Introduction

HMC3 Cells, also known as Human Microglia Clone 3, CHME-3, or CHME3, represent one of the most widely used human microglial cell lines in neuroscience research. The line was established in 1995 by Janabi, Peudenier, Héron and colleagues through SV40 large T antigen-dependent immortalization of human embryonic brain-derived macrophages. [1] HMC3 cells retain core microglial characteristics, including constitutive expression of the ionized calcium-binding adapter molecule Iba-1 and interferon-gamma-inducible expression of MHC class II antigens. [2] [3] As the resident innate immune cells of the central nervous system, microglia are pivotal mediators of neuroinflammatory diseases, Alzheimer disease, and other neurodegenerative diseases. HMC3 cells therefore serve as a tractable human in vitro platform for studying microglial activation, neuroprotective agents, viral neuroinfection, and the tumor microenvironment of glioblastoma.

Key Takeaways

• HMC3 cells are immortalized human fetal brain microglia derived by SV40 large T antigen transfection.
• The cell line expresses Iba-1 constitutively and upregulates MHC class II upon interferon-gamma stimulation; reports on CD14, CD11b and CD68 expression differ between laboratories and should be verified for each specific batch.
• HMC3 cells are a widely used in vitro model for studying neuroinflammatory diseases, Alzheimer disease, and neurodegenerative diseases.
• The line is susceptible to infection by multiple neurotropic viruses, including Zika virus, Borna disease virus 1, chikungunya virus, and rhinovirus.
• HMC3 cells constitutively express NOX4 and generate reactive oxygen species, making them relevant to oxidative stress research.
• The line has been applied in glioblastoma tumor microenvironment studies, drug pharmacology, and biomaterial scaffold research.
• Interleukin-1 beta — alone or combined with interferon-gamma — is the most effective inflammatory stimulus in this line; responses to LPS are comparatively modest, and TNF-alpha and nitric oxide are largely absent.

What is HMC3?

HMC3 (Cellosaurus accession CVCL_II76) is a transformed human microglial cell line derived from the fetal brain of an 8–10-week gestational age embryo. The sex of the donor is unspecified. No disease was associated with the donor. The line was established by Janabi and colleagues in 1995 through transfection of primary embryonic brain macrophage cultures with a plasmid encoding the SV40 large T antigen, yielding four continuous microglial cell lines of which clone 3 became the most widely adopted. [1] The transformed cells retained macrophagic characteristics such as adherence and non-specific esterase activity, and were able to phagocytize zymosan particles, although phagocytic activity remained low. Interleukin-6 was produced spontaneously by the cells, with production further increased after interleukin-1 alpha stimulation. [1] A comprehensive 2018 systematic literature review by Dello Russo and colleagues collated the available characterization data for this clone and clarified an important point of confusion: the same cell line has circulated under the names CHME3, C13-NJ and CHME-5. [3] The review concluded that, irrespective of the designation used, the cells share a comparable antigenic and functional profile and should be regarded as one experimental model — while cautioning that several CHME-5 aliquots in circulation were found to be cross-contaminated with rat glioma cells. The ATCC-authenticated HMC3 (ATCC CRL-3304) stock is free of this ambiguity.

HMC3 Cell Culture Information

HMC3 cells are robust with respect to the choice of basal medium: they have been maintained successfully in EMEM, MEM and DMEM:Ham's F12, each supplemented with 10% serum. [3] This choice is not phenotypically neutral, however. Dello Russo and colleagues reported that basal reactive oxygen species production was markedly lower in cells grown in MEM or DMEM:F12 than in EMEM, indicating a less activated resting phenotype. [3] Investigators comparing data across laboratories should therefore record the medium used alongside the passage number.

Advantages of HMC3 Cells

HMC3 cells offer a uniquely accessible human microglial model at a time when primary human microglia are difficult to obtain in sufficient quantities for large-scale research. The line grows adherently and is straightforward to maintain. Crucially, the cells express Iba-1 constitutively, upregulate MHC class II in response to interferon-gamma, and — in the ATCC-authenticated stock — transcribe the more recently defined microglial signature genes CX3CR1, CSF1R, P2RY12 and TMEM119, providing a biologically validated proxy for primary human microglia. [2] [3] These properties make HMC3 cells a widely used platform for mechanistic studies of neuroinflammatory diseases that require reproducible, scalable, and fully human cellular material.

