Macrophage

macrophagesM2 macrophagesTissue macrophagesCD68 + macrophagesM2 macrophagemacrophage biologymacrophage cellsmacrophage phagocytosismacrophagicmelanophages
Macrophages (big eaters, from Greek μακρός (makrós) = large, φαγεῖν (phagein) = to eat ) are a type of white blood cell, of the immune system, that engulfs and digests cellular debris, foreign substances, microbes, cancer cells, and anything else that does not have the type of proteins specific to healthy body cells on its surface in a process called phagocytosis.wikipedia
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Kupffer cell

Kupffer cellsKuppfer cellstellate
They take various forms (with various names) throughout the body (e.g., histiocytes, Kupffer cells, alveolar macrophages, microglia, and others), but all are part of the mononuclear phagocyte system.
Kupffer cells, also known as stellate macrophages and Kupffer–Browicz cells, are specialized macrophages located in the liver, lining the walls of the sinusoids.

Microglia

microglial cellsmicroglialmicroglial cell
They take various forms (with various names) throughout the body (e.g., histiocytes, Kupffer cells, alveolar macrophages, microglia, and others), but all are part of the mononuclear phagocyte system.
As the resident macrophage cells, they act as the first and main form of active immune defense in the central nervous system (CNS).

Alveolar macrophage

Alveolar macrophagesmacrophages, alveolardust cell
They take various forms (with various names) throughout the body (e.g., histiocytes, Kupffer cells, alveolar macrophages, microglia, and others), but all are part of the mononuclear phagocyte system.
An alveolar macrophage (or dust cell) is a type of macrophage, a professional phagocyte, found in the pulmonary alveoli, near the pneumocytes, but separated from the wall.

Histiocyte

histiocyteshistiocytichistiocytic-dendritic cells
They take various forms (with various names) throughout the body (e.g., histiocytes, Kupffer cells, alveolar macrophages, microglia, and others), but all are part of the mononuclear phagocyte system.
The histiocyte is a tissue macrophage or a dendritic cell (histio, diminutive of histo, meaning tissue, and cyte, meaning cell).

Phagocytosis

phagocyticphagocytosedphagocytose
Macrophages (big eaters, from Greek μακρός (makrós) = large, φαγεῖν (phagein) = to eat ) are a type of white blood cell, of the immune system, that engulfs and digests cellular debris, foreign substances, microbes, cancer cells, and anything else that does not have the type of proteins specific to healthy body cells on its surface in a process called phagocytosis.
Neutrophils, macrophages, monocytes, dendritic cells, osteoclasts and eosinophils can be classified as professional phagocytes.

Mononuclear phagocyte system

reticuloendothelialmononuclear phagocytic systemLymphoreticular
They take various forms (with various names) throughout the body (e.g., histiocytes, Kupffer cells, alveolar macrophages, microglia, and others), but all are part of the mononuclear phagocyte system.
The cells are primarily monocytes and macrophages, and they accumulate in lymph nodes and the spleen.

Monocyte

monocytesmonocyticmononuclear
Human macrophages are about 21 um in diameter and are produced by the differentiation of monocytes in tissues. When a monocyte enters damaged tissue through the endothelium of a blood vessel, a process known as leukocyte extravasation, it undergoes a series of changes to become a macrophage.
They are the largest type of leukocyte and can differentiate into macrophages and myeloid lineage dendritic cells.

Innate immune system

innate immunityinnateinnate immune response
Besides phagocytosis, they play a critical role in nonspecific defense (innate immunity) and also help initiate specific defense mechanisms (adaptive immunity) by recruiting other immune cells such as lymphocytes.
The process of acute inflammation is initiated by cells already present in all tissues, mainly resident macrophages, dendritic cells, histiocytes, Kupffer cells, and mast cells.

Immune system

immuneimmune responseimmune function
Macrophages (big eaters, from Greek μακρός (makrós) = large, φαγεῖν (phagein) = to eat ) are a type of white blood cell, of the immune system, that engulfs and digests cellular debris, foreign substances, microbes, cancer cells, and anything else that does not have the type of proteins specific to healthy body cells on its surface in a process called phagocytosis.
The innate leukocytes include the phagocytes (macrophages, neutrophils, and dendritic cells), innate lymphoid cells, mast cells, eosinophils, basophils, and natural killer cells.

White blood cell

leukocyteleukocyteswhite blood cells
Macrophages (big eaters, from Greek μακρός (makrós) = large, φαγεῖν (phagein) = to eat ) are a type of white blood cell, of the immune system, that engulfs and digests cellular debris, foreign substances, microbes, cancer cells, and anything else that does not have the type of proteins specific to healthy body cells on its surface in a process called phagocytosis.
Monocytes eventually leave the bloodstream and become tissue macrophages, which remove dead cell debris as well as attack microorganisms.

