- Also called leukocytes, are an important part of the immune system.

- They are produced in the bone marrow and circulate in the blood and lymphatic system.

- They help protect the body against infections and diseases.

There are several types of white blood cells, each with different functions:

1. Neutrophils are the most abundant type of white blood cells and are the first to respond to infections. They phagocytose (engulf and destroy) bacteria and other foreign particles.

2. Lymphocytes are responsible for the body's immune response. They include T cells, which kill infected cells, and B cells, which produce antibodies to neutralize antigens.

3. Monocytes are large phagocytic cells that engulf and destroy bacteria, viruses, and other foreign particles. They can also differentiate into macrophages, which are specialized cells that help to clear away dead cells and debris.

4. Eosinophils help to defend against parasitic infections and allergies. They can also release toxic chemicals that can damage parasitic cells.

5. Basophils are involved in allergic reactions and inflammation. They release histamine, which causes blood vessels to dilate and become more permeable, allowing fluid and white blood cells to leak out into the tissues.

6. Dendritic cells are specialized cells that capture antigens and present them to lymphocytes, thus activating the immune response.

White blood cells play a vital role in maintaining the body's health by protecting it from infections and diseases.

However, sometimes, white blood cells themselves can become cancerous or malfunction.

This can lead to various blood cancers, such as leukemia and lymphoma.

In addition, some conditions, such as autoimmune diseases and immunodeficiency disorders, can affect the function of white blood cells, making individuals more susceptible to infections.