1 · balance quartet
The lay phrase boost your immune system has no matching concept in medicine.The immune system is not one number (unlike blood pressure, it cannot simply rise or fall); it is a dynamic balance of several cell subsets:The four main T-helper (CD4 T cell) subsets:
· Th1 (IFN-γ + IL-2): fights intracellular pathogens (viruses, TB, Toxoplasma) + tumour surveillance
· Th17 (IL-17 + IL-22): fights extracellular bacteria and fungi (especially at mucosal surfaces) + maintains barriers
· Th2 (IL-4 + IL-5 + IL-13): fights parasites + makes mucus; out of balance → allergy, asthma
· Treg (IL-10 + TGF-β + FoxP3): keeps the peace by damping overreactions of the other three
Key: strong vs balanced
· Strong Th1 / Th17 + weak Treg: aggressive attack, but the risk is attacking yourself
· Weak Th1 / Th17 + strong Treg: peaceful, but the risk is pathogens and tumours escaping
· Strong Th2 / weak Treg: → allergy, asthma
· Well balanced: steps up when needed (acute infection), returns to baseline when not, with Treg holding the floor
The two directions of imbalance:
Direction A · Th2 / allergy: allergic rhinitis, asthma, food allergy, eczema, with IgE overreacting to pollen, food or dust mites; common in modern populations and clearly more frequent over recent decades in Western and urbanised regions. The hygiene hypothesis and its revision, the old friends hypothesis, argue that what is missing is not bacteria as such but the immune training that evolved alongside commensal microbes and parasites.
Direction B · autoimmunity: Hashimoto thyroiditis (), type 1 diabetes (beta cells), rheumatoid arthritis (synovium), multiple sclerosis (myelin), lupus (nuclear antigens); most are clearly more common in women, and they have been rising alongside allergy. The shared feature is strong Th17 / Th1 with too little Treg restraint.
What people mean by weak immunity is usually:
· Frequent colds: mostly exposure (children, crowding, poor ventilation) + short sleep + stress, not a weak immune system
· Long-term fatigue: often thyroid, anaemia, depression, vitamin D deficiency or sleep apnoea, not weak immunity
· True immunodeficiency: primary immunodeficiency diseases are rare and need a doctor to diagnose and treat
The real tests (not an immunity test): a full blood count with differential, immunoglobulins (IgG / IgA / IgM / IgE); with a specific suspicion, T-cell subsets, NK-cell activity, complement and autoantibodies.