CCR8 Gene

CCR8 Gene — C-C Chemokine Receptor Type 8

Overview

<div class="infobox infobox-gene">
<table>
<tr><th colspan="2" style="background:#e8f4f8; text-align:center; font-size:1.1em;">CCR8 Gene</th></tr>
<tr><td><strong>Gene Symbol</strong></td><td>CCR8</td></tr>
<tr><td><strong>Full Name</strong></td><td>C-C Chemokine Receptor Type 8</td></tr>
<tr><td><strong>Chromosomal Location</strong></td><td>3p22.2</td></tr>
<tr><td><strong>NCBI Gene ID</strong></td><td>[2919](https://www.ncbi.nlm.nih.gov/gene/2919)</td></tr>
<tr><td><strong>OMIM</strong></td><td>[604468](https://www.omim.org/entry/604468)</td></tr>
<tr><td><strong>Ensembl ID</strong></td><td>ENSG00000179934</td></tr>
<tr><td><strong>UniProt ID</strong></td><td>[P41597](https://www.uniprot.org/uniprot/P41597)</td></tr>
<tr><td><strong>Protein Size</strong></td><td>355 amino acids</td></tr>
<tr><td><strong>Associated Diseases</strong></td><td>Multiple Sclerosis, Alzheimer's Disease, Atopic Dermatitis, Cancer</td></tr>
</table>
</div>

CCR8 Gene — C-C Chemokine Receptor Type 8

Overview

<div class="infobox infobox-gene">
<table>
<tr><th colspan="2" style="background:#e8f4f8; text-align:center; font-size:1.1em;">CCR8 Gene</th></tr>
<tr><td><strong>Gene Symbol</strong></td><td>CCR8</td></tr>
<tr><td><strong>Full Name</strong></td><td>C-C Chemokine Receptor Type 8</td></tr>
<tr><td><strong>Chromosomal Location</strong></td><td>3p22.2</td></tr>
<tr><td><strong>NCBI Gene ID</strong></td><td>[2919](https://www.ncbi.nlm.nih.gov/gene/2919)</td></tr>
<tr><td><strong>OMIM</strong></td><td>[604468](https://www.omim.org/entry/604468)</td></tr>
<tr><td><strong>Ensembl ID</strong></td><td>ENSG00000179934</td></tr>
<tr><td><strong>UniProt ID</strong></td><td>[P41597](https://www.uniprot.org/uniprot/P41597)</td></tr>
<tr><td><strong>Protein Size</strong></td><td>355 amino acids</td></tr>
<tr><td><strong>Associated Diseases</strong></td><td>Multiple Sclerosis, Alzheimer's Disease, Atopic Dermatitis, Cancer</td></tr>
</table>
</div>

CCR8 encodes the C-C Chemokine Receptor Type 8, a G protein-coupled receptor primarily expressed on type 2 helper T cells (Th2), regulatory T cells (Tregs), and certain myeloid cell populations. This receptor binds multiple ligands including CCL1 (I-309), CCL16 (MCC-1), CCL17 (TARC), and CCL18 (PARC), making it a central regulator of immune cell trafficking and inflammatory responses. In the nervous system, CCR8-expressing T cells can infiltrate the central nervous system during neuroinflammatory conditions, contributing to disease pathogenesis in multiple sclerosis, Alzheimer's disease, and other neurodegenerative disorders [@chen2018].

Gene Structure and Expression

Genomic Organization

• Chromosomal location: 3p22.2
• Genomic size: ~2.5 kb coding region
• Exon count: 2 exons
• Protein: 355 amino acids, ~40 kDa

Tissue Distribution

CCR8 exhibits restricted expression patterns:

• T cells: Highest expression on Th2 cells and Tregs
• Skin: Enriched in cutaneous T cells (skin-homing memory T cells)
• Thymus: Expressed on medullary thymocytes
• Brain: Low baseline, upregulated during neuroinflammation
• Peripheral organs: Detectable in spleen, lymph nodes

Cellular Localization

CCR8 is a seven-transmembrane receptor that:

