Immunology Flashcards
Define antigen
A protein that stimulates an immune response that results in the production of a specific antibody
Describe phagocytosis (Non-Specific Response) (6 marks)
- Pathogen engulfed by phagocyte
- Pathogen enters cytoplasm of phagocyte in a vesicle
- Lysosomes fuse with phagocyte and release hydrolytic enzymes
- Enzymes break down/hydrolyse pathogen
- Waste materials from cell released via exocytosis
- Pathogen antigens presented on phagocyte CSM and becomes an Antigen-Presenting Cell (APC).
Two types of T-cell
T-Helper Cell
Cytotoxic Killer T-Cell
Describe the primary immune response
- T-Helper cell with specific receptor molecule binds to presented antigen on phagocyte (APC)
- Once T-Helper cell binds, it is activated.
- Activated T-Helper cell rapidly clones by mitosis
Describe clonal selection
- Specific T-Helper cell binds to presented antigen on APC
- T-Helper cell is now activated and rapidly clones by mitosis to produce many T-Helper cells with complementary receptors to the antigen.
Why is clonal selection necessary?
- Not be enough room in the body to have lots of every T-Helper cell for every antigen you encounter.
- Increased number of cells would increase total energy demands of organism
Roles of T-Helper cell
- Specific TH Cell binds to APC
- Release cytokines that attract phagocytes to area of infection
- Activates specifically complementary B-Cell (lymphocyte)
- Form memory TH Cells
What is the humoral response? (1 mark)
Involves activation of B-Cells to produce antibodies
Describe humoural response
- Specific TH Cell with correct receptor binds to presented antigen then locates and activates specifically complementary B- Cell
- Specific TH releases cytokine chemicals that signal the specific B-Cell to clone by mitosis (clonal selection)
- B-Cell then differentiates into 2 type of cell:
- Plasma Cell and Memory B-Cell
Describe the role of plasma cells in the humoral response
Produce and secrete vast quantities of specific antibodies into the blood
Describe the role of memory b-cells
Remain in the body to respond to pathogen rapidly and extensively should there be future re-infection
Define antibody
Protein made in response to a foreign antigen
Define agglutination
Specific antibodies bind to antigens on pathogen and clump them together
Define oponisation
Marking pathogens so phagocytes recognise and destroy them more efficiently
Why is antigenic variability bad?
Gene mutations in pathogens may lead to a change in tertiary structure specific to the B-Cell, meaning memory B-Cells will no longer be complementary to antigen so do not form antigen-antibody complex therefore not able to initiate a secondary response.
