What are types of white blood cells?

There are five types of white blood cells. These five types can be grouped into two categories – granulocytes and agranulocytes - based on the presence or absence of small protein granules in the cytoplasm. 

Granulocytes are white blood cells that have granules in their cytoplasm. The 3 types of granulated cells include:

1. Neutrophils: Neutrophils are the most abundant type of white blood cells in the body. They form the first line of defense by identifying foreign invaders such as bacteria and fungi and migrating through tissue toward the infection sites. On encountering the infectious pathogen, neutrophils engulf and destroy them in a process known as phagocytosis. 
2. Eosinophils: Eosinophils are generally found in the connective tissues of the stomach and intestines. They are primarily involved in destroying parasitic cells and cancer cells. Eosinophils also play a role in the body’s general immune and inflammatory responses and assist basophils with allergic responses. These white blood cells are most active during allergic reactions and parasitic infections. 
3. Basophils: Basophils are involved with producing allergic responses. They produce histamine, a chemical that’s associated with combating allergies. Under normal circumstances, basophils form less than 1% of the white blood cells in circulation but their numbers increase significantly during an allergic reaction. 

Agranulocytes are white blood cells that are characterized by the absence of granules in their cytoplasm. The 2 types of agranulocytes include:

1. Lymphocytes: The most abundant type of white blood cells in the body, lymphocytes play a crucial role in producing proteins called antibodies that defend the body against microbes and other harmful pathogens. There are three types of lymphocytes. T cells are responsible for identifying and attacking foreign invaders and eliminating them from the body. B cells are responsible for producing antibodies to help the immune system fight off infections. Natural killer cells are involved in attacking and destroying viral and cancer cells. 
2. Monocytes: Monocytes are involved in fighting off chronic infections by cleaning up damaged cells. They are the largest in size of all white blood cells and migrate from blood to tissue and develop into either dendritic cells or macrophages.