Skip to main content
1. Immune System Overview
- The immune system protects the body from harmful pathogens like bacteria, viruses, fungi, and toxins.
- It consists of cells, tissues, and organs that work together to defend the body.
- Key components: White Blood Cells (WBCs), antibodies, lymphatic system, bone marrow, thymus, spleen.
- The immune system is classified into innate immunity and adaptive immunity.
2. Types of Immunity
(A) Innate Immunity
- Innate immunity is the body's first line of defense, present from birth.
- It provides non-specific defense against all pathogens.
- Composed of:
- Physical barriers: Skin, mucous membranes.
- Chemical barriers: Enzymes in saliva, stomach acid, tears.
- Cellular barriers: Macrophages, neutrophils, natural killer (NK) cells.
- Inflammatory response: Redness, swelling, fever to fight infections.
(B) Adaptive Immunity
- Adaptive immunity (acquired immunity) develops after exposure to pathogens.
- It provides a specific defense mechanism and retains memory of past infections.
- Divided into:
- Humoral immunity: Involves B cells that produce antibodies to neutralize pathogens.
- Cell-mediated immunity: Involves T cells that destroy infected cells.
- It is further divided into:
- Active immunity: Developed by the body after infection or vaccination.
- Passive immunity: Antibodies are received from another source (e.g., mother’s milk, antibody injections).
3. Immune Responses
(A) Primary Immune Response
- Occurs when the body encounters a pathogen for the first time.
- B cells recognize the antigen and produce antibodies after a few days.
- Response is slow and weak but helps in developing memory cells.
(B) Secondary Immune Response
- Occurs when the body encounters the same pathogen again.
- Memory cells recognize the antigen and trigger a strong and quick response.
- Prevents reinfection and provides long-term protection.
4. Components of the Immune System
- White Blood Cells (WBCs): Also called leukocytes, they fight infections.
- Lymphocytes: Include B cells and T cells, responsible for adaptive immunity.
- Macrophages: Engulf and digest pathogens.
- Antibodies: Proteins that neutralize pathogens.
- Lymphatic System: Includes lymph nodes and lymph vessels that filter pathogens.
- Thymus: Site of T cell maturation.
- Spleen: Helps filter blood and remove infected cells.
5. Disorders of the Immune System
(A) Autoimmune Diseases
- Occurs when the immune system attacks the body's own cells.
- Examples: Rheumatoid arthritis, Type 1 diabetes, Lupus.
(B) Immunodeficiency Diseases
- Occurs when the immune system is weakened or defective.
- Examples: HIV/AIDS (Human Immunodeficiency Virus).
(C) Allergies
- Overreaction of the immune system to harmless substances (allergens).
- Common allergens: Pollen, dust, certain foods, insect stings.
- Symptoms: Skin rash, sneezing, difficulty breathing, anaphylaxis.
6. Vaccination and Immunization
- Vaccination introduces a weakened or dead pathogen to stimulate immunity.
- Immunization is the process of developing resistance to a disease through vaccines.
- Examples of vaccines: BCG (Tuberculosis), Polio, Hepatitis B, COVID-19.
- Vaccines help in herd immunity, protecting the larger population.
7. Conclusion
- The immune system is the body's defense mechanism against diseases.
- Innate immunity provides general protection, while adaptive immunity offers specific and long-term protection.
- Vaccines play a crucial role in preventing infectious diseases.
- A balanced diet, exercise, and a healthy lifestyle help strengthen immune function.