Cell recognition and the immune system Flashcards
What is phagocytosis?
A cellular process for ingesting and eliminating particles larger than 0.5 μm in diameter
What types of particles are ingested through phagocytosis?
Microorganisms, foreign substances, and apoptotic cells
In what types of cells is phagocytosis found?
Many types of cells
Why is phagocytosis essential?
It is essential for tissue homeostasis
Fill in the blank: Phagocytosis is a cellular process for ingesting and eliminating particles larger than _______ in diameter.
0.5 μm
Non-specific immunity
response is immediate and the same for all pathogens.
e.g. Physical Barriers- skin tears mucus
Phagocytosis
Specific immunity
Response is slower and specific to each pathogen
e.g. cell mediated response- t lymphocytes
humoral response- b lymphocytes
What can the immune system identify?
-pathogens
-abnormal body cells
-toxins
Phagocytosis
- The phagocyte is attracted to the pathogen.
- The phagocyte has several receptors on its cell surface membrane that attaches to the surface of the pathogen.
- The pathogen is then engulfed by the phagocyte and wrapped in a membrane forming a phagasome.
- The lysosomes move towards the phagosome and join to the phagosome.
- Lysozymes are released into the phagosome, where they hydrolyse the bacterium.
- Hydrolysed products are absorbed by the phagocyte
T-Lymphocytes
found in bone marrow
cell mediated immunity:
Cell mediated immunity
(overview)
T-cells cannot recognise foreign antigens directly they can only respond to body cells which display non-self antigens
Cell mediated immunity
(explanation)
- phagocyte presents one of the pathogens antigens
- the correct t-cell with complementary receptor combines with the antigen on the phagocyte
- replication of the correct t-cell occurs- mitosis
- t-cell roles - memory cells -stimulate more phagocytes -stimulate B-cells
-destroy any cell which has the specific antigen on
what do Cytotoxic t-cells do
-kill abnormal cells and body cells that are infected by pathogen
-produce perforin that makes holes in cell membrane surface which makes the cell membrane permeable so the cell dies
Humoral response
B-cells + lymphocytes (antibodies)
(explanation)
- B-cell engulfs antigen and presents this antigen on cell surface
- T-helper cell with complementary receptor for specific antigen joins its receptor to the antigen and stimulates the B cell to divide - mitosis
- Most cloned will turn to plasma cells, which manufacture specific antibodies to bind to the antigen, (primary response)
some are then released into the blood as long-living memory cells if you encounter the pathogen again (secondary response)
Primary response
-slow- takes time for original b-cell to come in contact with correct antigen. then have to multiply before forming plasma cells takes time to then produce antibodies
in which pathogen can multiply and cause damage leading to symptoms before antibodies can destroy.
Secondary response
body meets pathogen already with a large colony of memory b-cells specific to the pathogen.
so much quicker
concentration of antibodies much greater more plasma cells generated
so pathogen destroyed before multiplication and damage
why do antibodies break down leaving only memory cells long-term?
Antibodies are proteins which gradually break down so concentration will drop
so secondary response appears ‘not to work’
Antibodies
-made of proteins
-binding site that is complementary to specific antigen forming an antigen-antibody complex
Agglutination
Antibodies can cause microbes to stick together. This makes it speedier and easier for phagocytes to engulf them which reduces the chances of them being spread throughout the body.
Neutralisation
Some pathogens make us ill by producing toxins. Some antibodies work by neutralising the toxins
Damaging the cells
Binding of the antibodies can cause holes in the wall of the bacterium water then moves in and swells and bursts the cell.
