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Definition of Antigens and Immunogens
What are antigens?
Substances that can provoke an immune response.
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Definition of Antigens and Immunogens
What are immunogens?
Antigens that are capable of inducing an immune response.
What are common types of antigens?
Proteins, polysaccharides, lipids, and nucleic acids.
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Immunogenicity Factors
What is the relationship between chemical complexity and immunogenicity?
Complex antigens with multiple epitopes can be recognized by antibodies or immune cells, increasing immunogenicity.
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Epitopes and Their Recognition
How do B cells recognize antigens?
B cells recognize native, unprocessed antigens with epitopes formed by various molecules (e.g., peptides, carbohydrates, lipopolysaccharides).
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Immunogenicity Factors
Why are protein antigens considered the most immunogenic?
Because proteins are usually large, complex structures with multiple epitopes.
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Molecules Involved in Antigen Recognition
What is the result of PRRs binding to PAMPs?
An inflammatory response leading to the killing of pathogens.
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Immunogenicity Factors
How does molecular weight affect the immunogenicity of polysaccharide antigens?
Polysaccharide antigens are more immunogenic if they have high molecular weight.
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Major Histocompatibility Complex (MHC) Molecules
What is the primary function of MHC molecules?
For antigen presentation and to discriminate self from non-self.
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Haptens and Their Role
What are haptens?
Small epitopes that are non-immunogenic.
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Haptens and Their Role
What is the formula for making haptens immunogenic?
Hapten + Carrier Molecule = Immunogenic Complex.
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Molecules Involved in Antigen Recognition
What do pattern recognition receptors (PRRs) recognize?
Pathogen-associated molecular patterns (PAMPs) characteristic of pathogens.
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Immunogenicity Factors
What are the pros of antibody cross reactivity?
Can provide broader immune protection.
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B-cell and T-cell Receptors
Where is the T-cell receptor (TCR) found?
On the surface of T-cell membranes.
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Molecules Involved in Antigen Recognition
What role do T-cell receptors play in antigen recognition?
They recognize processed antigens presented by Major Histocompatibility Complex (MHC) molecules.
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B-cell and T-cell Receptors
What is the role of CD4 and CD8 co-receptors on T cells?
They bind to MHC molecules.
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Haptens and Their Role
What can haptens be made immunogenic by?
Attaching covalently to larger carrier molecules.
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Haptens and Their Role
What is the application of haptens in immunology?
Production of conjugate vaccines.
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Haptens and Their Role
What is an example of an antigen that cannot induce an immune response?
Haptens can react with specific antibodies but cannot induce any immune response.
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Immunogenicity Factors
What does avidity refer to in the context of antibodies?
The overall binding strength between multiple epitopes and antigen binding sites.
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Chemical Composition of Antigens
What are polysaccharide antigens?
Antigens that are composed of polysaccharides and vary in immunogenicity.
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Molecules Involved in Antigen Recognition
What is the function of Major Histocompatibility Complex (MHC) molecules?
To present antigen fragments to T-cells.
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Molecules Involved in Antigen Recognition
What is the significance of the specificity of antibodies?
It allows for targeted immune responses against specific pathogens.
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Epitopes and Their Recognition
What is antibody cross reactivity?
The ability of an antibody to react with more than one epitope or antigen.
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Molecules Involved in Antigen Recognition
Which immune system utilizes pattern recognition receptors?
The innate immune system.
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Immunogenicity Factors
What factors determine the immunogenicity of antigens?
Size, complexity, foreignness, and the presence of adjuvants.
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Molecules Involved in Antigen Recognition
How do antibodies recognize antigens?
By binding to specific epitopes on the antigen.
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B-cell and T-cell Receptors
What type of antigens do T-cell receptors recognize?
Processed peptide antigen fragments displayed on MHC molecules.
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Immunogenicity Factors
How does the complexity of an antigen affect its immunogenicity?
More complex antigens tend to be more immunogenic due to increased epitope diversity.
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Major Histocompatibility Complex (MHC) Molecules
How are non-self antigens presented?
On self Major Histocompatibility Complex (MHC) molecules.
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B-cell and T-cell Receptors
What happens when B cells are stimulated by an antigen?
They secrete antibodies with antigen-binding sites identical to those on their BCR.
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Immunogenicity Factors
What is a potential application of spherical nucleic acids?
Drug delivery without provoking undesirable host immune response.
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Epitopes and Their Recognition
What are the two types of epitopes found in protein antigens?
Linear epitopes and conformational epitopes.
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Chemical Composition of Antigens
How are lipid antigens recognized in the immune response?
They are recognized by some T cells.
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Antibody Structure and Function
What are antibodies primarily composed of?
Glycoproteins that bind antigens with high specificity and affinity.
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Immunogenicity Factors
What is immunogenicity?
The ability of an antigen to provoke an immune response.
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Antibody Structure and Function
What are the five different classes of antibodies?
IgM, IgD, IgG, IgA, and IgE.
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Immunogenicity Factors
What is the importance of the host's genetic background in immunogenicity?
Genetic factors can influence how effectively an antigen is recognized and responded to.
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Definition of Antigens and Immunogens
What are non-self antigens?
Antigens that are foreign to the body and are more immunogenic.
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Chemical Composition of Antigens
Which types of lipid antigens can be presented by antigen-presenting cells (APC)?
Some glycolipids and phospholipids.
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Epitopes and Their Recognition
What defines linear epitopes?
They consist of 6-8 contiguous amino acids.
