Nature of Antigens and the Major Histocompatibility Complex Flashcards
An ____ is a substance that is specifically recognized by the adaptive immune system.
Antigen
____ is capable of binding to antibodies.
Antigen
____ can’t stimulate antibody production.
Antigen
Antigens can be ____.
Immunogenic or Non-immunogenic
An ____ is a substance capable of causing adaptive response.
Immunogen
____ can bind to antibodies and stimulate its production.
Immunogen
What is the chief distinction between antigens and immunogens?
- Antigen = cannot stimulate immune response.
- Immunogen = can stimulate immune response.
TRUE OR FALSE.
All immunogens are antigens, and all antigens are immunogens.
False
Reason: Antigens cannot stimulate antibody production.
TRUE OR FALSE.
Hapten alone can stimulate antibody production.
False
Reason: Haptens need to bind to carrier-protein first.
Factors Influencing the Immune Response
- Age
- Dose
- Route of Inoculation
- Health status
- Genetics
↑ immune dose = ____.
↑ immune response
____ is the ability of an immunogen to stimulate a host response.
Immunogenicity
Traits of Immunogen
- Macromolecular size
- Chemical composition and molecular complexity
- Foreigness
- Ability to be processed and presented with MHC molecules
The best immunogens have a molecular weight of ____.
100,000 Da
Immunogens should have a molecular weight of at least ____ in order to be recognized.
10,000 Da
The best immunogens have a chemical composition of ____.
proteins and polysaccharides
Immunogens composed of ____ are less immunogenic.
carbohydrates
Immunogens composed of ____ are non-immunogenic.
lipids and nucleic acid
What kind of antigens are not foreign in the body?
Self-antigens
Why can’t Haptens cause immune response on their own?
Because they’re small in size
Main Parts of Antigen
- Antigenic determinant/ Epitope
- Carrier
____ are molecular shapes or configurations that are recognized by B or T cells.
Antigenic determinants (Epitope)
____ is where the antibody binds.
Antigenic determinant (Epitope)
An epitope can be ____.
- Sequential
- Linear
- Conformational
____ are non-immunogenic materials that, when combined with a carrier, create new antigenic determinants.
Haptens
____ is responsible to give the antigen its required size.
Carrier
____ are usually made up of protein.
Carriers
Carriers are usually made up of ____.
protein
The ____ is the number of combining sites.
Valence
____ are precise molecular shapes or configurations recognized by B cells, or the peptide sequences detected by T cells.
Epitopes
Kinds of Epitope
- Linear
- Conformational
Kinds of Epitope
____ consist of sequential amino acids on a single polypeptide chain.
Linear epitopes
Kinds of Epitope
____ result from the folding of one or more polypeptide chains.
Conformational epitopes
____ are capable to recognize both linear and conformational epitopes.
B cells
B cells are capable to recognize ____ epitope.
linear and conformational epitopes
____ respond to linear epitopes.
T cells
T cells are capable to recognize ____ epitope.
linear
____ are substances administered with an immunogen that increases the immune response.
Adjuvants
____ are substances added to the vaccine in order to enhance the immune response.
Adjuvants
How do adjuvants enhance the immune response?
- By prolonging the existence of immunogen.
- By increasing the effective size of immunogen.
- By increasing the number of macrophages involved in antigen processing.
Types of Antigens
- Autoantigens
- Alloantigens
- Heteroantigens
- Heterophile antigens
Types of Antigens
____ are those antigens that belong to the host.
Autoantigens (self-antigens)
Types of Antigens
____ are from other members of the host’s species, and these are capable of eliciting an immune response.
Alloantigens
Types of Antigens
____ are from other species, such as plants, animals, or microorganisms.
Heteroantigens
Types of Antigens
____ are heteroantigens that exist in unrelated plants or animals but are either identical or closely related in structure so that antibody to one will cross-react with antigen of the other.
Heterophile antigens
____ is a large multi-gene locus consisting of several thousand kilobase pair of DNA on a single chromosome.
Major Histocompatibility Complex (MHC)
MHC is also known as ____.
Human Leukocyte Antigens (HLA)
HLA is a complex located at ____.
chromosome 6
____ brings antigen to the cell surface for recognition by T cells.
Human Leukocyte Antigens (HLA)
MHC is found on ____.
human chromosome 6
Roles of MHC
- Intercellular recognition and discrimination of self/non-self.
- Development of humoral and cell-mediated immune responses.
