macrophages

WKP

See also : histiocytes

Images

 sea-blue histiocytes

• https://twitter.com/KyleBradleyMD/status/748512208993271808

 leishmania bodies in macrophages

• https://twitter.com/JCandidoXavier/status/1509085650066284545

Macrophages exist in almost all animals. In some invertebrates, mesenchymal cells, endothelial cells or fibroblast-like cells can transform into macrophages.

In vertebrates, primitive macrophages first develop in yolk sac hematopoiesis and differentiate into fetal macrophages. Monocytes are differentiated from hematopoietic stem cells in the late stage of fetal hematopoietic organs and bone marrow. Macrophages serve as an effector in metabolism and host defense.

Depletion of macrophages severely reduced bilirubin production and host resistance to infection.

Macrophage scavenger receptors are involved in host defense.

Macrophage growth factors are critical for macrophage differentiation and function. In macrophage colony-stimulating factor (M-CSF)-deficient osteopetrotic mice, monocytes, tissue macrophages and osteoclasts are deficient.

Granulocyte-macrophage colony-stimulating factor (GM-CSF)-deficient mice develop alveolar proteinosis due to impaired surfactant catabolism by alveolar macrophages.

Accumulation of glucocerebroside in macrophages due to the deficiency of glucocerebrosidase in lysosomes produces Gaucher cells.

Macrophages in the arterial wall incorporate chemically modified low-density lipoprotein (LDL) and transform into foam cells.

Binding oxidized LDL to liver X receptor alpha (LXRalpha) upregulates the expression of its target genes, which act as cholesterol removers from macrophages.

Inflammatory signals downregulate the expression of LXRalpha and enhance lipid accumulation. Thus, macrophages play a pivotal role in metabolism and host defense.

Localization

 hepatic macrophages

• hepatic ceroid-laden macrophages
• portal lipid-laden macrophages

 renal macrophages

• foamy macrophages in renal tubules

Pathology

 enlarged macrophages

• lipid-laden marcophages (foamy macrophages)
• ceroid-laden macrophages
• cellular debris-laden macrophages
• sea-blue histiocytes

 siderophages
 epithelioid cells

Immunophenotype

 CD68+
 HAM-56+
 alpha 1-antitrypsin +
 alpha 1-antichymotrypsin +
 lisozyme +
 alpha-subunit of S-100 protein +
 CD1a-

Pathology

 histiocytoses / histiocytosis
 macrophagic activation syndrome
  histiocytic tumors / histiocytic proliferation

Localization

 hepatic macrophages
 pulmonary macrophages
 splenic macrophages

See also

 Histiocytes

• dendritic cells

 tumor-educated macrophages
 foamy macrophages

References

 Naito M. Macrophage differentiation and function in health and disease. Pathol Int. 2008 Mar;58(3):143-55. Review. PMID: 18251777

 Vignery A. Macrophage fusion: are somatic and cancer cells possible partners? Trends Cell Biol. 2005 Apr;15(4):188-93. PMID: 15817374

 Fujiwara N, Kobayashi K. Macrophages in inflammation.
Curr Drug Targets Inflamm Allergy. 2005 Jun;4(3):281-6. PMID: 16101534