Functions of macrophages in the immune system
The macrophages are so-called scavenger cells and belong to the leukocytes . As large particles of this type, their development occurs from peripheral blood-borne monocytes . These have a half-life of three days. Experts understand macrophages to be mobile cells that only have a cell nucleus. These are part of the cellular immune system and remain in the human body as tissue macrophages for several months.
The definition of this particular cell type
The main task of the macrophages is to recognize and destroy foreign pathogens and antigens. Thus, these cells also function as phagocytes .
They ensure the elimination of micro-organisms. To do this, the scavenger cells ingest them and decompose them inside. Scientists call the process phagocytosis . Basically, these cell types serve the innate immune system.
The classification of this cell type
On the one hand, the macrophages are divided into mobile – also called motile – cells , which are independent of location. If necessary, they get from the blood to the appropriate areas of their activity. On the other hand, there are the tissue macrophages. This form makes up the bulk of the macrophage population in the human body. The tissue macrophages have a tight bond with a specific tissue. The macrophages differ significantly in their structure:
- In the connective tissue, this cell form is called histiocyt.
- The microglial cell is located in the brain.
- The alveolar macrophages and the Kupffer cell exist in the lungs and liver.
- The Hofbauer cell is found in the placenta and the osteoclast is found in the bones.
- The Langerhans cells are found in the skin, especially in the epidermis. Due to their special function, these also belong to the dendritic cells.
The development and appearance of this cell type
The macrophages develop exclusively from the monocytes . They are formed in the bone marrow. Macrophages become swollen within the blood vessels.
Through the flow of blood, they follow the circulation through the organism. If an infection develops within the body, chemotaxis develops there, which lures this cell to the focus of the disease. With the help of cytokines and antigens, the cells in the tissue differentiate.
Depending on their stimulation, the macrophages take on different shapes. A large number of cells reduce their cytoplasm. Due to the resulting similarity to epithelial cells, they are called epitheloid cells after this change in shape.
If the activated macrophages fuse together, multinucleated giant cells are formed. These engulf predominantly larger antigens during phagocytosis . A normal macrophage is 21 micrometers in size. The various cell types of this type usually have specific surface proteins.
The tasks of these cells
All macrophages belong to the mononuclear phagocytic system (MPS). Within it, however, the cells perform different functions. The most relevant task of this cell type is phagocytosis . This is a non-specific defense against antigens. To destroy the pathogens, a macrophage uses lysosomes, which have lytic enzymes. This substance activates the macrophages.
Only in the case of inflammation and other pathological processes are macrophages recruited from the bone marrow. (1)
Likewise, these cells assume an antigen-presenting function. Incorporated foreign bodies break down the cell types into peptide fragments. They present these with the help of certain molecules on the surface of their cell membrane. The pathogen particles recognize a T helper cell and then trigger the production of the appropriate antibodies. Another task of the cells is the production of cytokines . These help to combat dangerous foreign bodies such as viruses and bacteria.
A macrophage may be involved in the regeneration of muscle fibers. Furthermore, the cell takes care of the multiplication of viruses. If a few viruses enter the organism, the large phagocytes multiply them by one
induce an immune response. This increase in virus concentration occurs within the macrophage cell. Healthy cell types surround the cell infected with the virus. If the pathogen accidentally escapes, they catch it and destroy it. Due to their function, the scavenger cells belong to the leukocytes . Within the white blood cells, the macrophages belong to the cell types capable of phagocytosis .
A macrophage consists of a scavenger cell derived from a monocyte. This cell type incorporates and decomposes antigens as mobile or tissue-adherent particles. In addition to phagocytosis, the presentation of foreign bodies and the formation of cytokines are among the relevant functions of the cell.
Sources and literature
- (1) www.aerzteblatt.de/nachrichten/61450/Makrophagen-erneuern-sich-meist-selbst
- http://www.oekoplus.sepeur-media.de/RUBgesundheitarbeitsplatz/Makrophagen.php
- Prof. Dr. Albert Haas, Institute of Cell Biology, read on
