Antigen MHC Flashcards
Factors influencing the immune response
- age
- overall health
- dose
- route of inoculation
What is the molecular weight or macromolecular size of an antigen to be an immunogen?
at least 10,000 delton
considered as the best immunogenic
immunogens.
- protein
- polysaccharide or carbohydrate
The more complex the structure is, the more
immunogenicity of that antigen. The lesser the
complex structure is, the lesser the immunogenicity.
molecular complexity
It is the key determinant site
Epitope
amino acids follows one another on a single chain.
Linear epitope
results from the folding of
one chain or multiple chains, bringing certain amino acids from different segments of a linear sequence or
sequences into close proximity with each other so they can be recognized together
conformational epitope
may react with
both linear and conformational epitopes present on the surface of an immunogen
B-cell
recognize an epitope only as a part of a
complex formed with MHC proteins on the surface of an antigen presenting cell.
T cells
non-immunogenic materials that, when
combined with a carrier create
new antigenic determinants
Haptens
Rhus radicans contains chemical substances
called
catechols
Examples of haptens
- poison ivy
- drug related
Example of drug related - where there are low numbers of platelets
Drug induced thrombocytopenia
conducted the study of haptens
Karl landsteiner
What is the title of the book Karl Landsteiner written?
The Specificity of Serological
Reactions
antigens that belong to the
host
Autoantigens
Human body don’t tend to have immune
response to autoantigen. If that happens, the process is called
AUTOIMMUNITY
It is from other members of the host’s species, and these are capable of eliciting an immune
response.
Alloantigens
tissues and organs are transplanted to the same host
autograft
example of autograft
severe burns and rhinoplasty
came from different individual but fall on the same species
allograft
example of allograft
kidney transplant
also known as synograft
isograft
derived from different class but identical individual
identical twins
came from different species
hetrograft
heterograft also known as
xenograft
example of heterograft
heart transplant came from pig
came from other animals , plants, microorganisms
heteroantigen
came from other species like unrelated plants, animals
Heterophile antigen
example of heterophile antigen
reaction to Anti-A antisera
substance administered with an
immunogen that increases the immune response.
adjuvants
Example of adjuvants
- aluminum salts
- freund’s adjuvant
It must be injected into the muscle to work
adjuvant
the only ones approved for
clinical use in the United States, and these are used
to complex with the immunogen to increase its size
and to prevent a rapid escape from the tissues.
Aluminum salts
produces granulomas, or large
areas of scar tissue, and thus is not used in
humans
Freund’s adjuvant
Different effects of adjuvants
- stimulate b cells
- stimulate t cells
- stimulate phagocytic cells
- increase processing of antigen
- prevent rapid escape from the tissue
Major Histocompatibility complex originally referred to as
Human
Leukocyte Antigen
Gene coding for the MHC molecules in humans are
found in the
short arm of chromosome 6
coded for at three different locations or loci.
Class I
example of class I molecules
HLA-A, HLA-B, HLA-C
situated in the D region, and there are several
different loci.
Class II molecules
located in between class I and Class II regions within
the short arm of chromosomes 6.
Class III molecules
Example of Class II molecule
DP, DQ, DR
Example of Class III
C2, C4, factor B, and cytokines such as Tumor Necrosis Factor
Found mostly on nucleated cells.
class I
Found mostly on B cells, APCs
Class II
Not expressed on
the cell surfaces.
Class III
Non-classical Class I
HLA-E, HLA-F HLA-G
Non-classical Class II
HLA-DM, HLA-DN, HLA-DO
alternate forms of a gene that code
for slightly different varieties of the same product
alleles
How many different alleles are there in HLA-A
580
How many different alleles are there in HLA-B
921
How many different alleles are there in HLA-C
312
Since the MHC genes are closely linked, they are
inherited together as a package called a
haplotype
The have the same alleles
Homozygous
Found on lymphocytes
MHC Class I
MHC class I is made up of
Polypeptide chains
MHC class II is made up of
two alpha chains and two beta chains.
folded into three domains, α1, α2, and
α3
Alpha chain
does not penetrate the cell
membrane, but it is essential for proper folding of
the α chain
Beta 2 - microglobulin
most polymorphic among the class II
DR
main role of class I and class II
bind peptides within cells and transport them to plasma membrane
Class I molecules mainly present peptides that have
been synthesized within the cell to
CD8+ T cells
Class II molecules mainly bind exogenous proteins
and present it to
CD4+ T cell
process those infection agents that attack
from the inside
Class I
Example of Class I that attack from the inside
viruses,
tumors, parasites
process those infection agents that attack
from the outside
Class II
Example of Class II that attack from the outside
Bacteria
synthesized in the
rough ER
Class I and Class II
Calnexin also known as
Chaperone
3 chaperone molecules
Calreticulin, tapasin, ERp67
What are the transporting peptides?
TAP 1 and TAP 2
steps in antigen presentation by MHC class I
1st step - digestion of early proteins carried out by proteases
2nd step - Once cleaved, peptides must be pumped
into the lumen by specialized transporter proteins
3rd step - alpha-chain has bound the peptide and ready for the presentation to CD8+ T
cells.
pocket of enzyme
proteasome
most potent activators of T
cells, and they are excellent at capturing and
digesting exogenous antigens such as bacteria.
Dendritic cells
prevents interaction of the
binding site with any endogenous peptides in the
endoplasmic reticulum.
invariant chain
Applications of MHC typing (HLA typing)
- tissue/organ transplantation
- paternity testing
- forensic medicine
reactive arthritis
HLA-B27
