What are International Units?
International Units (IU) represent units of functional or biological activity that indicate potency of biologically active substances when measured against international standards or reference materials. These biological substances may include a wide variety of substances such as recombinant proteins, hormones, or vaccines. IU values allow assessment of biological substances in a consistent, internationally accepted manner. Specifically, for recombinant proteins, IU values are determined by measuring functional activity against international standards provided by World Health Organization (WHO). These standards can be obtained from NIBSC.
Why are International Units important?
Recombinant proteins are manufactured by different laboratories using different protocols, making it difficult to assess and compare biological potency. The use of IU provides a standardized measurement of biological potency that simplifies comparison of recombinant proteins from different sources.
How are International Units measured for Cell-Vive GMP recombinant proteins?
At BioLegend, we assess biological potency using bioassays, during which we test our Cell-Vive™ GMP recombinant proteins side-by-side with a WHO international standard. Potency is expressed as IU/mg. In general, we follow these 4 steps to determine IU values for Cell-Vive GMP recombinant proteins:
- Perform bioassay comparing WHO international standard versus Cell-Vive GMP recombinant protein.
- Determine specific activity of WHO international standard.
- Establish ED50 ratio of WHO international standard versus Cell-Vive GMP recombinant protein.
- Based on the ratio established, determine specific activity of Cell-Vive GMP recombinant protein.
Sample Method for IU Calculations using Cell-Vive GMP Recombinant Human G-CSF
- Both the WHO international standard and Cell-Vive GMP Recombinant Human G-CSF were run in the same bioassay to induce proliferation of M-NFS-60 mouse myelogenous leukemia lymphoblast cells.
- The specific activity of WHO International Standard Human G-CSF (09/136) was determined to be 95,000 IU/µg.
- WHO assigned potency of international standard: 95,000 IU/mL
- Concentration of Cell-Vive GMP Recombinant Human G-CSF in ampoule: 1 µg/mL
- Specific activity of international standard: 95,000 IU/µg
- From the bioassay performed, ED50 in ng/mL was determined, thus establishing a ratio between the WHO international standard and Cell-Vive GMP Recombinant Human G-CSF.
- WHO international standard ED50: 0.027 ng/mL
- Cell-Vive GMP Recombinant Human G-CSF ED50: 0.08 ng/mL
- Ratio: 0.338
- The specific activity of Cell-Vive GMP Recombinant Human G-CSF was determined to be ≥ 3.2 x 107 IU/mg.
- Cell-Vive GMP Recombinant Human G-CSF specific activity = standard specific activity x ratio
- International standard specific activity: 9.5x107 IU/mg
- Ratio: 0.338
- Cell-Vive GMP Recombinant Human G-CSF specific activity: 3.2 x 107 IU/mg
Cell-Vive GMP Recombinant Proteins IU Measurements Table
Cell-Vive GMP Recombinant Protein | Cat. No. | Reference Cytokine | NIBSC Code | Cell Line used for Bioassay | Type of Bioassay | IU measurement (IU/mg) |
---|---|---|---|---|---|---|
Human BDNF | 788916 | Human BDNF | 96/534 | N/A | Binding assay | ≥ 5.5x105 |
Human BMP-2 | 767314, 767316 | Human BMP-2 | 93/574 | ATDC5 | ALP induction | ≥ 1.4x105 |
Human EGF | 585514, 585516 | Human EGF | 91/530 | A431 | Proliferation | ≥ 2.6x106 |
Human FGF-basic (146 aa) | 792524, 792526 | Human FGF basic (146 aa) | 90/712 | NIH/3T3 | Proliferation | ≥ 8.8x106 |
Human G-CSF | 578614, 578616 | Human G-CSF | 09/136 | M-NFS-60 | Proliferation | ≥ 3.2x107 |
Human GDNF | 798425 | Human GDNF | 09/266 | N/A | Binding assay | ≥ 1.1x105 |
Human GM-CSF | 572914, 572916 | Human GM-CSF | 88/646 | TF-1 | Proliferation | ≥ 1.8x107 |
Human IL-1β | 579414, 579416 | Human IL-1β | 86/680 | D10.G4.1 | Proliferation | ≥ 4.5x107 |
Human IL-2 | 791925 | Human IL-2 | 86/500 | HT-2 | Proliferation | ≥ 2.4x106 |
Human IL-3 | 564314, 564316 | Human IL-3 | 91/510 | TF-1 | Proliferation | ≥ 1.6x105 |
Human IL-4 | 574014, 574016 | Human IL-4 | 88/656 | TF-1 | Proliferation | ≥ 7.7x107 |
Human IL-6 | 570814, 570816 | Human IL-6 | 89/548 | 7TD1 | Proliferation | ≥ 3.5x107 |
Human IL-7 | 581914, 581916 | Human IL-7 | 90/530 | Peripheral Blood Lymphocytes | Proliferation | ≥ 1x108 |
Human IL-10 | 571014, 571016 | Human IL-10 | 93/722 | PBMCs | IFNγ induction | ≥ 1.3x106 |
Human IL-12 | 573014, 573016 | Human IL-12 | 95/544 | PBMCs | IFNγ induction | ≥ 2.8x106 |
Human IL-13 | 571114, 571116 | Human IL-13 | 94/622 | TF-1 | Proliferation | ≥ 2.8x105 |
Human IL-15 | 570314, 570316 | Human IL-15 | 95/554 | MO7e | Proliferation | ≥ 3.7x106 |
Human LIF | 593924 | Human LIF | 93/562 | TF-1 | Proliferation | ≥ 1.4x107 |
Human M-CSF | 574814, 574816 | Human M-CSF | 89/512 | M-NFS-60 | Proliferation | ≥ 9.4x107 |
Human TGF-β1 | 781816 | Human TGF-β | 89/514 | HT-2 | Proliferation | ≥ 1x107 |
Human TNF-α | 570114, 570116 | Human TNFα | 12/154 | L929 | Cytotoxicity | ≥ 1.5x107 |
Human TPO | 763714, 763716 | Human TPO | 03/124 | MO7e | Proliferation | ≥ 1.5x106 |
Human VEGF-165 | 583714, 583716 | Human VEGF-165 | 19/246 | HUVEC | Proliferation | ≥ 1.4x106 |
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