GPI and paroxysmal nocturnal hemoglobinuria: Apoptosis rate in response to serum starvation was lower in granulocytes of PNH patients compared to controls. There were no differences in Fas antigen expression. Apoptosis rate did not correlate with PNH clone size. There were no differences in apoptosis of GPI (-) and GPI (+) B lymphoblastoid lines after serum starvation, γ-radiation, and anti-Fas antibody treatment.