School › Immune system › Ages 10–11
How the body fights germs
Barriers, white blood cells that engulf germs, antibodies and immune memory, and how germs spread from hand to hand. With a germ-spreading experiment.
Read
The immune system's job is to prevent or limit infection. Its cells all start in the bone marrow, and organs such as the thymus, lymph nodes and spleen help it work.[1]
The first line of defence is barriers: skin resists entry, sticky mucus traps germs, tears and saliva contain an enzyme that breaks down bacteria, and stomach acid kills many germs we swallow.[2]
If germs get in, the innate response acts quickly. White blood cells such as neutrophils and macrophages engulf and digest germs. The area may become red, swollen, warm and painful: this is inflammation.[2][1]
The adaptive response is slower but targets one particular germ. B cells make antibodies, proteins that stick to that germ, and T cells help or destroy infected cells.[4]
After an infection, memory cells stay in the body. If the same germ comes back, they respond much faster. Vaccines use this memory.[4]
Germs spread when we touch our eyes, nose or mouth with unwashed hands, eat with dirty hands, or sneeze into our hands and touch others. Washing hands with soap helps prevent infections.[6]
Try it: How far do germs travel?
You need
- Hand cream
- Fine biodegradable glitter
- Everyday objects: a pencil, a door handle model, a ball
- Magnifying glasses
- Soap, water and paper towels
- Tally chart
Safety
Use biodegradable glitter; keep hands away from eyes and mouths during the activity. Check for skin allergies to the cream. Wash and dry hands at the end and wipe objects clean.
What to do
- One pupil (the 'germ carrier') has hand cream and glitter on their hands. Nobody else does.
- The carrier shakes hands with pupil 2, who then shakes hands with pupil 3, and so on down a line of six pupils. One pupil also passes the ball around.
- Use magnifying glasses to score each person's hands and each object: 0 = no glitter, 1 = a little, 2 = some, 3 = lots.
- Record the scores in a table. Plot score against position in the line.
- Everyone washes hands with soap for 20 seconds. Score the hands again.
Play: Barrier, fast or targeted?
Sort each defender: is it a barrier, part of the fast innate response, or part of the slower targeted (adaptive) response?
Your best score is kept only on this device. Nothing is sent anywhere.
Quiz
Other ages: Ages 6–7 · Ages 15–16