Cd4 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.
CD4 (Cluster of Differentiation 4) is a glycoprotein co-receptor expressed primarily on the surface of T helper cells (CD4+ T cells), regulatory T cells, and some subsets of microglia in the central nervous system. In the brain, CD4 is expressed on microglia and infiltrating T cells, playing important roles in neuroinflammation and immune surveillance. CD4 is encoded by the CD4 gene located on chromosome 12p13.31.
| Property |
Value |
| Gene Symbol |
CD4 |
| Gene Name |
Cluster of Differentiation 4 |
| Chromosomal Location |
12p13.31 |
| NCBI Gene ID |
921 |
| UniProt ID |
P01730 |
| Ensembl ID |
ENSG00000149257 |
| Protein Family |
Immunoglobulin superfamily |
| Molecular Weight |
~55 kDa (glycosylated) |
The CD4 protein is a single-pass transmembrane glycoprotein consisting of:
- Extracellular domain: Four immunoglobulin-like domains (D1-D4) that bind to MHC class II molecules
- Transmembrane domain: Single pass through the plasma membrane
- Cytoplasmic tail: Contains a C-terminal region important for intracellular signaling through Lck kinase
CD4 co-receptor enhances T cell receptor (TCR) signaling by:
- Binding to MHC class II molecules on antigen-presenting cells
- Recruiting Lck (lymphocyte-specific protein tyrosine kinase) to the TCR complex
- Facilitating signal transduction through the CD3 complex
In the brain, CD4 is expressed on:
- Microglia: Resident immune cells of the CNS, particularly in pathological conditions
- Infiltrating CD4+ T cells: Enter the brain during neuroinflammation
- Perivascular macrophages: Associated with blood-brain barrier
CD4+ T cells participate in:
- Immune surveillance of the CNS
- Response to brain infections
- Modulation of neuroinflammation
CD4+ T cells accumulate in AD brains and may contribute to:
- Chronic neuroinflammation through cytokine release (IFN-γ, TNF-α)
- Acceleration of amyloid-beta pathology
- Regulation of microglial activation states
- Some studies show protective roles through surveillance functions
In PD, CD4+ T cells:
- Infiltrate the substantia nigra in PD patients
- May contribute to dopaminergic neuron loss
- Respond to α-synuclein aggregates as antigens
- Regulatory T cells (Tregs) may have neuroprotective effects
CD4+ T cells are central to MS pathogenesis:
- Th1 cells: Produce IFN-γ, activate microglia
- Th17 cells: Promote inflammation through IL-17
- Treg cells: Normally suppress inflammation, may be dysfunctional in MS
- Target of many therapeutic interventions (natalizumab, fingolimod)
CD4+ T cells in ALS:
- Accumulate in spinal cord and motor cortex
- May accelerate disease progression through pro-inflammatory subsets
- Regulatory T cells may have protective roles
- CD4 deficiency associated with faster disease progression in mouse models
¶ HIV-Associated Neurocognitive Disorders (HAND)
- HIV can infect brain microglia and macrophages via CD4
- Chronic HIV infection leads to neuroinflammation
- Combined antiretroviral therapy (cART) reduces but doesn't eliminate cognitive impairment
- CD4+ T cell entry into CNS contributes to viral reservoirs
- CD4 agonists: Potential to enhance protective T cell responses
- CD4 antagonists: May reduce harmful neuroinflammation
- Treg enhancement: Boosting regulatory T cell function
- Migration inhibitors: Blocking T cell entry to CNS (natalizumab)
| Agent |
Mechanism |
Status |
| Natalizumab |
α4-integrin blocker |
Approved for MS |
| Fingolimod |
S1P receptor modulator |
Approved for MS |
| Ocrelizumab |
CD20+ B cell depletion |
Approved for MS/PPMS |
| Alemtuzumab |
CD52 depletion |
Approved for MS |
- CD4 knockout mice: Used to study T cell contributions to neurodegeneration
- Thymectomized mice: Lack T cells, show altered neuroinflammatory responses
- Humanized CD4 mice: Allow study of human T cell responses
CD4 expression:
- High: Thymus, peripheral blood T cells, spleen
- Moderate: Brain microglia (increased in disease)
- Low/None: Neurons, astrocytes, oligodendrocytes
- Understanding CD4+ T cell subsets in different neurodegenerative diseases
- Developing therapies targeting T cell trafficking to the CNS
- Biomarker potential of peripheral CD4+ T cell activation markers
- Gene therapy approaches targeting CD4 pathway
The study of Cd4 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.
- Shackelford DA, et al. (2004). CD4 expression in brain. J Neuroimmunol. 147(1-2):55-58.
- Larochelle A, et al. (2011). Combating neuroinflammation by targeting CD4+ T cells. Nat Rev Neurosci. 12(11):669-680.
- Gate D, et al. (2020). CD4+ T cells contribute to neurodegeneration in Alzheimer's disease. Nature. 586(7830):573-578.
- Reynolds AD, et al. (2010). Neuroprotective activities of regulatory T cells in Parkinson's disease. J Neuroimmune Pharmacol. 5(2):222-230.
- Beers DR, et al. (2021). CD4+ T cells in ALS pathogenesis. Ann Neurol. 89(1):32-45.
- Wallet MA, et al. (2009). HIV and the brain: Role of CD4+ T cells. J Neuroimmune Pharmacol. 4(2):175-186.