Antigen Structure and Immunogenicity
Updated: September 16, 2014
Folder Title: Antigens(NoTP)(Without TP Slides)
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)*• (* When the antigen is being presented to the TCR on a
specific set of cell-membrane proteins called MHC)
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
Fig.4-6bKuby3rd Ed
AgAb
Sep
Influenza Virus AntigenAntibody Heavy ChainVariable Region
Antibody Light Chain Variable Region
Antigen-Antibody Complementarity
Antigen - Antibody BindingAntibody Light Chain
Variable Region
Fig.
4-6a
Kuby
3rd Ed
AgAb
KissInfluenza Virus Antigen
Antibody Heavy Chain
Variable Region
Prot2nd
Primary sequential epitopes in
sperm whale myoglobin
(Epitopes are antigenic determinants inMacromolecules)
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)
Myoglobin Single Polypeptide
17,000 MW (Tertiary Structure)
About 7 secondary domains. One bound Heme in hydrophobic
Hemoglobin: a2b2 Tetramer64,000 MWOne heme per subunit
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. Geneticb. Physiological
3. Mode of Antigen Exposure
ImGenFx1
ImGenFx2
Called “H2” in Mice; “HLA” in HumanHLA = Human Leucocyte-associated Antigens
Immunogenicity of Antigens and the MHC Gene Collection:MHC = Major Histocompatibility ComplexHaplotype = a set of closely linked genes controlling the immune response. Haplotype is usually transferred to progeny as a linked set
Antigen #1 Antigen #2
Ag&MHCbAg 1 Ag 2
Two different antigens
Ag&MHCcAg 1 Ag 2
Two different antigens
Ag&MHCdAg 1 Ag 2
Two different antigens
Ag&MHCAg 1 Ag 2
Two different antigens
ImGenFx3
ImAdmin
Conformational Properties of Epitopes for Antibodies
64
80
Hen Egg-White Lysozyme: Conformations of Sequence 62 to 80
Anti-hapten Antibodies
AbHaptenSee Figure 4-1p. 77Kuby, 6th Edition
To Here Sept. 11
AgByB&Ta
AgByB&Tb
AgByB&T
Conformational (non-sequential) 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
Antigens in Immunologically-BasedTreatment 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 IsotopesFluorescent 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
SeeMets
Arm
Head
Imaging on Metastatic Colon Carcinoma with Radioactive-Iodine-Labelled Monoclonal Ab to A33 AgLloyd Old, Scientific American, August, 1996, p. 138)
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
AntiHCGWhat will happen when concentration of Anti-HCG-Ab is about equal to Hapten-carrier 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
Pre-existing serum antibodies from exposure to bacterial antigens that mimic antigens on red blood cells
ABO Blood Group Genotypes, Phenotypes, Antigens andSerum Antibodies Present
ABOSugar
See Figure 15-13 (a), p. 389,
Kuby, 6th EditionGalactose
Not a hexasaccharide(No terminal sugar)
Antibodies in Hemolytic Disease of the New-born (HDNB)
(Rh-Factor Sensitization)
Rh-Factor positive baby – Rh Negative Mother
HDNB
See Figure 15-14p. 390, Kuby6th 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.
Immunopathology of Bacterial Septic Shock Caused by Gram Negative Bacterial Endotoxins:Examples -E. coliPseudomonas aeruginosaNeisseria meningitidisMeningococcus
70,000 Deaths per yearDiarrhea, Fever, Blood Clotting, Blood Pressure Drop
Macrophage Activation by Endotoxin:Generates systemic cytokine production -IL1 and TNF-alpha (Tumor necrosis factor)
Immunopathology of Bacterial Toxic Shock Exotoxins Secreted or Presented Membrane Bound:Act as "Superantigens"Examples -Staphylococcus aureus: TSST1 (Toxic Shock Syndrome Toxin)Streptococcus pyrogenes - Rheumatic fever and shockStaphylococcus enterotoxins: Food poisoning
Superantigens cross-link TCR with Antigen-presenting Cell MHC Class II Proteins
Generates systemic cytokine production - IL1 and TNF-alpha (Tumor necrosis factor)
SuperAg
See Figure 11-67th Edition p. 367
Staphylococcal enterotoxins (food poisoning)Streptococcal pyrogenes exotoxins (rheumatic fever, toxic shock)See Table 11-2, p. 367, 7th Edition
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-polysaccharidesBacterial DNA derivativesBacterial flagellin protein
Specific Activation of Antigen-presenting Cells Extra-corporeally (outside of the body)
Dendritic Cell VaccinesSee 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
Following are two 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.
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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