Macrophage Markers

Macrophage Types, Development, Functions & Markers

Macrophage Markers

Macrophages are generally studied using immunohistochemistry and flow cytometry. Various macrophage markers are commonly chosen, such as CD68, F4/80, CD11b, etc., but the markers selected for your experiment should be based on the macrophage subset and the local environment conditions. There are a limited number of unique macrophage markers, so we recommend using several markers to detect and determine the cell type in your samples. Example of factors to consider when choosing macrophage markers are cell surface markers, secreted cytokines, transcription factor profiles, induced enzymes, etc.

Common Macrophage Markers

M1 & M2 Macrophage Markers

M1 Markers.

M2a Markers.

M2b Markers.

M2c Markers.

M2d Markers.

Macrophage Development

After van Furth and Cohn’s research in the 1960s, it has long been believed that tissue-resident macrophages primarily arise from blood-circulating monocytes that originate from the bone marrow. This model became a foundational concept for the “mononuclear phagocyte system”, which was proposed by van Furth in 1972 as a classification system for macrophages, monocytes, and their progenitor cells.

However, relatively recent studies utilizing genetic fate-mapping techniques have demonstrated that macrophage development is not limited to circulating blood monocytes arising from the bone marrow. Rather, many tissue-resident macrophages develop from embryonic precursors already residing in the tissues before birth. These tissue-resident macrophages have the ability to maintain and replenish themselves through self-renewal, independent of BM-derived precursors.

What Is A Macrophage?

A macrophage is a large white blood cell that detects and eliminates dead cells and foreign antigens of parasitic, viral, or bacterial pathogens via phagocytosis.

Although macrophages are part of the innate immune system, they are also capable of triggering the adaptive immune system by stimulating other immune cells like lymphocytes. Macrophages are present throughout the body in all tissues where they help maintain tissue homeostasis and induce both inflammatory and anti-inflammatory responses.

Macrophage Types

By Location

Tissue-resident macrophages are a heterogenous group of multifunctional immune cells that carry out tissue-specific functions as well as regulate tissue homeostasis and provide the first line of defence.

Below are some examples of tissue-resident macrophages and their locations.

Cell Name Location
Adipose tissue macrophages Adipose tissue (fat)
Osteoclasts Bone
Monocytes Bone marrow/blood
Meningeal macrophages Central nervous system
Microglia Central nervous system
Perivascular macrophages Central nervous system
Tissue macrophages (histiocytes) leading to giant cells Connective tissue
Intestinal lamina propria macrophages Gastrointestinal tract
Epithelioid cells Granulomas
Kupffer cells Liver
Interstitial macrophages Lung tissue interstitium
Alveolar macrophages (aka dust cells) Lungs (pulmonary alveoli)
Peritoneal macrophages Peritoneal cavity (serosal tissues)
LysoMac Peyer's patch
Hofbauer cells Placenta
Pleural macrophages Pleural cavity (serosal tissues)
Langerhans cells Skin
Marginal metallophilic macrophages Spleen (marginal zone)
Marginal zone macrophages Spleen (marginal zone)
Red pulp macrophages Spleen (red pulp)
White pulp (tingible body) macrophages Spleen (white pulp)

M1 & M2 Phenotypes

Aside from classifying by location, macrophages have also been divided into 2 main phenotypes: M1 (classically activated macrophages) and M2 (alternatively activated macrophages).

Through macrophage polarization, macrophages differentiate into specific functional phenotypes depending on the signals received from their microenvironment. Examples of environmental cues in tissues include damaged cells, stimulated lymphocytes, microbes, etc.

M1 Macrophages

Classically activated macrophages (M1) are generally triggered by IFN-gamma and lipopolysaccharide (LPS) to generate immune responses through high levels of proinflammatory cytokines. As a defence against bacteria and viruses, M1 macrophages are capable of metabolizing arginine to nitric oxide (NO) and citrulline. Studies have shown that nitric oxide exhibit antimicrobial and tumoricidal properties.

M1 Macrophage Markers

M2 Macrophages

Alternatively activated macrophages (M2) are typically initiated by some cytokines, such as IL-4, IL-10, or IL-13 to induce anti-inflammatory responses. In contrast to M1 macrophages, M2 macrophages metabolize arginine to urea and ornithine for wound healing and tissue repair and remodeling processes. Ornithine is a precursor of polyamines and proline, which regulate cell proliferation and stimulate collagen production respectively. Scientists have observed M2 phenotypic variations with varying activating stimuli, which has resulted in a classification of M2 subsets - M2a, M2b, M2c, and M2d.

M2 Macrophage Markers

Macrophage Functions

Innate & Adaptive Immunity

As part of the innate immune system, macrophages act as the first line of defense against microorganisms to fight infections. In adaptive immunity, macrophages play roles in antigen presentation, cell debris removal, immune regulation, and inflammation.

Erythrocyte & Iron Homeostasis

Macrophages help regulate erythropoiesis and erythrophagocytosis thereby managing iron metabolism. To maintain iron homeostasis, macrophages must ensure sufficient iron availability while avoiding cytotoxic iron levels.


