The course of the differentiation and proliferation of the human erythroid burst-forming units (BFU-E) to colony-forming units (CFU-E) was directly investigated using a combination of highly purified BFU-E, a liquid culture system, and the following clonal assay. Highly purified human blood BFU-E with a purity of 45-79% were cultured in liquid medium with recombinant human erythropoietin (rEP) and recombinant human interleukin-3 (rIL-3) to generate more differentiated erythroid progenitors. The cultured cells were collected daily for investigating the morphology, the increment in the number of cells and the clonality. Ninety percent of purified BFU-E required not only rEP but also rIL-3 for clonal development. By 7 days of liquid culture, the total cell number increased 237 +/- 20-fold above the starting cells, while erythroid progenitors increased 156 +/- 74-fold. As the incubation time in liquid culture increased, the cells continuously differentiated in morphology. Replating experiments with rEP combined with or without rIL-3 showed the following: 1) The number of erythroblasts that were part of erythroid colonies decreased with accompanying erythroid progenitor differentiation and proliferation. 2) As the incubation time in liquid culture increased, erythroid progenitors had a graded loss of their dependency on rIL-3 and a complete loss of dependency was observed after 3 days of liquid culture. At that time 85% of the erythroid progenitors gave rise to colonies of more than 100 erythroblasts which were equivalent to mature BFU-E. These studies provide a quantitative assessment of the loss of IL-3 dependency by BFU-E and indicate that the size of the generated erythroid colonies and their IL-3 requirement correlate with the erythroid differentiated state.

The presence of serum or contaminant cells may alter clonal development of haematopoietic progenitor cells in vitro. To investigate the pathogenesis of myelodysplastic syndromes (MDS), marrow progenitor cells from 13 MDS patients were highly purified using monoclonal antibodies including CD34 and immunomagnetic microspheres. The cells positive for CD34 in the purified cells were in the range from 87% to 98%. These purified cells were cultured in serum-free medium with individual colony stimulating factors (CSFs) to investigate whether CD34+ cells from MDS patients have abnormal responses to individual CSFs. Dose response experiments with the purified CD34+ cells and recombinant human macrophage-CSF (rM-CSF), granulocyte-CSF (rG-CSF), granulocyte/macrophage-CSF (rGM-CSF), interleukin-3 (rIL-3) or erythropoietin (rEP) were performed in serum-free fibrin clots in 11 patients. Five patients showed a diminished response to rG-CSF and one patient to rEP. In the remaining six patients the purified CD34+ cells did not respond to a stimulation of any individual CSFs. The results indicate that the progenitor cell growth abnormalities in these disorders involve a defect in the capacity of progenitor cells to respond to stimulation with G-CSF, and present direct evidence for the manner in which myelodysplastic CD34+ cells are impaired.

Marked thrombocytopenia developed during pregnancy in both identical twins mothers who had systemic lupus erythematosus (SLE) and also type IIB von Willebrand's disease (vWD). The proband's platelet count decreased in the third trimester of pregnancy. Large-dose gamma-globulin and prednisolone treatments were performed because of the suspicion of immune thrombocytopenic reaction associated with SLE. These treatments were not effective. Her platelet count returned to the normal range immediately after delivery. Postpartum examinations revealed the decreased ristocetin cofactor activity and the deficiency of large von Willebrand factor (vWF) multimers in preserved plasma samples from the third trimester. These abnormal findings improved after delivery. Investigation of family members revealed that the proband had inherited type IIB vWD from her mother. The other twin, who was also under treatment for SLE, became pregnant about 1 year after delivery in the proband and followed almost the same course as that observed in the proband. As bleeding tendency was observed a few days before delivery, a factor VIII concentrate (Haemate P) was administered to compete with her variant vWF. This concentrate could prevent the further decrease in her platelet count, thereby correcting the hemorrhagic tendency. It seems evident that factor VII concentrate would be effective in treating thrombocytopenia associated with type IIB vWD.

To facilitate the investigation of the direct interaction between hematopoietic progenitors and colony-stimulating factors, we have developed a method to purify human marrow progenitor cells. Using density centrifugation, negative panning with concanavalin A coated plates, positive selection of CD34-positive cells with immunomagnetic microspheres, overnight adherence to a plastic dish, negative selection with a panel of monoclonal antibodies, and density centrifugation, human marrow progenitor cells were purified from 1.5% to 53.2%, a 42- fold purification, with a 4.8% yield. The purified cells consisted of 38% erythroid, 9% colony forming unit-granulocyte (CFU-G), 29% CFU- macrophage (CFU-M), 12% CFU-eosinophil/basophil (CFU-Eo/Ba), and 4% CFU- mix. The purified cells cultured in serum-free fibrin clots with recombinant human macrophage colony-stimulating factor (rM-CSF) for 14 days developed a pure population of CFU-M colonies. An appearance of CFU-M colonies was present after the addition of 1 U/mL of rM-CSF and the maximum stimulation was found at 100 U/mL. When the purified cells were cultured in serum-free medium with rM-CSF in a limiting dilution assay and the percentage of nonresponder wells for CFU-M colonies was plotted against cell concentration, serum-free cultures yielded a straight line through the origin, indicating that CFU-M development did not depend on accessory cells and that rM-CSF acted directly on the CFU- M.

An autopsy case of amyloidosis associated with factor X deficiency is reported. The patient showed a markedly decreased level of factor X (9% normal) and an extremely shortened half‐life of intravenously infused factor X. Amyloid deposition was present in most of the visceral organs with special involvement of the liver and spleen. The amyloid in this case was thought to be AL protein, since it was potassium‐permanganate‐resistent and a small amount of Bence Jones protein was detected after dimethyl sulfoxide therapy. Electron microscopic study revealed a typical appearance of amyloid fibrils radiating from invaginated cell membrane of Kupffer cells, which may indicate rather rapid turnover of the amyloid. Rapidity and severity of amyloid deposition, especially in the liver and spleen, may play an important role in the development of the factor X deficiency associated with systemic amyloidosis. ACTA PATHOL. JPN. 34: 639–647, 1984.