CD33, a type I transmembrane protein, is a sialic acid-binding Ig-like lectin (Siglec-3) of the Ig superfamily, and human CD33 binds preferentially to alpha-2, 6-linked sialic acid. Upon binding to its ligands CD33 transduces an inhibitory signaling through the immunoreceptor tyrosine-based inhibitory motif (ITIM) in its intracellular domain, inhibiting cellular function such as phagocytosis. In addition, CD33 is also involved in other processes, such as adhesion. Due to its exclusive expression on hematopoietic cells, particularly the myeloid lineage and their progenitors, CD33 has been actively pursued as a therapeutic target against acute myeloid leukemia (AML). CD33 may also be involved in Alzheimers Disease.
