Clonal Cell Proliferation in Paroxysmal Nocturnal Hemoglobinuria: Evaluation of Mutations and T-cell Receptor Clonality.

BACKGROUND

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired pluripotent hematopoietic stem cell disorder associated with an increase in the number of glycosyl-phosphatidyl inositol (GPI)-deficient blood cells. We investigated PNH clonal proliferation in the three cell lineages-granulocytes, T lymphocytes, and red blood cells (RBCs)-by analyzing gene mutations and T-cell receptor (TCR) clonality.

METHODS

Flow cytometry was used on peripheral blood samples from 24 PNH patients to measure the GPI-anchored protein (GPI-AP) deficient fraction in each blood cell lineage. gene mutations were analyzed in granulocytes and T lymphocytes by Sanger sequencing. A TCR clonality assay was performed in isolated GPI-AP deficient T lymphocytes.

RESULTS

The GPI-AP deficient fraction among the three lineages was the highest in granulocytes, followed by RBCs and T lymphocytes. mutations were detected in both granulocytes and T lymphocytes of 19 patients (79.2%), with a higher mutation burden in granulocytes. The GPI-AP deficient fractions of granulocytes and T lymphocytes correlated moderately (r=0.519, =0.049) and strongly (r=0.696, =0.006) with mutation burden, respectively. mutations were more frequently observed in patients with clonal rearrangements in TCR genes (=0.015). The mutation burden of T lymphocytes was higher in patients with clonal rearrangement.

CONCLUSIONS

mutations were present in approximately 80% of PNH patients. PNH clone size varies according to blood cell lineage, and clonal cells may obtain proliferation potential or gain a survival advantage over normal cells.