6: Antigens and Antigenicity Flashcards
Antigen
any substance that can induce antibody generation
T cell receptors only recognize peptides that have been ____ or degraded and are on an antigen presenting cell
processed
Allergen
an antigen that induces an allergic reaction
What presents T-dependent antigens?
MHC
2 types of epitopes
linear and discontinuous
What factors make a good antigen?
size, stability, antigenicity, foreignness, complexity
Proteins are ___ antigens
good
Simple polysaccharides are ___ antigens
poor (readily degraded in cells)
Complex carbohydrates are ___ antigens
usually good
Nucleic acids are ___ antigens
usually poor
Lipids are ____ antigens
usually poor
What are some factors that influence immunogenicity?
genetics, age, health status, dose, route of exposure, adjuvants
T-independent antigens
doesn’t need a T cell to trigger antibody secretion
T-dependent antigens
needs a T cells to trigger antibody secretion (more common)
Haptens
small molecules that are not normally immunogenic, but become antigens when liked to another structure
What 3 types of antibodies will haptens generate?
- against the carrier
- against the hapten
3.against the new epitope generated by the hapten-carrier linkage
Autoantigens
self antigens that antibodies and T cells are generated against in error
Molecular mimicry
some pathogens express proteins or carbohydrate residues that resemble host molecules, resulting in activation of T cells
Cross-reactivity
the process by which one epitope is similar enough to another epitote, resulting in specific immunity against unrelated antigens
What are some diseases caused by cross-reactivity?
rheumatic fever, false positive tests, autoimmunity
Superantigens
secreted exotoxins that are highly mitogenic and stimulatory for T cells; do not require prior processing to bind to T cell receptor