Élie Metchnikoff

Ilya Ilyich MechnikovIlya MechnikovElie Metchnikoff
Macrophages were first discovered by Élie Metchnikoff, a Russian zoologist, in 1884.
In particular, he is credited with the discovery of phagocytes (macrophages) in 1882.

Inflammation

inflammatoryinflammatory responseinflamed
Beyond increasing inflammation and stimulating the immune system, macrophages also play an important anti-inflammatory role and can decrease immune reactions through the release of cytokines.
The process of acute inflammation is initiated by resident immune cells already present in the involved tissue, mainly resident macrophages, dendritic cells, histiocytes, Kupffer cells and mast cells.

Adaptive immune system

adaptive immunityadaptive immune responseadaptive
Besides phagocytosis, they play a critical role in nonspecific defense (innate immunity) and also help initiate specific defense mechanisms (adaptive immunity) by recruiting other immune cells such as lymphocytes.
Dendritic cells, B-cells, and macrophages are equipped with special "co-stimulatory" ligands recognized by co-stimulatory receptors on T cells, and are termed professional antigen-presenting cells (APCs).

Adipose tissue macrophages

ATMs) comprise tissue resident macrophages present in adipose tissue.

CD68

ED1macrosialin
They can be identified using flow cytometry or immunohistochemical staining by their specific expression of proteins such as CD14, CD40, CD11b, CD64, F4/80 (mice)/EMR1 (human), lysozyme M, MAC-1/MAC-3 and CD68.
CD68 (Cluster of Differentiation 68) is a protein highly expressed by cells in the monocyte lineage (e.g., monocytic phagocytes, osteoclasts), by circulating macrophages, and by tissue macrophages (e.g., Kupffer cells, microglia).

Lysozyme

LYZmuramidaselysozymes
They can be identified using flow cytometry or immunohistochemical staining by their specific expression of proteins such as CD14, CD40, CD11b, CD64, F4/80 (mice)/EMR1 (human), lysozyme M, MAC-1/MAC-3 and CD68.
It is also present in cytoplasmic granules of the macrophages and the polymorphonuclear neutrophils (PMNs).

Adipose tissue

adiposebody fatfat
Within the fat (adipose) tissue of CCR2 deficient mice, there is an increased number of eosinophils, greater alternative macrophage activation, and a propensity towards type 2 cytokine expression.
SVF includes preadipocytes, fibroblasts, adipose tissue macrophages, and endothelial cells.

Testicle

testestestistesticles
In the testis, for example, macrophages have been shown to be able to interact with Leydig cells by secreting 25-hydroxycholesterol, an oxysterol that can be converted to testosterone by neighbouring Leydig cells.

Antigen presentation

antigen recognitionpresentedpresent
For example, they are important as antigen presenters to T cells.
Only APCs do express the class II of MHC molecules on the surface in large quantity, such as dendritic cells, B cells or macrophages, so expression of MHC-II molecules is more cell-specific than MHC-I.

Osteoclast

osteoclastsodontoclastanti-osteoclastogenic
When osteoclast-inducing cytokines are used to convert macrophages to osteoclasts, very large cells that may reach 100 µm in diameter occur.

Central nervous system

CNScentralcentral nervous system (CNS)
Different forms of glial cells have different functions, some acting almost as scaffolding for neuroblasts to climb during neurogenesis such as bergmann glia, while others such as microglia are a specialized form of macrophage, involved in the immune system of the brain as well as the clearance of various metabolites from the brain tissue.

Leukocyte extravasation

diapedesisleukocyte adhesion cascadeextravasate
When a monocyte enters damaged tissue through the endothelium of a blood vessel, a process known as leukocyte extravasation, it undergoes a series of changes to become a macrophage.
Monocytes also use this process in the absence of infection or tissue damage during their development into macrophages.

Bone

cortical bonebone tissuecancellous bone
Osteoblasts and osteocytes are derived from osteoprogenitor cells, but osteoclasts are derived from the same cells that differentiate to form macrophages and monocytes.

Connective tissue

fibrous tissuefibrous connective tissueconnective
The cells of connective tissue include fibroblasts, adipocytes, macrophages, mast cells and leucocytes.

Spleen

splenicsplenetichilum
The spleen contains half the body's monocytes in reserve ready to be deployed to injured tissue.
These monocytes, upon moving to injured tissue (such as the heart after myocardial infarction), turn into dendritic cells and macrophages while promoting tissue healing.