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CD8A
CD8 subunit alpha
CD8A is located on the short (p) arm of chromosome 2, at band 2p11.2. Arm ratio per GRCh38 - banding schematic.
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Overview
CD8A is located on chromosome 2 and encodes one of two chains that together form the CD8 co-receptor molecule. This protein is expressed predominantly on cytotoxic T lymphocytes and some natural killer cells, where it stabilises interactions between T cell receptors and major histocompatibility complex class I molecules on target cells. The CD8 complex serves as a critical component of cell-mediated immunity, enabling the immune system to identify and eliminate virus-infected cells, tumour cells, and other compromised host cells. Proper CD8A function is essential for effective adaptive immune responses, particularly in clearing intracellular pathogens.
What the gene does
The CD8A protein functions as part of a heterodimeric transmembrane glycoprotein, typically pairing with the CD8B chain to form the complete CD8 co-receptor. This co-receptor binds to major histocompatibility complex class I molecules on antigen-presenting cells, providing structural support during T cell receptor engagement with peptide-MHC complexes. CD8A enhances the sensitivity of cytotoxic T cells to antigen recognition, lowering the threshold required for T cell activation. The cytoplasmic tail of CD8A associates with lymphocyte-specific protein tyrosine kinase, facilitating signal transduction pathways that lead to T cell activation, proliferation, and cytotoxic effector functions. This molecular partnership ensures precise targeting of infected or transformed cells whilst maintaining tolerance to healthy tissue.
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Chromosome location
CD8A is positioned on the short arm of chromosome 2 at band 2p11.2. The gene spans this chromosomal region and is transcribed to produce the alpha chain component of the CD8 surface marker. This genomic location places CD8A within a region containing several other immune-related genes.
Protein structure
Domain architecture has not been experimentally characterised in detail for this protein.
Key variants
Genetic variation in CD8A can affect the expression level or structural integrity of the CD8 co-receptor. Whilst specific pathogenic variants are not commonly described in routine clinical genetics databases, alterations affecting CD8A expression or function may influence T cell development and immune surveillance capacity. Research continues to explore how variation in this gene might contribute to individual differences in immune response.
Sample of pathogenic variants
2 pathogenic / likely-pathogenic variants from ClinVar, ranked by review status (expert-panel-reviewed first). This is a sample; recurrent founder variants in a specific population may not appear here - see the full ClinVar listing via the link above.
| Variant (HGVS) | Protein change | Classification | Evidence | Associated condition |
|---|---|---|---|---|
c.319C>T | p.Arg107Ter | Pathogenic | ★☆☆☆ | Susceptibility to respiratory infections associated with CD8alpha chain mutation |
c.331G>A | p.Gly111Ser | Pathogenic | ★☆☆☆ | Susceptibility to respiratory infections associated with CD8alpha chain mutation |
Evidence stars indicate ClinVar review status. Individual variant interpretation should always be performed by a qualified clinical laboratory - many variants remain classified as Variants of Uncertain Significance (VUS) pending more research.
Associated conditions
CD8A is primarily studied in the context of immune system development and function rather than being associated with specific Mendelian disease conditions in mainstream clinical genetics. Experimental studies have examined CD8A in the broader context of immunodeficiency states and autoimmune phenomena, but it is not typically included in standard inherited disease gene panels. Understanding CD8A biology remains important for research into transplant compatibility, vaccine responses, and cancer immunotherapy.
No disease links recorded for this gene in our reference set.
UK clinical status
Frequently asked questions
What is the role of CD8A in the immune system?
CD8A encodes the alpha chain of the CD8 co-receptor found on cytotoxic T cells. This protein helps T cells recognise infected or abnormal cells by stabilising the interaction between T cell receptors and major histocompatibility complex molecules, enabling effective immune responses against viruses and tumours.
Does CD8A appear on genetic testing panels?
CD8A is not typically included in standard clinical genetics panels for inherited conditions. It is primarily studied in research settings examining immune function, transplantation biology, and cancer immunology rather than in the context of Mendelian disease diagnosis.
How does CD8A differ from CD8B?
CD8A and CD8B encode separate protein chains that combine to form the complete CD8 co-receptor on T cell surfaces. Whilst both contribute to the functional complex, CD8A can also form homodimers in certain cell types, whereas CD8B typically requires pairing with CD8A for stable expression.