Question

The increased number of white blood cells is considered as an indication of infection in a patient. why?

Answer 1

White blood cells are known for defense mechanism.
WBC are divided into five types - Neutrophil, Eosinophil, Basophil, Lymphocyte, and Monocyte.

Complete answer: White blood cells (WBC) are also known as leukocytes.
White blood cells are produced from multipotent cells in the bone marrow known as hematopoietic stem cells. It is found throughout the body including blood and lymphatic system.
The increase in WBC acts as an indicator of infection in the body because white blood cells help the immune system by acting as a defense mechanism against infection by destroying foreign bodies.

WBC basically is of granulocytes and agranulocyte nature.
Granulocyte refers to having a fine granule like structure and agranulocyte shows to not have granules.
1. Neutrophils are believed to act as a defense mechanism against bacterial and fungal disease.
2. Eosinophil target parasites and they act against allergic inflammatory response.
The rise in eosinophil count can be observed in response to allergic reactions, parasitic infections, etc.
3. Basophils react to allergic reaction and antigen response by releasing the chemical histamine. Basophil can release another chemical name heparin which is an anticoagulant. Basophil can also release chemical signals that can be responded by neutrophil and eosinophil to act on an infection site.
4. Lymphocytes are divided into – B cells, T cells, and Natural killer cells.
Lymphocytes help in binding with an antigen, activates the complement system, kills the cells that do not display MHC class I.
Monocyte helps in presenting pathogens to T cells so that the pathogen can be recognized by T cells and can be killed.

Note: Some disorders which can be caused due to excessive increase in WBC are -
Neutrophilia and Eosinophilia.