Specificity: Recognizes human CD221, a 155kD receptor tyrosine kinase, also known as Insulin-like growth factor I receptor (IGF-I Receptor). CD221 is composed of two extracellular alpha-subunits and two transmembrane beta-subunits. Recognizes an epitope in the alpha subunits of CD221, demonstrated by Western blotting. CD221 is expressed in a range of tissues, including kidney, liver, placenta, mammary gland, brain, ovary and skin. The ligands for CD221 include IGF-I and IGF-II, which bind to CD221 and activate tyrosine kinase activity, resulting in phosphorylation of several intracellular signalling proteins. Clone 1H7 is reported to partially block binding of IGF-I and IGF-II to CD221