Dr. Safaa Al Meani PhD Biotechnology lecture No.4 Page 1
رابنلاا ةعماج
مولعلا ةيلك
تاينقتلا مسقةيئايحلأا
ةداملا مسا: ةعانملا
Antigen : ة ر
ضاحملا ناونع
ر
نيعملا فيطل دبع ءافص روتكدلا دعاسملا ذاتسلاا
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A lecture on antigens and immunogens given by Dr. Safaa Al Meani at the University of Anbar. It defines and explains the different types of antigens, including immunogens, haptens, and epitopes. It also discusses the chemical nature of immunogens and the types of antigens, including T-independent and T-dependent antigens and superantigens.
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2022/2023
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Antigen ة :عنوان المحاض ر
االستاذ المساعد الدكتور صفاء عبد لطيف المعين^ ر
ANTIGENS
DEFINITIONS
Immunogen : A substance that induces a specific immune response.
Antigen (Ag): A substance that reacts with the products of a specific immune response.
Hapten: A substance that is non-immunogenic but which can react with the products of a specific immune response. Haptens are small molecules which could never induce an immune response when administered by themselves but which can when coupled to a carrier molecule. Free haptens, however, can react with products of the immune response after such products have been elicited. Haptens have the property of antigenicity but not immunogenicity.
Epitope or Antigenic Determinant That portion of an antigen that combines with the products of a specific immune response.
Antibody (Ab): A specific protein which is produced in response to an immunogen and which reacts with an antigen.
2 - Contribution of the Biological System
Genetic Factors
Some substances are immunogenic in one species but not in another. Similarly, some substances are immunogenic in one individual but not in others ( i.e. responders and non- responders). The species or individuals may lack or have altered genes that code for the receptors for antigen on B cells and T cells or they may not have the appropriate genes needed for the APC to present antigen to the helper T cells.
Age Age can also influence immunogenicity. Usually the very young and the very old have a diminished ability to mount and immune response in response to an immunogen.
3 - Method of Administration
Dose The dose of administration of an immunogen can influence its immunogenicity. There is a dose of antigen above or below which the immune response will not be optimal.
Route Generally the subcutaneous route is better than the intravenous or intragastric routes. The route of antigen administration can also alter the nature of the response
Adjuvants Substances that can enhance the immune response to an immunogen are called adjuvants. The use of adjuvants, however, is often hampered by undesirable side effects such as fever and inflammation
CHEMICAL NATURE OF IMMUNOGENS
Proteins The vast majority of immunogens are proteins. These may be pure proteins or they may be glycoproteins or lipoproteins. In general, proteins are usually very good immunogens.
Polysaccharides Pure polysaccharides and lipopolysaccharides are good immunogens.
Nucleic Acids Nucleic acids are usually poorly immunogenic. However, they may become immunogenic when single stranded or when complexed with proteins.
Lipids In general lipids are non-immunogenic, although they may be haptens.
References:-
1- Richard Coioco and Geoffery Sunshine (2014). Immunology.Seventh edition.Wiley Blackwell.