Separation of the acetylcholinesterase-deficient red cells in paroxysmal nocturnal hemoglobinuria.

Blood of patients with paroxysmal nocturnal hemoglobinuria (PNH) most often contains two or more populations of erythrocytes--one population with normal sensitivity to lysis by complement (PNH I cells) and a second population of moderately abnormal cells (PNH II cells) or markedly abnormal cells (PNH III cells). PNH II and III cells exhibit moderately and markedly increased sensitivity to lysis by complement, respectively, as well as other membrane defects. We have devised a method for isolating pure, intact PNH II and III cells from mixed populations by use of monoclonal antibodies and cell affinity chromatography. Study of purified cell populations has led to the identification of a further subtype, PNH IIIb, of PNH erythrocytes. PNH IIIb erythrocytes are less sensitive to complement lysis than PNH IIIa cells but are lysed by fluid-phase activation of complement, unlike PNH II erythrocytes.