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| Targets |
MHC class I Ld molecules and the 2C T-cell receptor (TCR). QL9 is a high-affinity alloantigen for the 2C T-cell receptor. The peptide binds to MHC class I Ld molecules and is presented to 2C TCR transgenic T cells. QL9 binding to MHC Ld is influenced by the majority of peptide side chains, distributed across the entire length of the peptide. It acts as a strong and specific agonist when bound to Kb and Ld, respectively.
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| ln Vitro |
Mouse T cell clone 2C recognizes two distinct major histocompatibility (MHC) ligands: autoMHC Kb and allogeneic MHC Ld. Two distinct peptides, SIY (SIYRYYGL) and QL9 (QLSPFPFDL), act as potent and selective agonists when bound to Kb and Ld, respectively. QL9 binding to MHC Ld is impacted by majority of the peptide side chains, dispersed along the whole length of the peptide. Results from studies of these two systems, especially QL9-Ld, reveal that multiple single-residue substitutions are incorporated into the peptide to improve its binding to MHC, hence enhancing its vaccination potential, but due to their simultaneous effects on TCR binding, May reduce T cell responsiveness. A T cell activation experiment was done to determine the effect of peptide SIY and QL9 residues on T cell activity [2].
In vitro, QL9 is used to stimulate 2C TCR transgenic T cells in T-cell activation assays. The peptide binds to MHC class I Ld molecules and is recognized by the 2C TCR, leading to T-cell activation, proliferation, and cytokine production. It is commonly used in ELISPOT assays, intracellular cytokine staining (ICS), and tetramer staining to quantify antigen-specific T-cell responses. QL9 is derived from the enzyme 2-oxoglutarate dehydrogenase and belongs to the endogenous peptide repertoire of all H-2d APCs. |
| ln Vivo |
In vivo, QL9 is used in mouse models to study T-cell responses to alloantigens and in models of transplantation and autoimmunity. Administration of the peptide (typically with adjuvant) induces antigen-specific CD8+ T-cell responses in H-2d mice. The peptide is used in adoptive transfer experiments where 2C TCR transgenic T cells are transferred into recipient mice, followed by peptide immunization to study T-cell expansion, differentiation, and memory formation. It is also used in models of allograft rejection.
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| Enzyme Assay |
In vitro peptide-MHC binding assays for QL9 measure the peptide's affinity for H-2Ld MHC class I molecules. The assay uses purified H-2Ld molecules (or cell lines expressing H-2Ld) and fluorescently labeled reference peptides. Varying concentrations of QL9 are incubated with H-2Ld molecules and beta2-microglobulin. After equilibration, bound peptide is detected by ELISA or fluorescence polarization. The peptide's binding affinity (IC50 or Kd) is calculated from competition curves. Alternatively, T2 cell lines are used to measure peptide-MHC stabilization by flow cytometry.
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| Cell Assay |
In vitro T-cell activation assays using QL9 are performed with splenocytes or purified CD8+ T cells from 2C TCR transgenic mice. Cells are cultured with varying concentrations of the peptide (typically 0.001-10 microg/mL) for 2-6 hours in the presence of brefeldin A or monensin for cytokine detection. T-cell activation is measured by intracellular cytokine staining (IFN-gamma, TNF-alpha, IL-2) followed by flow cytometry. Alternatively, ELISPOT assays are used to enumerate peptide-specific IFN-gamma-producing cells. CFSE dilution assays measure peptide-induced T-cell proliferation after 3-5 days of culture.
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| Animal Protocol |
In vivo mouse studies with QL9 are conducted in H-2d mice (e.g., BALB/c). For immunization, mice receive the peptide (typically 10-100 microg) emulsified in adjuvant (e.g., CFA, IFA, or CpG) via subcutaneous or intraperitoneal injection. For T-cell tracking, 2C TCR transgenic T cells are labeled with CFSE or a cell tracer and adoptively transferred into recipient mice. Mice are then immunized with peptide or challenged with alloantigen. Spleen and lymph nodes are harvested for flow cytometric analysis of T-cell expansion, activation, and differentiation.
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| ADME/Pharmacokinetics |
Pharmacokinetic properties of QL9 are characteristic of peptide antigens. With a molecular weight of 1063.21, the peptide is soluble in water and DMSO. It is typically stored as a powder at -20degC for up to 3 years or in solution at -80degC for up to 1 year. As a research peptide, pharmacokinetic studies are not typically performed as it is used as an antigen rather than a therapeutic agent.
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| Toxicity/Toxicokinetics |
QL9 is intended for research use only and is not for human therapeutic use. As a short peptide antigen, it is generally well-tolerated in mouse studies at immunogenic doses. Standard safety precautions for handling peptides apply. No significant toxicity has been reported in the literature for this research peptide.
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| References |
[1]. Speir JA, et al. Structural basis of 2C TCR allorecognition of H-2Ld peptide complexes. Immunity. 1998 May;8(5):553-62.
