Finding Out How Your Child Fights Infections
Keeping bacteria, viruses, and any other potential invaders at bay is a complex operation involving the efforts of several essential organs, blood cells, glands, and hormones. The immune system is often compared to an army because it comprises many different forces that work together to protect the body from unwanted bugs.
Do not enter: keeping the invaders out
The most visible part of the immune system is the skin. Supplying our first line of defense, it provides a primary boundary between germs and the body. Part of the skin’s job is to act as a barrier in much the same way as you use cling film to protect food. Healthy skin is tough and impermeable to bacteria and viruses, not only because it seals the body’s organs but also because it contains special cells that secrete antibacterial substances, such as the salt found in sweat, to kill off invaders.
The nose, mouth, and eyes are obvious entry points for germs. They too contain germ-fighting chemicals: Tears, nasal mucus, and saliva contain enzymes that destroy the cells of many kinds of bacteria. And since the nasal passage and lungs are coated in mucus, many germs that aren’t killed immediately are trapped in the mucus, swallowed, and then destroyed by stomach acid.
Looking for troublemakers
If harmful germs do manage to get inside the body, the immune system needs to deal with them in order to stop them overrunning the body. It has to detect and eliminate the invaders before they can make themselves at home and reproduce – which they can do rapidly. If this mission is accomplished, then the viruses or bacteria are killed off before they cause feelings of illness; if the mission fails, however, the germs temporarily get the better of the immune system and illness ensues, continuing until the system has tackled and destroyed the invaders.
The main defenders of the immune system are white blood cells. They travel through the bloodstream and the lymphatic system, and are programmed to recognise troublemakers, whether bacteria, viruses, or other infecting agents, so that they can mount an organised attack against them.
Taking a systematic approach
The lymph system is a pivotal part of the immune system. It consists of an internal network of vessels throughout the body that are saturated with a special clear liquid called lymph, which contains white blood cells and carries them around the body. The whole body is soaked in lymph, although you rarely see it. Unlike blood, which is pumped around the body by the heart, lymph relies on exercise and muscular activity in order to circulate.
Lymph also carries away waste products, which are filtered out by the lymph nodes located all over the body. Within the lymph nodes, harmful micro-organisms are trapped, attacked, and destroyed by white blood cells. This is one of the body’s most efficient lines of defense. Lymph nodes are storage sites for cells – they’re the ‘swollen glands’ often present during an infection. The tonsils, adenoids, and appendix are all important parts of the lymph system. If any of them is swollen, your child’s body is probably fighting an infection.
Antibodies are manufactured in the lymph system. They are protective substances that the body produces in response to invasion by a hostile organism or the presence of a foreign substance. Antibodies counteract a number of the invading bacteria and viruses by inactivating them and making them powerless.
Like an elephant, the immune system never forgets
One of the remarkable things about the immune system is its ability to remember and recognize past invaders, allowing the body to respond quickly to a second attack. Disease-causing viruses and bacteria invade and reproduce rapidly in their millions, with an ability to respond quickly that is extremely important. Immunity is the body’s ability to resist an invasion of disease-causing bacteria and viruses. Once antibodies have been made to fight a certain type of micro-organism, that micro-organism usually no longer poses a threat to the body, which is why one attack of a disease often prevents its recurrence later down the road.
This ‘memory’ is the basis of immunization. Hundreds of years ago, forward thinking scientists realized that having one infection not only allowed us to fight off that same disease if we came across it again, but also would be resistant to related diseases. Three hundred years ago, Edward Jenner worked out that milkmaids who had been infected in the course of their work with a relatively mild disease called cowpox never caught the infinitely more serious smallpox. He ‘inoculated’ his first patient by exposing them to material taken from a cowpox blister – sure enough, they, like the milkmaids, became immune to smallpox.