Protein Structure and Function

Structure-Function Relationships

The CCR8 protein contains the canonical GPCR structure:

| Domain | Position | Function |
|--------|----------|----------|
| N-terminus | 1-50 aa | Ligand binding, glycosylation |
| Transmembrane helices | 51-280 aa | 7 TM domains, signal transduction |
| Extracellular loops | Variable | Ligand recognition |
| Intracellular loops | Variable | G protein coupling |
| C-terminus | 281-355 aa | Internalization, desensitization |

Signal Transduction Pathways

Ligand Specificity

CCR8 binds multiple chemokines with different affinities:

• CCL1 (I-309): Highest affinity, primary ligand
• CCL17 (TARC): Intermediate affinity
• CCL16 (MCC-1/LEC): Lower affinity
• CCL18 (PARC): Lower affinity, implicated in allergy

Role in Immune Function

T Cell Trafficking

CCR8 plays a critical role in T cell migration:

Regulatory T Cell Function

Tregs expressing CCR8 have distinct functional properties [@barsema2021]:

• Suppressive capacity: High FoxP3 expression, strong inhibitory function
• Tissue residence: Preferentially localizes to non-lymphoid tissues
• Plasticity: Can convert to effector T cells under certain conditions
• Tolerance maintenance: Essential for peripheral immune tolerance

Type 2 Immunity

In type 2 immune responses, CCR8:

• Recruits Th2 cells to allergic inflammation sites
• Modulates eosinophil and basophil recruitment
• Participates in anti-helminth defense mechanisms
• Contributes to tissue repair and remodeling

Role in Neurodegeneration

Multiple Sclerosis

CCR8 is implicated in MS through multiple mechanisms [@mitsdoerffer2005]:

T cell infiltration:

• CCR8+ T cells are found in active MS lesions
• CCL1 expression is upregulated in demyelinating regions
• Treg dysfunction allows auto-reactive T cell expansion

• CCR8 blockade reduces T cell infiltration in animal models
• Anti-CCR8 antibodies are in development for MS treatment

Alzheimer's Disease

In AD, CCR8 contributes to neuroinflammation [@rostamian2021]:

• Peripheral inflammation: Tregs modulate systemic inflammatory responses
• CNS infiltration: CCR8+ T cells may cross the blood-brain barrier
• Tau pathology: T cell-derived cytokines may accelerate tau pathology
• Amyloid clearance: Impaired Treg function affects Aβ clearance mechanisms

Other Neurodegenerative Conditions

• Parkinson's disease: Altered CCR8 expression on peripheral immune cells
• Amyotrophic lateral sclerosis: T cell dysregulation contributes to motor neuron injury
• Stroke: Post-stroke inflammation involves CCR8-mediated immune responses

Therapeutic Implications

Targeting CCR8 in Disease

| Approach | Mechanism | Status |
|----------|-----------|--------|
| Anti-CCR8 antibodies | Deplete CCR8+ T cells | Preclinical/Phase 1 |
| CCR8 antagonists | Block ligand binding | Discovery |
| CCL1 neutralizing antibodies | Prevent receptor activation | Research |
| Treg modulation | Enhance suppressive function | Clinical trials |

Potential Applications

• Autoimmune diseases: Reduce pathogenic T cell infiltration
• Cancer immunotherapy: Deplete tumor-infiltrating Tregs
• Allergic diseases: Block Th2 cell recruitment
• Neurodegeneration: Modulate neuroinflammation

Clinical Development Pipeline

Several CCR8-targeted approaches are in development:

Monoclonal antibodies:

• BMS-986340 (Bristol Myers Squibb) — anti-CCR8 for cancer
• Other anti-CCR8 antibodies in preclinical development

• CCR8 receptor blockers
• Allosteric modulators
• Peptide antagonists

• CCR8 blockade with checkpoint inhibitors
• CCR8 modulation with disease-modifying therapies

Challenges and Considerations

• Complexity of immune system: CCR8 is one element of a network
• Tissue-specific effects: Peripheral vs CNS effects differ
• Redundancy: Other chemokine receptors can compensate
• Safety concerns: Global immune modulation risks
• Biomarker development: Patient selection criteria

