Details for: CL0000794

Cell ID: CL0000794

Cell Name: CD8-positive, alpha-beta cytotoxic T cell

Description: Note that while T cells of this subset are loosely referred to 'cytotoxic T cells,' as many other T cell types, including CD4-positive, alpha-beta T cells and gamma-delta T cells exhibit cytotoxicity in vitro and in vivo.

Synonyms: CD8-positive, alpha-beta cytotoxic T lymphocyte, CD8-positive, alpha-beta cytotoxic T-cell, CD8-positive, alpha-beta cytotoxic T-lymphocyte, cytotoxic T cell, cytotoxic T lymphocyte, cytotoxic T-cell, cytotoxic T-lymphocyte, killer T cell, killer T lymphocyte, killer T-cell, killer T-lymphocyte

Selected Context(s): Overall

Gene Significance Landscape

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Score:
Display
Genes

Contexts:

Cell Significance Index (CSI) is uniquely calculated to reveal cell-specific gene markers. More info here

Significant Genes List

Genes with the highest and lowest Percentile Rank Scores (PRS) for CD8-positive, alpha-beta cytotoxic T cell within the selected context(s).

Gene ID: A unique numerical identifier for this specific gene.
Symbol: Shortened abbreviation or name that represents this gene.
Ensembl Gene ID: A unique identifier assigned by Ensembl for genomic data mapping.
CSI Score: A combined effect size and statistical significance measure for CD8-positive, alpha-beta cytotoxic T cell. Higher scores indicate a stronger, more significant difference in expression.
(Previously described as "Fold Change", but now represents Cliff's Delta × –log10(p).)

Gene ID: A unique numerical identifier for this specific gene.
Symbol: Shortened abbreviation or name that represents this gene.
Ensembl Gene ID: A unique identifier assigned by Ensembl for genomic data mapping.
CSI Score: A combined effect size and statistical significance measure for CD8-positive, alpha-beta cytotoxic T cell. Higher scores indicate a stronger, more significant difference in expression.
Average CSI: csi sum / gene count
Cell network configuration

This network visualizes key genes for CD8-positive, alpha-beta cytotoxic T cell. It primarily includes:
1. Top genes highly significant for this cell (Num. Top Cell Genes - based on the 'Min. CSI' setting).
2. Any additional specific 'Context Genes' you add below.
The final network is a combined view. Choose an Interaction Source (pathways or protein interactions) and optionally compare CSI scores with a Baseline Cell Type.

Maximum number of selected genes.
Select a context for the baseline cell.
Select a context for the target cell.
Target Cell for CSI:  CD8-positive, alpha-beta cytotoxic T cell (CL0000794)

 Legend
Nodes (Genes):
 Query Gene
Node size also reflects Target Cell CSI magnitude.
Node Color (Target Cell CSI in specific network):
 Very High
 High
 Medium
 Low
 Very Low
 N/A or Not Sig.
Edges (Interactions):
 STRING (Protein-Protein)
 ONTOLOGY (Shared Pathway)
 Colors vary by pathway category; default arrow applies.

