The immune response Flashcards
(18 cards)
What are phagocytes
Cells that engulf and destroy foreign cells
They are non specific (no immune memory is required or generated)
How are pathogens recognisable
They are recognisable due to pathogen associated patterns (pamps) on the surface
Pamps bind to patter recognition receptors (PRR) on the phagocyte
phagocytosis follows this recognition
How does phagocytosis work
- The ingested pathogen is held within a phagosome
- A lysosome fuses with the phagosomes creating a phagolysosome
- The pathogen is destroyed by hydrolytic enzymes and the debris is removed from the cell as it is displayed on the membrane
what is phagocytosis an example of
It is an example of endocytosis
What is the cell division of lymphocytes like and what does this mean
They produce non identical daughter cells this means each lymphocyte has a different T-cell receptor
Where are t-cells made, mature and stored
T-cells are made in the bone marrow, they mature in the thymus gland and are stored in lymph nodes in the lymphocytes
What are the steps of clonal selection and expansion in the innate response
- ACPs containing the pathogen after phagocytosis presents antigens (MHT ll) and travels to the lymph nodes
- T-h (helper) cells are in the lymph nodes
- The APCs antigen (MHC ll) bind to the complementary t-h cell receptor
the t-helper cell is then activated - The t-helper cells can rapidly replicate to form clones via mitosis
(Can take anywhere up to 2 weeks that why vaccines and the secondary response are important)
What do cytotoxic t-cells do and what is the process linking
why is this important
cytotoxic t-cells kill infected or damaged cells
- cells which are no specialised APCs can present an antigen (MHC l) on their cell surface
- T-cells bind specifically to the antigens on the surface an initiate the cells death by the use of perforin punching holes the cell membrane allowing substances to freely move in and out of the cell
This is important against viruses and other intracellular parasites
what are the 3 ways t-cells can act
- perforin = destroys the plasma membrane
- granzymes - stimulates apoptosis
- lymphotoxin - disrupts the intracellular metabolism
What do t-cells do when they are active
- Stimulate B-cells to become activated and become antibody-secreting plasma cells
- Stimulate memory B-cells
- Activate cytotoxic t-cells which directly kill infected or damaged cells
- Stimulate phagocytosis
What is clonal selection like in B-cells
- B-cells are activated by a similar method to T-cells
- Antigens on the pathogen bind to specific complimentary receptors on the B-cell
- The B-cell then becomes active but has to present the antigen to a Th-cell to become complete activation
What is the colonial expansion like in a B-cell
why is this important
The active b-cell differentiates into plasma cells and memory cells via cytokines released by the t-helper cells
the cells proliferate to create many copies
Why is colonial selection important in B-cells
crucial for an adaptive immune system ensuring only the B-cells needed are activated
Describe how presentation of a virus antigen leads to the secretion of an antibody against the virus?
t-helper cells bind with the antigen via its complementary receptor. The t-cells are then activated and can complete the activation of a B-cell which then divides producing plasma cells.
What are the three roles of antibodies
- neutralisation = preventing pathogens from entering the cell
- opsonisation = stimulating the action of phagocytes on the pathogen
- Agglutination = Clumping pathogens together, impairing their functions and increasing the likelihood of phagocytosis
What do regulatory t-cells do
Moderate the immune response to ensure that autoimmune disease does not develop
the mechanisms are unclear, but inhibitory cytokines probably play a role
What do cytokines do
speed up B-cells
What causes the immune response
An antigen
