Antigens Block 4 Toka Flashcards
What is an antigen?
An antibody generator
induces an immune response when it enters the body
What do antigens bind to?
Antibodies, MHC molecules or lymphocyte receptors like TCRs and BCRs
What are the 2 subcategories of antigens?
- Immunogens
- Haptens
What are immunogens? Give examples
antigens that directly stimulate an immune response
Ex: polysaccharides
What are haptens? give an example
antigens that INDIRECTLY induce an immune response, only when bound to a protein
Ex: lipids
What is immunogenicity?
when antigens induce an immune response that causes T and B cells to make antibodies
What is the difference between immunogenicity vs antigenicity?
Immunogenicity focuses on the ability of an antigen to induce an immune response
while antigenicity focuses on the ability of an antigen to be recognized by the immune system
What is antigenicity?
ability of an antigen to bind to receptors on T and B cells and initiate an immune response
What is an epitope?
An antigenic determinant
part of the antigen that actually induces the immune response and binding of T and B lymphocytes
True or False: Antigens can have many epitopes
TRUE
What are the sources of antigens?
Infectious agents like:
1. Bacteria
2. viruses
3. Parasites
4. Fungi
What are structural viral antigens vs non structural?
Structural- found in envelope or nucleocapsid of virus
Non structural- proteins that the virus makes when attacking a cell
What are some fungal antigens?
- Chlamydoconidia
- Blastoconidia
- Hypha
Why are parasitic antigens challenging to control?
Because the changes in a parasite are involved in changes in the antigen structure
difficult to break the cycle
What are cell surface antigens?
They dont induce an immune response unless transferred to different hosts
What factors affect immunogenicity of antigens?
- Foreignness
- Size
- Chemical composition
- Physical properties
- Degradability
- Genetic factors
- Age
How does the size of the antigen affect immunogenicity?
The larger the antigen the more immunogenic (can be recognized easier)
How does the chemical composition of the antigen affect immunogenicity?
The more complex the molecule the more antigenic determinants that can be recognized by the immune system
What age group is most immunogenic?
middle age! best protected
old and young are less capable of recognizing pathogens
What is the chemical nature of antigens?
- Proteins (largest group of antigens)
- polysaccharides (good immunogens)
- Nucleic acids
- Lipids
nucleic acids
weak antigens that become immunogenic when conjugated to a protein
What is an adjuvant?
A substance that enhances immune response to antigens
this is added to vaccines
What are T- independent antigens?
those that dont require help from helper T cells
directly stimulates B cells to make antibodies
does not produce memory B cells tho
Ex: lipopolysaccharides
What is the properties of T independent antigens?
Polymeric structure that has the same antigenic determinant that repeats throughout its length
Because of this BCR can bind many at the same time
What are the cons of T independent antigens?
they may activate lymphocytes polyclonally- meaning B cells have different antigenic specificity that might not be as effective
they are resistant to degradation- making them last longer in the body
binds to BCRs
What are T-dependent antigens?
antigens that req. helper T cells
they indirectly stimulate B cells to make antibodies
most are proteins
contains only few copies of antigenic determinants
binds to TCRs
Which of the following best describes T-independent antigens?
a) Antigens that require T cells for activation
b) Antigens that activate B cells directly without the involvement of T cells
c) Antigens that activate both B cells and T cells simultaneously
d) Antigens that are resistant to degradation in the body
b) Antigens that activate B cells directly without the involvement of T cells
Which of the following factors can affect the immunogenicity of a substance?
a) Route of administration
b) Chemical composition
c) Dose
d) All of the above
d) All of the above
Which of the following is NOT a source of antigens?
a) Parasites
b) Bacteria
c) Fungi
d) Prions
e. Viruses
d) Prions
What are superantigens?
antigens that can activate alot of lymphocytes at 1 time (non specifically)
Activates pro inflammatory cytokinesis leading to system toxicity
