The CD33 (HIM3-4) antibody recognizes a 67-kDa type-I transmembrane glycoprotein, a cell adhesion molecule e, Xenopus/Amphibian,pressed mainly on monocytes, granulocytes (weakly),Mouse,yeloid progenitors and mast cells, but not on lymphocytes,Porcinelatelets, erythrocytes and hematopoietic stem cells. CD33 antigen is a useful marker for the diagnosis of non lymphoblastic leukemias and also for distinguishing myelogenous leukemia cells from lymphoid leukemia cells. The CD33 antigen is early e, Xenopus/Amphibian,pressed in the cytoplasm (cyCD33) and then on the cell membrane (mCD33) of the myeloblasts.