Macrophages (Greek: "big eaters", makros = large, phagein = eat) are cells within the tissues that originate from specific white blood cells called monocytes. Monocytes and macrophages are phagocytes, acting in both nonspecific defence (or innate immunity) as well as specific defense (or cell-mediated immunity) of vertebrate animals. Their role is to phagocytize (engulf and then digest) cellular debris and pathogens either as stationary or mobile cells, and to stimulate lymphocytes and other immune cells to respond to the pathogen.

AM-3K

• In routine pathological specimens, AM-3K is a useful marker for anti-inflammatory macrophages because these cells can be distinguished from inflammatory or classically activated macrophages. Immunohistochemical staining of routinely processed pathological specimens revealed that AM-3K recognized a specialized subpopulation of macrophages. PMID: 16517975

7C3

• a marker for the differentiation of human macrophage cell lines. PMID: 3119752

25F9

• a marker for endocytosis rather than maturation. PMID: 3500252
• resident macrophage marker. PMID: 7541406
• late stage inflammation marker. PMID: 7599096

27E10

• a distinct marker for macrophage activation and differentiation. PMID: 10066957
• inflammatory macrophage marker. PMID: 7541406
• early stage inflammation marker. PMID: 7599096

Carboxypeptidase M (CPM)

• a marker of macrophage maturation in vitro and in vivo. PMID: 10849748; PMID: 9553769

Cathepsin K

• a marker of macrophage differentiation. PMID: 11673837

Chitotriosidase

• a marker of macrophage stimulation. PMID: 11177289

CD14

• The soluble form of the CD14 molecule (sCD14), a macrophage activity marker. PMID: 12446022
• CD14 surface molecule is predominantly expressed by cells of myeloid origin and regarded as a specific marker for macrophages (M phi). PMID: 9286353

CD68 (Ki-M7, Y2/131, Y1/82A, EBM11)

• classical macrophage marker. PMID: 16888915
• a 110-Kd transmembrane glycoprotein. PMID: 7680921, PMID: 7680921
• expressed by human monocytes and tissue macrophages. PMID: 7680921, PMID: 7680921
• not restricted to the macrophage lineage, but also expressed in fibroblasts. PMID: 16888915
• more frequently positive than the other examined macrophage markers, and proved to be almost as reliable as the recently discovered CD1a. PMID: 9254359

CD163

• a specific marker of macrophages in paraffin-embedded tissue samples. PMID: 15491976
• Within RA synovium, CD163 has major advantages as a macrophage marker and does not appear to be restricted to "mature" macrophages. CD163 discriminates between synovial macrophages and synovial intimal fibroblasts, which also stain positively for CD68 in diseased tissue. PMID: 12115225
• CD163 is a marker of activated macrophages. PMID: 16047947

CD163 soluble (sCD163)

• a marker molecule for monocyte/macrophage activity in disease. PMID: 12570164
• a macrophage-specific serum marker. PMID: 16915112

CSF-1R (colony-stimulating factor-1 receptor)

• a specific marker of macrophages. PMID: 16137767

ED-1

• used widely as a marker for rat macrophages. PMID: 7821959
• expressed on the membranes of cytoplasmic granules, like phagolysosomes, as well as on the cell surface. PMID: 7821959
• a macrophage and monocyte marker. PMID: 15634662, PMID: 8327856
• recognizes a cytoplasmic antigen in monocytes and in most macrophages. PMID: 3882559

ED-2

• a resident macrophage marker. PMID: 9777585  
• ED2 and ED3 recognize membrane antigens of tissue macrophages. PMID: 3882559

EMR1 (epidermal growth factor module-containing mucin-like receptor 1)

• EMR1 is the best macrophage marker to date and CD14 and CD68 are not macrophage-specific proteins. PMID: 16213494

F4/80

• F4/80 is the best macrophage marker to date and CD14 and CD68 are not macrophage-specific proteins. PMID: 16213494

Factor XIII-A

• a marker of alternative macrophage activation. PMID: 16132226

Ferritin

• The combination of high ferritin level and low percentage of glycosylation may be a marker of excessive macrophage activation. PMID: 12734900

HAM-56

• pan-macrophage marker. PMID: 2143883
• a sensitive, specific (with the exception of endothelial cells), and reliable marker of central nervous system macrophages. PMID: 1376020

Ki-M1P

• a reliable marker for brain macrophages and microglial cells in routinely processed normal and non-neoplastic tissues. PMID: 1462766

Lysozyme M

• a macrophage-specific marker. PMID: 9831245

MAC-1/MAC-3

• mannose receptor as a specific marker in flow cytometry and immunohistochemistry for macrophages. PMID: 9000538

Myeloid-related protein (MRP) 14

• an intracellular protein involved in calcium-dependent activation of myeloid cells, presents a differentiation marker for a subtype of macrophages. PMID: 11205374

RFD7/RFD9

• RFD7 is a marker of mature macrophages, RFD9 is a marker of epithelioid cells and macrophages of germinal centers. PMID: 11354548

RM3/1

• intermediate stage inflammation marker. PMID: 7599096
• macrophages of late phase inflammation. PMID: 11354548