Questions and Answers
What is a pathogen?
A biological infectious agent that causes disease or illness to its host.
Which of the following are types of antigens?
What must T cells require for recognizing an antigen?
What is the definition of an immunogen?
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Haptens are complete antigens that can stimulate antibody production without a carrier.
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What are exogenous antigens?
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What is an epitope?
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Which factor does NOT determine antigenicity?
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Study Notes
Definition of Pathogens and Antigens
- Pathogens are infectious biological agents causing disease or illness in hosts.
- Antigens (Ags) can be foreign substances like microorganisms and toxins, or body proteins expressed abnormally (e.g., tumor cells, transfused blood, transplanted organs).
- Immunogenicity refers to the ability to induce an immune response.
Recognition of Antigens
- Antigens are found on the surface and inside bacteria or viruses.
- T cells and B cells recognize these antigens.
- T cells need antigens to be ingested, degraded, and presented by Antigen Presenting Cells (APCs) alongside Major Histocompatibility Complex (MHC) proteins.
Classification of Antigens
- Antigens can be classified based on:
- Immunogenicity
- Origin
- Source
- Biological classification
Immunogenicity
- Complete antigens (immunogens) can stimulate antibody formation.
- Haptens are small molecules that require conjugation with larger molecules to induce antibody production.
Origin of Antigens
- Exogenous antigens enter the body from outside sources (inhalation, ingestion, injection) and are processed by APCs, presented to helper T cells via MHC type II.
- Endogenous antigens are generated within cells, either from metabolism or pathogen infections, and presented to cytotoxic T cells with MHC type I.
Epitope or Antigenic Determinant
- An epitope is a specific site on an antigen that binds with antibodies or T cell receptors.
Determinants of Antigenicity
- Factors affecting antigenicity include:
- Size: Larger molecules are more antigenic.
- Nature of the antigen
- Foreignness of the substance
- Susceptibility to tissue enzymes
- Exposure to the antigen
- Presence of adjuvants
- Antigenic specificity
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Description
This quiz covers the definitions, recognition, and classification of pathogens and antigens. It explores the roles of T cells and B cells in recognizing these biological agents and the concept of immunogenicity. Test your knowledge on how these components interact in the immune response.
