Detailed immunophenotypic characterization of different major and minor subsets of peripheral blood cells in patients with paroxysmal nocturnal hemoglobinuria

BACKGROUND: Paroxysmal nocturnal hemoglobinuria (PNH) is characterized by a deficient expression of glycosylphosphatidylinositol‐anchored proteins (GPI‐APs), due to somatic mutations of the phosphatidylinositolglycan complementation Class A (PIG‐A) gene. STUDY DESIGN AND METHODS: In this study, the expression of a high number of GPI‐APs on different subsets of peripheral blood (PB) cells from 14 PNH patients and their potential association with underlying genetic abnormalities has been analyzed. RESULTS: This study confirms the existence of variable patterns of expression of different GPI‐APs on both major and minor PB‐cell subsets from PNH patients. The size of the PNH clone within PB neutrophils and monocytes was systematically higher than that of other cell populations. Genetic changes were detected in the PIG‐A gene in 5 of 13 cases analyzed. Interestingly, the reactivity for many GPI‐APs was significantly higher on different subsets of normal PB cells from PNH patients than those observed on healthy volunteers. CONCLUSION: The best combination of markers for the diagnostic screening of PNH would include evaluation of CD14 on monocytes and of CD16 on neutrophils, although further analysis of CD55 and CD59 expression may contain additional clinically useful information. Clear association between the genetic changes detected in the PIG‐A gene in 5 of 13 cases analyzed, and the phenotypic profile of PNH cells has not been found. Additionally, an abnormally higher expression of several GPI‐APs among normal residual cells from PNH patients in comparison to healthy donors was observed, suggesting that factors other than the PIG‐A mutation could determine the phenotypic profile of PB cells in PNH.