Expression in the Nervous System

Brain Expression Patterns

Under normal conditions, CCR8 expression in the brain is minimal. However, during neuroinflammation:

• Microglia: Low-level CCR8 expression on activated microglia
• Infiltrating T cells: Primary source of CCR8+ cells in CNS
• Astrocytes: Some evidence of CCL1/CCR8 axis in astrocyte responses
• Endothelial cells: Upregulation of CCL1 during BBB inflammation

Blood-Brain Barrier Interactions

The CCR8-CCL1 axis influences BBB function:

Animal Models

• CCR8 knockout mice: Viable with altered Treg populations
• Humanized mice: CCR8+ human T cell infiltration models
• EAE models: CCR8 blockade reduces disease severity
• Transgenic overexpression: Skin-specific CCR8 expression

Cross-Links

• [Chemokines](/mechanisms/chemokine-signaling)
• [Neuroinflammation](/mechanisms/neuroinflammation-pathway)
• [Regulatory T Cells](/cell-types/regulatory-t-cells)
• [Multiple Sclerosis](/diseases/multiple-sclerosis)
• [Alzheimer's Disease](/diseases/alzheimers-disease)
• [T Cell Trafficking](/mechanisms/t-cell-trafficking)

See Also

• [Genes Index](/genes)
• [Proteins Index](/proteins)
• [Mechanisms Index](/mechanisms)
• [Chemokine Receptors](/proteins/chemokine-receptors)

External Links

• [NCBI Gene: CCR8](https://www.ncbi.nlm.nih.gov/gene/2919)
• [UniProt: P41597](https://www.uniprot.org/uniprot/P41597)
• [Ensembl: ENSG00000179934](https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000179934)

Molecular Mechanisms of CCR8 Signaling

G Protein Coupling and Intracellular Signaling

CCR8 couples primarily to Gi/o family G proteins, initiating a cascade of intracellular signaling events that regulate immune cell function [@iwasaki2019]. Upon ligand binding, the receptor undergoes conformational changes that promote GDP release from the Gα subunit and GTP binding, leading to dissociation of the Gα-GTP and Gβγ subunits. The Gi/o α subunit inhibits adenylate cyclase activity, reducing intracellular cAMP levels, while the Gβγ subunit activates phosphatidylinositol 3-kinase (PI3K) and phospholipase C (PLC) pathways.

The downstream signaling consequences include activation of the MAPK cascade (ERK1/2, p38, JNK), which regulates gene expression programs controlling cell survival, proliferation, and cytokine production. The PI3K-AKT pathway promotes cell survival and metabolic reprogramming, while PLCγ generates inositol trisphosphate (IP3) and diacylglycerol (DAG), leading to calcium mobilization and protein kinase C (PKC) activation. These signaling events collectively shape the functional responses of CCR8-expressing cells.

β-Arrestin Recruitment and Receptor Desensitization

Like other GPCRs, CCR8 undergoes desensitization through β-arrestin-mediated processes. Following phosphorylation by G protein-coupled receptor kinases (GRKs), β-arrestin binding sterically blocks further G protein coupling and targets the receptor for internalization via clathrin-coated pits. The internalized receptor can be recycled back to the plasma membrane or targeted for lysosomal degradation, providing a mechanism to modulate receptor availability and signal duration.

β-arrestins also serve as signaling scaffolds, linking CCR8 to downstream effectors independent of G protein signaling. This bias toward β-arrestin-dependent pathways offers opportunities for therapeutic targeting, as selective biased agonists could potentially promote beneficial signaling while minimizing adverse effects.

Transcriptional Regulation and Gene Expression

CCR8 activation triggers distinct transcriptional programs in different immune cell subsets. In Th2 cells, CCR8 signaling promotes expression of GATA3, IL-4, IL-5, and IL-13, reinforcing the Th2 polarization state. In Tregs, CCR8 activation enhances FoxP3 expression and immunosuppressive function, characterized by increased IL-10, TGF-β, and CTLA-4 expression. The transcriptional outcomes depend on the cellular context and integration with other signaling inputs, including T cell receptor engagement and cytokine milieu.

