gloved hands placing a tray of blue-capped vials into a stainless-steel storage chamber

Bioactive proteins such as cytokines and growth factors interact with cells to modulate their behavior. They do this with a certain potency which may be expressed as an EC50, specific activity, or in international units (IU).

What are international units?

An international unit (IU) is a unit of activity for a biological substance that has been tested against an international standard or reference reagent. Potency (IU/ng) of a given biological reference standard is determined by an International Collaborative Study conducted by the World Health Organization (WHO).

What are WHO international standards?

Bioactive proteins that have been tested and assigned an internationally accepted unit of biological potency (i.e., IU/ng) are available as international standards or reference materials. Organizations such as the National Institute for Biological Standards and Control (NISBC) test, store, and distribute biological reference standards to allow laboratories across the world to compare their bioactive proteins to these standards.

Why are IU used?

Bioactive recombinant proteins can have different activities when produced by different labs and protocols, so they should be compared to a reference standard to determine relative potency. The use of IU is intended to simplify comparisons of biological activity of proteins or enzymes obtained from different sources.

IU standard charts for PeproTech bioactive proteins

Where possible, Thermo Fisher Scientific determines International Unit (IU) values for Gibco PeproTech recombinant proteins through multiple side-by-side comparisons of the PeproTech protein against the analogous WHO international standard or reference standard in a standard biological activity assay. Performing multiple comparison tests helps account for any outliers due to possible variations with the assay. These tests provide a reliable quantification of the PeproTech product’s activity in relation to the activity of the WHO international standard.

The IU values provided are applicable across all lot numbers of a specific catalog number, as testing covers multiple lots of bioactive protein with comparable activity. These values are based on comparison testing and are subject to change.

Table of potencies (IU/ng) for PeproTech GMP recombinant proteins

Table 1. PeproGMP cytokine bioactivity (IU/ng)

Cytokine nameCatalog number
beginning with		Bioassay cell lineWHO catalog numberPeproTech protein activity (IU/ng)
Human Activin AGMP120-14Emouse MPC-1191/626
(0.001 IU/ng)		0.001
Human EGFGMP100-15mouse Balb/c 3T391/530
(1.0 IU/ng)		3.15
Human FGF-basicGMP100-18Bmouse Balb/c 3T390/172
(0.8 IU/ng)		2.1
Human Flt3-LigandGMP300-19human AML596/532
(1.0 IU/ng)		1.0
Human IL-2GMP200-02mouse CTLL-286/500
(13.7 IU/ng)		3.59
Human IL-3GMP200-03human TF-191/510
(1.7 IU/ng)		1.42
Human IL-6GMP200-06mouse 7TD189/548
(100 IU/ng)		115
Human IL-7GMP200-07mouse 2E890/530
(100 IU/ng)		183
Human IL-15GMP200-15mouse CTLL-295/554
(10 IU/ng)		34
Human SCFGMP300-07human TF-191/682
(1.0 IU/ng)		0.79
Human TPOGMP300-18human MO7e03/124
(10 IU/ng)		0.97
Table of potencies (IU/ng) for PeproTech RUO and animal-free recombinant proteins

Table 2. RUO and animal-free protein bioactivity (IU/ng)

Cytokine nameCatalog number
beginning with		Bioassay cell lineWHO catalog numberPeproTech protein activity (IU/ng)
Human IL-1α200-01A
AF-200-01A		mouse D10S86/63264.9
Human IL-1β200-01B
AF-200-01B		mouse D10S86/68070.3
Human IL-2200-02
AF-200-02		mouse CTLL-286/5002.18
Human IL-3200-03human TF-191/5102.8
Human IL-4200-04human TF-188/65616.1
Human IL-6AF-200-06mouse 7TD189/548123
Human IL-7200-07
AF-200-07		mouse 2E890/530117
Human IL-10200-10
AF-200-10		mouse MC/993/72222.6
Human IL-13200-13
AF-200-13		human TF-194/6220.79
Human IL-15200-15
AF-200-15		mouse CTLL-295/55428.7
H/M/R Activin A120-14
120-14P
AF-120-14E		mouse MPC-1191/626.001
Human BDNF450-02
AF-450-02		rat C696/5341.9
H/M/R BMP-2120-02Cmouse ATDC-593/5740.9
Human EGFAF-100-15mouse Balb/c 3T391/5301.0
Human EPO100-64human TF-111/1700.16
Human FGF-basic100-18B
AF-100-18B		mouse Balb/c 3T390/7120.65
Human Flt3-Ligand300-19
AF-300-19		human AML596/5321.1
Human G-CSF300-23
AF-300-23		mouse NFS-6009/136101.3
Human GDNF450-10
AF-450-10		human SH-SY5Y09/2660.78
Human GM-CSF300-03
AF-300-03		human TF-188/64612.8
Human HGF100-39monkey 4MBr-596/5640.21
Human IFN-β300-02BChuman TF-100/572504
Human IFN-γ300-02
AF-300-02		human HT-2987/5861.94
Human IGF-I100-11
AF-100-11		mouse FDC-P191/554.001
Human IGF-II100-12
AF-100-12		mouse FDC-P196/5380.6
Human KGF100-19
AF-100-19		monkey 4MBr-503/1502.33
Human LIF300-05
AF-300-05		human TF-193/56212.2
Human M-CSF300-25
AF-300-25		mouse M-NSF-6089/512100
Human β-NGF450-01human TF-193/5560.53
Human PDGF-BB100-14B
AF-100-14B		mouse Balb/c 3T394/7282.65
Human SCF300-07human TF-191/6821.7
Human TGF-β1100-21
100-21C
AF-100-21C		mouse HT-289/5149
Human TGF-β3100-36E
AF-100-36E		mouse HT-209/2345.64
Human TNF-α300-01Amouse L92912/15439.1
Human sTRAIL/Apo2L310-04human LN-1804/1661.45
Human VEGF165100-20
AF-100-20		HUVEC02/2860.69
Murine IL-2212-12
AF-212-12		mouse CTLL-293/566129
Murine IL-3213-13
AF-213-13		mouse NFS-6091/662132
Murine IL-4214-14
AF-214-14		mouse HT-291/65619.8
Murine IL-6216-16
AF-216-16		mouse 7TD193/730322
Murine GM-CSF315-03
AF-315-03		mouse FDC-P191/65844.3
Resources for biological reference standards and international units
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