White blood cells are also known as leukocytes, are cells of the immune system that defends the body against infectious disease and invaders. During Haemopoiesis as explained earlier, white blood cell differentiates from hematopoietic stem cells. Unlike red blood cells, white blood cells have a nucleus. Granulocytes and macrophages are controlled by several colony-stimulating factors (CSF). Normally, these cells are kept in a constant number relative to low levels of CSF. However, during an infection, their production can increase to counteract the infection such as bacterial endotoxins. CSFs are commonly secreted by mature lymphocytes and macrophages but can be produced, if needed, by any organ or cell type.
Typical WBC count is around 4.5 x109/L – 1.1 x1010/L. An increase or decrease from this range could indicate disease. A high WBC count would indicate infection or inflammation, while a low WBC count (leukopenia) could indicate a medical condition that is destroying the WBC caused by cancer such as leukaemia or an autoimmune disorder.
Stop and Reflect:
List down all the function of the Leukocytes.<br>For example :
- Neutrophils defend against bacterial or fungal infection and other very small inflammatory processes. They are usually the first responders to microbial infection. Their activity and death in large numbers from degranulation forms purulent necrosis (pus).