Innate Immunity: Your Body’s First Line of Defense
Innate Immunity: Your Body’s Defense System
Your body produces a variety of white blood cells that defend against pathogens. A healthy immune system is always ready, providing innate immunity, which defends against all pathogens.
How Skin and Body Secretions Protect You
The skin is the first barrier against microorganisms. Body secretions like mucus, oil, sweat, tears, and saliva also play a crucial role. Mucus traps microorganisms in the respiratory and digestive tracts, which are then destroyed by acidic gastric juice in the stomach. Sweat, tears, and saliva contain lysozyme, an enzyme that breaks down bacterial cell walls.
Inflammation: A Sign of Your Body’s Defense
If pathogens breach the initial defenses, the body employs nonspecific defense mechanisms to restore homeostasis. Inflammation occurs when bacteria or other pathogens damage body tissues. The four key symptoms of inflammation are redness, swelling, pain, and heat.
The Inflammatory Response
When inflammation begins, damaged tissue cells (mast cells) and white blood cells (basophils) release histamine. Histamine dilates blood vessels in the injured area, causing redness. Fluid leaks from the vessels into the tissue, helping to destroy toxic agents and restore homeostasis. This fluid increase causes swelling and pain, and may also cause the area to become warmer. Inflammation can be triggered by physical force, chemical substances, extreme temperatures, and radiation, as well as infections.
Phagocytes: The Body’s Defenders
Phagocytes are white blood cells that destroy pathogens by engulfing them. They include:
- Monocytes: Develop into macrophages.
- Neutrophils
- Eosinophils
Macrophages: The Big Eaters
Macrophages are white blood cells that provide the first defense against pathogens in tissues. They engulf pathogens or damaged cells, digesting them with enzymes.
Monocytes: Immature Macrophages
Monocytes are small, immature macrophages that circulate in the bloodstream. They move into infected areas, mature into macrophages, and consume pathogens and dead neutrophils. Some monocytes mature into tissue macrophages, guarding against new infections.
Pus: A Byproduct of the Immune Response
Pus consists of living and dead white blood cells, living and dead pathogens, and body fluids.
Interferons: Fighting Viral Infections
Interferons are proteins that protect cells from viruses. Human interferons protect human cells from viruses but are species-specific.
Acquired Immunity: Building Resistance
When a pathogen invades, certain white blood cells develop the ability to recognize a specific foreign substance. This acquired immune response destroys the pathogen. Defending against a specific pathogen by gradually building up resistance is called acquired immunity.