Children’s immune systems are both complex and remarkable. A normally healthy infant is born with some antibodies that are supplied by the mother. This is called maternally acquired immunity, but it is considered to be a temporary, passive immunity and it is not a guarantee against all types of infection. In order for children’s immune systems to develop normally, some exposure to foreign antigens is necessary and a routine schedule of vaccinations helps provide those antibodies that cannot be acquired passively.
Children’s immune systems are based on interdependent cells and organs that protect the body from infections. Tonsils, adenoids, lymph nodes, bone marrow, white blood cells, and even the intestinal tract are all parts of the body that help protect children’s bodies from various types of infection. A normal infant can begin to develop immune responses to foreign antigens beginning at birth, providing all cells and organs are functioning properly.
Antibodies are developed over time as the body becomes more capable of synthesizing antibodies in response to antigens. Maternally acquired immunity begins to disappear within six to eight months of age and it takes about six to eight years for children’s immune systems to acquire concentrated levels of antibodies. In part, this timeline explains why many children experience more illnesses, such as colds, early on, but fewer and fewer as they approach adolescence.
The nature of the developing immune system is such that it becomes stronger when it is able to fight infection on its own. Conversely, infections that the body cannot fight and ones that are treated indiscriminately with antibiotics only weaken the immune system. Antibiotics are extremely useful medicines when used to treat infections that the body cannot fight on its own, but overuse should be avoided.
As a child grows, their immune system components change slightly. For instance, the adenoids and tonsils often shrink to a smaller size with the onset of puberty. This is because children’s immune systems are less dependent on them as they develop. In some cases, these organs may show signs of chronic infection or abnormal enlargement and are often removed to avoid interference with other bodily functions.
Children with abnormal immune systems are unable to fight infection the way a healthy child can. Parents should pay close attention to signs of persistent infection, including chronic and high grade fevers, night sweats, and tender or swollen lymph nodes. Children should be routinely evaluated for physical and emotional development, a healthcare process that also monitors development of the immune system.
To help children’s immune systems develop normally, pregnant women should avoid alcohol and tobacco, eat healthy foods and take prenatal vitamins. Exposure to secondhand smoke in infancy and childhood also has a depressive effect on children’s immune systems. Other conditions such as vitamin deficiency, blood disease, and cancer will affect immunity.