CD131, also known as the IL-3R common beta subunit (betaC), is a 95-120 kD type I transmembrane glycoprotein and belongs to the Ig superfamily. The common beta subunit associates with the specific alpha subunits of IL-3 receptor, IL-5 receptor and GM-CSF receptor to form high affinity receptors for these cytokines. These cytokine receptors are expressed by neutrophils, eosinophils, monocytes, endothelial cells, fibroblasts and hematopoietic progenitor cells and play a crucial role in growth/activation of eosinophils and in the inflammatory response. The 1C1 antibody is a non-blocking antibody.