Granulopoiesis in Shwachman's syndrome (pancreatic insufficiency and bone marrow dysfunction).

Granulopoiesis was studied in 10 children with Shwachman's syndrome (chronic neutropenia and exocrine pancreatic insufficiency). Marrow proliferative activity assessed by determination of mitotic indices and tritiated thymidine uptake into granulocytic cells was normal. Assay of bone marrow granulocyte colony-forming cells (CFU-C) in a methylcellulose tissue culture system demonstrated normal CFU-C numbers in four patients and reduced numbers in five. The granulocyte colonies formed were indistinguishable from normal colonies morphologically. Production of colony-stimulating activity (CSA) from patients' peripheral blood leukocytes appeared normal when tested on control marrow. No serum inhibitors against CFU-C or CSA could be demonstrated using both control and autologous marrow, and co-culture of patients' peripheral blood lymphocytes with control marrow did not inhibit CFU-C growth. We conclude that in Shwachman's syndrome committed granulocytic stem cells are present, and the numbers detected in vitro vary widely as does the clinical neutropenia. The proliferative activity of recognizable granulocytic cells is normal and neither a deficiency of humoral stimulators nor the presence of serum or cellular inhibitors of granulopoiesis can be demonstrated.