CCD8A Antibody
Description
Introduction to CD8A Antibody
CD8A antibodies are monoclonal antibodies (mAbs) or engineered constructs targeting the CD8α subunit of the CD8 co-receptor. CD8 exists as either a CD8αα homodimer or CD8αβ heterodimer, with the α chain playing a pivotal role in stabilizing T cell receptor (TCR)-major histocompatibility complex class I (MHC-I) interactions and recruiting signaling molecules like Lck kinase . These antibodies are utilized for immunomodulation, diagnostic staining, and therapeutic interventions in oncology and autoimmune diseases.
Domains of CD8α
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Ectodomain: Binds MHC-I via conserved residues (e.g., Cys in Ig-like folds) to stabilize TCR-antigen-MHC-I complexes .
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Hinge/Transmembrane domains: Facilitate dimerization (αα or αβ) and membrane localization .
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Cytoplasmic tail: Recruits Lck kinase via a conserved CXC motif to phosphorylate CD3 ITAM domains .
Isoform-Specific Roles
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CD8αβ: Enhances TCR sensitivity by 100-fold compared to CD8αα due to lipid raft localization .
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CD8αα: Reduces TCR sensitivity in intraepithelial T cells and supports memory T cell generation .
Mechanisms of Action
CD8A antibodies modulate immune responses through:
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Stabilization of TCR-pMHC-I Interactions:
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Co-Stimulatory or Co-Repressive Signaling:
Key Studies
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OKT8 Antibody:
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CARbodies:
Therapeutic Potential
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Targeted Treg Depletion: Bispecific antibodies (e.g., 2MW4691) combining CD8α with CTLA-4 or CCR8 targets selectively deplete intratumor regulatory T cells while activating cytotoxic T cells .
Key Anti-CD8A Antibodies and Their Effects
Product Specs
Components: 50% Glycerol, 0.01M PBS, pH 7.4
Target Background
Q&A
What molecular mechanisms underlie CD8A's role in cytotoxic T lymphocyte (CTL) activation?
CD8A functions as a co-receptor with the T-cell receptor (TCR) to stabilize interactions between CTLs and MHC class I-peptide complexes on antigen-presenting cells. The CD8α chain contains an immunoglobulin variable (IgV)-like domain that binds to the α3 region of MHC-I, enhancing TCR signal transduction by ~10–100-fold . Methodologically, researchers should:
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Use phospho-specific flow cytometry to quantify Lck kinase activation (Y394 phosphorylation) post-CD8A/MHC-I engagement
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Employ FRET-based imaging to visualize CD8A-TCR clustering dynamics during immune synapse formation
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Validate functional consequences via IL-2/IFN-γ ELISpot assays following CD8A blockade
Table 1: Key CD8A Isoforms and Their Functional Domains
| Domain | Structure | Binding Partners | Knockout Phenotype |
|---|---|---|---|
| Extracellular | IgV-like (AA 1–110) | MHC-I α3, Lck kinase | Impaired CTL differentiation |
| Transmembrane | α-helix (AA 111–135) | TCR-CD3 complex | Reduced TCR signal duration |
| Cytoplasmic | P56lck binding (AA 136–206) | ZAP-70, LAT | Defective granzyme B release |
Data source: Structural analyses from cryo-EM studies
How to validate CD8A antibody specificity across experimental models?
Four orthogonal validation strategies are recommended:
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Genetic knockout controls: Compare staining in WT vs. CD8A-/- Jurkat cells using CRISPR-Cas9 (≥3 clones)
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Cross-reactivity screening: Test against CD8β, CD4, and CD3ε via flow cytometry (MFI ratio < 1:5)
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Epitope mapping: Perform hydrogen-deuterium exchange mass spectrometry to confirm antibody binding to residues 65–78 of CD8α
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Functional blockade: Verify inhibition of MHC-I tetramer binding (IC50 ≤ 10 nM for neutralizing clones)
Recent multi-laboratory studies identified 23% of commercial CD8A antibodies showing ≥20% cross-reactivity with CD8β .
How to design a 30-parameter spectral flow panel for rare CD8A+ T cell subsets?
