Transcript Antigen Structure and Immunogenicity

Antigen Structure and
Immunogenicity
Folder Title: Antigens
(With TP Slides)
Updated: September 17, 2013
Antigen Recognition by the Specific
Immune System:
Recognition by B-cell and T-cell Receptors
Antigen (Ag): Binds specifically to an antibody
binding site (Ab), or to a T-cell receptor (TCR)
Immunogen: Binds specifically to an antibody
binding site or to a T-cell receptor,
and generates a humoral or cellular immune
response.
All immunogens must be antigens,
Not all antigens can generate a response.
Haptens and Epitopes
Haptens: Small organic molecule
(e.g. 1-Fluoro-2,4-dinitrobenzene)
Not Immunogenic by themselves
Can be immunogenic when attached to an immunogenic
macromolecular carrier
The Anti-hapten antibody so generated will bind the Hapten
Epitope: A region of a macromolecular antigen
that is actually an antigenic determinant,
a molecular sub-region that is actually recognized and
bound by an Antibody or T-Cell Receptor
Antigen-Antibody Complementarity
Antibody Light Chain
Variable Region
Fig.
4-6b
Kuby
3rd Ed
AgAb
Sep
Influenza Virus Antigen
Antibody Heavy
ChainVariable Region
Antigen - Antibody Binding
Antibody Light Chain
Variable Region
Fig.
4-6a
Kuby
3rd Ed
AgAb
Kiss
Antibody Heavy Chain
Influenza Virus Antigen
Variable Region
Prot2nd
Primary
sequential
epitopes in
sperm whale
myoglobin
Conformational
(non-sequential)
Epitope in Hen
Egg White
Lysozyme.
(Colors show amino
acid side chains
contacting the two
different chains of the
antibody, or
contacting both
chains. Antibody
structure to be
covered later)
What Determines Immunogenicity of
an Antigen?
1. Properties of the immunogen
(See detailed breakdown next slide)
2. Properties of the Host (Slides 12 and 18)
a. Genetic
b. Physiological
3. Mode of Antigen Exposure
ImGenFx1
ImGenFx2
Ag&MHCa
Ag&MHCb
Ag&MHCc
Ag&MHCd
Ag&MHC
ImGenFx3
ImAdmin
Conformational Properties of
Epitopes for Antibodies
64
80
Hen Egg-White Lysozyme: Conformations of Sequence 62 to 80
Anti-hapten Antibodies
See Figure 4-1
p. 77
Kuby, 6th Edition
AbHapten
“Fill-in-the Blank” Question:
When a small organic molecule is made immunogenic
by attaching it to a macromolecule it is called a
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What is this molecular
model showing?
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Immunogenicity of Antigens is Controlled by the Nature of the Antigen,
the Genetics of the Host, and the Mode of Immunogen Exposure.
Give an example of what is meant by “Mode of Immunogen or Antigen
Exposure”
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AgByB&Ta
AgByB&Tb
AgByB&T
Conformational (nonsequential) Epitope in
Hen Egg White
Lysozyme.
Antigens in Immunologically-Based
Clinical Diagnosis and Pathology
Cancer Antigens in Diagnosis of Cancer
Carcino-Embryonic Antigen (CEA)
Prostate Specific Antigen (PSA)
Ovarian Cancer Antigen (CA 125)
Whole-body Imaging of Metastatic Colon Carcinoma
A33 Antigen
Anti-Human Chorionic Gonadotropin Pregnancy Test
(Early Home Pregnancy Test)
Type II Allergic Hypersensitivity
Blood Group Antigens in Transfusions
Hemolytic Disease of New-Borns: Rh Antigen incompatibility
Super-Antigens in Toxic Shock Syndrome
Med&Ags
Antigens in Immunologically-Based
Treatment of Cancers and Other Pathologies:
(Specifics Later)
Cancer Antigens as Targets for Therapy
Radioactively-labeled Antibodies
Cytolytic Antibodies
Specifically Activated Antigen-presenting Cells.
Imaging with Antibodies Carrying
“Reporter Groups”
Radioactive Isotopes
Fluorescent Groups (“Chromophores”)
Metals
Antigen-Antibody Interactions in Research and Clinical
Medicine
e.g. Radioactively labeled monoclonal antibody
reacting with tumor cell antigens in detection of
metastatic colon cancer
Imaging on Metastatic Colon Carcinoma with
Radioactive-Iodine-Labelled Monoclonal Ab to A33 Ag
Lloyd Old, Scientific American, August, 1996, p. 138)
SeeMets
Arm
Head
Antihapten Antibodies in the Detection and
Measurement of Small Molecules
For example:
Anti-HCG (Human chorionic gonadotrophin) antibody
in the detection of soluble HCG in urine
AntiHCG
What will happen
when concentration of
Anti-HCG-Ab is about
equal to Haptencarrier conjugate?
What will happen when you put excess soluble hapten in the
way of the anti-HCG-Ab?
