B5 Immune System Flashcards
Antigen
A protein found on the cell surface membrane of pathogens and stimulate an immune response
4 stages of Immune Response
- Phagocytosis
- T cells
- B cells
- Antibodies
Phagocytosis
Phagocyte recognises foreign antigens on pathogen.
Engulfs it
Forms a phagosome/vesicle
Fuses with a lysosome
Lysosome releases lysozymes which digest and break down pathogenic material
What happens to a phagocyte after phagocytosis
Becomes an APC
- T cells
Receptors on cell surface membrane are complementary to antigens on phagocytes
Activates T cell
What are the diff types of T cells
- T helper cells
- Cytotoxic T cells
- Regulatory T cells
- Memory T cells
What do T helper cells do
Release chemicals called cytotoxins which activate B cells and phagocytosis
What do cytotoxic T cells do
Kill and destroy abnormal or foreign cells
- B cells
Activated by T helper cells
They divide and differentiate via mitosis / clonal selection
Diff types of B cells
Plasma - produce antibodies with a complementary shape to antigens
Memory - remain in bloodstream until secondary immune response occurs where clonal selection occurs quicker
Plasma B cells
Secrete many monoclonal antibodies specific to the antigen.
Antibodies
Agglutination - clump tgt as they can bind to 2 pathogens
Neutralise toxins
Prevents pathogens from entering host cells
Cellular immune response
T cells
Phagocytosis
Humoral Immune Response
B cells, clonal selection, production of monoclonal antibodies
Active Immunity
Your body makes its own antibodies
Passive Immunity
Given antibodies made by another organism
Pregnancy Testing
Application area contains antibodies for hCG bound to a coloured bead/enzyme
If hCG is present in urine, hCG will bind to the antibodies
And form antigen-antibody complexes
Urine moves up the stick to the test strip carrying any beads with it
Test strip contains antibodies with hCG that are immobilised
If hCG is present, the test strip will turn blue because the immobilised antibody binds to hCG
ELISA test process
HIV antigen is bound to the bottom of a well
Blood added.
Any HIV-specific antibodies will bind to antigens on bottom of the well
Wash out the well to remove any unbound antibodies
Secondary antibody with coloured enzyme attached is added to the well
Secondary antibody can bind to the HIV- specific antibodies
Well is washed out to remove any unbound secondary antibodies
Solution with substrate for enzyme is added
If there were HIV antibodies then it forms a coloured product
What changes occur when someone has AIDS
Very low T helper cells
HIV replication
Attachment protein attaches to receptor of host cell
Capsid is injected into the cell which releases its genetic material
Reverse transcriptase makes a complementary strand of DNA from viral RNA template
Double stranded DNA is inserted into humans DNA via integrase
Host cells enzymes are used to make viral proteins from the viral DNA
Viral proteins assemble into new viruses
Why does antibiotics not work against viruses
Antibiotics kill bacteria by targeting metabolic reactions within bacterial enzymes and ribosomes.
Viruses don’t have enzymes or ribosomes
