The ICRF44 monoclonal antibody reacts with CD11b, the 165-kDa adhesion glycoprotein that associates with the 95-kDa integrin beta2 (CD18) to form the CD11b/CD18 complex, also known as Mac-1 or CR3. CD11b is expressed on activated lymphocytes, monocytes, granulocytes, and a subset of NK cells. CD11b functions in cell-cell and cell-substrate interactions and is a receptor for iC3b, CD54 (ICAM-1), CD102 (ICAM-2) and CD50 (ICAM-3). This antibody significantly inhibits polymorphonuclear leukocyte aggregation in response to fMLP. Synonyms: Mac-1alpha, integrin alphaM subunit, CR3 alpha chain