CCR8 in Specific Neurodegenerative Diseases

Alzheimer's Disease Pathogenesis

In Alzheimer's disease, CCR8 contributes to neuroinflammation through multiple mechanisms [@yang2021]. The amyloid-β (Aβ) peptide, the primary component of amyloid plaques in AD brain, induces expression of CCL1 and other CCR8 ligands in astrocytes and microglia. This creates a chemotactic gradient that recruits CCR8-expressing T cells to the brain parenchyma.

The recruited T cells release pro-inflammatory cytokines that potentiate microglial activation, creating a feed-forward loop of neuroinflammation. Elevated levels of CCL1 have been detected in cerebrospinal fluid from AD patients, and CCR8+ T cell infiltration has been observed in post-mortem AD brain tissue. The specific roles of CCR8+ Tregs in this context remain complex—while Tregs typically suppress inflammation, their dysfunction in AD may lead to inappropriate immune responses that exacerbate neuronal damage.

Therapeutic strategies targeting the CCL1-CCR8 axis in AD include neutralizing antibodies against CCL1, small molecule CCR8 antagonists, and approaches to enhance Treg function. Preclinical studies in AD mouse models have shown promise, with CCR8 blockade reducing T cell infiltration and ameliorating cognitive deficits.

Parkinson's Disease

In Parkinson's disease, CCR8-mediated immune responses contribute to the progressive loss of dopaminergic neurons in the substantia nigra pars compacta [@petrovic2022]. Neuroinflammation is a hallmark of PD, with activated microglia and infiltrating T cells surrounding remaining neurons and contributing to their demise.

CCR8+ T cells have been detected in the cerebrospinal fluid and substantia nigra of PD patients. The chemotactic recruitment of these cells is driven by upregulated CCL1 expression in the PD brain, particularly in regions of active neurodegeneration. Once in the CNS, CCR8+ cells release cytokines that activate microglia and promote oxidative stress, contributing to neuronal death.

Interestingly, CCR8+ Tregs may play dual roles in PD—they can suppress harmful inflammation but may also become dysfunctional and lose their immunosuppressive capacity as disease progresses. This "Treg exhaustion" phenomenon is observed in multiple neurodegenerative conditions and represents a potential therapeutic target.

Amyotrophic Lateral Sclerosis

In ALS, CCR8 expression is altered on both peripheral immune cells and CNS-infiltrating lymphocytes. The progressive loss of motor neurons in ALS is accompanied by robust neuroinflammation, with T cells contributing to both protective and pathogenic processes.

CCR8+ T cells have been identified in ALS spinal cord, where they may influence microglial activation states and motor neuron survival. Studies in mouse models of ALS suggest that CCR8 blockade could modify disease progression by altering the balance between pro-inflammatory and regulatory T cell populations.

Multiple Sclerosis and Related Demyelinating Diseases

Multiple sclerosis represents perhaps the clearest case for CCR8 involvement in neuroinflammatory disease [@nishikazi2019]. In MS, CCR8+ T cells accumulate in active demyelinating lesions, where they contribute to myelin destruction and impede remyelination. The CCL1-CCR8 axis promotes recruitment of Th2 cells and Tregs to the CNS, with the net effect being immunopathology.

Therapeutic targeting of CCR8 in MS has shown promise in preclinical models. Anti-CCR8 antibodies reduce T cell infiltration into the CNS, decrease demyelination, and improve functional outcomes in experimental autoimmune encephalomyelitis (EAE), the standard mouse model of MS. Several pharmaceutical companies have advanced CCR8-targeting agents into clinical development for autoimmune diseases.

CCR8+ T Cell Subsets and Their Functions

Th2 Cells

CCR8 is highly expressed on type 2 helper T cells, which produce IL-4, IL-5, IL-13, and other cytokines that drive eosinophil recruitment, IgE production, and tissue remodeling. In the context of neuroinflammation, Th2 cells may contribute to repair processes through their production of growth factors, though they can also perpetuate pathology in chronic conditions.

