Cedarlane’santi-rat CD11b/c monoclonal antibody recognizes most macrophages includingresident peritoneal macrophages, kupffer cells, but only approximately 35% ofalveolar macrophages (2). It also labels dendritic cells extensively,granulocytes and cells with morphology of microglia in the brain. Itprecipitates three polypeptides of M.W. 160, 103 and 95kDa. OX-42 inhibitscomplement mediated rosettes and is probably the rat equivalent of the humanreceptor for iC3b called CR3. Cedarlane’s anti-rat CD11b/c mAb should proveuseful in the recognition of macrophages and microglia.