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Molecules Involved in Antigen Recognition
What are the primary molecules involved in the recognition of antigens?
Antibodies and T-cell receptors.
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Antibody Structure and Function
What forms the antigen binding sites in antibodies?
Variable heavy (VH) and light (VL) chains.
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Epitopes and Their Recognition
What is an epitope?
The smallest unit of an antigen to which an antibody or immune cell can bind.
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Chemical Composition of Antigens
What are lipid antigens characterized by?
They are weakly immunogenic.
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Chemical Composition of Antigens
What are spherical nucleic acids composed of?
A shell of nucleic acids conjugated to solid nanoparticles.
What is an example of a polysaccharide antigen?
ABO blood group antigens.
What are examples of antigens?
Microbes, parasites, and toxins.
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Immunogenicity Factors
How does the route of exposure influence immunogenicity?
Different routes (e.g., injection, ingestion) can affect the immune response generated.
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Immunogenicity Factors
What happens if the body is not tolerant to self antigens?
An autoimmune disease occurs.
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Major Histocompatibility Complex (MHC) Molecules
On what molecules are T cell epitopes presented?
On Major Histocompatibility Complex (MHC) molecules.
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Immunogenicity Factors
What is antibody affinity?
The strength of binding between an epitope and an antigen binding site.
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Chemical Composition of Antigens
What type of immune response is triggered by lipid antigens?
Cell-mediated immune response.
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Antibody Structure and Function
What is the basic structure of an antibody?
A Y-shaped structure formed by 4 polypeptide chains: 2 identical pairs of light (L) chains and heavy (H) chains joined by disulphide bonds.
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Molecules Involved in Antigen Recognition
What types of MHC molecules are there?
MHC class I and MHC class II.
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Immunogenicity Factors
What is the significance of the chemical composition of an antigen?
Certain chemical structures are more likely to elicit an immune response.
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B-cell and T-cell Receptors
What is a B-cell receptor (BCR)?
A membrane-bound antibody molecule (IgM and IgD isotypes).
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Definition of Antigens and Immunogens
What are immunogens?
Antigens that can stimulate an immune response.
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Immunogenicity Factors
What is the immunogenicity of molecules with a molecular weight less than 10,000 Da?
They are weak immunogens.
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Epitopes and Their Recognition
What causes antibody cross reactivity?
The similarity of some epitopes or antigens.
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Immunogenicity Factors
What are the cons of antibody cross reactivity?
May lead to false positives in tests or autoimmune reactions.
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Antibody Structure and Function
Why does IgM have high avidity despite its low affinity?
Because IgM has 10 binding sites, which increases overall binding strength.
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Antibody Structure and Function
How many antigen binding sites do antibodies have?
Two antigen binding sites (paratopes).
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Immunogenicity Factors
How does the presence of adjuvants affect immunogenicity?
Adjuvants enhance the immune response to antigens, increasing their immunogenicity.
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Immunogenicity Factors
Which type of egg is more immunogenic, raw or boiled?
Raw eggs are more immunogenic than boiled eggs.
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Epitopes and Their Recognition
What type of epitopes do T cells recognize?
Processed peptide epitopes that are approximately 10 amino acids long.
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Immunogenicity Factors
Are very small molecules, such as a single amino acid, immunogenic?
No, they are non-immunogenic.
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Molecules Involved in Antigen Recognition
Where are PRRs mainly expressed?
By phagocytes and antigen-presenting cells.
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Molecules Involved in Antigen Recognition
How are antigens recognized in the immune system?
By antibodies, B-cell receptors, and T-cell receptors.
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Antibody Structure and Function
What are the two main fragments of an antibody?
Antigen binding (Fab) and constant (Fc) fragments.
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Major Histocompatibility Complex (MHC) Molecules
Where are MHC class II molecules located?
On antigen-presenting cells.
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Definition of Antigens and Immunogens
What are antigens?
Molecules that can be recognized by the immune system (e.g., by B-cell receptors or T-cell receptors).
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Chemical Composition of Antigens
What are the primary chemical compositions of most antigens?
Proteins, carbohydrates, and some may contain lipids and nucleic acids.
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Definition of Antigens and Immunogens
Can all antigens induce an immune response?
No, not all antigens are immunogens.
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Epitopes and Their Recognition
What are conformational epitopes?
Protein segments that are folded into a tertiary structure.
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B-cell and T-cell Receptors
What are the two polypeptide chains that make up the T-cell receptor?
Alpha (α) and beta (β) chains.
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Major Histocompatibility Complex (MHC) Molecules
What do MHC class I molecules present?
Peptide fragments from intracellular antigens.
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B-cell and T-cell Receptors
What type of structure do B-cell receptors recognize?
3D structure (conformation) of unprocessed antigens.
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Definition of Antigens and Immunogens
Are all immunogens considered antigens?
Yes, all immunogens are antigens.
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Chemical Composition of Antigens
What do dendritic cells use to present lipid antigens?
CD1, which is functionally similar to MHC II.
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Antibody Structure and Function
How does the affinity of IgG compare to that of IgM?
IgG has high affinity for its target, while IgM has low affinity.
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Antibody Structure and Function
What is the significance of high affinity in IgG?
It allows for more specific binding to its target.
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Immunogenicity Factors
What role does the size of an antigen play in immunogenicity?
Larger antigens are generally more immunogenic than smaller ones.
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Major Histocompatibility Complex (MHC) Molecules
What do MHC class II molecules present?
Peptide fragments from extracellular antigens.
