Phagocyte

From Free net encyclopedia

A phagocyte is a cell that ingests and destroys foreign matter through phagocytosis, such as microorganisms or debris via a process known as phagocytosis, in which these cells ingest and kill offending cells by a process analogous to cellular digestion, usually using lysosomes which carry potent enzymes that digests cell components such as other lipids or proteins. These phagocytes are extremely useful as an initial immune system response to tissue damage.

They are also involved in cell death, usually programmed cell death through apoptosis, in which the phagocytes are responsible for cleaning up the debris and effectively "recycling" the dead cell parts. They are capable of cleaning up the debris of necrosis, but this is less orderly than apoptosis. Because the resulting disorder makes it more difficult to pick up debris, and unlike apoptosis, cells which undergo necrosis does not transmit the proper signals that alert phagocytes to a dying cell, and therefore is less effective.

Types

The two types of phagocytes, polymorphonuclear leukocytes and macrophages, each have an important role in the immune system. While polymorphonuclear leukocytes typically respond swiftly and efficiently to invading pathogens; they are mainly adapted for short term response. Macrophages, on the other hand, are initially slow to react, but are capable of engulfing and digesting almost any foreign agent, and last for a longer period of time.

Polymorphonuclear leukocytes

The polymorphonuclear leukocytes, also known as granulocytes, include neutrophils, eosinophils and basophils. Neutrophils are the most abundant kind of phagocytes. They reduce bacterial cells to their constituent amino acids by ingesting, killing, and digesting them. Eosinophils secrete special enzymes intended to create holes in parasitic worms. Finally, basophils secrete substances such as histamine, in order to extend the period of inflammation.

Macrophages

Macrophages adapted specially for sustained battles against foreign agents. In addition, they help to clean up and remove damaged tissues. Immature macrophages which are circulating in the bloodstream are called monocytes. These macrophages cannot react immediately, but once they have developed, they are often referred to as 'killing machines' they act by phagocytizing and destroying anything that isn't recognized as belonging to the body.de:Phagozyt es:Fagocito fr:Phagocyte he:פגוציט pt:Fagócito