Immunology is the study of the immune system and its functions of protecting the body from infectious organisms like viruses, bacteria, fungi, and parasites. The immune system is a complex system consisting of organs, molecules, cells, and pathways that work together to fight pathogens, provide protection, and distinguish self from non-self. Antigens are substances that can generate an immune response by binding to immune cells and antibodies. Immunogens are antigens that are capable of eliciting an immune response, while haptens are small molecules that need a carrier like a protein to elicit an antibody response.

1. IMMUNOLOGY
Basic Fundamentals
 What is immunology?
 Infectious organisms
 Immune system
 Antigenicity
 Types of antigens
 Sources of antigens
 Immunogenicity
 Immunogens
 Haptens

2. DEFINITION OF IMMUNOLOGY
Immunology is the study of the immune system and its functioning.
Immune system protects us from attack by microbes and worms.
The fully functioning immune system involves various organs,
molecules, cells and pathwaysin such an interconnected and sometimes
circular process.
Range of infectious organisms:
1. Worms eg. Tapeworms, Filaria
2. Protozoans eg. Trypanosomes, Leishmania, Plasmodium
3. Fungi eg. Candida, Aspergillus
4. Bacteria eg. Staphylococcus
5. Viruses eg. Polio virus, Hepatitis B

3. PROPERTIES OF IMMUNE SYSTEM
COMPLEX SYSTEM CONSISTING OF VARIOUS COMPONENTS WORKING
TOGETHER
BLOCKS AND FIGHTS THE PATHOGENS AND PROVIDES PROTECTION
PROVIDES IMMUNE RESPONSE
HELPS IN COMMUNICATION BETWEEN CELLS
PLAYS AN IMPORTANT ROLE IN SELF AND NON-SELF DISTINCTION

4. ANTIGENICITY:
o IT IS THE ABILITY OF A SUBSTANCE TO BIND TO THE PRODUCT OF AN IMMUNE
RESPONSE.
o SUBSTANCES THAT CAN GENERATE IMMUNE RESPONSE ARE CALLED ANTIGENS.
o SUBSTANCES THAT ARE CAPABLE OF ELICITING AN IMMUNE RESPONSE ARE
CALLED IMMUNOGENS.
o ALL IMMUNOGENS ARE ANTIGENS BUT ALL ANTIGENS ARE NOT IMMUNOGENS.
o AN ANTIGEN WHICH CANNOT ELICITE AN IMMUNE RESPONSE OR ANTIGENS
WHICH ARE NOT IMMUNOGENS ARE CALLED HAPTENS.
o EPITOPE: IMMUNOLOGICALLY ACTIVE REGION OF AN IMMUNOGEN (OR AN
ANTIGEN) THAT BIND TO ANTIGENIC SPECIFIC MEMBRANE RECEPTOR OR
ANTIBODY.
o MULTIVALENT ANTIGEN: THESE ARE ANTIGENS HAVING MANY EPITOPES.

5. TYPES OF ANTIGEN BASED ON NATURE
• PROTEINS (highly immunogenic)
• POLYSACCHARIDES (less immunogenic)
• NUCLEIC ACIDS (poor immunogenic)
• LIPIDS (no or poor immunogenic)
SOURCES OF ANTIGENS:
 Exogenous antigens eg. Bacteria, virus, parasite, fungi,etc
 Endogenous antigens eg. Faulty proteins, nucleoproteins, infected
cells,etc

6. IMMUNOGENICITY
It is the ability of a substance to induce immune response.
When an immunogen binds with immune cells, an immune response
is produced.
HAPTENS:
They are small molecules which when combined with a larger carrier
such as proteins can elicit the production of antibodies.
Haptens are antigenic but not immunogenic.
Examples of hapten: DNP, fluorescein, penicillin, etc