The proliferative states of circulating granulopoietic stem cells in man

Hemopoietic progenitor cells in the blood as indicators of the functional status of the bone marrow after total-body and partial-body irradiation: experiences from studies in dogs

The granulocyte-macrophage colony-forming cells (GM-CFC) were studied in the blood of dogs to evaluate their relationship to the bone marrow GM-CFC under normal conditions and their involvement in hemopoietic regeneration after different types of exposure to ionizing radiation. The GM-CFC could be defined as regular blood elements showing characteristic levels of their concentration in individual dogs in the range from 20 to 300 cells per ml. In relative terms, the GM-CFC numbers present in the whole blood of normal dogs were found to be on the order of 0.1% of the GM-CFC numbers present in the bone marrow. A small fraction of the GM-CFC population in the bone marrow, i.e., about 1%, can be mobilized into the peripheral blood within three h by intravenous injection of dextran sulfate (DS). These cells are characterized by a small size and a low S-phase fraction similar to the GM-CFC that are normally present in the blood. Total-body irradiation with single doses of 0.8 Gy and more caused a characteristic pattern of sequential changes in the blood GM-CFC concentration that were related to the recovery of the bone marrow GM-CFC population. The blood GM-CFC concentration showed an extreme depression within the first 15 days, a transient increase from day 17 to day 35 and remained at subnormal values for several weeks and months. The regeneration of the GM-CFC population in the bone marrow that could be mobilized into the blood by DS was similarly delayed as the recovery of the blood GM-CFC values. In dogs which were kept under continuous radiation exposure (0.019 Gy/day) causing permanent damage to the hemopoietic system, the GM-CFC numbers in the blood remained permanently depressed. Partial-body irradiation of dogs with a myeloablative dose (11.7 Gy) given to the anterior part of their body was followed by sequential changes in the blood GM-CFC concentration specific for this type of exposure. The pattern of changes was determined by direct radiation effects, the compensatory responses in the protected bone marrow and the regeneration events in the irradiated bone marrow. On the other hand, it could be shown that the repopulation and the restoration of the hemopoietic tissue is initiated by the seeding of hemopoietic cells (including GM-CFC) from the protected marrow.

New evaluations of circulating granulocyte and macrophage stem cells in healthy adults using conditioned media and recombinant human growth factors

Peripheral human blood contains granulo-monocyte (CFU-GM) and eosinophil (CFU-Eo) progenitors. In vitro, the number of colony forming units is thought to range from 0.1-14 per 2 x 10(5) plated cells. We show that the number of CFU-GM, Eo depends on culture methods. By modifying the usual assay method (using human umbilical cord plasma and the association of 2 stimulating conditioned media: activated lymphocyte conditioned medium and bone marrow fibroblast conditioned medium), we found different circulating CFU-GM, Eo numbers. The mean number of circulating CFU-GM, Eo in 107 healthy adults was 22.4 per 2 x 10(5) plated cells (range: 1-84). There was a slight difference between males (mean number: 23.6) and females (mean number: 20.4). The mean number of CFU-GM, Eo harvested on Percoll gradient was 123/ml of peripheral blood (range: 7-513). These results are far over those commonly reported in literature. This suggests that these latter results were probably underestimated. The use of recombinant human interleukin 3 and recombinant human GM (granulocyte-monocyte) colony-stimulating factors shows that CFU-GM, Eo numbers are found to be comparatively increased compared to that obtained with our modified method (using rhIL-3 alone), or that the size of those colonies is notably increased (using rhIL-3 + rhGM-CSF).

Relationship between myeloblasts and cluster-forming cells in acute non-lymphocytic leukemia

The relationship between myeloblast-like cells and cluster-forming cells detected by growth in agar has been studied in 22 untreated patients with acute non-lymphocytic leukemia by means of comparing data for 3H-TdR labelling of myeloblast-like cells and 3H-TdR suiciding of cluster-forming cells. The fraction of myeloblast-like cells in S-phase was significantly smaller (13.1 +/- 8.7 per cent) than the fraction of cluster-forming cells in S-phase (35.5 +/- 15.3 per cent). In 2/22 patients approximately half of the myeloblast-like cells in DNA-synthesis were calculated to produce clusters in agar which may suggest similarity for cell cycle active myeloblast-like cells and cluster-forming cells. The other patients showed decreased plating efficiency for myeloblast-like cells in S-phase indicating non-identity or modification of the growth pattern due to environmental factors and variations in death rate during culture. Sequential studies in three patients indicated a changing relationship between myeloblast-like cells and cluster-forming cells suggesting non-identity or differences in growth regulation during the course of the disease.

Behaviour of myeloid precursors in homozygous beta thalassaemia

Maintaining a high haemoglobin level, through a high transfusion regime, is the best method for treating thalassaemia. Not much is known about the effect of this treatment on medullary or extramedullary haemopoiesis, particularly on the extent of erythropoietic inhibition and on the behaviour of myelopoiesis. In order to analyse some aspects of the problem, we studied the myeloid stem cells (CFU-c) in the bone marrow and in the peripheral blood of children with homozygous thalassaemia, using the agar culture technique. The number of circulating CFU-c observed in 68 patients was higher than in normal subjects. This number was significantly increased after splenectomy. A positive correlation was demonstrated between the number of circulating CFU-c and the time elapsed since the last transfusion. Patients with a high Hb level displayed a marked reduction in the number of CFU-c in their peripheral blood. In 10 patients, before the beginning of transfusions, bone marrow CFU-c were lower than in normal subjects; their number increased after therapy. Most circulating CFU-c were proliferating as shown by the thymidine suicide technique.