Immune System
Your internal army. The immune system is a complex network of cells, tissues, and organs that defend against pathogens while tolerating your own cells and beneficial microbes. Too weak = infections. Too strong = autoimmunity. Balance is everything.
Two Arms of Immunity
Innate Immunity
- First responders: Immediate, non-specific response
- Physical barriers: Skin, mucous membranes, stomach acid
- Cells: Neutrophils, macrophages, NK cells, dendritic cells
- Inflammation: Recruitment signal for immune cells
- Pattern recognition: Detects common pathogen features
Adaptive Immunity
- Slower but specific: Takes days to weeks to develop
- T cells: Kill infected cells, coordinate response
- B cells: Make antibodies for specific pathogens
- Memory: Remembers past infections for faster response
- Vaccination: Trains adaptive immunity safely
Key Immune Cells
Neutrophils
First to arrive. Engulf bacteria. Short-lived but numerous. Form pus.
Macrophages
Engulf pathogens and debris. Present antigens. M1 (inflammatory) vs M2 (repair).
NK Cells
Natural killers. Destroy infected and cancer cells. Part of innate immunity.
T Helper Cells
CD4+ cells. Coordinate response. Th1 (intracellular), Th2 (parasites/allergies), Th17.
Cytotoxic T Cells
CD8+ cells. Kill virus-infected and cancer cells directly. Key for viral defense.
B Cells / Plasma Cells
Make antibodies. Memory B cells provide long-term immunity.
What Weakens Immunity
Poor Sleep
Immune restoration happens during sleep. One night of poor sleep impairs function.
Chronic Stress
Cortisol suppresses immunity. Shifts from Th1 to Th2. Reactivates latent viruses.
Nutrient Deficiency
Zinc, vitamin D, vitamin C, selenium all critical. Deficiency = weak response.
High Sugar
Impairs neutrophil function for hours after consumption. Feeds pathogens.
Gut Dysbiosis
70% of immunity is in gut. Poor microbiome = poor immune training and regulation.
Sedentary Lifestyle
Moderate exercise boosts immunity. Too little or too much impairs it.
Supporting Immune Function
Vitamin D
Modulates both innate and adaptive immunity. Most people deficient. 40-60 ng/mL optimal.
Zinc
Required for immune cell development and function. 15-30mg daily. Don't overdo long-term.
Vitamin C
Supports neutrophil function. Concentrated in immune cells. Higher doses during illness.
Sleep
7-9 hours. Immune memory consolidation happens during sleep. Prioritize when sick.