Regulatory T Cells

A subset of Tregs expressing CCR8 has been identified in both mouse and human tissues [@sawatzky2020]. These CCR8+ Tregs exhibit enhanced suppressive function compared to CCR8- Tregs and are enriched in non-lymphoid tissues. In the CNS, CCR8+ Tregs may play crucial roles in maintaining immune homeostasis and preventing excessive inflammation following injury or infection.

Tissue-Resident Memory T Cells

CCR8 is a marker for tissue-resident memory T cells (Trm) in certain tissues, particularly skin and mucosal surfaces. These cells provide rapid recall responses to pathogens but can also contribute to autoimmune pathology when self-antigens are targeted.

CCR8+ Effector T Cells

Beyond Th2 and Tregs, CCR8 can be expressed on effector T cells with various polarization states. The functional consequences of CCR8 signaling depend on the broader transcriptional program of the cell, which is determined by differentiation history and tissue microenvironment.

Clinical Implications and Therapeutic Development

Anti-CCR8 Monoclonal Antibodies

Several anti-CCR8 antibodies are in development for oncology and autoimmune disease applications [@tommi2021]. In cancer, the goal is to deplete tumor-infiltrating CCR8+ Tregs, thereby releasing anti-tumor immune responses. In autoimmune conditions, blocking CCR8 prevents pathogenic T cell recruitment to target tissues.

Early clinical trials have demonstrated target engagement and preliminary efficacy signals, though optimal dosing and combination strategies continue to be explored. Key considerations include the need for peripheral versus tissue-resident targeting and potential effects on beneficial T cell populations.

Small Molecule CCR8 Antagonists

Small molecule antagonists offer advantages including oral bioavailability and potential for tissue penetration. Several pharmaceutical companies have identified CCR8 antagonists through high-throughput screening and structure-based design. These compounds block CCL1 binding and prevent receptor activation, providing an alternative to antibody-based approaches.

CCR8 as Biomarker

CCR8 expression may serve as a biomarker for disease activity and treatment response in neuroinflammatory conditions. CCR8+ T cell counts in cerebrospinal fluid correlate with disease severity in MS, and changes following treatment may predict outcomes. Similarly, in AD and PD, CCR8+ T cell measurements could provide insights into neuroinflammatory status.

Combination Therapies

The most effective therapeutic strategies may involve combination approaches targeting multiple aspects of neuroinflammation. Potential combinations include CCR8 blockade with:

• Checkpoint inhibitors (PD-1, CTLA-4 blockade)
• Cytokine inhibitors (IL-6R, TNF-α)
• Cell trafficking inhibitors (VLA-4, CXCR4)
• Metabolic modulators

Research Tools and Model Systems

Experimental Models

Several model systems are used to study CCR8 function:

• CCR8 knockout mice: Reveal developmental and functional consequences of CCR8 deficiency
• Humanized mice: Allow study of human CCR8+ T cells in vivo
• EAE models: MS-like disease for neuroinflammation studies
• Transgenic models: Tissue-specific CCR8 overexpression

Flow Cytometry and Cell Sorting

Surface CCR8 detection uses specific antibodies for flow cytometry. Common markers for characterizing CCR8+ populations include:

• CD3, CD4, CD8 for T cells
• CD25, FoxP3 for Tregs
• CCR4, CRTH2 for Th2 cells
• CD45RA, CCR7 for memory subsets

In Vitro Systems

Cell culture models allow mechanistic study of CCR8 signaling:

• Primary T cell cultures with CCR8 expression
• Reporter cell lines for ligand screening
• Organoid systems for tissue-level responses

Future Directions and Unanswered Questions

Key Knowledge Gaps

Several important questions remain about CCR8 biology:

Emerging Research Areas

New directions include:

• Single-cell analysis of CCR8+ cells in human disease
• Development of biased agonists favoring beneficial signaling
• Understanding CCR8 in aging and immunosenescence
• CCR8-independent functions of CCL1

References

Pathway Diagram

The following diagram shows the key molecular relationships involving CCR8 Gene discovered through SciDEX knowledge graph analysis: