Understanding Your Child’s Defense System

There are tiny invaders thriving in our environment, and they come in the form of viruses, bacteria, and parasites. Your child, whose immune system is still maturing, may be exposed to these pathogens, making him susceptible to infections.

You can strengthen your child’s immune system effectively with good nutrition and hygiene practices as well as immunisation.

How it works

Your child’s body is actually able to protect itself through his body’s defense system – made up of an intricate network of cells, tissues and organs. Our immune system protects us by first creating a barrier that stops invaders from entering the body. This barrier fends off the initial invasion by organisms outside the body.

A. First line of defense: Non-specific immunity (innate immunity)

• Skin. A physical barrier, which produces mildly antiseptic sweat and sebum.
• Eyes. Tears wash away dirt and contain an antiseptic substance.
• Mouth. Saliva, a mixture of mucus and enzymes, helps clean the mouth.
• Respiratory tract. Mucus produced here traps organisms and moves them to the throat by tiny hairs called cilia.
• Stomach. Hydrochloric acid in the stomach kills most invading organisms.
• Genital and urinary tracts. ‘Good bacteria’ in these tracts help prevent the growth of harmful organisms.
• Intestines. Mucus protects the lining of intestines from digestive chemicals and harmful organisms.
• Cellular defences. If an invader slips through the barriers above, the immune system reacts by producing white blood cells, other chemicals and proteins to attack and destroy the pathogens. The invaders are sought out and destroyed before they can reproduce. In fact, if they manage to multiply, the immune system responds by increasing in productivity to defeat them.

B. Second line of defense: Specific immunity (acquired immunity)

• Lymphocytes. A type of white blood cell which the main type, T cells and B cells, recognise and eliminate foreign molecules (antigens). This occurs a few days after the exposure of foreign microorganism.
• Antibodies. Proteins produced by B cells destroys microorganisms by binding to the antigens. Only T cells directly attack the invaders.
• Memory T and B cells. Once the microorganism is destroyed, some of the active T and B cells become memory cells. If the body encounters the same microorganism in the future, the second line of defense acts faster.