Erythrocyte Acetylcholinesterase Deficiency in Paroxysmal Nocturnal Hemoglobinuria (PNH)—A Comparison of the Complement-Sensitive and Insensitive Populations

1. The complement-sensitive and -insensitive cells of patients with paroxysmal nocturnal hemoglobinuria have been separated by differential lysis using a cold agglutinin antibody and limiting concentrations of complement. The erythrocyte acetylcholinesterase (AChE) activity of each population of cells was determined.

2. The membranes of the complement-sensitive cells characteristic of PNH completely lack AChE activity.

3. The membranes of the complement-insensitive cells usually contain less AChE than normal and the degree of decrease roughly parallels the degree of increased sensitivity to complement.

4. Lysis of normal cells by complement does not alter the AChE activity of their membranes.

5. The inhibition of AChE activity by neostigmine methylsulfate (Prostigmin®) does not increase the sensitivity of normal red cells to lysis by C’.