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## Summary The [CD8-positive, alpha-beta cytotoxic T cell](/details-cell/CL0000794), also known as a cytotoxic T lymphocyte (CTL), is a critical effector cell of the adaptive immune system. The gene significance profile for the **Overall** context underscores its identity as a highly specialized cell, defined by a unique expression (`csi_z`) of genes essential for antigen presentation, cytotoxicity, and immune signaling. Top markers such as [B2M](/details-gene/567) and [HLA E](/details-gene/3133) highlight the cell's reliance on MHC class I-mediated interactions for recognizing and eliminating target cells, such as those infected with viruses or transformed by cancer. The data suggest a cell state optimized for effector functions, supported by a distinct metabolic and transcriptional program. ## Key Characteristics and Function Analysis of gene expression specificity (`csi_z`) reveals several functional clusters that define the core biology of the [CD8-positive, alpha-beta cytotoxic T cell](/details-cell/CL0000794). * **Antigen Presentation and Recognition:** The highest-scoring markers are integral to MHC class I antigen presentation pathways. [B2M](/details-gene/567) (CSI: 77.33), the light chain of MHC class I molecules, and [HLA E](/details-gene/3133) (CSI: 74.38), a non-classical MHC-I molecule involved in modulating immune responses, are exceptionally specific to this cell type. The high specificity of the pan-leukocyte marker [PTPRC](/details-gene/5788) (CD45) further solidifies its identity as a mature lymphocyte, where specific isoforms of this tyrosine phosphatase are crucial for T-cell receptor signal transduction. * **Cytotoxic Machinery and Immune Signaling:** The cell's role as a "killer T cell" is confirmed by the high specificity of genes encoding effector molecules and chemokines. [GNLY](/details-gene/10578) (Granulysin), a lipid-disrupting protein stored in cytotoxic granules, shows high specificity (CSI: 52.79). Concurrently, [CCL5](/details-gene/6352) (RANTES), a potent chemoattractant for other immune cells, is a defining marker (CSI: 56.74), suggesting these cells not only eliminate targets directly but also orchestrate a broader inflammatory response by recruiting other leukocytes. * **Metabolic and Biosynthetic Priming:** A distinct set of metabolic and housekeeping genes exhibit high specificity, suggesting a cellular state primed for high energy expenditure and protein synthesis. The high score for [FTL](/details-gene/2512) (Ferritin light chain, CSI: 74.91) may indicate a specialized mechanism to manage iron, a critical but potentially toxic cofactor for metabolic enzymes. The specificity of genes involved in glycolysis ([GAPDH](/details-gene/2597)), protein translation ([PABPC1](/details-gene/26986), [EEF1D](/details-gene/1936)), and protein degradation ([UBC](/details-gene/7316)) is consistent with the metabolic reprogramming required to support rapid proliferation and effector molecule production upon activation. * **Cytoskeletal Organization:** The specific expression of cytoskeletal components like [MYL6](/details-gene/4637) and [CFL1](/details-gene/1072) likely reflects the cell's need for dynamic actin remodeling during migration, target cell scanning, and the formation of the immunological synapse required for directed cytotoxicity. The anti-marker profile helps refine this cell's identity. The low specificity for several components of the mitochondrial electron transport chain (e.g., [COX5B](/details-gene/1329), [NDUFA4](/details-gene/4697), [COX6C](/details-gene/1345)) contrasts with the high specificity of glycolytic genes, which may point towards a reliance on aerobic glycolysis for rapid energy production. Furthermore, the low score for [KLRC2](/details-gene/3822) (NKG2C), a receptor often associated with [natural killer cells](/details-cell/CL0000623), helps distinguish this population from NK-like T cell subsets. ## Clinical Significance and Contextual Roles Given the analysis is based on an **Overall** context, the clinical significance is inferred from the established roles of its key marker genes. The defining markers of the [CD8-positive, alpha-beta cytotoxic T cell](/details-cell/CL0000794) are deeply implicated in human health and disease. Its fundamental role in clearing viral infections and performing cancer immunosurveillance makes it a primary target for immunotherapies, including checkpoint blockade and CAR-T cell engineering. The high specificity of [CCL5](/details-gene/6352) is clinically relevant, as this chemokine is associated with the recruitment of immune cells in various inflammatory conditions, including autoimmune diseases, but also contributes to anti-tumor immunity by attracting effector cells to the tumor microenvironment ([Link](https://doi.org/10.1089/107999099314153)). Similarly, [GNLY](/details-gene/10578) expression is a direct indicator of cytotoxic potential and is being explored as a biomarker for effective immune responses in tuberculosis and certain cancers. Mutations or downregulation of [B2M](/details-gene/567) is a known mechanism of tumor immune evasion, as it prevents the assembly and surface expression of MHC class I molecules, rendering cancer cells invisible to these T cells ([Link](https://pubmed.ncbi.nlm.nih.gov/3312414/)). The high specificity of the anti-proliferative gene [BTG1](/details-gene/694) suggests it may be a key regulator of T-cell expansion and memory formation, a process critical for long-term immunity and vaccine efficacy. ## Potential Mechanisms and Research Directions 1. **Hypothesis:** The unique metabolic signature of [CD8-positive, alpha-beta cytotoxic T cells](/details-cell/CL0000794), marked by a high specificity for glycolytic genes like [GAPDH](/details-gene/2597) alongside a low specificity for multiple oxidative phosphorylation components (e.g., [COX5B](/details-gene/1329), [NDUFA4](/details-gene/4697)), reflects a metabolic posture geared towards aerobic glycolysis. This program may be essential for providing the rapid bursts of energy and biosynthetic precursors needed for effector functions, such as cytotoxicity and cytokine production. * **Surprising Findings:** It is unexpected that certain mitochondrial genes like [COX1](/details-gene/4512) are specific markers, while many other components of the same respiratory complexes are not. This suggests a highly selective regulation of mitochondrial function rather than a simple global downregulation. * **Testable Questions:** How does selective inhibition of glycolysis versus oxidative phosphorylation impact key effector functions, such as the secretion of [GNLY](/details-gene/10578) and [CCL5](/details-gene/6352), in activated [CD8-positive, alpha-beta cytotoxic T cells](/details-cell/CL0000794)? 2. **Hypothesis:** The high expression specificity of genes not classically considered primary immune effectors, notably the iron-sequestering protein [FTL](/details-gene/2512) and the transcriptional coregulator [BTG1](/details-gene/694), indicates they perform specialized, non-canonical roles in regulating T-cell homeostasis and function. [FTL](/details-gene/2512) may be critical for mitigating iron-dependent oxidative stress during periods of high metabolic activity, while [BTG1](/details-gene/694) could serve as a crucial checkpoint controlling clonal expansion and subsequent contraction following an immune response. * **Surprising Findings:** The ranking of [FTL](/details-gene/2512) as the second most specific marker is highly unusual for a "housekeeping" gene. This suggests that iron metabolism is a uniquely regulated and critical process in these cells, potentially representing a key vulnerability or control point. * **Testable Questions:** Does siRNA-mediated knockdown of [FTL](/details-gene/2512) in [CD8-positive, alpha-beta cytotoxic T cells](/details-cell/CL0000794) lead to increased sensitivity to oxidative stress and impaired cytotoxic function following activation?