Abstract: Neutrophils and platelets from human blood are stabilized for storage and subsequent reconstitution for use by reacting with a chemical cross-linking agent having functional groups reactive to form covalent linkages with the neutrophils or platelets, the functional groups being covalently bonded to a molecular backbone including a group subject to cleavage under conditions which are non-destructive of the neutrophils or platelets. After storage at reduced temperature, the composition can be reconstituted by cleavage and substantially regains its original physiological properties.