Unit 11 - Immunity Flashcards
Define the term phagocyte
Specialised white blood cells that engulf and destroy pathogens. there are two types: neutrophils and macrophages
Define the term phagocytosis
The process by which phagocytes engulf and destroy pathogen
Outline the process of phagocytosis [5]
- Phagocyte move toward pathogen via chemotaxis
- Phagocyte engulf pathogen via endocytosis
- Phagosome fuses with lysosome forming a phagolysosome
- Lysozymes digest pathogen
- Product of pathogen hydrolysis absorbed by the phagocyte or released into the cytoplasm
Define the term immune response
The body response to ‘non self’ antigens. It consists of a non specific phase involving neutrophils and macrophages, and a specific phase involving T and B lymphcytes
What is an antigen?
A chemical present on the surface of a cell that induces an immune response
What is meant by the term self antigen?
Antigens present on an organism’s cells that are tolerated by their own immune system. They induce antibody formation
What are antigen presenting cells?
Any type of immune cell which displays parts of a pathogen on its surface to elicit an immune response
What is meant by the term non self antigen?
Foreign antigens that originate from outside the body and induce an immune response
What are the types of T lymphocyte? [3]
- T helper
- T killer
- T memory
What do T helper do?
Bind to antigens on antigen presenting cells and secrete interleukins
What do t killer do?
Secrete perforin (hydrogen peroxide) , destroying pathogens with a specific antigen
What do t memory do
provide immunological memory
Describe the structure of B lymphocytes [2]
- Mature in bone marrow
- many specific receptors and immunoglobulins on surface
What are the main types of B lymphocyte? [3]
- Plasma cells
- B effectors
- B memory
What do plasma cells do?
Produce antibodies specific to a particular pathogen
What do B effectors do?
Divide to form plasma cells
What do B memory do?
provide immunological memory
Define the humoral immune response
Immunity regulated specifically by the production of antibodies. Associated with B lymphocytes
Outline the process of the cell mediated response [3]
- Complementary T helper lymphocytes bind to foreign antigens on antigen presenting cell.
- T cells undergo clonal expansion
- 4 main types of T lymphocyte produced
Outline the process of the humoral response [4]
- Complementary T helper lymphocytes bind to foreign antigens on antigen presenting T cells
- Cytokines released that stimulate the clonal expansion of complementary B lymphocytes
- B lymphocytes differentiate into plasma cells
- Plasma cells secrete antibodies with complementary variable region to antigen. Antibodies destroy the pathogen
Compare the primary and secondary immune responses [2]
Primary immune response - initial response when a pathogen is first encountered. A small number of antibodies produced slowly
Secondary immune response - pathogen encountered for a second (3rd, 4th etc) time. Immunological memory gives a rapid production of a large number of antibodies
What is the function of memory cells? [2]
- They remain in the body for a long time following an infection and provide long term immunity.
- If the organism encounters the same pathogen in the future, they can rapidly divide to provide an effective secondary immune response
Describe the structure of an antibody [3]
- Y shaped. Two light chains bonded to two longer heavy chains by disulphide bridges
- Binding sites on variable region of light chains have specific tertiary structure complementary to an antigen
- The rest of the molecule is known as the constant region
How do antibodies destroy pathogens? [4]
- Agglutinins form antigen-antibody complexes to enhance phagocytosis (pathogens clump, engulfing occurs more efficiently)
- Bind to foreign cells and attract ‘complement’, a collection of proteins which form pores in the cell surface membrane of pathogens, destroying them
- opsonins mark microbes for phagocytosis
- Antitoxins make toxins insoluble via precipitation/neutralisation
