immunology Flashcards
State 2 ways that pathogens cause harm /disease?
- bacteria can produce toxins which can directly damage tissue
- viruses can replicate inside and destroy host cells
what is an antigen
An antigen is a molecule (usually a protein) that stimulates an immune response that results in the production of a specific antibody. (Antibody generator)
why is the surface of all own cells and foreign cells or pathogens covered in specifically shaped antigen
These antigens help identify each particular type of cell to the host organism
what will the body do if the antigens are not recognized
the body will treat that cell/pathogen as non-self and initiate an immune response which will lead to the destruction of the pathogen
what are phagocytes
Phagocytes are a groups of white blood cells which can distinguish between cells which do or do not display the self-antigen
what are macrophages
A type of white blood cell that surrounds and kills microorganisms, removes dead cells, and stimulates the action of other immune system cells.
what is phagocytosis
Phagocytes will ingest / engulf and destroy any cell that presents a non-self-antigen.
describe phagocytosis
1 + 2) Pathogen is engulfed by the phagocyte.
3) Engulfed pathogen enters the cytoplasm of the phagocyte in a vesicle which is now called a phagosome.
4) Lysosomes fuse with phagosome releasing hydrolytic digestive enzymes
5) Lysosome enzymes hydrolyse the pathogen. Phagolysosomes are formed
6+7) Waste materials are released from the cell by exocytosis and antigens presented on the cell surface membrane and the phagocyte becomes an antigen presenting cell (APC)
why does a phagocyte have lots of mitochondria
because the cell needs lots of energy to do endocytosis or exocytosis , energy is from hydrolysis of atp and atp is produced in respiration
which response is the same for all pathogens
non-specific immunity , gives no immunity
which response results in immunity
specific immune response
Some white blood cells are phagocytic. Describe how these phagocytic white blood cells destroy bacteria.
- Phagocyte attracted to bacteria by chemicals / recognise antigens on bacteria as foreign;
- Engulf / ingest bacteria;
- Bacteria in vacuole / vesicle;
- Lysosome fuses with / empties enzymes into vacuole;
- Bacteria digested / hydrolysed;
what is a lymphocyte
A lymphocyte is a type of white blood cell in the immune system made in the lymph nodes. Lymphocytes include T cells, B cells
what is a specific cellular response
A specific response to a specific antigen on the surface of a cell or pathogen that has been recognized as non-self.
what is the cell -mediated immunity
response of T cells
(part of primary response)
describe the cellular / cell mediated response
1) Phagocyte engulfs & hydrolyses the pathogen and presents the antigen on the cell surface membrane.
2) TH cell with specific receptor molecule binds to presented antigen
3) Once TH cell binds to the presented antigen it is activated. It then rapidly clones by mitosis and then differentiate.
what is clonal expansion /selection
A specific TH cell binds to presented antigen via its complementary receptor
TH cell is activated and clones to produce many TH cells with complementary receptors to the antigen
what are the roles of T cells
T helper cells
- Specific TH cell binds to the antigen presenting cell and Release cytokines that attract phagocytes to the area of infection.
- Release cytokines that activate Cytotoxic Killer T cell (TC).
- Activates a specifically complementary B cell.
-Forms memory TH cells
Cytotoxic Killer T cell
- Locate and destroys infected body cells that present the correct antigen.
- Binds to antigen-presenting-cells and releases perforin ) which creates holes in the cell surface membrane which destroys the APC.
what is the humoral response (part of primary response)
The humoral response involves the activation of B cells to produce antibodies.
B cells must be stimulated by their complementary TH cell by the release of cytokines.
what is the primary response
The whole process from initially recognising a pathogen as non self, up to producing antibodies is called the Primary response.
describe the humoral response
- A specific TH cell with the correct receptor binds to presented antigen and then locates AND activates a specifically complementary B cell. The specific TH releases cytokine chemicals that signal the specific B cell to clone by mitosis (clonal selection).
- The B cell then differentiates into two types of cell:
Plasma cells
Memory (B) cells
what is the function of plasma cells
Produce and secrete vast quantities of SPECIFIC antibodies into the blood plasma.
what is the function of memory b cells
Remain in the body (bloodstream) to respond to pathogen rapidly and extensively should there be a future re-infection.
what is an antibody
Protein made in response to foreign antigen – has binding sites which bind SPECIFICALLY to an antigen.
