Living Examples: Seeing the Immune System in Action

In order to understand how the immune system works, you need to see it in operation. Here are a few examples of how the system does such an amazing job:

• Cuts and grazes: If your child cuts herself, all sorts of germs enter her body through the break in the skin. Her immune system responds by producing white blood cells to eliminate the invaders while the skin heals itself. In rare cases, the cut is infected: Then the area becomes inflamed because germ-fighting cells collect at the site of an infection, or the cut fills with pus, which is made up of millions of dead cells from the immune system that have tried to deal with the infection.
• Insect bites: If an insect nibbles your child’s skin, your child gets a red itchy bump – a sign that the immune system’s doing its job. The bump consists of a collection of millions of fighter cells that have gathered to protect the invading substance entering the bloodstream.
• Colds and ‘flu: Each day your child inhales thousands of bacteria and viruses that are floating in the air. The immune system normally deals with these without a problem, but occasionally a germ gets past the first lines of defense and your child catches a cold or another bug. This is a visible sign that her immune system failed to stop the invading germ. Cells from the immune system rush to the mucus membranes in the nose and upper airways, killing off the germs before they get a hold deeper in the body, such as in the lungs. The fact that not every cold develops into pneumonia or life-threatening blood poisoning shows just how well your child’s immune system is working each and every day. In time, the immune system kills off all the germs causing symptoms, and your child recovers completely. Getting over the illness is a visible sign that your child’s immune system is working. In some cases, a bug is so virulent that antibiotics or other medication are needed to help your child’s body fight the invaders.
• Tummy upsets: Every day, your child swallows hundreds of germs, most of which die in her saliva or the acid in the stomach. Occasionally, however, a germ gets through and causes food poisoning, with obvious visible effects – vomiting and diarrhoea are two of the most common symptoms. Again, the immune system can usually prevent these germs from taking over the whole body, so their effects tend to be local to the gut and digestive system (hence the copious quantities being produced at both ends!). Within a few days your child’s immune system fights them off completely.

A helping hand: antibiotics

Sometimes the immune system can’t respond quickly enough to outpace the reproductive rate of the invading bacteria, or the bacteria produce toxins so quickly that the toxins cause damage before the immune system can get to work. When this happens, antibiotics help the body kill off the bacteria without affecting the body’s own cells. Different antibiotics work on different bacteria. But antibiotics do not work on viruses.

If your child is prescribed an antibiotic, the drug should kill off all the target bacteria over 5–10 days. Your child will feel better within just a day or two because the antibiotic kills the majority of the bacteria extremely quickly. Even though she feels better, however, your child should finish the course in order to prevent the illness recurring.

Although antibiotics can be real lifesavers, overuse of these drugs is a growing problem. Sometimes bacteria mutate (change the way they’re made) and are able to survive the antibiotic. These bacteria then reproduce, the disease changes, and the antibiotic becomes totally ineffective in fighting that disease in everyone. This process is known as antibiotic resistance, and it has become a large concern among doctors, who are now much more measured in their prescriptions.

If an antibiotic worked the first time for an infection your child contracted, but not the second, the reason is not that your child has become resistant to the effects of the antibiotic. The germ, not the child, mutates! That also means that just because an antibiotic hasn’t worked for your child in the past doesn’t mean it won’t work in the future.

Many infections are self-limiting – your child’s immune system fights them off on its own within a few days. If the cause is a virus infection, the antibiotics won’t do any good, but you may assume that they have because your child recovers.

Looking at disorders of the immune system

Many human ailments are caused by the immune system working in an unexpected or incorrect way. Allergies, for example, are a sign that the immune system is overreacting to certain stimuli that other people don’t react to. Diabetes is caused by the immune system inappropriately attacking and destroying cells in the pancreas. Both allergies and diabetes are becoming more common in children.