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The immune system is the body’s defense against infection. A network of special cells, tissues, and organs work together to protect the body from a variety of “invaders” or germs. These germs or pathogens include bacteria, parasites, viruses, and fungi. In most cases, the body can defend itself from harmful attacks. Some people have weak immune systems and cannot fight off germs as well.
The first line of defense in the immune system is a shield that prevents germs from entering the body. The skin is the body’s main armor that acts as a physical barrier against attack. The linings of the respiratory and digestive tracts (mucous membranes) also stop the entry of harmful pathogens.
What happens if a pathogen invader gets past the shield? The body responds with its next line of defense. Special cells of the immune system patrol the body and travel through the blood and lymphatic system to look for and destroy pathogens.
A foreign invader that causes a response in the immune system is called an antigen. Some immune cells act to attack any invading pathogen. Other cells are trained to recognize and remember specific pathogens. The immune system produces antibodies that lock onto specific antigens so that they can be destroyed. This is how immunizations or vaccines work to protect against certain diseases.
Cancer and cancer treatments can weaken the immune system. This means that a child with cancer is often at higher risk for infection and illness. Someone with a weak immune system is said to be immunocompromised.
There are several ways that cancer can lower immunity:
Infections can be very dangerous for cancer patients with weak immune systems for several reasons.
White blood cells (leukocytes) are some of the most important cells of the immune system. White blood cells are made in bone marrow, and they travel through the lymphatic system throughout the body. Their main job is to fight infection and disease. A white blood cell count (WBC) is a test to measure the number of white blood cells in a patient’s blood. A low number of white blood cells puts a person at risk for infection.
Reviewed: June 2018