A further strength of HMC3 cells is their responsiveness to a defined panel of inflammatory stimuli. The most effective inducer of interleukin-6 is interleukin-1 beta, which raises basal release by up to fiftyfold and acts synergistically with interferon-gamma; LPS and amyloid beta-peptides elicit more modest, concentration-dependent increases. [3] This graded, reproducible response profile enables concentration-dependent and time-course experiments that are difficult to achieve in primary cell preparations. Their responsiveness to both pro-inflammatory and anti-inflammatory stimuli — including pharmacological agents such as rapamycin and dexmedetomidine — further extends their utility in drug pharmacology and the screening of neuroprotective agents. [4] [5] The cells are also susceptible to multiple neurotropic viruses, broadening their use to neuroinfectiology research.

Limitations of HMC3 Cells

As a transformed cell line, HMC3 cells carry the SV40 large T antigen, which confers immortality but also alters aspects of cell biology relative to primary microglia. Li and colleagues reported unexpected NOX isoform expression patterns — abundant NOX4 but almost no NOX2 mRNA — which contrasts with primary microglia and limits the utility of this line as a model for NOX2-mediated respiratory burst. [2] [3] Researchers should therefore verify that the specific pathway under study is faithfully recapitulated in this line before drawing broad mechanistic conclusions.

Three further constraints deserve attention. First, the inflammatory mediator repertoire is incomplete: HMC3 cells secrete only marginal amounts of the anti-inflammatory cytokine IL-10 (in the range of a few pg/ml), produce little or no TNF-alpha either spontaneously or after pro-inflammatory activation, and show constitutively elevated IL-6 driven by NOX4-dependent reactive oxygen species. [2] [3] Second, and in marked contrast to rodent microglia, resting HMC3 cells do not express iNOS, and neither iNOS induction nor measurable nitrite accumulation has been observed after stimulation with LPS, LPS plus interferon-gamma, IL-1 beta or TNF-alpha. [3] Studies centred on the nitric oxide axis are therefore not well served by this model.

Third, the line was established from fetal brain tissue, meaning its transcriptional and functional profile may differ from adult-onset microglial states relevant to late-life neurodegenerative diseases. Investigators modelling adult Alzheimer disease or Parkinson's disease should interpret HMC3-derived data alongside complementary adult primary or iPSC-derived microglial systems where feasible. Finally, reports on the surface marker profile are not fully concordant: whereas Li and colleagues described constitutive Iba-1 and CD14 with interferon-gamma-inducible CD11b, CD68 and MHC class II, [2] both the original characterization by Janabi and colleagues [1] and the flow cytometric data reported by Dello Russo and colleagues for ATCC CRL-3304 found resting cells to be CD14- and CD11b-negative, with neither marker induced by interferon-gamma. [3] Antibody clone, culture medium and passage number all influence these readouts, and genetic drift on serial passaging is documented for continuous lines generally; marker expression should be confirmed in-house rather than assumed.

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Applications of HMC3 Cells

Neuroinflammation and Microglial Activation

The study of neuroinflammatory diseases represents the most extensively developed application of HMC3 cells. Li and colleagues demonstrated that HMC3 cells constitutively express NOX4, which drives continuous reactive oxygen species production and sustained IL-6 expression — a finding that positioned these cells as a model for chronic, low-grade neuroinflammation. [2] This constitutive inflammatory tone mirrors aspects of microglial priming observed in neurodegenerative conditions, providing a relevant baseline for intervention studies.

An influential study by Baek and colleagues examined BET bromodomain inhibition in HMC3 cells using RNA sequencing. [6] The authors showed that the BET inhibitor JQ1 attenuated the inflammatory and migratory response of LPS-activated HMC3 cells, and identified the mechanism: LPS induces the transcription factor IRF1, which directly regulates chemokine, cytokine, interferon-stimulated and migration-related genes, and JQ1 markedly reduces IRF1 together with its target genes. Knockdown of IRF1 reproduced the effect and inhibited microglial migration. [6] This work established the BET–IRF1 axis as a druggable target in human microglial neuroinflammation and demonstrated the suitability of HMC3 cells for pharmacological intervention studies at a mechanistic level.

