The M1/70 monoclonal antibody specifically reacts with the 170 kDa αM integrin chain of mouse CD11b from the Mac-1 integrin (CD11b/CD18). Mac-1 binds to C3bi, CD54 (ICAM-1), and fibrinogen, and it is expressed by granulocytes, macrophages, NK cells, myeloid-derived dendritic cells, microglia, activated lymphocytes, and mouse B-1 cells. The expression is up-regulated on activated neutrophils at the same time that L-selectin is shed from the cell surface. The M1/70 antibody is used for the detection of monocytes, granulocytes, and a subset of natural killer cells in human peripheral blood.

M1/70 blocks C3bi binding and cell adherence, but not cell-mediated lysis and it cross-reacts with human CD11b.