Key considerations for high-dimensional phenotyping:
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Antibody clone selection:
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Use SK1 clone (BD Biosciences) for bright PE/Cy7 conjugation (Qdot® 800 compatible)
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Avoid OKT8 clone in panels containing CD4 due to spectral overlap in UV lasers
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Compensation strategy:
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Implement single-stained anti-CD8A capture beads (ArC™) for spillover matrix calculation
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Include CD8α expression gradient controls (naive → effector → exhausted T cells)
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Validation metrics:
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Achieve ≤2% coefficient of variation (CV) across 10 replicates
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Maintain ≥95% recovery of spiked CD8A+ NALM-6 cells in PBMC backgrounds
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Table 2: Optimization Parameters for Multi-Omics Studies
| Parameter | Single-Cell RNAseq | CITE-seq | CyTOF |
|---|---|---|---|
| CD8A detection rate | 85–92% | 78–85% | 93–97% |
| Ambient noise | 15% UMIs | 22% ADT counts | 8% metal spill |
| Multiplex capacity | 10⁴ cells | 5×10⁴ cells | 10⁶ cells |
Data from demonstrates CITE-seq requires stringent background subtraction due to 22% ambient antibody noise.
What strategies resolve contradictory CD8A expression data between flow cytometry and IHC?
Three common scenarios and solutions:
Case 1: Discrepant positivity rates (flow: 25% vs. IHC: 12%)
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Cause: Epitope masking by formalin fixation (AA 45–53 conformational epitopes)
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Solution: Implement HIER antigen retrieval at pH 9.0 for 20 min
Case 2: Variable staining in tumor-infiltrating lymphocytes
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Cause: Transient CD8α internalization during activation (t1/2 = 8–15 min)
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Solution: Use protein transport inhibitors (brefeldin A) during tissue processing
Case 3: Non-specific binding in splenic macrophages
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Cause: Fcγ receptor-mediated uptake of antibody aggregates
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Solution: Pre-treat with 10% normal goat serum + anti-CD16/32 F(ab')₂ fragments
How to engineer bispecific antibodies targeting CD8A and checkpoint molecules?
The 2MW4691 bispecific format provides a template for CD8A-based constructs:
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Scaffold design:
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Utilize knob-into-hole IgG1 with CD8A Fab (KD = 0.8 nM) × CTLA-4 scFv (KD = 12 nM)
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Introduce L234A/L235A mutations to reduce FcγR binding
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Functional validation:
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Demonstrate ≥50% ADCC against CD8A+CTLA-4+ Tregs (effector:target = 15:1)
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Maintain <10% lysis of CD8A+CTLA-4- Teffs in PBMC co-cultures
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Safety profiling:
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Screen for CRS risk via CD8A+ monocyte IL-6 release (threshold < 50 pg/mL)
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Assess peripheral neuropathy potential in DRG neuron-CD8A binding assays
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What computational tools predict CD8A-antibody binding landscapes?
Recent advances integrate molecular dynamics and deep learning:
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ABodyBuilder2: Predicts paratope-epitope contacts with 2.8 Å RMSD accuracy
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SCINA: Deconvolutes single-cell CITE-seq data to resolve CD8A+ subset trajectories
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Requires ≥5,000 cells with 15 ADT markers
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Achieves 89% concordance with manual gating
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TCRmodel: Simulates CD8A-MHC-I docking geometries under force (1–10 pN)
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Critical for engineering pH-sensitive antibodies (Koff > 0.1 s⁻¹ at pH 5.5)
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What standards apply to CD8A antibody validation in IND-enabling studies?
FDA/EMA guidelines mandate six-tiered characterization:
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Identity: MALDI-TOF confirmation of 34 kDa heavy chain + 12 kDa light chain
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Purity: SEC-HPLC ≥95% monomer with ≤3% high molecular weight species
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Potency: IC50 ≤ 5 nM in MHC-I blocking ELISA (NIBSC reference standard)
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Stability: Maintain binding affinity (KD drift <15%) after 6mo at -80°C
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Safety: ≤0.5 EU/mg endotoxin via LAL assay; ≤5% aggregation in serum stability
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Comparability: Demonstrate ≤1.5-fold difference in ADCC between GMP lots