Mitochondrial damage-associated molecular patterns were also examined in this line. Nasi and colleagues found that stimulation with mitochondrial DNA and cardiolipin increased cellular oxidative stress in HMC3 cells, while notably failing to trigger a classical pro-inflammatory response: HLA-DR expression was not upregulated and neither TNF-alpha nor IL-6 secretion increased. [7] The authors interpreted this as a possible endogenous regulatory mechanism limiting microglial activation. Separately, Cappoli and colleagues showed that the mTOR inhibitor rapamycin paradoxically enhanced IL-6 expression and release in HMC3 cells activated with an interferon-gamma/IL-1 beta cocktail, while simultaneously reducing reactive oxygen species production — challenging assumptions about rapamycin's anti-inflammatory actions in human brain-resident immune cells. [4] These studies collectively demonstrate HMC3 cells as a sensitive, human-relevant system for dissecting the molecular pathways underlying neuroinflammatory diseases.

Alzheimer Disease and Neurodegenerative Disease Modelling

HMC3 cells have become an important tool for modelling the microglial contribution to Alzheimer disease. An early characterization study by Lindberg and colleagues, performed on this clone under the name CHME3, established that freshly dissolved amyloid beta(1–40) produced a dose-dependent increase in IL-6 release alongside a dose-dependent loss of viability. [8] Alpha-melanocyte-stimulating hormone did not modify the amyloid beta-induced IL-6 response, but raised basal IL-6 release dose-dependently, an effect attributed to the melanocortin receptor subtypes MCR3 or MCR5. [8] This work validated HMC3 cells as a tractable platform for studying the relationship between amyloid beta-peptides and microglial inflammatory responses that are central to Alzheimer disease pathogenesis.

González-Prieto and colleagues investigated CX3CR1 — the sole receptor for the neuronal chemokine CX3CL1 — in Alzheimer disease. [9] CX3CR1 production was increased in the cortex of 5xFAD mice and human Alzheimer disease brain samples, and administration of the noradrenaline reuptake inhibitor reboxetine increased it further in vivo. Direct application of noradrenaline to HMC3 cells and to primary rat microglia, by contrast, inhibited CX3CR1 production. [9] The authors concluded that microglial responses to noradrenaline may be altered in the absence of CX3CL1-producing neurons or other non-microglial factors — an instructive example of how HMC3 cells can isolate a cell-autonomous response and thereby expose the contribution of the wider tissue context.

The dexmedetomidine study by Li and colleagues used LPS- and ATP-stimulated HMC3 cells as a model of NLRP3 inflammasome-driven neuroinflammation relevant to Alzheimer disease. [5] Dexmedetomidine suppressed IL-1β and IL-18 release via a c-Fos/NLRP3/caspase-1 cascade, identifying a mechanistically novel anti-inflammatory axis in human microglia. HMC3 cells have also served as a model to investigate microglial polarization in response to phytoestrogen-containing plant extracts, further extending their utility in neurodegenerative disease drug discovery. [10] [11]

Virology and CNS Infection

HMC3 cells have proven highly versatile for studying viral neuroinfection, given their human origin and their position as a model for the microglial first line of defense in the central nervous system. Martinez Viedma and Pickett compared the host response of HMC3 microglial cells and JEG-3 placental cells to Zika virus infection using a panel of 84 innate and adaptive immune genes profiled at 24 and 72 hours post-infection. [12] The two cell types showed distinct sets of differentially expressed genes, and pathway analysis indicated that TLR7/8 signalling was suppressed in the microglial cells while being activated in the placental cells — a divergence subsequently probed by siRNA experiments. The study established HMC3 cells as a suitable platform for host–pathogen transcriptomics in CNS virology.

Zhang and colleagues used BoDV-1-infected HMC3 cells to demonstrate that miR-146a facilitates viral replication by suppressing the IRAK1/TRAF6/NF-κB innate immune signalling axis. [13] This finding provided mechanistic insight into how a highly neurotropic RNA virus evades microglial antiviral responses. In a separate infection model, Angel-Ambrocio and colleagues demonstrated for the first time that human rhinovirus completes its entire viral cycle in HMC3 cells, establishing microglia as a potential cellular reservoir for rhinovirus-associated CNS complications. [14] The line also supports chikungunya virus replication without significant loss of viability until 72 hours post-infection. [19]

Sharma and colleagues identified prohibitin 1/2 as a putative entry receptor for dengue virus serotype 3 in microglial CHME-3 cells — a synonym of HMC3 — using virus overlay protein binding assays, LC-MS/MS proteomics, siRNA knockdown and co-immunoprecipitation. [15] Notably, the same dependency was found in neuronal SH-SY5Y cells but not in astroglial U-87 MG cells, indicating that the entry route is cell-type specific. Taken together, these virology studies underline HMC3 cells as a broadly applicable human microglial model for investigating the pathogenesis and immune evasion strategies of neurotropic viruses.

