The OX-42 antibody reacts with the CR3 complement (C3bi) receptor expressed on monocytes, granulocytes, macrophages, dendritic cells, NK cells, and a subset of lymphocytes. This antibody appears to recognize a common epitope shared between CD11b and CD11c (integrin alphaM and alphaX chains). The OX-42 antibody precipitates three polypeptides with apparent molecular weights of 160, 103, and 95 kD, respectively. This antibody has been shown to block the formation of complement-mediated rosettes and leukocyte migration.