The Immune System Flashcards
What is a pathogen?
An organism that causes communicable disease by destroying cells or secreting toxins
What is an antigen?
A protein on the cell membrane which initiates an immune response
What is cellular immune response?
- White blood cells (lymphocytes) destroy pathogens or toxins directly
- (Phagocytes / Killer T-cells)
What is the humoral immune response?
- Antibodies destroy pathogens or toxins
- B-cells and Plasma cells
Describe the non-specific immune response of a white blood cell.
- Phagocyte recognises foreign antigen on pathogen
- Phagocyte engulfs pathogen into a phagosome
- Lysosomes fuse with the phagosome
- Lysozymes are releases which hydrolyse the pathogen
Describe specific immune response of a white blood cell.
- Phagocyte presents the pathogens antigen on its cell surface membrane
- Phagocytes are antigen presenting cells
- T-helper cell with complementary receptor binds to the presented antigen
- This activates complementary T-killer and B-lymphocytes
- By releasing cell signaling molecules
-e.g. cytokines
What activates T-cells?
- Activated by antigens presented by phagocytes
What are the 2 types of T-Cells?
- T-Helper Cells -> activate B-Cells / Cytotoxic T-Cells
- Cytotoxic T-Cells -> kill pathogens (Cellular response)
What is an antibody?
Proteins that bind to antigens to kill pathogens
What is clonal selection?
Only the B-Cell that forms an antigen-antibody complex is selected to divide into plasma cells
What do B-Cells do?
- The B-Cells with the complementary antibody forms an antigen-antibody complex and activates the right B-Cell
- Selected B-cell divides / clones itself -> many copies called plasma cells
What are plasma cells?
- Clones of the selected B-Cell with complementary antibody to pathogens antigen
What is the purpose of plasma cells?
- Make monoclonal antibodies -> antigen - antibody complex with antigen
- Stick pathogens together = agglutination
- Phagocytes can destroy many pathogens at once
- When infection is over. Plasma cells are saved as memory B-Cells
What is the structure of an antibody?
- Y shaped protein with a quaternary structure
- Constant region is the same for all antibodies
- Variable region is specific and only complementary to one antigen
What is agglutination?
Attaching of multiple proteins to form a clump
What is the benefit of the agglutination of phagocytes?
Many pathogens can be destroyed at once by a single phagocyte
What is the primary immune response?
- First immune response to a pathogen
- Longer lag time
- No memory cells - Clonal selection
- Pathogens multiply and damage host cells
- T-Cells and B-Cells become memory cells
What is the secondary immune response?
- Second infection by some pathogen / antigen
- Shorter lag time
- More antibodies produced
- Rate of antibody production is faster
- You will not feel symptoms
What is a monoclonal antibody?
Identical antibodies made from the same B-Cell / Plasma Cell
How are monoclonal antibodies used to deliver drugs?
- All cells have different / specific antigens on their surface
- Attach drugs to antibodies -> bind to target cells
- Drug + Antibody will only bind to target cells
What is a vaccine?
Contains antigens / antigenic material (dead / weakened pathogens) to stimulate an immune response
What is active immunity?
When you make your own antibodies
What is Natural active immunity?
Antibodies made after exposure to a pathogen
What is artificial active immunity?
Antibodies made after a vaccination
What is passive immunity?
When you are given antibodies by another organism
What is natural passive immunity?
Antibodies transmitted from mother to baby via placenta or breast milk
What is artificial passive immunity?
Antibodies are acquired from a blood transfusion or immune serum medicine
What is an ELISA test?
Enzyme Linked Immuno Solvent Assay
Describe the Direct test for antigens?
- Immobilised antibodies are attached to well
- Sample added
- 4 Blood Plasma contains antigen
- form antigen - antibody complex
- Rinse to remove unbound antigens
- Antibody + enzyme is added
- Rinse to remove the unbound antibodies
- Add substrate -> if it’s positive -> colour change
Describe the indirect test for antibodies?
- Antigen is fixed to the well
- A sample is added -> if complementary it will form an antigen - antibody complex
- Rinsed to remove unbound antibodies
- A different antibody is added with an enzyme attached
- Rinsed to remove unbound antibodies + enzyme
What does HIV do?
Infect Helper T-Cells and weakens the immune system
How does HIV replicate?
- Virus attachment protein binds to receptor on host
- Reverse transcriptase -> makes double stranded DNA from RNA
- DNA entered nucleus via nuclear port
- TH-Cells makes more copies of the virus genetic material (RNA) + proteins (reverse transcription)
- Reforms Capsid
- Leaves host cell -> takes an envelope from hosts membrane
