The immune system recognises and responds to pathogens — Science, 14–17 years
Your immune system distinguishes familiar body markers from features of viruses, bacteria and other threats. It uses barriers, cells and molecules to contain an infection and can remember some encounters.
A coordinated defence
The immune system is not one organ or one cell. Skin and mucus block entry; white blood cells detect unusual molecules, destroy infected cells or microbes, and release signals that organise a wider response.
The problem of telling friend from foe
Cells constantly face microbes, but attacking everything would damage the body itself. Immune recognition solves this problem by targeting patterns associated with danger while normally tolerating the body’s own cells.
Worked example: a vaccine response
A vaccine presents a harmless form or piece of a pathogen. Step 1: immune cells recognise its antigen. Step 2: some lymphocytes make matching antibodies and memory cells. Step 3: on later exposure, memory cells respond faster, often preventing serious illness.
The antibody trap
It is reasonable to think antibodies are general-purpose weapons that kill every infection. They are actually specific proteins that bind particular targets, and they are only one part of immunity; cells, barriers and inflammation also matter.
Immune science in medicine
Vaccines train immune memory, while allergy treatments try to reduce harmless but excessive responses. Doctors also use immune tests to detect past exposure and medicines that boost, replace or suppress parts of the immune response.
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