Relationship between the expression of complement regulatory proteins and PIG-A gene abnormalities in CD34^+ cells of PNH.

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We investigated the expression of glycosylphosphatidylinositol (GPI)-anchored membrane proteins (CD55 and CD59) by erythrocytes, platelets, granulocytes, erythroblasts, T and B lymphocytes, and CD34^+ cells from patients with paroxysmal nocturnal hemoglobinuria (PNH) and healthy volunteers using flow cytometric two-color analysis. In addition, we also studied the abnormality of phosphatidylinositol glycan-class A (PIG-A) gene derived from granulocytes, Tlymphocytes, and CD34^+ cells in the patients. The results are as follows :1. We found that the expression of CD55 and CD59 by various cells as described above was discordant in PNH patients. In particular, we studied relationship between the phenotypes of circulating erythrocytes and cultured erythroblasts in the patients. Our results showed that the cultured erythroblasts in all the patients consisted of PNH I,II,and III erythroblasts or PNH II and III erythroblasts in spite of the final phenotype of mature erythrocytes. These finding … More s suggest that the final phenotype of erythrocytes in PNH is determined during maturation from erythroblasts to erythrocytes by the disappearance or persistence of PNH II erythroblasts (Shichishima et al., Blood, In press).2. We investigated PIG-A gene abnormalities in peripheral blood granulocytes and T lymphocytes obtained from PNH patients by PCR and RT-PCR followed by nucleotide sequence analysis. Our present study focused on the relationship between the phenotypes of these cells detected by flow cytometric analysis and proportion of abnormal clone of the PIG-A gene. Our results suggest that PIG-A gene abnormalities can not prescribe the phenotypes of granulocytes from PNH patients but the volume of GPI-core, although a defect of PIG-A gene certainly underlies the occurence of PNH (Noji, Shichishima et al., Blood 86 : 132a, 1995).3. One-color flow cytometric analysis showed that the CD34^+ cells derived from bone marrow blood from healthy volunteers consisted of a single population positive for CD59, while those from PNH patients had a continuous population from negative to positive for CD59. Moreover, we found that PIG-A gene abnormalities in bone marrow blood CD34^+ cells were same as those in peripheral blood granulocytes obtained from patients with PNH.We will have to evaluate carefully whether the CD34^+ cells could have the above two abnormalities of PIG-A gene in PNH. Less