16 Questions
What is the definition of an antigen?
An agent that can specifically bind to components of the immune response
What is the definition of an immunogen?
An agent that can induce an immune response
What happens to haptens when coupled with carrier macromolecules?
They become immunogenic
What are antigen determinants (ADS) or epitopes?
Small sites on the antigen surface to which antibodies or T-lymphocytes can bind
Why do changes in antigen determinants influence the specificity of antigen molecules?
They lead to changes in the binding sites for antibodies or T-lymphocytes
What type of molecule is penicillin antibiotic?
A hapten
What is antigen valency?
The number of epitopes on an antigen molecule that bind to the antibodies
What is cross reactivity?
The production of antibodies that react with shared epitopes on unrelated antigens
Which factor influences immunogenicity by increasing the degree of foreignness?
Genetic constitution of the animal
What type of substances are potent immunogens according to the text?
Proteins and polysaccharides
What is the function of an adjuvant in immunogenicity?
To induce a stronger immune response against the antigenic substance
What is the minimum molecular weight for a substance to be considered a potent immunogen?
Above 100,000 Dalton
Which route of administration induces better immune response according to the text?
Subcutaneous or intramuscular injection
What is the disadvantage of cross reactivity mentioned in the text?
Development of autoimmune disease
What type of substances are non-immunogenic unless conjugated with proteins according to the text?
Pure lipids and nucleic acids
What influences the degree of immunogenicity as chemical complexity increases?
As the degree of chemical complexity increased, the degree of immunogenicity increased.
Study Notes
Antigens and Immunogens
- An antigen is a substance that can trigger an immune response, binding to antibodies or immune cells.
- An immunogen is a type of antigen that can induce an immune response, generating antibodies or immune cells.
Haptens
- Haptens are small molecules that can bind to antibodies but cannot induce an immune response on their own.
- When haptens are coupled with carrier macromolecules, they can trigger an immune response.
Antigen Determinants (Epitopes)
- Antigen determinants (ADS) or epitopes are the specific regions on an antigen molecule that are recognized by antibodies or immune cells.
- Changes in antigen determinants influence the specificity of antigen molecules because they affect the binding sites for antibodies or immune cells.
Antigen Properties
- Penicillin antibiotic is a hapten, a small molecule that can bind to antibodies but cannot induce an immune response on its own.
- Antigen valency refers to the number of binding sites on an antigen molecule.
- Cross-reactivity occurs when an antibody or immune cell binds to multiple antigens with similar epitopes.
Immunogenicity
- Increasing the degree of foreignness of an antigen influences its immunogenicity.
- Potent immunogens are typically complex molecules, such as proteins, polysaccharides, or lipids.
- The function of an adjuvant is to enhance the immunogenicity of an antigen by increasing the immune response.
- The minimum molecular weight for a substance to be considered a potent immunogen is approximately 4,000-6,000 Da.
Administration and Immune Response
- The route of administration that induces a better immune response is parenteral (injection), as it allows for direct delivery of the antigen to immune cells.
Disadvantages and Limitations
- The disadvantage of cross-reactivity is that it can lead to false positive results in diagnostic tests or autoimmune diseases.
Non-Immunogenic Substances
- Small molecules, such as haptens, are non-immunogenic unless conjugated with proteins.
- Chemical complexity influences the degree of immunogenicity, with more complex molecules being more immunogenic.
Test your knowledge about immunogens and antigens with this quiz from the Microbiology department at Faculty of Veterinary Medicine, Alexandria University. Explore concepts such as the definition of antigens and immunogens, and their roles in inducing an immune response.
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