Response to Pathogens Flashcards
Phagocytosis, Cell Mediated, Humoral
What is phagocytosis?
The defence mechanism we produced once the body’s 1st line of defence has been crossed. A non specific mechanism that destroys any pathogen the cell encounters.
What is a phagocyte?
A cell that has the ability to engulf others.
Where are phagocytes most often found?
Circulating in the blood.
- In phagocytosis, how does the phagocyte draw to the pathogen?
Phagocyte attracts to the pathogen by responding to chemicals released by the pathogen. Therefore, the phagocyte moves towards it along a concentration gradient.
- In phagocytosis, how do the phagocyte and the cell attach to eachother?
Receptors on the phagocytes cell surface surface attach to chemicals on the pathogen’s surface.
- In phagocytosis, which organelle moves close to where the pathogen has started to bind and become and engulfed?
Lysosomes.
- In phagocytosis, what do lysosomes do once the pathogen has fully engulfed?
What is the name of the region where the pathogen has been engulfed?
Lysosomes secrete lysozymes into the phagosome, which are hydrolytic enzymes. These can hydrolyse the bacterial cell wall, so the cell breaks and bursts open.
- In phagocytosis, what happens to the remaining products from the pathogen?
Any remaining products from the hydrolysed pathogen are absorbed by the phagocyte.
What does the cell mediated response aim to target?
Any pathogen that invades a cell or has been engulfed by the cell.
What is a T lymphocyte?
A type of white blood cell which is able to destroy pathogens.
Name 4 different types of reason why antigens are displayed on a cell surface and can be recognised.
They recognise APCs created in phagocytosis.
They recognise antigens on cells invaded by viruses
Transplanted cells have different antigens
Cancer cells have different antigens
Describe Th cell receptors.
Highly specific to one type of antigen only.
What do T lymphocytes respond to?
Antigen presenting cells.
- In cell mediated immunity, how does the invaded cell become recognisable by T lymphocytes?
The cell uses the antigens from the pathogen and displays it on its cell surface, producing an APC.
- In cell mediated immunity, what do T lymphocytes bind to?
Antigens that have been displayed on the cell surface.
- In cell mediated immunity, what happens once T lymphocytes have bound to the cell?
Attachment between the T lymphocyte and the APC stimulates the Th cell to divide rapidly by mitosis into clones of the Th cell.
- In cell mediated immunity, once the T cells have been cloned, what 4 things could they potentially develop into or do?
Memory cells
Activate Tc cells
Stimulate B cells to divide
Stimulate phagocytosis.
What is a memory cell?
What do these cells prevent?
A cell that circulates in the blood after infection so a rapid response can be produced should you encounter the same pathogen again.
They prevent symptoms from being produced, as the pathogen is often destroyed before it can cause harm.
What is a cytotoxic T cell?
A type of T cell that can destroy pathogens by making holes in their cell surface membrane using the perforin protein.
What is a B lymphocyte?
A type of lymphocyte that can produce antibodies.
What are plasma cells?
Cells with a short lifespan that can rapidly produce antibodies.
What are effector B cells?
Cells that can give rise to plasma cells when activated by Th cells.
What is a humoral response?
A response to pathogens using antibodies.
- In a humoral response, what happens once a pathogen has been taken up by a cell?
Antigens are displayed on the cell surface.
- Th cells, activated in cell mediated immunity, attach to what?
What does this do?
Th cells attach to processed antigens on the antigen presenting B cell. This activates the B cell.
- In humoral immunity, by what type of cell division do B cells divide by? Clones of what type of cell are produced?
Mitosis. This produces a clone of plasma cells.
- In humoral immunity, what do plasma cells produce?
Antibodies
- In humoral immunity, how are the pathogens destroyed?
Antibodies produced by the plasma cells bind to the pathogen and destroy it.
- In humoral immunity, B cells can then develop into what type of cell?
Memory cells