In addition to eliminating dying cells, macrophages engulf and ingest pathogens and tumor cells. Although macrophages remove a majority of abnormal cells, some pathogens have unfortunately developed anti-phagocytic strategies against macrophages.

Tissue Repair & Regeneration

Tissue-resident macrophages are key players in wounding healing, which involves inflammation followed by tissue repair, remodeling, and regeneration. If the macrophage fails to adopt a tissue-healing phenotype, pathological fibrosis could occur.

Immune Surveillance

Immune surveillance refers to how the immune system patrols the body to detect and destroy virally infected cells and neoplasms. Macrophages play a critical role in this monitoring process.

Macrophage Clinical Significance

Macrophage dysfunction has been linked to a broad range of diseases and disorders, such as obesity, osteoporosis, type 2 diabetes, cancer, hepatic fibrosis, fatty liver disease, asthma, neurodegeneration, atherosclerosis, inflammatory bowel disease, multiple sclerosis, rheumatoid arthritis, and other chronic inflammatory and autoimmune diseases. Aberrant activation and abnormal proliferation of macrophages could also lead to macrophage activation syndrome, a severe complication of pediatric rheumatic disease most prevalent in systemic juvenile idiopathic arthritis (SJIA).

While normal macrophages identify, engulf, and destroy invading microorganisms, they can be hijacked by tumor cells during cancer progression to induce tumor-associated macrophage (TAMs) for tumor growth. TAMs are recognized to infiltrate tumor tissue or reside in the tumor microenvironment (TME) to exert immunosuppressive and pro-tumorigenic effects so that tumor angiogenesis, tumor cell proliferation, metastasis, and chemoresistance can occur.

Due to the association of macrophages with cancer and a wide range of diseases, macrophages and TAMs are being investigated as potential therapeutic targets. However, more research is required to discover and understand the complexity of macrophage development, phenotypes, and functions.

Featured Antibodies As Macrophage Markers

Boster Antibodies & ELISA Kits In Macrophage Research

Anti-CD68 Antibody

Anti-CD68 Antibody

Anti-CD68 Antibody

Researchers investigated iron levels in tumor and metastasis-associated macrophages of breast cancer metastatic mouse models by mapping and measuring hemosiderin-laden macrophage (HLM) deposits through MRI and iron and macrophage histological evaluation. Boster’s anti-CD68 antibody (Catalog no. PA1518) was used as a macrophage marker in the study’s IHC and IF analyses.

Leftin, A., Ben-Chetrit, N., Klemm, F., Joyce, J. A., & Koutcher, J. A. (2017). Iron imaging reveals tumor and metastasis macrophage hemosiderin deposits in breast cancer. Plos One. doi: 10.1371/journal.pone.0184765

Antibodies Of CCR2/4 & ELISA Kits Of CCL2/5/7, TNF-Α, IL-1β, -6, And PGE2

Antibodies Of CCR2/4 & ELISA Kits Of CCL2/5/7, TNF-Α, IL-1β, -6, And PGE2

Antibodies Of CCR2/4 & ELISA Kits Of CCL2/5/7, TNF-Α, IL-1β, -6, And PGE2

Scientists studied the role of Wnt54/SFRP5 axis in macrophage chemotaxis and activation. The researchers used Boster’s CCR2/4 antibodies for western blot to determine if there was CCL2 receptor expression upon Wnt5a transfection. In addition, Boster’s ELISA kits for CCL2/5/7, TNF-α, IL-1β, IL-6, PGE2 were used to quantify concentration in cell culture supernatants.

Zhao, C., Bu, X., Wang, W., Ma, T., & Ma, H. (2014). GEC-derived SFRP5 Inhibits Wnt5a-Induced Macrophage Chemotaxis and Activation. PLoS ONE. doi: 10.1371/journal.pone.0085058

ELISA Kits For IL-1β, IL-6, IL-12, IL-10

ELISA Kits For IL-1β, IL-6, IL-12, IL-10

ELISA Kits For IL-1β, IL-6, IL-12, IL-10

This research studied how β-sitosterol could impact immune regulation of macrophages and serve as a potential therapeutic for rheumatoid arthritis. To measure cytokine production in mouse serum, Boster’s mouse IL-1β, IL-6, IL-12, and IL-10 ELISA kits were used for the study.

Liu, R., Hao, D., Xu, W., Li, J., Li, X., Shen, D., … Zhang, Y. (2019). β-Sitosterol modulates macrophage polarization and attenuates rheumatoid inflammation in mice. Pharmaceutical Biology, 57(1), 161–168. doi: 10.1080/13880209.2019.1577461

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Protocol Overview

Immunohistochemistry (IHC-P)

  • Tissue Preparation
  • Deparaffinization
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  • Blocking
  • Primary Antibody Incubation
  • Secondary Antibody Incubation
  • Staining
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  • In Vitro Cell Stimulation Reference Table
  • Dye efflux staining
  • DNA content or Cell cycle analysis
View FC Protocol

Western Blot

  • Protein Extraction
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  • Protein Transfer
  • Blocking
  • Primary Antibody Incubation
  • Secondary Antibody Incubation
  • Chromogenic or Chemiluminescent Detection
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  • Capture Antibody Coating
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  • Signal Detection
  • Data Analysis
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