Question

What is leukocytosis?

Answer 1

Hint: Leukocytes are also known as white blood cells. White blood cells (leukocytes) are one of the components of blood. White blood cells (WBCs) are the cells that provide immunity to the body to fight against pathogens.

Complete answer:
Leukocytes are also known as White blood cells. The white blood cells are the cells that are found in blood with red blood cells and platelets. White blood cells are required by the body as they help the body to get rid of pathogens and infections. Its amount is very less in comparison to the red blood cell. The normal range of white blood cells is 4000-11000 WBCs per microliter.
So, an increase in the leukocytes (WBCs) count above the normal range is termed Leukocytosis. As the leukocytes are of different types so the leukocytosis can be due to a rise in the count by any of these cases:
1. Neutrophilia: Increase in neutrophils count.
2. Lymphocytosis: increase in lymphocytes count.
3. Monocytosis: increase in monocyte count.
4. Eosinophilia: increase in eosinophil count.
5. Basophilia: increase in basophils count.
Among all Neutrophilia and lymphocytosis is the most common cause for leukocytosis. Neutrophils comprise 40-$60\%$ of total WBC. Lymphocytes are 20-$40\%$ of total WBC. Monocytes are 3-$8\%$ of total WBC, Eosinophil is present up to 1-$4\%$ of total WBC whereas Basophil is least in count that is less than $1\%$. The most common cause for leukocytosis is infection and increased stress in the body. The cause can be physiological or pathological, the physiological cause is found in pregnant women and the pathological causes can be due to infection, stroke, leukaemia, tuberculosis, cancer, long term inflammation and many more.

Note:
Leukocytosis can be found by laboratory diagnoses such as CBC (complete blood count), peripheral blood smear and bone marrow biopsy. The complete blood count is the most commonly used method and this helps to get an idea about the particular type of leukocytosis and then only the other two methods are used.