When mice without endometriosis were injected with mouse rIL-33 or PBS, the plasma of mice treated with mouse rIL-33 had elevated levels of CXCL1, IL-6, GM-CSF, IL-7, IL-5 and Eotaxin, further suggesting that IL-33 likely perpetuates inflammation by interacting with immune cells rather than interacting with the endometriotic lesion itself. This evidence concerns the gene IL6 and endometriosis.