10th Page Flashcards
What is an immunogen?
A substance capable of triggering an adaptive immune response by inducing formation of antibodies or sensitized T cells.
Immunogens are typically proteins with a molecular weight (MW) that is immunogenic.
What is an antigen?
A substance that can combine with an antibody but may or may not invoke an immune response.
Antigens can be non-protein and are classified as antigenic.
Increase MW, protein, immunogenic
Immunogen
Decrease MW, protein, immunogenic
Antigen
Relationship of host to immunogenic
The more different an antigen is from the host, the more immunogenic it is.
What are the categories of antigens in relation to the host?
- Autoantigen:
- Alloantigen
- Heterologous antigen
- Heterophile antigen
Autoantigen
same individual
different individual, same species
Alloantigen
Relationship of size to immunogenic
The greater the size, the more immunogenic.
Ag in unrelated plants/animals but cross-reacting with other Abs
Heterophile antigen
different individual, different species
Heterologous antigen
Size requirement for immunogenicity?
The molecular weight (MW) should be at least 10,000 daltons
second most immunogenic (less immunogenic than proteins)
Carbohydrates
least or non-immunogenic alone
Lipids and nucleic acids
What is an epitope?
An epitope is a specific part of an antigen that is recognized by the immune system.
What is an epitope?
Part of an antigen/immunogen that binds to the paratope of the antibody.
What is a paratope?
Part of an antibody that binds to the antigenic determinant site
What are the types of epitopes?
The types of epitopes are linear and conformational.
What is a linear epitope?
consists of sequential amino acids on a single polypeptide chain.
What is a conformational epitope?
result from folding a polypeptide chain or chains, bringing non-sequential amino acids into close proximity.
What is a hapten?
A hapten is a nonimmunogenic material that, when combined with a carrier, creates new antigenic determinants.
What are adjuvants?
Adjuvants are substances added to vaccines to enhance immune adherence.
Major Histocompatibility Complex (MHC)?
A tightly linked cluster of genes whose products play an important role in intercellular recognition and in discrimination between self and non-self.
MHC is originally referred as
MHA / HLA.
Where are the genes coding for MHC molecules found in humans?
On the short arm of chromosome 6 at band 21.
What is the function of T MHC?
To bring or present antigens in the body to the surface cells for recognition of T cells.
Where are MHC molecules synthesized/produced?
In the rough endoplasmic reticulum.
What are the genetic loci for MHC Class I?
HLA - A, B, C.
What are the genetic loci for MHC Class II?
HLA - DP, DQ, DP.
What is the cell distribution for MHC Class I?
Found in all nucleated cells.
What is the cell distribution for MHC Class II?
Limited to antigen-presenting cells (APCs).
What is the chain structure of MHC Class I?
Contains an alpha chain (2) and a beta microglobulin (1).
What is the chain structure of MHC Class II?
Contains two beta chains (2).
Alpha and Beta
What is the size of peptides bound by MHC Class I?
8 to 11 amino acids.
What is the size of peptides bound by MHC Class II?
13 to 18 amino acids.
What is the nature of the peptide binding cleft for MHC Class I?
Closed at both ends.
What is the nature of the peptide binding cleft for MHC Class II?
Open at both ends.
To whom does MHC Class I present antigens?
CD8
To whom does MHC Class II present antigens?
CD4
What type of antigen presentation does MHC Class I use?
Endogenous pathway.
What type of antigen presentation does MHC Class II use?
Exogenous pathway.
What degrades endogenous antigen within the cytosol?
proteasome
How are peptides transported into the endoplasmic reticulum?
TAP (transporter associated with antigen processing).
What does the alpha chain of class I MHC bind to?
beta microglobulin.
What does the alpha chain of class I MHC bind?
peptide
Where is the peptide-class I MHC transported?
Golgi complex and then to the cell surface.
To which T cell does class I MHC peptide bind?
CD8+ T cell.
What does class II MHC bind to block endogenous antigen binding?
invariant chain
What happens to the MHC complex after binding the invariant chain?
goes through the Golgi complex.
What is left after the invariant chain is degraded?
CLIP (class II invariant chain peptide) fragment.
How is exogenous antigen processed?
taken in, degraded, and routed to intracellular vesicle.
What replaces the CLIP fragment?
antigenic peptide.
Where is the class II MHC antigenic peptide transported?
cell surface.
To which T cell does class II MHC peptide complex bind?
CD4+ T cell.
