Regulation of granulopoiesis: positive feed-back

Leukemic samples characteristics associated with clonogenic growth

In this study, we attempted to delineate readily assessable characteristics from 100 leukemic samples associated with in-vitro growth. Successful growth defined as production of greater than 30 clusters and/or colonies per culture dish was obtained in 68% of samples. More than 10 colonies were found in 59% and greater than 30 colonies in 51% of cultures, respectively. Leukemic cells from patients previously treated with aggressive cytotoxic chemotherapy grew significantly better than cells from untreated patients, independently of the above definitions of cloning success. Cells from peripheral blood had a weak, albeit significant growth advantage over bone marrow cells (p = 0.032) when cluster growth was taken into account for growth success. When colony growth alone was used as criterium, no growth advantage was found. The morphological subtype and the proliferation kinetics prior to cell plating did not affect cloning success. A high labeling index had predictive value for subsequent growth, but only in bone marrow cells. By multivariate analysis, we found that treatment status was the most important factor correlated with in-vitro growth.

Modulation of murine hemopoiesis in vivo by a synthetic hemoregulatory pentapeptide (HP 5b)

A synthetic pentapeptide analogous to an inhibitory factor associated with human granulocytes was tested in vivo on female C3H mice. The relative and absolute numbers of myelopoietic and erythropoietic cells in the bone marrow were measured following injections as well as the continuous infusion of the pentapeptide in dose ranges between 10(-8)M and 10(-4)M (0.12 micrograms to 1.2 mg/mouse). In low doses, the pentapeptide reduced the number of myelopoietic cells in the bone marrow, and this was accompanied by reduced numbers of granulocytes and monocytes and peripheral blood. Elevated doses also decreased erythropoiesis. In contrast, continuous infusion of 14 micrograms/h for 19 days seemed to make the myelopoietic cells refractory to further action. A regulatory function of the pentapeptide is proposed.

The role of granulocytes in colony stimulation by human white blood cells in agar cultures. Enhancement and inhibition of CSA

The effect of polymorphonuclear granulocytes (PMN) on colony stimulating activity (CSA) was studied in double layer cultures of human Ficoll Isopaque separated white blood cells (mononuclear cells = MNC). Previously published data have been confirmed that granulocytes are able to enhance or inhibit MNC derived CSA. Further analysis of the mode of action of PMN in vitro indicates that the enhancing activity ascribed to granulocytes coincides with low CSA in MNC basal layers. In contrast, in cultures with high levels of CSA as provided by lysed red blood cell enhancement rather than concentrations of PMN are sufficient to induce inhibition of colony growth. A very similar effect to that achieved with basal layer derived CSA could be obtained with conditioned media of PMN and MNC short term liquid cultures. The data indicate, that enhancement and inhibition of colony growth reflect a specific reactivity of granulocytes (PMN) to a given CSA level in the cultures. These findings are discussed in terms of a speculative role of PMN in a negative feed back control mechanism regulating granulopoiesis in vivo.

Effects of nitrogen mustard and splenectomy on mouse bone marrow colony formation in vitro

Improved tolerance of splenectomized patients with Hodgkin's disease (HD) to radiotherapy and chemotherapy has been reported. The present study was undertaken to determine the effects of splenectomy and nitrogen mustard (NM) on colony-forming cells (CFC's) of bone marrow cells obtained from CF1 male mice by in bitro agar-gel technique. Splenectomized mice were given NM intraperitoneally on day 11. On day 15, they were sacrificed and the bone marrow was cultured with a source of colony-stimulating factor (CSF). Spleen extract was prepared by grinding spleens from CF1 mice. On the eighth day of incubation, significantly higher numbers of CFC's were found in splenectomized animals at 1% confidence level (F Test) compared with the nonsplenectomized animals. Both splenectomized and non-splenectomized mice had a greater colony response after NM (at 5% confidence level) than saline-treated controls. Maximum numbers of colonies were obtained in the nustard-treated asplenic animals. Splenic extract, as well as extracts from other organs, when added to the culture plates resulted in inhibition of colony formation. The significance of in vitro inhibition after addition of organ extract is uncertain.

Chronic neutropenia: Response to plasma with high colony-stimulating activity

A child with repeated infections was immunologically normal but was found to have neutropenia with periodic elevations of the absolute mature polymorphonuclear count at 21-day intervals. Immediately following the PMN rise, bone marrow morphology and in vitro cultures demonstrated a maturation arrest at the myelocyte stage with an increase in proliferative capacity. His cycle was not altered by infusions of normal plasma or by injections of epinephrine or typhoid vaccine. Infusion of 10 ml/kg of "stimulated" plasma from donors reactive to TV, obtained 60 minutes following immunization, resulted in an out-of-phase rise in PMN cells and clinical improvement. In vitro assays, using normal or patient marrow, detected high levels of colony-stimulating activity only in those plasma samples that were effective in the patient. These observations support a role of CSA as a physiologic regulator of granulopoiesis in man.