The thymus filters and monitors your blood content. It produces the white blood cells called T-lymphocytes.
Bone marrow is the spongy tissue found inside your bones. It produces the red blood cells our bodies need to carry oxygen, the white blood cells we use to fight infection, and the platelets we need to help our blood clot.
The spleen is a blood-filtering organ that removes microbes and destroys old or damaged red blood cells. It also makes disease-fighting components of the immune system (including antibodies and lymphocytes).
The lymphatic system is a network of delicate tubes throughout the body. The main roles of the lymphatic system are to:
- manage the fluid levels in the body
- react to bacteria
- deal with cancer cells
- deal with cell products that otherwise would result in disease or disorders
- absorb some of the fats in our diet from the intestine.
The lymphatic system is made up of:
- lymph nodes (also called lymph glands) — which trap microbes
- lymph vessels — tubes that carry lymph, the colourless fluid that bathes your body’s tissues and contains infection-fighting white blood cells
- white blood cells (lymphocytes).
The complement system is made up of proteins whose actions complement the work done by antibodies.
Antibodies help the body to fight microbes or the toxins (poisons) they produce. They do this by recognising substances called antigens on the surface of the microbe, or in the chemicals they produce, which mark the microbe or toxin as being foreign. The antibodies then mark these antigens for destruction. There are many cells, proteins and chemicals involved in this attack.
White blood cells are the key players in your immune system. They are made in your bone marrow and are part of the lymphatic system.
White blood cells move through blood and tissue throughout your body, looking for foreign invaders (microbes) such as bacteria, viruses, parasites and fungi. When they find them, they launch an immune attack.
White blood cells include lymphocytes (such as B-cells, T-cells and natural killer cells), and many other types of immune cells.
The immune system keeps a record of every microbe it has ever defeated, in types of white blood cells (B- and T-lymphocytes) known as memory cells. This means it can recognise and destroy the microbe quickly if it enters the body again, before it can multiply and make you feel sick.
Some infections, like the flu and the common cold, have to be fought many times because so many different viruses or strains of the same type of virus can cause these illnesses. Catching a cold or flu from one virus does not give you immunity against the others.
Parts of the immune system
The main parts of the immune system are:
- white blood cells
- complement system
- lymphatic system
- bone marrow
Just like the rest of your body, your immune system needs nourishment, rest, and a healthy environment to stay strong. Certain lifestyle changes can boost your immune system and help you avoid illness. To keep your immune system running smoothly, you should:
- Quit smoking.
- Lose weight or maintain a healthy body mass.
- Eat a healthy diet that includes lots of fruits and vegetables.
- Avoid alcohol or use it only in moderation.
- Get enough sleep.
- Exercise regularly.
- Wash your hands often.
- Try to stress less and focus on mind/body wellness.
- Make sure you’re up-to-date on vaccines.
Many deficiencies and disorders can damage or disrupt your immune system. Some medicines make it harder for your body to fight infection. Certain health conditions cause your immune system to attack healthy cells or make it hard for your immune system to protect you from harmful germs. They include:
- Allergies: When the body overreacts to a harmless substance (such as food or pollen), the immune system launches a response. Your body fights its allergy triggers by releasing histamines that cause allergy symptoms. An allergic reaction can range from mild (sneezing or stuffy nose) to severe (breathing problems and even death). Antihistamine medications help calm the symptoms.
- Autoimmune disorders: These disorders occur when the immune system mistakenly attacks its own healthy cells. Lupus, diabetes, Hashimoto’s disease and rheumatoid arthritis are examples of common autoimmune diseases.
- Primary immunodeficiency disorders: These disorders are inherited (passed along in families). There are more than 100 primary immunodeficiency diseases (PIDD) that prevent the immune system from working as it should.
- Infections: HIV and mononucleosis (mono) are well-known infections that weaken the immune system. They lead to serious illness.
- Cancer: Certain types of cancer, like leukemia, lymphoma and myeloma affect the immune system directly. These cancers occur when immune cells grow uncontrollably.
- Sepsis: Sepsis is an overwhelming response of your body’s immune system to an infection. This triggers widespread inflammation and causes a downward spiral of events that can end in organ damage, organ failure and death.
- Medications: Some medications, such as corticosteroids, can weaken the immune system. And after an organ transplant, people take immunosuppressant medications. These medicines help prevent a failed transplant (rejection). However, these drugs increase your risk of infection and disease.