Glioblastoma Tumor Microenvironment

HMC3 cells have been applied as a model of glioma-associated microglia to study how glioblastoma tumor cells co-opt the microglial inflammatory phenotype. Li and colleagues demonstrated that co-culturing temozolomide-resistant glioblastoma cells with HMC3 cells promoted M2 polarization of HMC3 cells and increased secretion of the pro-tumorigenic cytokines TGF-β and IL-6. [16] This polarization was linked to the lncRNA SNHG15/miR-627-5p/CDK6 circuit, and the CDK4/6 inhibitor palbociclib reduced M2 markers while overcoming temozolomide resistance in patient-derived xenograft models.

These findings position HMC3 cells as a relevant human model for studying microglial contributions to the immunosuppressive glioblastoma tumor microenvironment. The ability to model microglia–glioblastoma crosstalk in vitro using HMC3 cells provides a tractable system for identifying therapeutic targets that simultaneously address tumor cell resistance and immune evasion. [16]

Neuroprotective Agents and Drug Pharmacology

HMC3 cells have been extensively employed for screening neuroprotective agents and characterising their mechanisms of action in human microglia. Martínez Leo and Segura Campos evaluated peptide fractions from Salvia hispanica seeds for neuroprotective activity in HMC3 cells, finding that the 1–3 kDa fraction reduced reactive oxygen species production by 51.3% and lowered the release of nitric oxide, TNF-alpha and IL-6, with an overall protective effect of 79.0%. [17] This type of study illustrates how HMC3 cells enable rapid, human-relevant screening of food-derived bioactive compounds.

Ma'arif and colleagues conducted two related studies using HMC3 cells to evaluate plant-derived phytoestrogens from Marsilea crenata leaves. The n-butanol fraction reduced MHC class II expression in interferon-gamma-activated cells, consistent with inhibition of classical M1 activation, although the reported dose–response was non-monotonic. [10] A 96% ethanol extract increased expression of the M2 marker Arginase-1; the same study reported a decrease in activated estrogen receptor beta expression at 125 and 250 ppm, a result that sits in tension with the paper's own title and should be treated as unresolved. [11] Both studies leveraged the well-characterised interferon-gamma polarization protocol in HMC3 cells to investigate potential phytoestrogenic neuroprotection in postmenopausal neuroinflammation.

In the field of biomaterials and tissue engineering, Venkateswarlu and colleagues used live HMC3 cells cultured on electrospun scaffold matrices to develop a real-time volumetric imaging workflow for cytosolic calcium oscillations using laser scanning confocal microscopy. [18] This work extended the application of HMC3 cells beyond classical pharmacology into next-generation biomaterial testing, illustrating the versatility of the line across diverse technological contexts in neuroscience research.

Conclusion

HMC3 cells — the human microglial clone 3 — have established themselves as a cornerstone in vitro model for neuroinflammatory diseases, Alzheimer disease, neurodegenerative diseases, CNS virology, glioblastoma tumor microenvironment research, and neuroprotective agent discovery. Derived from human fetal brain tissue and immortalized by SV40 transfection, the line expresses key microglial markers and responds to a defined range of inflammatory, pharmacological, and infectious stimuli. Studies such as the BET inhibitor work by Baek and colleagues have demonstrated the line's power for identifying druggable targets in human microglial neuroinflammation. From fundamental mechanistic studies of reactive oxygen species and NLRP3 inflammasome signalling to applied screens of plant-derived neuroprotective agents and scaffold-based biomaterial testing, HMC3 cells offer exceptional versatility — provided their documented limitations regarding TNF-alpha, nitric oxide and NOX2 biology are taken into account when designing experiments. Researchers seeking a validated, scalable, and fully human microglial model will find HMC3 cells a valuable resource for advancing understanding of brain immunity and disease. To order HMC3 cells or request further information about product specifications, visit cytion.com.

