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
Outline hybridoma method [3]
- An antigen is injected into a mammal to stimulate clonal expansion of complementary B cells.
- These B cells are harvested and fused with a myeloma, which can undergo mitosis an indefinite number of times
- The hybrid cell is called a hybridoma
How can monoclonal antibodies be used in diagnosis? [2]
- MAs for specific antigens can be attached to radioactive markers, allowing for specific cells or proteins to be found in the body
- Also useful in blood typing and tissue matching
How can monoclonal antibodies be used in treatment? [2]
- Can bind to certain cells, marking them for destruction
- Useful in treatment of cancers and autoimmune diseases
State an issue with using monoclonal antibodies in treatment and how it is overcome [2]
- MAs require multiple treatment rounds. As they are sourced from animals this may trigger an immune response
- To overcome this, the MAs are humanised by altering the amino acid sequence to those found within humans
compare and contrast passive and active immunity [5]
- Both involve antibodies
- no memory cells produced in passive, produced in active
- passive is immediate, active has a time lag
- passive antibodies from external source, active lymphocytes produce antibodies
- passive no direct contact with antigen needed, active needs direct contact with antigen
Give examples of passive and active immunity [4]
- Passive natural - antibodies in colostrum or transferred across placenta
- Passive artificial - anti venom, needle stick infections
- Active natural - humoral response to infection
- Active artificial - vaccination
Define vaccination
The deliberate expose of an individual to antigens from a pathogen to provide artificial active immunity
How do vaccinations that use antigens provide long lasting immunity? [2]
- Antigens in vaccine trigger primary immune response without infection
- If pathogen is encountered, secondary immune response destroys the pathogen before symptoms develop
How do vaccines that use antibodies provide short term immunity? [2]
- Antibodies give rapid protection against harmful microorganism
- Allows time for the development of an active immune response
How can vaccination programs control the spread of infectious dieases? [3]
- herd immunity - significant proportion of population is vaccinated so pathogeen is likely to affect a non immunised individual. Diseases cannot spread in immune individuals
- Ring vaccination - all individuals within a radius of a known case are immunised, preventing spread from localised areas
- Boosters - Where a vaccine does not induce a strong response, these maintain immunity.
