Specificity: Recognizes the murine CD11b cell surface antigen (also known as the alpha M integrin chain or MAC-1), a differentiation antigen expressed by granulocytes, monocytes, NK cells and tissue macrophages. The expression of CD11b increases during monocyte maturation and expression levels vary on tissue macrophages. Peritoneal macrophages are reported to express higher levels of CD11b than splenic macrophages. Clone M1/70.15 has been reported to block iC3b binding to its receptor. This product is routinely tested in flow cytometry on mouse peritoneal macrophages.