Deficient surface expression of glycosylphosphatidylinositol-anchored proteins in B cell lines established from patients with paroxysmal nocturnal hemoglobinuria

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired type hemolytic disorder. Hematopoietic cells of patients with PNH are deficient in glycosylphosphatidylinositol (GPI) anchored membrane proteins. Since some membrane-bound complement inhibitors, such as CD59 and decay accelerating factor (DAF), are GPI anchored proteins, abnormal cells from patients with PNH are sensitive to complement attack. Their myeloid and erythroid cells are affected more than their lymphoid cells. Patients whose B cells were severely deficient in GPI anchored proteins were chosen to establish cell lines by Epstein-Barr virus mediated transformation. The lines established (SS-1-, TK-1-, and TK-14- cell lines) had the following characteristics of PNH. First, GPI anchored proteins were completely absent from the surface of SS-1- and TK-14- cells, and were expressed at very low levels on TK-1- cells, whereas polypeptide anchored proteins were normally expressed on these three lines. Secondly, DAF mRNAs of the SS-1- cell line were qualitatively and quantitatively indistinguishable from those of a control, wild-type cell line. Third, pro-CD59 and pro-DAF molecules were detected intracellularly in these cell lines, their pro-CD59 being smaller and more hydrophilic than that from a wild-type cell line. These cell lines should be useful in further studies on the pathogenesis of PNH.