Abstract
Summary: The number of cells capable of synthesizing deoxyribonucleic acid was estimated in the peripheral blood of patients with a variety of disorders. A significant increase above normal was found in patients with a group of “autoimmune” disorders, including systemic lupus erythematosus, progressive hepatitis, acquired hæmolytic anæmia and rheumatoid arthritis, and three further patients with aplastic A normal level of these cells was observed in two patients with paroxysmal nocturnal hæmoglobinuria, and in a patient with hæmolytic anæmia and renal insufficiency. However, in four patients with hereditary spherocytosis the level of these cells was elevated. The significance of these findings is discussed.