BIO101 ‒ Topic 11: The Immune System and Cellular Defense
Mechanisms
1. Introduction to the Immune System
The immune system is the body's natural defense mechanism that protects against harmful
pathogens such as bacteria, viruses, fungi, and parasites. It identifies and eliminates foreign
substances while distinguishing them from the body s own cells. The immune system
maintains homeostasis by preventing infections and diseases.
2. Types of Immunity
Innate Immunity (Non-Specific Defense): Present at birth; provides the first line of defense
using physical, chemical, and cellular barriers such as skin, mucous membranes, and
phagocytic cells.
Acquired Immunity (Specific Defense): Develops after exposure to a pathogen and
involves lymphocytes (B and T cells). It has memory, enabling faster responses upon
re-exposure.
3. Components of the Immune System
a) Organs: Bone marrow, thymus, spleen, lymph nodes, tonsils.
b) Cells: Lymphocytes (B and T cells), macrophages, neutrophils, and natural killer cells.
c) Molecules: Antibodies, cytokines, complement proteins.
4. Mechanisms of Immune Response
a) Primary Response: Occurs during the first exposure; slow but forms memory cells.
b) Secondary Response: Rapid and strong due to memory cell activation.
c) Cell-Mediated Response: T lymphocytes attack infected or abnormal cells directly.
d) Humoral Response: B lymphocytes produce antibodies that neutralize pathogens in body
fluids.
5. Immune Disorders and Diseases
- Allergies: Overreaction to harmless substances.
- Autoimmune Diseases: Body attacks its own tissues (e.g., lupus).
- Immunodeficiency: Weakened immune function (e.g., HIV/AIDS).
6. Artificial Immunity
Vaccination: Introducing weakened or killed pathogens to stimulate immunity.
Immunization: The process of becoming protected through vaccination.
© Lesuyai Organic Guides
Mechanisms
1. Introduction to the Immune System
The immune system is the body's natural defense mechanism that protects against harmful
pathogens such as bacteria, viruses, fungi, and parasites. It identifies and eliminates foreign
substances while distinguishing them from the body s own cells. The immune system
maintains homeostasis by preventing infections and diseases.
2. Types of Immunity
Innate Immunity (Non-Specific Defense): Present at birth; provides the first line of defense
using physical, chemical, and cellular barriers such as skin, mucous membranes, and
phagocytic cells.
Acquired Immunity (Specific Defense): Develops after exposure to a pathogen and
involves lymphocytes (B and T cells). It has memory, enabling faster responses upon
re-exposure.
3. Components of the Immune System
a) Organs: Bone marrow, thymus, spleen, lymph nodes, tonsils.
b) Cells: Lymphocytes (B and T cells), macrophages, neutrophils, and natural killer cells.
c) Molecules: Antibodies, cytokines, complement proteins.
4. Mechanisms of Immune Response
a) Primary Response: Occurs during the first exposure; slow but forms memory cells.
b) Secondary Response: Rapid and strong due to memory cell activation.
c) Cell-Mediated Response: T lymphocytes attack infected or abnormal cells directly.
d) Humoral Response: B lymphocytes produce antibodies that neutralize pathogens in body
fluids.
5. Immune Disorders and Diseases
- Allergies: Overreaction to harmless substances.
- Autoimmune Diseases: Body attacks its own tissues (e.g., lupus).
- Immunodeficiency: Weakened immune function (e.g., HIV/AIDS).
6. Artificial Immunity
Vaccination: Introducing weakened or killed pathogens to stimulate immunity.
Immunization: The process of becoming protected through vaccination.
© Lesuyai Organic Guides
