Our immune system is essential for our survival. We don’t live alone on the planet and our environment is by no means sterile. In the sci-fi novel “War of The Worlds”, the writer postulates that aliens would die from a virus when they reach earth, and this will be our condition without our adaptive immune system. Your body contains bacteria roughly 10 times the number of its cells, yet clinical infections by such bacteria remain minimal. These bacteria live on the surface of our skin, in our gastrointestinal system and our reproductive organs. Our immune system consists of static barriers such as the skin and mucosa as well as adaptive components in the form of blood cells, antibodies and other chemical mediators.
Types of white blood cells
Our white blood cells form the backbone of our immunity. They are formed mostly in the bone marrow from mother cells called hemopoietic stem cells and then differentiate into different types with each type mostly responsible for a certain group of functions. White blood cells are found all over the body with the greater majority circulating in the blood and to a lesser extent the lymphatic system. They are also found in the skin, the gastrointestinal system, the respiratory tract and genital tract. White blood cell count in the blood ranges from 4000-11,000 cell per cubic microliter. The main types of white blood cells are:
- Neutrophils: They form 65-70% of white blood cells. They are the first line of defense against intruders and are more specialized in bacterial infections. Those cells are responsible for the formation of pus when certain bacteria invade our body.
- Lymphocytes: They form around 30% of white blood cells. They carry a wide variety of functions from fighting bacterial and viral infections to destroying cancerous cells. They are also responsible for the development of most autoimmune diseases.
- Eosinophils: They constitute around 2% of white blood cells. They are responsible for fighting parasites and can be responsible for the development of allergy.
- Basophils: They are the fewest among white blood cells. Their function is not well understood, but they release a wide range of inflammatory products and mediate inflammation in various ways.
- Monocytes: Monocytes form around 5% of white blood cells and their main function is to settle in different tissues, differentiate and form macrophages which are cells that eat intruders and foreign bodies.