Types of White Blood Cells

white blood cellsWhite blood cells (WBCs) or as we also call it, leukocytes, are the most important cells within the body when it comes to fighting infections. They are responsible for the protective property of the immune system and they attack the pathogens which intrude our body. They can be found in the blood, also inside connective tissue and lymph system. The source of this type of cells is hematopoietic stem cell which is made inside the bone marrow. The primary cell is called multipotent cell, from which the other five types of cells become later. These are the 5 white blood cells.

Leukocytes and Their Function

The first division between the white blood cells is either they have granule or they don’t, so they are divided into two types of groups which are agranulocytes and granulocytes.

Agranulocytes are the cells that don’t have any visible grains which can be spotted over a microscope. This is the group that has two types of cells, monocytes, and lymphocytes.

Granulocytes are the ones that contain grain which determine their function. According to the coloring under the microscope, the names of the corresponding cells linked with a certain grain inside are neutrophils, basophils, and eosinophils.

They are all important for fighting cancer, infections or any other kind of body damage. They are there to prevent any foreign objects and microorganisms from entering the system.


Neutrophils take up to 75% of leukocytes. They are the most common cells in the bloodstream and they can rise in number in case of an infection. They are medium-sized white blood cells which have granule and they contain nuclei inside the cell which can be 3-5 numbers per cell.

Function: They are the most important cells when it comes to bacterial infections. They are tied to the blood vessel walls and they stop all the foreign objects from entering the body. This can be a cut, an infection origin. The cells surround the foreign substance and “eat” them in the process called phagocytosis. Although they can kill the germs by phagocytosis, they also have multiple superoxides which can kill the bacteria via enzyme reaction.


Lymphocytes are the second most common white blood cell, which can be present from 20% up to 35% of the white blood cells. They are the small rounded cells with big nuclei inside which covers up the cell, leaving the small leftover for the cytoplasm. They play an important part in the viral infections where they can peak and induce the immune system answer. They help the antibody production since there is more than one type of cell. They usually habitat the lymph system, including lymph nodes and the spleen, tonsils and lymph vessels.

Function: There are two main types of lymphocytes, B and T lymphocytes. B lymphocytes are in charge of antibody production via plasma cells. They can make antibodies which are important in the humoral immune system and also can make memory cells which can attack the same pathogen in the future if the body ever comes in touch. This creates a protection in the future, where the body creates an immunity to certain diseases. T lymphocytes are another types of cells, which help the antibody activity.


Monocytes can be present in the blood in percentage from 1% to 6%. They are the largest of them all and they don’t have granule inside, which makes them agranulocytes. They can be found inside the blood system in the form of monocyte cell or to turn into a macrophage inside the tissue.

Function: Monocytes or macrophages are the cells that primarily attack foreign particles, but can also eat another dead cell such as neutrophils and other dead cells. They also use phagocytosis and they digest the other cells inside.


Eosinophils can be present from 1% to 3% in the blood where they have granule which has eosinophil coloring under the microscope. They are the cells that are linked with parasite infections and also allergies and allergic reaction linked diseases such as asthma.

Function: Eosinophils have specific granule which has a function of releasing the enzymes which degrade and kill pathogens. They are important for parasite infections and also rise when allergies are present.


At the end, the least present cells among the white blood cells are the basophil. It is a cell which has a dark large granule which has a function in allergies as well, but also in other types of conditions. They can be present from 0% to 1% inside the blood among the white blood cells.

Function: Since their granule secrete certain antibodies and cytokines, they are involved in hypersensitivity reactions. They also have some kind of anticoagulants. Among the acute inflammation substances, histamine is one of those which is released from the cells that dilate that blood vessel and allows other cells to pass to the injury spot.

White Blood Cell Count

This can be important to check as a regular blood test called CBC (Complete Blood Count). This is used frequently in order to have an insight in white blood cell behavior. As we mentioned above, the neutrophils are the ones that peak the most when a bacterial infection is present, and lymphocytes can be high when the virus is a cause. Eosinophils and basophils can be present in allergic reactions, and eosinophils are important during parasite invasion. Leukopenia and leukocytosis are the changes which reflect decrease and increase of white blood cells.

Leukopenia is rare and can be present in some cancer conditions, during chemotherapy, radiation and also diseases which affect the immune system such as HIV infection.