Immunogens and Antigens: pgs 10-14 Flashcards
What is a substance which can react with products of the immune system?
Antigen
What is a substance which can elicit an immune response?
Immunogen
What is an antigen which cannot elicit an immune response alone?
Hapten
T/F - While all immunogens are antigens, not all antigens are immunogens.
True
What must happen in order for an immune response to be developed against a hapten?
A hapten must be covalently bound to a larger molecule which is immunogenic (aka: carrier).
What effect causes some people to become allergic to drugs like penicillin?
Hapten-Carrier effect
What four properties contribute to the immunogenicity of an antigen?
1) Foreignness
2) Size
3) Chemical complexity
4) Degradability
T/F - The more different a compound is from the equivalent host compound, the weaker the immunogen.
FALSE - The more different a compound is from the equivalent host compound, the STRONGER the immunogen.
The __________(size) the antigen, the better the immune response.
larger
What molecular weight in Da is a very good immunogen?
100,000 Da or larger
Substances with molecular weights less than _________ Da are usually NOT very strong immunogens.
10,000 Da
What are some examples of large compounds that are poor antigens?
Starch and glycogen
What are some examples of good antigens?
Proteins and carbohydrates
What is the process of how T cells present antigen?
Antigens must be taken up and degraded into smaller pieces. These pieces are then displayed on the surface of the cell in the context of class II MHC proteins. This is why it’s important that an antigen be able to be degraded in order to be a good immunogen.
Only a small portion of the antigen actually binds with the antibody. This region of antibody binding is termed the antigenic determinant or __________.
Epitope
How many epitopes does an antigen have?
It has several distinct epitopes (antibodies would be produced against all available ones) which depend on the size and chemical complexity of the antigen.
How big is a B cell epitope usually?
6-7 amino acids or carbohydrate residues - sometimes they are spread out but due to the 3D structure they will be located close together
T/F - T cells cannot respond to a native or intact immunogen.
True
An epitope must be able to bind to both _____ molecule and the ______.
MHC molecule and TCR
Antigens recognized by T cells often contain ___________ peptides.
Amphipathic
B cell epitopes in native proteins generally are ______________ amino acids on the proteins surface that are topographically accessible to membrane-bound or free antibody.
Hydrophilic
What biomolecule is NOT immunogenic?
Lipids
What biomolecule is a poor immunogen?
Nucleic acids
What is an immune reaction to nucleic acids?
Systemic Lupus Erythematosus (SLE)
T/F - Immune responses to sphingolipids have been reported.
True
Is it possible for two antigens to share a common epitope?
Yes
What is an example of cross-reactivity?
Transfusion reactions - ABO blood group - The blood group antigens have similarities with the cell wall of certain enteric (gut) bacteria. If you get a transfusion could cause issues. Reaction between an antibody and an antigen that differs from the immunogen.
What compound increases the immunogenicity of an antigen preparation and causes the antigen to precipitate, thus causing the antigen to remain longer?
Adjuvant
What is usually used as an adjuvant in experimental animals?
FCA (Freund’s Complete Adjuvant)
What is used as an adjuvant for humans?
Alum (FCA is too strong for humans)
