The immune system

The immune system is the body's defence against disease-causing agents such as bacteria, viruses, fungi and parasites. It distinguishes the body's own cells from foreign invaders and acts to destroy or neutralise threats. Because its responses involve cells moving, recognising targets and multiplying over hours and days, animation is a natural way to illustrate how an infection is detected and cleared.

Defence operates at two main levels. The innate immune system provides a fast, general first response: physical barriers such as the skin, chemical defences, and white blood cells that engulf and digest invaders, together with inflammation that brings more defenders to the site. The adaptive immune system is slower but highly specific. It relies on white blood cells called lymphocytes, including B cells, which produce antibodies that lock onto a particular pathogen, and T cells, which help coordinate the response and destroy infected cells.

A key feature of adaptive immunity is memory. After an infection, some lymphocytes persist so that a later encounter with the same pathogen triggers a faster, stronger response, often preventing illness altogether. Vaccination uses this principle deliberately, presenting a harmless form or fragment of a pathogen so that immunity develops in advance. When the system misfires it can attack the body's own tissues, causing autoimmune disease, or overreact to harmless substances, causing allergies.

Frequently asked questions

What is the difference between innate and adaptive immunity?

Innate immunity is a fast, general defence present from birth. Adaptive immunity is slower but specific to a particular pathogen and improves with exposure.

What are antibodies?

Antibodies are proteins made by B cells that bind to a specific pathogen, marking it for destruction or neutralising it directly.

How do vaccines use the immune system?

Vaccines present a harmless version or fragment of a pathogen, prompting the immune system to build memory so it can respond quickly to a real infection later.