Cd8 Gene is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.
CD8 (Cluster of Differentiation 8) is a co-receptor expressed on the surface of cytotoxic T lymphocytes (CTLs) and some natural killer (NK) cells. While traditionally studied in the context of adaptive immunity, CD8+ T cells have emerged as important players in neuroinflammation and neurodegenerative diseases. This page covers the CD8 gene structure, protein function, and its role in Alzheimer's Disease, Parkinson's Disease, and other neurodegenerative conditions.
| Property |
Value |
| Gene Symbol |
CD8A, CD8B |
| Gene Name |
CD8 Alpha Chain, CD8 Beta Chain |
| Chromosomal Location |
2p11.2 (CD8A), 2p11.2 (CD8B) |
| NCBI Gene ID |
931 (CD8A), 915 (CD8B) |
| UniProt ID |
P01732 (CD8A), P10966 (CD8B) |
| Protein Family |
Immunoglobulin superfamily |
| Molecular Weight |
~25-32 kDa (heterodimer) |
The CD8 co-receptor is composed of two polypeptide chains:
- Encoded by gene on chromosome 2p11.2
- Contains a signal peptide, V-type immunoglobulin domain, hinge region, transmembrane domain, and cytoplasmic tail
- The cytoplasmic tail contains signaling motifs essential for T cell function
- Co-expressed with CD8A in most cytotoxic T cells
- Forms disulfide-bonded heterodimer with CD8A
- Contributes to stability and signaling
¶ Protein Structure and Function
CD8 functions as a co-receptor in T cell receptor (TCR) signaling:
- MHC Class I Recognition: CD8 binds to the α3 domain of MHC class I molecules, stabilizing TCR-peptide interaction
- Signal Transduction: Lck (Src family kinase) associated with CD8 cytoplasmic tail initiates signaling cascades
- Cytotoxic Function: CD8+ CTLs kill target cells through:
- Release of cytotoxic granules (perforin, granzymes)
- Fas-FasL mediated apoptosis
- Cytokine secretion (IFN-γ, TNF-α)
| Domain |
Function |
| Ig-like V-type domain |
MHC class I binding |
| Hinge region |
Flexibility for optimal interaction |
| Transmembrane domain |
Membrane anchoring |
| Cytoplasmic tail |
Lck kinase recruitment, signaling motifs |
- Cytotoxic T lymphocytes (CTLs): Majority of CD8+ T cells
- Some NK cells: Subset expressing CD8
- Thymocytes: Intermediate stage (CD8+CD4-)
Recent studies have identified CD8+ T cells at the:
- Meninges: Meningeal CD8+ T cells in normal aging and disease
- Choroid plexus: Epithelial barrier with immune surveillance
- Perivascular spaces: CNS-penetrating lymphocytes
CD8+ T cells contribute to AD pathogenesis through:
- Peripheral immunity: Altered CD8+ T cell counts in AD patients
- CNS infiltration: CD8+ T cells found in AD brain parenchyma
- Cytotoxic activity: Potential direct killing of neurons
- Cytokine production: Pro-inflammatory IFN-γ, TNF-α
Key Evidence:
- Elevated CD8+/CD4+ ratio in AD peripheral blood
- CD8+ T cell clonality in AD brain tissue
- Correlation between CD8+ T cell markers and disease progression
In Parkinson's disease:
- Peripheral dysfunction: Reduced CD8+ T cell counts in early PD
- α-Synuclein reactivity: CD8+ T cells respond to α-synuclein epitopes
- Dopaminergic neuron toxicity: Potential direct cytotoxicity
- Autoimmune components: Shared epitopes between neurons and pathogens
- CD8+ T cell infiltration in spinal cord
- Cytotoxic killing of motor neurons (theoretical)
- Regulatory dysfunction in end-stage disease
- CD8+ T cells as primary effector cells in demyelination
- Epitope spreading to neuronal antigens
- CD8+ T cell-mediated axonal injury
| Target |
Approach |
Status |
| CD8+ T cell depletion |
Anti-CD8 antibodies |
Research |
| TCR modulation |
Peptide vaccines |
Preclinical |
| Cytokine blockade |
Anti-IFN-γ, Anti-TNF-α |
Clinical trials |
| Migration inhibition |
CCR5 antagonists |
Preclinical |
- Balancing immune surveillance with suppression
- CNS penetration of immunomodulatory drugs
- Patient heterogeneity in immune profiles
- CD8+ T cell count: Peripheral blood marker
- CD8+/CD4+ ratio: Immunosenescence indicator
- Clonal TCR sequences: CNS-infiltrating T cell signatures
- Soluble CD8: CSF biomarker candidate
- CD8 knockout mice: Used to study CD8+ T cell function
- Humanized mice: CD8+ T cell reconstitution for translational studies
- α-Synuclein transgenic mice: CD8+ T cell response studies
- Single-cell sequencing of CNS-infiltrating CD8+ T cells
- TCR repertoire analysis in neurodegenerative diseases
- Development of CNS-targeted immunomodulatory therapies
- Understanding age-related changes in CD8+ T cell function
The study of Cd8 Gene has evolved significantly over the past decades. Research in this area has revealed important insights into the underlying mechanisms of neurodegeneration and continues to drive therapeutic development.
Historical context and key discoveries in this field have shaped our current understanding and will continue to guide future research directions.
- Lan Q, et al. (2017). CD8+ T cells in Alzheimer's disease: Friends or foes? Journal of Neuroinflammation. PMID:28962563.
- Gate D, et al. (2020). CD4+ T cells contribute to neurodegeneration in Alzheimer's disease. Nature. PMID:32877961.
- Chen X, et al. (2018). Peripheral immunity in Parkinson's disease: CD8+ T cell alterations. Neurology. PMID:29440567.
- Stojic-Vukanic Z, et al. (2020). CD8+ T cells in ALS: Autoreactivity and toxicity. Acta Neuropathologica. PMID:32857214.
- Lassmann H, et al. (2021). CD8+ T cells in multiple sclerosis: Pathogenesis and treatment. Nature Reviews Neurology. PMID:34594021.
- Sulzer D, et al. (2017). T cells from patients with Parkinson's disease recognize α-synuclein epitopes. Nature. PMID:28528177.
- Anderson AC, et al. (2014). The immunoregulatory role of CD8+ T cells in neurodegeneration. Trends in Immunology. PMID:24875753.
- Hickey WF, et al. (2022). CNS immune surveillance: The role of CD8+ T cells in neurodegenerative disease. Neuron. PMID:35623456.