Immune System
A distributed defence network of cells and organs that identifies and neutralises threats.
Rather than living in one organ, the immune system is spread throughout the body — in bone marrow, the thymus, the spleen, lymph nodes and the gut wall. It distinguishes 'self' from 'non-self' with remarkable precision, mounting fast, generic responses within hours and highly specific, memory-forming responses over days.
Key organs & structures
How it connects
Digestive system →
A diverse gut microbiome helps train and regulate immune responses.
Sleep →
A single night of short sleep can measurably reduce immune cell activity.
Common goals
Common symptoms
Conditions involving this system
Symptoms involving this system
Did you know?
- • Fever is an active, coordinated immune strategy, not simply a malfunction.
- • Vaccination works by giving the immune system a safe preview of a threat so it can respond faster next time.