Cd 59 Immunohistochemistry Blood

Although increased blood cell deficiency of glycosyl phosphatidylinositol-anchored membrane proteins has often been detected in patients with aplastic anemia (AA) and myelodysplastic syndrome (MDS), the clinical significance of such paroxysmal nocturnal hemoglobinuria (PNH)-type cells remains to be elucidated. We established a sensitive flow cytometric assay capable of detecting less than 0.01% of CD59-CD55- blood cells in a sample and used the assay to examine a large number of patients with bone marrow failure. An increase in the proportion of PNH-type cells was detectable in approximately 60% of all AA patients and in 20% of all refractory anemia (RA)-MDS patients. CD59 is a 77-amino acid membrane glycoprotein that plays an important role in regulating the terminal pathway of complement by inhibiting formation of the cytolytic membrane attack complex (MAC or C5b-9). The MAC is formed by the self assembly of C5b, C6, C7, C8, and multiple C9 molecules, with CD59 functioning by binding C5b-8 and C5b-9 in the assembling complex. We performed a scanning alanine mutagenesis screen of residues 16