Background: Paroxysmal nocturnal hemoglobinuria (NPH) is a clonal disease in which a deficit in the expression of molecules bound to the cell membrane by glycosyl-phosphatidylinositol (MUGFI) groups has been demonstrated. The MUGFI are widely distributed and among them proteins regulating the action of complement may be found. The development of monoclonal antibodies (MoAb) against MUGFI may allow the introduction of a new diagnostic method in this disease and increase the sensitivity, particularly in transfused individuals.
Methods: The erythrocytic and leukocytic phenotype of 14 patients with NPH clonality demonstrated by the classic tests of sensitivity to the complement was analyzed by immunofluorescence techniques and flow cytometry with the use of MoAb which recognize MUGFI (CD55, CD59, CD14, CD16 and CD24).
Results: Cells with a decrease or absence of MUGFI were observed in all the patients. The defect was demonstrated in the red cells, monocytes and neutrophils of all the patients, while it was only observed in the lymphocytes of three patients. The percentage of cells with a decrease in MUGFI was variable (2-100%) as well the pattern of deficiency against the different MoAb used. The MoAb with greatest sensitivity for the detection of clonal population were the CD59 in erythrocytes, the CD14 in monocytes and the CD24 in neutrophils. The CD16 was normal in one patient and the CD55 in two. The transfusion of packed red cells did not influence the abnormal leukocyte pattern, with abnormalities even being observed in the erythrocytary CD59. The Ham test was negative in those cases in which the percentage of negative CD59 erythrocytes was lower than 5% of the total erythrocytic population.
Conclusions: The study of glucosylphosphatidylinositol by flow cytometry and monoclonal antibodies is a useful technique for the detection and quantification of the nocturnal paroxistic hemoglobinuria clone even in transfused patients.