The clone OKM1, a mouse monoclonal antibody, binds with a 165 kDa adhesion glycoprotein present in human cells known as CD11b. CD11b associates with the 95 kDa integrin ?2 (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).