- Susceptibility to disease and autoimmunity
____ have a role in intercellular recognition and discrimination of self/non-self.
Major Histocompatibility Complex (MHC)
____ have a role in development of humoral and cell-mediated immune responses.
Major Histocompatibility Complex (MHC)
____ plays a role in susceptibility to disease and autoimmunity.
Major Histocompatibility Complex (MHC)
Nature of HLA Antigens
- Glycoprotein component of cell membrane
- Present in all nucleated cells
- Products of the genes of MHC
MHC molecules are found on the ____ of chromosome 6.
short arm
Three Categories of MHC
- Class I
- Class II
- Class III
Categories of MHC
____ are coded for at three different locations or loci, termed A, B, and C.
Class I molecules
Categories of MHC
____ are situated in D region, and have several different loci, known as DR, DQ, and DP.
Class II
Categories of MHC
____ code for complement proteins and cytokines such as tumor necrosis factor.
Class III
Class I MHC Molecules
Cellular Distribution
- All nucleated cells
- Low/undetectable in: liver hepatocyte, neural cells, muscle cells, and sperm cells.
Which MHC Category?
Present in all nucleated cells
Class I MHC
The highest concentration of MHC Class I molecules is found in ____.
- Lymphocytes
- Myeloid cells
Class I MHC Molecules
Structure
One α-chain + β2 microglobulin
Which MHC Category?
One α-chain + β2 microglobulin
Class I MHC
Class I MHC Molecules
The α-chain is located at ____.
chromosome 6
Class I MHC Molecules
The β2 microglobulin is located at ____.
chromosome 15
Class I MHC Molecules
Classes
HLA: A, B, C
Which MHC Category?
HLA: A, B, C
Class I MHC
Class I MHC Molecules
Non-classical classes
HLA: E, F, G
Which MHC Category?
HLA: E, F, G
Non-classical classes
Class I MHC
Class I MHC Molecules
Size of peptide bonds
8 - 11 amino acids
Which MHC Category?
8 - 11 amino acids
Class I MHC
Class I MHC Molecules
Nature of peptide binding cleft
Closed at both ends
Which MHC Category?
Nature of peptide binding cleft: Closed at both ends
Class I MHC
Class I MHC Molecules
Interaction with T-cells
Present endogenous (intracellular) antigen to CD8+ T-cells
Which MHC Category?
Present endogenous (intracellular) antigen to CD8+ T-cells
Class I MHC
Class II MHC Molecules
Cellular Distribution
- B cells
- Thymocytes
- Macrophages
- Dendritic cells
- Thymic epithelial cells
Which MHC Category?
____ are usually found in antigen-presenting cells (APCs).
Class II MHC
The most effective APC is the ____.
dendritic cells
____ have high levels of MHC Class II.
Dendritic cells
Class II MHC Molecules
Structure
α-chain + β chain
Which MHC Category?
α-chain + β chain
Class II MHC
Class II MHC Molecules
Classes
HLA: DP, DQ, DR
Which MHC Category?
HLA: DP, DQ, DR
Class II MHC
Class II MHC Molecules
Non-classical classes
HLA: DM, DN, DO
Which MHC Category?
HLA: DM, DN, DO
Class II MHC
Class II MHC Molecules
Size of peptide bonds
13 - 18 amino acids
Which MHC Category?
13 - 18 amino acids
Class II MHC
Class II MHC Molecules
Nature of peptide binding cleft
Open at both ends
Which MHC Category?
Nature of peptide binding cleft: Open at both ends
Class II MHC
Class II MHC Molecules
Interaction with T-cells
Present exogenous antigen to CD4+ T-cells
Which MHC Category?
Present exogenous (intracellular) antigen to CD4+ T-cells
Class II MHC
The main role of the ____ is to bind peptides within cells and transport them to the plasma membrane, where T cells can recognize them in a phenomenon.
Class I and Class II MHC molecules
Application of HLA Typing/Matching
- Organ transplantation
- Paternity Testing
- Forensic medicine, anthropology
- Studies of racial ancestry and migration
- Diagnostic and genetic counselling
- Basic research
HLA B27
Ankylosing Spondylitis,
Reiter’s Syndrome
Ankylosing Spondylitis,
Reiter’s Syndrome
HLA B27
HLA B47
Congenital Adrenal Hyperplasia
Congenital Adrenal Hyperplasia
HLA B47
HLA B5
Behcet’s Disease
Behcet’s Disease
HLA B5
HLA CW6
Psoriasis Bulgaris
Psoriasis Bulgaris
HLA CW6
HLA DR3
Type 1 Diabetes Mellitus
Type 1 Diabetes Mellitus
HLA DR3
HLA DR4
Rheumatoid Arthritis
HLA DR5
Gold Induce Nepropathy,
Kaposi’s Sarcoma, Chronic Lymphatic Leukemia
Gold Induce Nepropathy,
Kaposi’s Sarcoma, Chronic Lymphatic Leukemia
HLA DR5
HLA B8
HIV Infection
HIV Infection
HLA B8