Objective: To investigate the expression of membrane associated complement regulatory proteins (CRP)--CD55 and CD59 on the peripheral blood cells in patients with paroxysmal nocturnal hemoglobinuria (PNH), aplastic anemia(AA) and myelodysplastic syndrome (MDS) and its clinical implications.
Methods: Expression of CD55 and CD59 on neutrophils, lymphocytes and erythrocytes was analyzed with flow cytometry, using FITC and PE labeled anti-CD55 and CD59 monoclonal antibodies.
Results: CD55 and CD59 expression on neutrophils was significantly decreased in 21 PNH patients (including 2 cases of AA-PNH syndrome). CD59- cells in neutrophils were constantly in excess of 10% in all of the PNH patients. Reduction in CD59 expression on erythrocytes was related to the severity of the disease. CD55- neutrophils were also significantly increased in PNH patients but with a greater variation. Expressions of CD55 and CD59 on neutrophils were remarkably decreased in 31 AA patients but to a less extent as compared to PNH. No significant difference in the expressions of CD55 and CD59 was found in all the 21 MDS patients.
Conclusion: Expression of CRP is reduced in PNH and its related disorder-AA but remains unchanged in MDS. Flow cytometric analysis of complement regulatory proteins is of value in diagnosis and differential diagnosis of PNH, AA and MDS. In terms of diagnostic sensitivity and specificity, CD59 is superior to CD55, and neutrophil is superior to lymphocyte and erythrocyte.