3 - Antigens Flashcards
Antigen Characteristics
Typically Polymeric:
Proteins / Carbs / NA’s
Antigen Processing –> ENHANCES IMMUNOGENICITY
= susceptible to being broken down into immunogenic pieces
Epitope // Hapten
Part of the ANTIGEN that:
- *interacts w/ AB’s & T-Cell antigen receptors**
- rest of antigen = carrier forepitopes*
Best type of ANTIGEN?
The MORE ANTIGENIC DETERMINANTS means:
more likely / diverse of an immune response
PROTEINS
have greatest diversity in sequence
- *Carbohydrates**
- may be good antigens*
- Lipids / NA’s*
- not good*
LINEAR EPITOPES
of protein antigens
Since it is linear,
each peptide can be recognized by DIFFERENT CLONES
in an OVERLAPPING FASHION
can recognize neighboring epitopes
less complex vs conformational epitopes
Conformational Epitopes
of protein antigens
can ONLY be reconized as a SINGLE Epitope
so the STRUCTURE of the protein
Influences how the AG is being recognized
3D Conformations // Unprocessed Proteins // Peptides
Trypsin / Proteases
cleave what part of an ANTIBODY?
HINGE REGION
Plasmin / Trypsin –> controls metabolism at this region
Complementarity-Determining Region
CDR
- *CDR**
- *Binding site** for the EPITOPE / HAPTEN
Located @ the TIP of the Fab Regions
Variable AA sequences w/ hypervariability
to determine specificity
Antibody - Antigen
Interactions?
NON-Covalent Interactions
they are very strong
made up of many interactions
sum of all the attractions = specificity
Antiserum
- *Blood** that contains VARIOUS ANTIBODIES
- *complicated mixture** of ALL AB’s
can lead to:
CROSS REACTIONS
only partially fit / recognized
What type of Reaction?
Soluble antigen = protein / peptide / saccharide
that binds w/ AB
Crosslinked latticework of alternating AB + AG
–> forms a Massive network that can be insouble
= jelly like or comes out of solution
PRECIPITATION REACTION
AB + AG
What type of Reaction?
Insoluble particulate = whole virus / bacterium
binds with AB
crosslinking leads to clumping of particles
AGGLUTINATION REACTION
Insoluble particulate + AB
Univalent vs Multivalent
- *Univalent**
- *1 Hapten per Particle**
- *Multivalent**
- *2+ COPIES** of the same hapten per particle
Unideterminant vs Multideterminant
- *Unideterminant**
- *Single TYPE of hapten** per particle
- *Multideterminant**
- *2+ TYPES of hapten** per particle
Zeta Potential
the electrical potential (voltage) due to the:
Net NEGATIVE charge on cell surface of RBCs
this PREVENTS close approach of RBCs
that can BLOCK cross linking by IgG Antibodies
IgG AB’s are cheap/easy to prepare, more common
IgM AB’s are BIGGER, they can bridge the zeta potential
which can crosslink RBCs
Coombs Test
Useful in detecting Rh Factor Antibodies
- *AB#1**
- *IgG** AB’s, to coat the antigen w/ multiple haptens
AB#2
binds to the Fc region (TAIL) of AB#1
–> clumpling / agglutination of RBC’s
What is this?
Includes IgG ABs & Complement C3B fragments
a molecule that becomes attached @ surface of MICROBE
–> INCREASES efficiency of PHAGOCYTOSIS
by neutrophils & macrophages
OPSONIN
What is this?
Coating of a particle with AB or Complement component
leading to
ENHANCED PHAGOCYTOSIS
OPSONIZATION
- *Fc Regions** of IgG AB’s are recognized by
- *Fcg Receptors on Phagocytes**
Complement Proteins are recognized by
CR1 (CD35) and MAC-1 (CR3)
complement receptor 1 // Macrophage antigen 1
Diagnostic Applications of ANTIBODIES
- *Immunoassays**
- *RIA / IRMA / ELISA / EMIT / FPIA**
- *drug tests**
- *Diagnostic Precipitation & Agglutination** reactions
- *Pregnancy / blood typing / coombs**
- *Western blots** (immunoblots)
- *HIV Diagnostic**
What is this?
Unresponsiveness to an antigen
that is INDUCED by EXPOSURE to that antigen
antigen specific / NOT immunosupression
IMMUNOLOGICAL TOLERANCE
Self Tolerance
Induced Tolerance
REPEATED small doses –> desensitation
can be SubQ / IV / Inhaled / oral
What is this?
a bacterial toxin (staph. enterotoxin) that is capable of producing a
DRASTIC OVER-RESPONSE by the immune system
SUPERANTIGENS
not processed into smaller fragments
instead they bind to MHC2 receptors,
OUTSIDEthepeptide biding groove
which then CROSSLINKS these to T-Cell receptors
some may also bind to parts of the VH domain on AB’s
–> stimulating B-Cells
How do Superantigens work?
Bind to MHC2 & T-Cell Receptors
does NOT depend on the specificity of the receptors
so a LARGE # of receptors can be occupied/stimulated
VVVV
MASSIVE STIMULATION of T-CELL
possibly B-cells as well
What is this?
Substance that ENHANCES immune response to an immunogen
(↑immunogenecity)
by:
1) extending half-life of antigen in blood
2) raise cytokine production
3) help APCs take up & process antigen
ADJUVANTS
ex:
Microbial components / Alum / Detergents
Lipids / Hemaglutinin
