Description: The BM8 monoclonal antibody reacts with mouse F4/80 antigen, an approximately 125 kDa transmembrane protein. The F4/80 antigen is expressed by a majority of mature macrophages and is the best marker for this population of cells. However, other cell types such as Langerhans cells and liver Kupffer cells have been reported to express this antigen. Expression of F4/80 commences during early myeloid development and is upregulated on all BM cells stimulated \i{in vitro\i} with M-CSF. It has been shown that some cytokines downregulate the expression of F4/80 resulting in lack of F4/80 antigen on a subpopulation of macrophages, especially in the lymphoid microenvironment \i{in vivo\i}.