The document discusses antigens, which are mostly proteins or polysaccharides from foreign organisms that elicit an immune response. Antigens can come from microbes like bacteria or viruses, or be non-microbial in origin like pollen or transplanted tissues. They must have a molecular weight over 10,000 or be coupled to a carrier molecule to be recognized. Antigens have properties like their chemical composition, molecular weight, and ability to be processed. There are two main types of antigens: exogenous antigens from outside the body and endogenous antigens from within the body. Epitopes are small parts of antigens that specifically interact with antibodies.

1. Lecture on
Antigen
Deliverd by
Dr. Dinesh Dabhadkar
Department of Zoology, GSG, College, Umarkhed

2. Antigens
 Most are proteins or large polysaccharides from a foreign organism.
 Microbes: Capsules, cell walls, toxins, viral capsids, flagella, etc.
 Nonmicrobes: Pollen, egg white , red blood cell surface molecules, serum
proteins, and surface molecules from transplanted tissue.
 Lipids and nucleic acids are only antigenic when combined with proteins or
polysaccharides.
 Molecular weight of 10,000 or higher.
 Hapten: Small foreign molecule that is not antigenic. Must be coupled to a
carrier molecule to be antigenic. Once antibodies are formed they will
recognize hapten.

3. Properties of Antigen:
1) Chemical Composition & Heterogenicity
2) Molecular Weight
3) Foreignness
4) Ability Antigen Processing
5) Complexity

4. Types of Antigen:
1) Exogeneous
2) Endogenous

5. Epitopes:
Antigen Regions that Interact with Antibodies
Plays important role in antigen antibody interaction

6. Antigens
 Epitope:
 Small part of an antigen that interacts with
an antibody.
 Any given antigen may have several
epitopes.
 Each epitope is recognized by a different
antibody.