Immunology Flashcards
What is an antigen?
A molecule that stimulates an immune response that results in the production of a specific antibody
Phagocytosis (7) - non specific response
- Phagocyte attracted to bacteria by chemicals / recognise antigens on bacteria as foreign
- Engulf bacteria
- Bacteria trapped in vesicle called phagosome
- Lysosome fuses with phagosome to form a phagolysosome ( releases hydrolytic digestive enzymes)
5.lysosome enzymes hydrolyse pathogen - Waste materials released from cell by exocytosis
- Phagocyte becomes APC as the antigens are presented on the cell surface membrane
What is the role of T helper cells?
- Specific T helper cell binds to the APC
- Release cytokines that attract phagocytes to the area of infection
- Release cytokines that activate cytotoxic killer T cell
- Activates a specific complementary B cell
- Form memory T helper cells
What is the role of cytotoxic killer T cells?
- locate and destroy infected body cells that present the correct antigen
- binds to antigen presenting cells
- releases performing, which creates holes in the cell surface membrane, which destroys the APC
Describe the response of T lymphocytes/ cell- mediated immunity (primary response)
- Phagocyte engulfs and hydrolyses the pathogen and presents the antigen on the cell surface membrane
- T helper cell with specific receptor molecule binds to presented antigen
- Once T helper cell binds to the presented antigen, it is activated . It then rapidly clones by mitosis
Describe the humoral response ( activation of B cells)
- A specific T helper cell with the correct receptor binds to the presented antigen and then locates and activates a specifically complementary B cell
- The specific T helper cell 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: produce and secrete vast quantities of specific antibodies into the blood plasma
- memory B cells: remain in the body to respond to pathogen rapidly and extensively should there be a future re- infection
Describe the structure of an antibody
- antibodies are complex proteins with a quaternary structure made up of 4 polypeptide chains ( Y shaped)
- The main part of the antibody is the constant region which is the same in all antibodies
- variable regions have a different primary structure and, therefore, a different tertiary structure
What is agglutination?
Specific antibodies bind to the antigens on pathogen and clump them together
What is opsonisation?
Marking pathogens so phagocytes recognise and destroy the pathogen more efficiently
Features of passive immunity
- no exposure to antigen
- antibodies are given (eg. Mother)
- no memory cells are produced
- short term
- fast acting
Features of active immunity
- exposure to antigen
- antibodies are produced
- memory cells produced
- long term
- takes time to develop
What do vaccines contain?
Antigens from dead, weakened or attenuated pathogens
Describe how a vaccine leads to the production of antibodies against a disease causing organism (8)
- Vaccine contains antigen from pathogen
- Phagocyte presents antigen on its surface
- Specific T helper cell with specific receptor binds to complimentary antigen
- T helper cell stimulates specific B cell
- With complimentary antibody on its surface
- B cell divides by mitosis to form plasma cells
- Plasma cells secrete large amounts of antibody
- Formation of memory B cells with complimentary antibodies remain in blood
