What is the Immune System?

The immune system is the body’s defense mechanism that protects it from harmful invaders like bacteria, viruses, fungi, and parasites. It identifies and attacks foreign substances (antigens) to prevent infections and diseases. The immune system is made up of various organs, cells, and proteins that work together to defend the body.

Components of the Immune System

• White Blood Cells (Leukocytes): These cells are the primary defenders in the immune response. They include phagocytes (which consume invaders) and lymphocytes (T-cells and B-cells).
• Lymphatic System: It includes lymph nodes, spleen, and thymus. Lymph nodes filter harmful substances, and the spleen helps in fighting infections.
• Bone Marrow: Produces blood cells, including white blood cells.
• Antibodies: Proteins produced by B-cells that specifically target pathogens.
• Complement Proteins: Help in destroying pathogens by tagging them for destruction or directly attacking them.

Innate Immunity

Innate immunity is the body’s first line of defense and provides immediate, nonspecific protection against pathogens. It is present from birth and does not require prior exposure to a pathogen to function.

Key Features of Innate Immunity:

• Physical Barriers: The skin, mucous membranes, and fluids (like tears and saliva) prevent the entry of pathogens.
• Phagocytosis: White blood cells like macrophages and neutrophils engulf and digest harmful microorganisms.
• Inflammation: The body’s response to infection or injury, characterized by redness, heat, and swelling. It helps to isolate the infection.
• Natural Killer Cells: These cells destroy infected or cancerous cells directly.
• Complement System: A group of proteins that aid in the destruction of pathogens.

Illustration: When you get a cut, the skin barrier is broken. However, the body immediately sends white blood cells and inflammation occurs to prevent infection from spreading.

Summary

• The immune system defends the body from harmful invaders.
• Innate immunity provides quick, nonspecific protection and includes physical barriers, phagocytosis, and inflammation. It acts as the body’s first line of defense.