Immune System 101
Immune systems vary from person to person; some are stronger and some weaker. The immune system protects the body from disease and infection. It attacks dangerous germs that enter the body and fights them off: This is called the immune response. There are three different types of immune response: innate, adaptive and passive.
We're born with innate, or natural, immunity to certain diseases; for example, we can't catch certain ailments animals suffer from. Our skin and mucous membranes, like the inside of our noses, mouths and intestines, also make up our natural immune system--they are barriers guarding the body against infection.
Active, or adaptive, immunity develops as you age. The older you get, the more germs you become immune to because you've been exposed to more of them. You also can be immunized against diseases through vaccination with antigens.
Passive immunity is borrowed from a different source: A child receives antibodies through his mother's milk, for example. Passive immunity doesn't last very long. You can receive what's called "passive" inoculation if you're already infected with a particular disease or if you've been exposed to it. This type of inoculation will help you fight off the disease you already have, rather than prevent you from getting it in the first place. It's usually done with serum containing antibodies from immune people (often gamma globulin) or animals.
Children's Immune Systems
The immune system begins to develop from stem cells when an embryo is about five weeks old. When a baby is born, his immune system is stimulated by the new germs he's exposed to, and he begins to produce antibodies roughly six days after birth. He's already temporarily immune to some diseases, because his mother has given him passive immunity while he was in utero. If he's nursing, he'll also be receiving antibodies through her milk. This type of passive immunity, called maternal immunity, will slowly fade over about six to eight months. His own immune system will keep growing, and by the time he's 1 year old, he'll already have adult-level immunity to some diseases. He'll still constantly be exposed to new germs, however; if a cold is going around, an adult's body might already have "learned" fight it off, while the same cold might have a baby sniffling and sneezing because he's encountering the germ for the first time.
Vaccinations
Vaccinations work by introducing antigens into a child's body without making him ill. The body's B lymphocytes, cells in the bone marrow that protect the body against illness, then produce antibodies that lock onto the antigens and prevent them from doing harm. These antibodies stay in the body so that if the child comes in contact with those particular antigens again, the antibodies are ready to disable the antigen cells.
Vaccination Schedule and Controversy
Traditionally, a child will have a series of vaccinations at regular intervals after she is born. These include Hepatitis B, a diphtheria/tetanus/pertussis combination, polio, rotavirus and the measles/mumps/rubella combination. These immunization shots help to protect an infant or child from contracting diseases that could be very hard for an immature immune system to ward off and that, if contracted, could negatively affect growth and development. They also protect the community: The more children who are inoculated against a disease, the less likely that disease is to enter a community and affect children who haven't been vaccinated.
Some parents choose not to vaccinate their children due to concerns over the preservative used in the measles/mumps/rubella shot, which has been anecdotally linked to autism.
Immune System Problems
A child can be born with an immune disorder or can contract it after birth. Genetic immune disorders come in varying shapes and sizes. As a whole, they're called primary immune deficiency diseases, or PIDDs. They're hereditary. They manifest themselves through frequent, recurring illnesses, such as eight or more ear infections within a year. They're treatable, but the sooner they're identified, the better for the child's development. Treatments include intensive courses of antibiotics, antiviral drugs, antibody replacement and even bone marrow transplants.
Autoimmune disorders occur when the body attacks its own tissue, believing it to be a foreign invader. Autoimmune disorders common in children include rheumatic fever (a disease that can damage heart valves), juvenile arthritis, psoriatic arthritis (an inflammatory joint disease suffered by children who also have the skin disease psoriasis) and scleroderma (the hardening of the skin and mucous membranes). Each disorder has a different treatment.
Acquired immune disorders include HIV. A child can contract HIV through a blood transfusion or from her HIV-positive mother, either in the womb, during childbirth or during breastfeeding. HIV-positive children can be treated with antiretroviral drugs, but they may be slow to reach milestones such as crawling, walking and talking.
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