What the immune system is

The body's defence network

The immune system is the network of cells, tissues and organs that defends the body against infection and monitors for abnormal cells. It includes the skin and other barriers, white blood cells of many types, antibodies, the lymph nodes and vessels where immune cells gather and train, and organs such as the spleen, thymus and bone marrow where cells are made or mature.

Two layers of defence

The first layer, innate immunity, is fast and general: barriers, inflammation and cells that attack anything that looks foreign. It responds within minutes to hours.

The second layer, adaptive immunity, is slower but precise. It learns to recognize specific germs, produces matching antibodies, and keeps a memory so the next encounter with the same germ is met faster and more strongly. Vaccination works by giving this layer a safe practice run.

When defence goes wrong

Immune problems come in several directions. An underactive immune system, from illness, medicines or inherited conditions, leaves the body open to infections. An overactive one drives allergies, where harmless things like pollen are treated as threats. And in autoimmune disease the system attacks the body's own tissues, as in type 1 diabetes or rheumatoid arthritis.

What supports it

Everyday foundations matter more than any single product: vaccination, enough sleep, regular activity, a varied diet, not smoking and managing long-term stress. The immune system is a coordinated network, not a muscle to be 'boosted' - most claims to supercharge it are not grounded in evidence.