Antigens (7.1) Flashcards
Describe antigens
A substance that reacts with antibodies and T lymphocyte receptors that may induce an immune response
State what antigens can be classified as
- self
- non-self
State what an organism’s immune system is normally able to do
Differentiate between self and non-self antigens and respond accordingly
Provide a possible location to which antigens can be bound
Surface of B lymphocytes
State 2 agents which can detect antigens
- T lymphocytes
2. antibodies produced by B lymphocytes
State whether or not antibodies can be secreted and by what cell they may be secreted from
Yes. Secreted by B lymphocytes
State why antigens are important
Allow for recognition of potentially harmful pathogens to trigger immune response
State whether or not all antigens trigger an immune response
Although many antigens trigger an immune response, some do not.
Describe immunogens
Antigens that elicit an immune response
Describe the basic structure of an antigen
- protein-based
- one or more polypeptide chains
State where antigens are expressed or presented
Surface of the plasma membrane of cells
State what antigens pose as for the immune system
Recognition sites
State whether or not all antigens are attached to a cell
No. Some antigens can circulate freely within bodily fluid
Describe self-antigens
Organism’s own antigens which are normally tolerated and do not cause an immune response
Describe non-self antigens
Antigens that do not belong to an organism’s own cells
State what antigen recognition is dependent upon
Detection of antigens by receptors
Describe B lymphocytes
Lymphocytes that when stimulated produce large quantities of antibodies specific to a particular antigen
Provide an alternative term in reference to B lymphocytes
B cells
Describe T lymphocytes
Lymphocytes that originate in the bone marrow and a mature in the thymus that are responsible for cell-mediated immune responses
Provide an alternative term in reference to T lymphocytes
T cells
Describe T cell receptor
A molecule found on the surface of T lymphocytes that are responsible for recognising fragments of antigens
Describe B cell receptor
A molecule found on the surface of B lymphocytes that mirror the structure of produced antibodies, recognising antigens
State what the term ‘antigen’ stands for
Antibody generator
Describe antibodies
Proteins produced by B lymphocytes that bind to certain antigens
State what MHC stands for
Major histocompatability complex
Describe MHC proteins
Proteins found on the surfaces of cells that help the immune system recognize foreign substances.
Provide an alternative term to describe MHC proteins
Human leukocyte antigens (HLA)
Describe clonal deletion
Two-stage process of selecting T lymphocytes that recognise MHC proteins and eliminate those that react to self-antigens
Describe the 2 stages of clonal deletion
- T lymphocytes that do not react with MHC proteins are destroyed by apoptosis
- T lymphocytes that react with self-antigens bind tightly to cells in the thymus and die
State the process by which T lymphocytes that react with MHC proteins in clonal deletion are destroyed
Apoptosis
Describe self-tolerance
Inability to respond to self-antigens
State what occurs if self-tolerance breaks down
Autoimmune diseases prevail
State whether or not all self antigens elicit an immune response
Not all self antigens elicit an immune response
State whether or not all non-self antigens elicit an immune response
Not all non-self antigens elicit an immune response
Provide a term to describe antigens that elicit an immune response
Immunogens
Provide a term used to describe an inability to respond to self-antigens
Self-tolerance
Describe allergens
Antigens that trigger an allergic response
State what occurs in an allergy
Certain antigens elicit an allergic immune response
Describe pathogens
Agents that cause disease
State the 2 classifications of pathogens
- Primary
2. Opportunistic
Describe primary pathogens
Pathogens that cause disease any time they are present
Provide a term used to describe agents that cause disease
Pathogens
Describe opportunistic pathogens
Pathogens that only cause disease when the host’s defences have been weakened
Provide 2 examples of factors that may satisfactorily weaken the host’s defences for an attack by an opportunistic pathogen
- stress
2. poor nutrition
State what most pathogens contain
Unique antigens that can be recognised by the immune system
State whether or not toxins secreted by pathogens can act as antigens
Yes. Toxins secreted by pathogens can act as antigens.
State the 2 characteristics which further divide pathogens
- cellular
2. non-cellular
Describe cellular pathogens
Cellular organisms that are a source of non-self antigens and cause disease
Describe non-cellular pathogens
Non-living organisms that retain the ability to cause disease
Provide the 6 classes of cellular pathogens
- bacteria
- fungi
- oomycetes
- protozoans
- parasitic worms
- arthropods
Describe bacteria
Prokaryotes that are not members of the domain Archaea
Describe fungi
Non-phototrophic eukaryotes that have rigid cell walls composed of chitin
Describe oomycetes
Fungus-like pathogens of plants that penetrate living cells and absorb nutrient or release enzyme that digest cytoplasms
Describe protozoans
Unicellular, eukaryotic organism that can replicate within the cells of its host
Describe parasitic worms
Worms that derive nourishment from its host
Describe arthropods
Organisms with an exoskeleton
Describe viruses
Infectious agent composed of genetic material
Describe viroids
Infectious agents of plants that are self-cleaving RNA enzymes
Describe prion
Mutated protein that causes protein aggregation toxic to neurons
Provide the 3 classes of non-cellular pathogens
- viruses
- viroids
- prions
State what the first line of defence is for immunity
Infection barriers
State the 3 types of infection barriers
- physical
- chemical
- microbiological
State what the second line of defence is for immunity
Innate immune response
State what the third line of defence is for immunity
Adaptive immune response
State the process by which T lymphocytes that react to self-antigens and bind tightly to cells in the thymus die
Apoptosis
State what changes in the secondary structure of prions are caused by
Interaction of a defective prion with a normal PrPc molecule inside a cell, causing a change in folding pattern
Provide a term used to describe antigens that invade cells to replicate
Intracellular pathogens
State what pathogens antibiotics are useful against
Bacteria
State what a virus is composed of
Genetic material (DNA or RNA) enclosed in a protein coat
State what some viruses are surrounded by
Lipoprotein envelope
State what viroids are composed of
Short, circular strands of RNA
State whether or not viroids have a protein coat
No
State whether or not prions contain genetic material
No
State what is consistent on both arms of an antibody
Variable region