antigens and immunogens Flashcards
what is an immunogen?
used to define an antigen that is recognized by the immune system via binding and stimulates an immune response.
true or false: all antigens are immunogenic
false
define antigen
any substance that can bind to components of the immune system (antibodies, cells)
define immunogen
any substance that can induce an acquired/adaptive immune response (B or T cell response)
what is an example of an antigen that lacks immunogenicity?
hapten
how can hapten be visible to the immune system and induce an immune response?
by binding to a macromolecule like protein and function as a carrier protein
what is an example of a natural hapten?
urushiol in poison ivy
what is a monovalent monodeterminant compund?
antigen with one epitope
what is a polyvalent monodeterminant?
antigen with one epitope expressed multiple times
what is a monovalent polydeterminant?
antigen contains multiple epitopes that appear to be presented just once
what is a polyvalent multideterminant?
antigen is large and expressed different epitopes multiple times
what are the 5 characteristics of a strong antigen?
- foreign
- high molecular weight
- physicochemically complex
- stable
- degradable
what is autoimmunity?
rare circumstances in which select self-antigens can be immunogenic
what is an example of a physiochemically complex antigen?
insulin
why should a strong antigen be physiochemically complex?
the more structurally complex the antigen the more potential diverse antigenic binding sites there are to be recognized by the immune system
why did pharmaceutical companies switch from porcine insulin to recombinant insulin?
even though it was conserved across many species lowering its immunogenicity, the prolonged use can become immunogenic
why should a strong antigen be stable?
long enough for antigen processing by the phagocytic cells, if too flexible, it makes recognition and binding difficult
what is an example of a poor antigen?
flagellin
why are antigens that degrade rapidly not good antigens?
, because they can’t be processed efficiently by APCs for presentation to T cells and B cells. However, if the antigen enzymatically degrades poorly or doesn’t degrade at all, the immune system can’t recognize it.
when is the use of materials that are non-immunogenic highly desired?
use of inert metals in joint replacement or bone reconstruction
what are the 4 major classes of antigen?
- carbohydrates (polysaccharides)
- lipids
- nucleic acids
- proteins
when do carbs display immunogenic properties?
when bound to proteins to form glycoproteins
what are examples of carbs as antigens?
when on the surface of RBCs delineating ABO blood types
antibodies
what do lipids display immunogennicity?
when conjugated to proteins
what are glycolipids associated with?
cellular membranes
true or false: DNA in its helical form is usually non-immunogenic in individuals with healthy immune systems
true
what is a rare case in which individuals with hyperactive immune systems to self-antigen develop an immune response to DNA?
systemic lupus erythematosus (SLE)
which class of antigen is the most immunogenic and why?
proteins because of their large size and complexity are the most immunogenic. As a result, they typically display multiple epitopes allowing for a robust immune response
T cells have a T cell receptor (TCR) on its surface that only recognize a specific processed antigen in the form of a linear _______ presented through a specific surface protein (MHC) on APCs
peptide
B cells have a B cell receptor (BCR) that recognizes a specific ________
epitope
what is the difference between BCR and TCR?
BCRs are structurally much more different and as a result has more diverse properties
the BCR is an antibody that is semi-attached to the B cell surface, such that when the B cell is activated via its BCR receptor complex, it allows the BCR to _____ and become a functional secretory antibody
detach
true or false: TCRs can normally recognize and bind to free epitopes on proteins, polysaccharides, lipids that are bound to surfaces of cells, microbes or secretory products
false: BCRs
what is a similarity between TCR and BCR antigen recognition?
both receptors only recognize one specific epitope
define cross-reactivity
cells with their receptors encounter an epitope with structural properties similar to the original epitope, they could potentially bind to it
