells to the antigens
B cells differentiate into plasma and memory cells
Plasma cells, secrete antibodies = primary immune response
Memory cells remain in blood and provide the secondary immune response, upon encounter with antigen b memory cells rapidly divide to produce plasma cells
Describe the structure of antibodies
Peptides with specific bonding sites
Have a light chain that’s variable and a heavy non variable chain
Describe two ways antibodies work to destroy cells
Agglutination- clump bacteria together, makes them easyoer to phagocytose
Act as markers to phagocytic cells
What does monoclonal mean when talking about antibodies
All come from one clone
Describe antibody therapy
Specific antigens to cells created
Enter blood stream
Prevent cell processes of target eg. Cancer cells
How can antibodies be used in pregnancy tests?
Antibody that reacts with human chronic gonadotropin (produced in pregnant women)
Attach to hormone
Can calculate hormone concentration from this
What is the difference between passive and active immunity?
Passive involves no contact with pathogen e.g. Antibodies given from mother to child in womb
Active immunity is the stimulation of the humoral immune system, can be artificial i.e. Vaccine or natural through infection
Describe herd immunity
Where a sufficient amount of population has been vaccinated means the pathogen is less likely to spread
Why may vaccination fail?
Defective immune system
Pathogen mutation, new antibodies no longer recognised
Some pathogens “hide” e.g. Cholera
Describe how HIV replicates
Hiv enters blood stream
Binds to CD4 proteins on T helper cells
Capsid fuses to cell surface membrane RNA and reverse transcriptase enter
Reverse transcriptase makes DNA from RNA
DNA inserted into T helper cells DNA
Helper cell transcribes and translates viral DNA and makes more viral proteins
Describe why aids occurs as a result of HIV
HIV interferes with t helper cells
Immune system doesnt work
Describe how the ELISA test works
Apply antigens to surface
Add specific antibody + wash to remove unattached
Add 2nd antibody specific to the first with an enzyme on it,
Add colourless enzyme substrate, enzyme gives it a colour
How do antibiotics work in bacteria? Why then dont they work in viruses?
Inhibit enzyme that makes the bacterias murein cell walls
So bacteria bursts due to osmosis
However viruses dont have metabolic processes so cant be disrupted
