Measure by its ability to binding with recombinant ST2L (IL-33 receptor).
The ED50 for this effect is <54 ng/mL.
Measure by its ability to induce proliferation in D10.G4.1 cells.
The ED50 for this effect is < 0.1 ng/mL.
The specific activity of recombinant human IL-33 is approximately >4 x107 IU/ mg.