Key Publications

1. Janabi N, Peudenier S, Héron B (1995) Establishment of human microglial cell lines after transfection of primary cultures of embryonic microglial cells with the SV40 large T antigen. Neuroscience letters. PMID: 7478261
2. Li B, Bedard K, Sorce S (2009) NOX4 expression in human microglia leads to constitutive generation of reactive oxygen species and to constitutive IL-6 expression. Journal of innate immunity. PMID: 20375612
3. Dello Russo C, Cappoli N, Coletta I (2018) The human microglial HMC3 cell line: where do we stand? A systematic literature review. Journal of neuroinflammation. PMID: 30200996
4. Cappoli N, Mezzogori D, Tabolacci E (2019) The mTOR kinase inhibitor rapamycin enhances the expression and release of pro-inflammatory cytokine interleukin 6 modulating the activation of human microglial cells. EXCLI journal. PMID: 31645839
5. Li H, Zhang X, Chen M (2018) Dexmedetomidine inhibits inflammation in microglia cells under stimulation of LPS and ATP by c-Fos/NLRP3/caspase-1 cascades. EXCLI journal. PMID: 29743866
6. Baek M, Yoo E, Choi HI (2021) The BET inhibitor attenuates the inflammatory response and cell migration in human microglial HMC3 cell line. Scientific reports. PMID: 33893325
7. Nasi M, De Gaetano A, Bianchini E (2020) Mitochondrial damage-associated molecular patterns stimulate reactive oxygen species production in human microglia. Molecular and cellular neurosciences. PMID: 32828963
8. Lindberg C, Hjorth E, Post C (2005) Cytokine production by a human microglial cell line: effects of beta-amyloid and alpha-melanocyte-stimulating hormone. Neurotoxicity research. PMID: 16371321
9. González-Prieto M, Gutiérrez IL, García-Bueno B (2021) Microglial CX3CR1 production increases in Alzheimer's disease and is regulated by noradrenaline. Glia. PMID: 32662924
10. Ma'arif B, Mirza DM, Hasanah M (2020) Antineuroinflammation activity of n-butanol fraction of Marsilea crenata Presl. in microglia HMC3 cell line. Journal of basic and clinical physiology and pharmacology. PMID: 31967965
11. Ma'arif B, Agil M, Laswati H (2020) The enhancement of Arg1 and activated ERβ expression in microglia HMC3 by induction of 96% ethanol extract of Marsilea crenata Presl. leaves. Journal of basic and clinical physiology and pharmacology. PMID: 31981453
12. Martinez Viedma MDP, Pickett BE (2018) Characterizing the Different Effects of Zika Virus Infection in Placenta and Microglia Cells. Viruses. PMID: 30453684
13. Zhang X, Guo Y, Xu X (2019) miR-146a promotes Borna disease virus 1 replication through IRAK1/TRAF6/NF-κB signaling pathway. Virus research. PMID: 31330207
14. Angel-Ambrocio AH, Bautista-Carbajal P, García-León ML (2020) Microglia HMC3 cells are highly susceptible to Rhinovirus infection. Virus research. PMID: 32768491
15. Sharma A, Vasanthapuram R, M Venkataswamy M (2020) Prohibitin 1/2 mediates Dengue-3 entry into human neuroblastoma (SH-SY5Y) and microglia (CHME-3) cells. Journal of biomedical science. PMID: 32306962
16. Li Z, Zhang J, Zheng H (2019) Modulating lncRNA SNHG15/CDK6/miR-627 circuit by palbociclib, overcomes temozolomide resistance and reduces M2-polarization of glioma associated microglia in glioblastoma multiforme. Journal of experimental & clinical cancer research : CR. PMID: 31462285
17. Martínez Leo EE, Segura Campos MR (2020) Neuroprotective effect from Salvia hispanica peptide fractions on pro-inflammatory modulation of HMC3 microglial cells. Journal of food biochemistry. PMID: 32207175
18. Venkateswarlu K, Suman G, Dhyani V (2020) Three-dimensional imaging and quantification of real-time cytosolic calcium oscillations in microglial cells cultured on electrospun matrices using laser scanning confocal microscopy. Biotechnology and bioengineering. PMID: 32557561
19. Qadri SW, Kumar N, Santhoshkumar R (2022) Infection of human microglial cell line CHME-3 to study neuropathogenesis of Chikungunya virus. Journal of neurovirology. PMID: 35352315