PregTest
Antibodies in Blood Transfusions
Antibodies to A, B, O Blood Group Antigens
Pre-existing Antibodies to Non-tolerated (Unmatched)
Blood Group Antigens : “Isohemagglutinins”
ABOTypes
ABOAb
See Figure 15-13 (b), p. 389,
Kuby, 6th Edition
Not a hexasaccharide
(No terminal sugar)
ABOSugar
See Figure 15-13 (a), p. 389,
Kuby, 6th Edition
Galactose
Antibodies in Hemolytic Disease of the New-born
(HNDB)
(Rh-Factor Sensitization)
Rh-Factor positive baby – Rh Negative Mother
HDNB
See Figure 15-14
p. 390, Kuby
6th Edition
HDNBPhoto
AntiRhAb
Following are three Turning Point short answer questions.
Please put all notes on the floor.
Do not have any electronic devices other than your NXT transmitter.
No consulting with other students.
If you have a problem with your device, I can provide you with a
loaner NXT device.
If you have a problem using your NXT device, please ask Elisabeth
for help.
It is imperative that the integrity of these in-class Turning Point
quizzes be maintained at the same level as we will do with the three
written exams.
“Fill-in-the Blank” Question:
Hemolytic disease of the new-born is caused by maternal
__ __ __ __ __ __ __ __ __ __
attacking the fetus in utero.
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“Fill-in-the Blank” Question:
RhoGam is an antibody that prevents sensitization of the Rh- mother
by cells from her fetus. Why does that work?
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“Fill-in-the Blank” Question:
The antibody to Human Chorionic Gonadotrophin fails to cross link the
HCG-hapten carrier conjugate and fails to make a precipitate if urine
from a pregnant woman is added to the mixture. What is in the urine that
is preventing the formation of the precipitate? Abbreviations are OK
______________________________________
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Immunopathology of Bacterial Septic Shock
Caused by Gram Negative Bacterial Endotoxins:
Examples E. coli
Pseudomonas aeruginosa
Neisseria meningitidis
Meningococcus
70,000 Deaths per year
Diarrhea, Fever, Blood Clotting, Blood Pressure Drop
Macrophage Activation by Endotoxin:
Generates systemic cytokine production IL1 and TNF-alpha (Tumor necrosis factor)
SepticShock
Immunopathology of Bacterial Toxic Shock
Exotoxins Secreted or Present Membrane Bound:
Act as "Superantigens"
Examples Staphylococcus aureus:
TSST1 (Toxic Shock Syndrome Toxin)
Streptococcus pyrogenes - Rheumatic fever and shock
Staphylococcus enterotoxins: Food poisoning
Superantigens cross-link TCR with Antigen-presenting
Cell MHC Class II Proteins
Generates systemic cytokine production - IL1 and TNFalpha (Tumor necrosis factor)
ToxicShock
SuperAg
Staphylococcal enterotoxins (food poisoning)
Streptococcal pyrogenes exotoxins (rheumatic
fever, toxic shock)
See Table 11-2, p. 367
See Figure 11-6
7th Edition p. 367
Mitogens and Lectins
Mitogens: Stimulate mitosis and cell division non-specifically
(non-specific therefore stimulate polyclonally)
Lectins: Proteins that bind to carbohydrate in glycoproteins
(Can be potent mitogens)
Glycoproteins: Conjugated protein with covalently attached
carbohydrate residues
Examples of Mitogens
Concanavalin A (Con A) : Non-specific T-cell mitogen
Phytohemaglutinin (PHA): Non-specific T-cell mitogen
Pokeweed Mitogen (PWM): Non-specific T- and B-cell
Mitogen
Lipopolysaccharide (LPS): Gram negative bacterial cell wall
component
Potent Polyclonal (non-specific) B-Cell Mitogen
Immune Adjuvants and the Immunogenicity of Vaccines
(See Scientific American, October, 2009)
Boosting Vaccine Power, pp 72 to 79
Activating Antigen-presentation by Cells of the Innate
Natural Immune Response
e.g. Purified derivatives of bacterial lipo-polysaccharides
Bacterial DNA derivatives
Bacterial flagellin protein
Specific Activation of Antigen-presenting Cells
Extra-corporeally (outside of the body)
Dendritic Cell Vaccines
See Dendreon
Innate Natural Immunity and Systemic Sepsis:
NOVA Video on Meningitis (Meningococcal Meningitis,
Endotoxin, and Systemic Sepsis)
http://www.pbs.org/wgbh/nova/meningitis/
Has video links to steps in meningococcal sepsis
“Amy’s Story”
and related NOVA Stories
tpfondy.mysite.syr.edu
The Story of the Oakwood Children
See “Song of the Oakwood Children” as a self-running
presentation
“Fill-in-the Blank” Question:
Human chorionic gonadotrophin (HCG) is a small peptide made
immunogenic by being conjugated with a large molecular weight carrier
molecule. Thus HCG is a special kind of antigen and is an example of a
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We watched the first part of a NOVA video called
“Killer Disease on Campus”
What is the “Killer Disease”
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5. No problem. Please get moving!
4. Maybe a bit too fast, but mostly OK.
3. I’m following OK, I can catch up with what I miss.
4. I’m struggling to keep up. It’s too much too fast.
5. I’m lost
(This slide is anonymous. I won’t know who you are)
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Duration: 0 Seconds
Testing doing a “Fill-in-the Blank” Question:
Please send in your last name up to the first five
letters:
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“Fill-in-the Blank” Question:
A small organic molecule such as fluoro-dinitro benzene
can be made immunogenic by attaching it to a
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