[2]. Bowerman NA, et al. Different strategies adopted by K(b) and L(d) to generate T cell specificity directed against their respective bound peptides. J Biol Chem. 2009 Nov 20;284(47):32551-61 |
| Additional Infomation |
QL9 is a research-grade synthetic peptide used in immunology research. It is a 9-amino-acid peptide with the sequence QLSPFPFDL derived from the enzyme 2-oxoglutarate dehydrogenase. QL9 is a high-affinity alloantigen for the 2C T-cell receptor and belongs to the endogenous peptide repertoire of all H-2d APCs. It is used to study T-cell recognition, TCR signaling, and alloreactivity. Not approved for clinical use.
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| Molecular Formula |
C52H74N10O14
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| Molecular Weight |
1063.20257329941
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| CAS # |
159646-83-0
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| Related CAS # |
QL9 TFA
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| Appearance |
White to off-white solid powder
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| HS Tariff Code |
2934.99.9001
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| Storage |
Powder -20°C 3 years 4°C 2 years In solvent -80°C 6 months -20°C 1 month Note: Please store this product in a sealed and protected environment, avoid exposure to moisture. |
| Shipping Condition |
Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)
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| Solubility (In Vitro) |
May dissolve in DMSO (in most cases), if not, try other solvents such as H2O, Ethanol, or DMF with a minute amount of products to avoid loss of samples
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| Solubility (In Vivo) |
Note: Listed below are some common formulations that may be used to formulate products with low water solubility (e.g. < 1 mg/mL), you may test these formulations using a minute amount of products to avoid loss of samples.
Injection Formulations
Injection Formulation 1: DMSO : Tween 80： Saline = 10 : 5 : 85 (i.e. 100 μL DMSO stock solution → 50 μL Tween 80 → 850 μL Saline)(e.g. IP/IV/IM/SC) *Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH ₂ O to obtain a clear solution. Injection Formulation 2: DMSO : PEG300 ：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL DMSO → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline) Injection Formulation 3: DMSO : Corn oil = 10 : 90 (i.e. 100 μL DMSO → 900 μL Corn oil) Example: Take the Injection Formulation 3 (DMSO : Corn oil = 10 : 90) as an example, if 1 mL of 2.5 mg/mL working solution is to be prepared, you can take 100 μL 25 mg/mL DMSO stock solution and add to 900 μL corn oil, mix well to obtain a clear or suspension solution (2.5 mg/mL, ready for use in animals). View More
Injection Formulation 4: DMSO : 20% SBE-β-CD in saline = 10 : 90 [i.e. 100 μL DMSO → 900 μL (20% SBE-β-CD in saline)] Oral Formulations
Oral Formulation 1: Suspend in 0.5% CMC Na (carboxymethylcellulose sodium) Oral Formulation 2: Suspend in 0.5% Carboxymethyl cellulose Example: Take the Oral Formulation 1 (Suspend in 0.5% CMC Na) as an example, if 100 mL of 2.5 mg/mL working solution is to be prepared, you can first prepare 0.5% CMC Na solution by measuring 0.5 g CMC Na and dissolve it in 100 mL ddH2O to obtain a clear solution; then add 250 mg of the product to 100 mL 0.5% CMC Na solution, to make the suspension solution (2.5 mg/mL, ready for use in animals). View More
Oral Formulation 3: Dissolved in PEG400 (Please use freshly prepared in vivo formulations for optimal results.) |
| Preparing Stock Solutions | 1 mg | 5 mg | 10 mg | |
| 1 mM | 0.9406 mL | 4.7028 mL | 9.4056 mL | |
| 5 mM | 0.1881 mL | 0.9406 mL | 1.8811 mL | |
| 10 mM | 0.0941 mL | 0.4703 mL | 0.9406 mL |
*Note: Please select an appropriate solvent for the preparation of stock solution based on your experiment needs. For most products, DMSO can be used for preparing stock solutions (e.g. 5 mM, 10 mM, or 20 mM concentration); some products with high aqueous solubility may be dissolved in water directly. Solubility information is available at the above Solubility Data section. Once the stock solution is prepared, aliquot it to routine usage volumes and store at -20°C or -80°C. Avoid repeated freeze and thaw cycles.
Calculation results
Working concentration： mg/mL；
Method for preparing DMSO stock solution： mg drug pre-dissolved in μL DMSO (stock solution concentration mg/mL). Please contact us first if the concentration exceeds the DMSO solubility of the batch of drug.
Method for preparing in vivo formulation:：Take μL DMSO stock solution, next add μL PEG300, mix and clarify, next addμL Tween 80, mix and clarify, next add μL ddH2O，mix and clarify.
(1) Please be sure that the solution is clear before the addition of next solvent. Dissolution methods like vortex, ultrasound or warming and heat may be used to aid dissolving.
(2) Be sure to add the solvent(s) in order.
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