Agranulocyte

Agranulocytes or nongranulocytes, also mononuclear leukocytes, are one of the two types of white blood cells, also known as leukocytes. The other type of white blood cells are known as granulocytes. Agranular cells are noted by the absence of granules in their cytoplasm, which distinguishes them from granulocytes. The two types of agranulocytes in the blood circulation are lymphocytes and monocytes, and these make up about 35% of the hematologic blood values[1].

Not to be confused with agranulocytosis.
Monocyte under a light microscope (40x) from a peripheral blood smear surrounded by red blood cells.

The distinction between granulocytes and agranulocytes is not useful for several reasons. First, monocytes contain granules, which tend to be fine and weakly stained (see monocyte entry). Second monocytes and the granulocytes are closely related cell types developmentally, physiologically and functionally. Third, this distinction is not used by haematologists; it is an erroneous separation that has no meaning.

Lymphocytes are much more common in the lymphatic system, and include natural killer T-cells. The blood has three types of lymphocytes: B cells, T cells and natural killer cells (NK cells). B cells make antibodies that bind to pathogens to enable their destruction. CD4+ (helper) T cells co-ordinate the immune response (they are what becomes defective in an HIV infection). CD8+ (cytotoxic) T cells and natural killer cells are able to kill cells of the body that are infected by a virus. T cells are crucial to the immune response because they possess a unique 'memory' system which allows them to remember past invaders and prevent disease when a similar invader is encountered again.

Reference ranges for blood tests of white blood cells, comparing mononuclear leukocytes amount (shown in yellow) with other cells.

Monocytes share the phagocytosis function of neutrophils, but are much longer lived as they have an additional role: they present pieces of pathogens to T cells so that the pathogens may be recognized again and killed, or so that an antibody response may be mounted. Monocytes are also known as macrophages after they migrate from the bloodstream and enter tissue.

The granulocytes are neutrophils, eosinophils, basophils, and mast cells.

Additional images
  • Blood cell lineage
gollark: GTech™ is manipulating the refractive index of the local air.
gollark: Did you know? It was already too late. The bees had approached. GTech™ dominion over reality had begun, and none could escape. One night the bees reached the horizon of the sun, and all the specks began. The swarms of specks, all over the city, and even over the whole town. It would be next year that the bees reached the horizon on the night of December 14, 2011. After a week of resting they came to the end of October. They were too exhausted to continue their journey even upon midnight. In the morning they returned to the city to continue their "trip" that came along with the plague. The evening afternoon after dawn, they crossed to the eastern edge of the city, and began their journey on the night of December 15th. The next day, the bees went on their trip to the west of the city. They went on their journey along the northern coast with an aeroplane. When they arrived in the coast of the east of the city, they had a night sleep, as they had not come along the northern coast any further.
gollark: According to the osmarks.net™ future predictor cuboid™ you are actually.
gollark: Written in Macron, self-bootstrapping, and running literally everything optimally and hypermacronously.
gollark: As opposed to the upcoming MacronOS™.

References
  1. "What Are Agranulocytes? - Definition & Function - Video & Lesson Transcript | Study.com". study.com. Retrieved 2018-06-14.
This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.