What is the immune system composed of?

The immune system is composed of a vast and diverse network of white blood cells, antibodies, glands, and chemicals. All of these components work together to protect the body from disease-causing pathogens such as bacteria, viruses, fungi and parasites. 

• White blood cells: White blood cells are a key component of the immune system. They are responsible for identifying, attacking, and destroying harmful foreign invaders. There are many different types of white blood cells in the immune system, each of which plays a specific role in the body’s defense system. 
• Lymph nodes: Lymph nodes are tiny bean-shaped glands found in various parts of the body. They act as filters, trapping foreign invaders and activating the creation of special antibodies to fight them off. Swollen, tender lymph nodes are a sign that the immune system is actively fighting an infection. 
• Spleen: Located in the left upper abdomen, the spleen performs multiple functions in the immune system. It acts as storage for a while blood cells that fight off invading pathogens, destroys damaged and dysfunctional red blood cells, and breaks down platelets that are responsible for blood clotting   
• Tonsils and adenoids: Located in the throat and nasal passage, tonsils and adenoids trap germs before they can enter the body through the mouth or nose. The immune cells present in tonsils and adenoids produce antibodies that protect against pathogens that cause throat and lung infections. 
• Thymus: The thymus is a gland-like organ located behind the breastbone in the upper chest area. It is responsible for recognizing and remembering repeat invaders, which helps to mount a faster defense in the event of a repeat encounter. 
• Bone marrow: Bone marrow refers to the spongy tissue found inside the bones. It is rich in stem cells that develop into red blood cells and plasma cells as well as different types of immune cells and a variety of white blood cells, which are released into the bloodstream, from where they are transported to other organs and tissues through the blood. 
• Skin and mucous membranes: The skin and mucous membranes that line the respiratory, digestive, reproductive, and urinary tracts, are the first line of defense. They play pivotal roles in preventing germs from entering the body through different mechanisms.