Quantification of a Novel Dense Granule Protein (granulophysin) in Platelets of Patients With Dense Granule Storage Pool Deficiency

An antigen-capture sandwich enzyme-linked immunosor-bent assay (ELISA) was developed for a novel protein granu-lophysin, a constituent of the platelet dense granule (DG) membrane and used to characterize patients with dense granule storage pool deficiency (8-SPD). The assay uses two monoclonal antibodies against the protein, one of which is conjugated to peroxidase. Purified DGs, an enriched source of the protein, were used for the standard curve. Granulo-physin levels were only low in forms of 8-SPD associated with albinism. Granulophysin levels in platelet homogenates of 30 patients with the Hermansky-Pudlak syndrome form of I-SPD were %to ’/f of levels in controls or obligate heterozy-gotes. Two patients with the Chediak-Higashi form of 8-SPD ENSE GRANULES (DG) were originally identified D as storage organelles in the platelets of mammalian containing, in the human, serotonin (0.3 pmol