Flow cytometric analysis of glycosylphosphatidyl-inositol-anchored proteins to assess paroxysmal nocturnal hemoglobinuria clone size.

Paroxysmal nocturnal hemoglobinuria (PNH) is characterized by total or partial deficiency of membrane proteins anchored to the cell surface through a glycosylphosphatidyl-inositol (GPI) moiety. The relationship between the size of the PNH clone, determined by the expression of GPI-anchored proteins (AP; CD14, CD48, CD55, CD59, and CD66b) on erythrocytes, lymphocytes, monocytes, and granulocytes using forward and side scatter analysis, and severity of the disease was evaluated in 19 PNH patients. CD55 antigen expression did not delineate abnormal erythrocytes as well as did anti-CD59. The proportion of monocytes deficient in CD55, CD59, CD48, and CD14 (48-97%) and of granulocytes deficient in CD55, CD59, and CD66b (60-99%) was greater than the proportion of erythrocytes deficient in CD59 (24-95%) and the proportion of lymphocytes deficient in CD55 and CD59 (30-98%). There were no significant correlations among reticulocyte, leukocyte, and platelet counts and GPI-AP-deficient immunophenotypes in red and white blood cells. However, high coefficients of determination were seen between hemoglobin levels and granulocytes deficient in CD59 (r(2) = 0.76), CD55 (r(2) = 0.74), and CD66b (r(2) = 0.74) antigens and between hemoglobin and monocytes deficient in CD55 (r(2) = 0.73), CD59 (r(2) = 0.80), and CD14 (r(2) = 0.75) antigens. These results are interpreted as indicating that the size of PNH clone is better assessed by immunophenotypic analysis of monocytes and granulocytes rather than of lymphocytes and erythrocytes.