M.Sc. MICROBIOLOGY (MEERUT INSTITUTE OF ENGINEERING AND TECHNOLOGY ). IMMUNOLOGY. CDs are cell surface molecules expressed on leulocytes and other cells. CDs acts often as ligands or receptors (the molecule that activates the receptors) important to cell. a single cascade is usually initiated , altering the behaviour of cell. some CDs protien do not plaay role in cell signaling , but have oher functions , such as cell adhesion . there are approximately 250different proteins. reactivity of most common antibodies (CD MARKERS)used in flow cymetric evaluatin of hematolymphoid neoplasms.