• Skin - our skin is the largest organ of the body what is waterproof and secretes oil that has bacteria-killing properties
• Lungs - mucus in the lungs traps foreign bodies and the cilia waves the mucus upwards so that i can be coughed out by the body
• Digestive Tract - our stomach has mucus linings that contains antibodies and the stomach acid can kill most microbes
• The body's other defenses include body fluids (skin oil, saliva, and tears) these contain anti-bacterial enzymes that help reduce the risk of infection. Another one is the constant flushing of the urinary tract and bowel.

With some infections we may experience getting a fever or a rise in our body's temperature. This is actually an immune system response and by doing so can actually kill some microbes and trigger the body's repair process.

Overactivity of the immune system can cause:

• Allergic diseases; and
• Autoimmune diseases

Underactivity of the immune system (immunodefiency):

• These can be inherited such as CVID and SCID
• Sometimes arise as a result of medical treatment such as corticosteroids or chemotherapy
• It can also be caused by another disease such as HIV/AIDS or certain types of cancer

Having an underactive immune system simply means that it does not function correctly and this makes people who have them vulnerable to infections and in the most sever cases, could be life-threatening.

Immunoglobulins, also known as antibodies, are used to treat people who are unable to make enough antibodies of their own or those whose antibodies don't work properly.

This can be delivered through:

• a drip into the vein - IVIg (intravenous immunoglobulin); or
• it can be delivered into the fatty tissue under the skin - SCIg (subcutaneous immunoglobulin)

The immunization process works by copying the body's natural immune response. We are then injected with vaccines that contain the same germs that cause the diseases but they have been either killed or wekaned to the point that they don't make you severely sick; others contain only a part of the disease germ.

However, the immunizations we may need are decided by our health, age, lifestyle and occupation. So it's best to consult with your doctor first, before anything else.