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This study was designed to determine the effect of methylcellulose (MC)-induced reticuloendothelial (RE) hypertrophy on neutrophils and hematopoietic stem cells and to contrast its overall hematologic effect in the mouse to the more frequently studied rat model. Mice were given MC 3 times/wk and studies were done at 2, 3, and 4 wk, with maximal hematologic change by 2 wk. A stable, but incompletely compensated hemolytic anemia developed which was accompanied by a significant shift of erythropoiesis from marrow to spleen. Thrombocytopenia developed as did neutrophilia, accompanied by an increased number of marrow neutrophil precursors. Extramedullary hematopoiesis was observed in the liver. The number of cells forming spleen colonies in irradiated recipients increased in the spleen but not in marrow. The number of cells producing granulocyte and macrophage colonies in semisolid media increased in spleen and marrow. Splenectomized mice, treated with MC, developed changes very similar to intact mice. Thus, it appears that all three major hematopoietic lines may be destroyed by the MC-hypertrophied RE system. The mouse differs from the rat in its hematologic response to MC by destroying cells in organs other than the spleen, by increasing neutrophil production, by developing hepatic hematopoiesis, and by developing all changes more rapidly.

The marginal granulocyte pool (MGP) was measured by epinephrine infusion in normal and neutropenic subjects. Neutrophil response curves to doses of 0.025 to 0.3 mg. in three normal subjects indicated that maximal neutrophil response was achieved by 0.1 mg. In 21 normal subjects, absolute neutrophils increased from 700 to 3,100 per microliter. The percentage increase ranged from 18 to 107 per cent of baseline. The per cent increase tended to be greater with low-normal baseline neutrophils than with high-normal neutrophils, although this relationship was not observed when increase was determined in absolute values. In neutropenic patients mean per cent increase of neutrophils was greater than observed in normal subjects, 121 vs. 50 per cent. Although the increase expressed in absolute neutrophil numbers was less in subjects with lower baseline neutrophil concentrations, there was an inverse correlation between the baseline neutrophil concentrations, there was an inverse correlation between the baseline neutrophils and the per cent increment following epinephrine. Mean increase was 200 per cent in patients with less than 200 neutrophils per microliter, compared with 61 per cent in patients with 1,000 to 1,500 neutrophils per microliter. These results indicate that circulating granulocyte pool (CGP) size may be misleading with respect to total blood neutrophils and in a sense confirm the concept of shift neutropenia, a decreased CGP and MGP as neutropenia becomes more profound suggests that shift neutropenia may be a normal physiologic methanism rather than a distinct neutropenic syndrome.

Neutrophil production and distribution were studied in two families with autosomal dominantly inherited neutropenia to distinguish their illness from other neutropenic disorders. In addition to a reduced post-mitotic pool of bone-marrow neutrophils and neutrophil precursors, mitotic pool size was also reduced, ranging from 1.1 to 2.9 X 10(9) cells per kilogram (normal, 3.8 +/- 0.4 X 10(9) per kilogram). In vitro committed stem cells were reduced as well, ranging from 2 to 12/10(5) marrow cells (normal, 30 to 120/10(5)). In three patients neutrophil counts were observed to return to normal when they were adults. In one such subject studied, however, both the mitotic pool of neutrophil precursors and marrow committed stem cells were reduced. These abnormalities were in contrast to studies of a patient with chronic benign neutropenia of childhood and an infant with Kostmann-type congenital neutropenia, both of whom had increased marrow committed stem cells. These studies demonstrate several different mechanisms for production of neutropenia in these syndromes.

In 19 patients with Felty's syndrome, marrow production of neutrophils and neutrophil distribution were studied. Despite accelerated marrow release and disappearance of mature blood neutrophils, there was little or no increase in the marrow mitotic pool or in vitro progenitor cells. Only two patients had an increase in marrow neutrophils and precursors. Antineutrophil antibody was detected in seven of nine patients studied. Neither abnormal margination of blood neutrophils nor impaired marrow release of cells was detected. Skin exudate cellularity tended to correspond to prior history of infections, asymptomatic patients having more cellular exudates. Sustained neutrophil increments were observed in six of 10 patients following splenectomy, but in no patient did neutrophil kinetics return completely to normal. Three of four patients who failed to respond to splenectomy with sustained increments in blood neutrophils had a reduced mass of marrow neutrophils and neutrophil precursors when studied prior to splenectomy. No diminution in neutropenia was observed in any of five patients treated with lithium carbonate. This study indicates that multiple factors are involved in the pathogenesis of neutropenia in Felty's syndrome. In particular, neutropenia was associated with inadequate marrow granulocytopoiesis. The severity of the impairment, as determined by the mass of marrow neutrophils and precursor cells, may be useful in predicting response to splenectomy.

A transplantable murine breast carcinoma in mice was associated with marked leukemoid reaction. Within 1 week of subcutaneous implantation of tumor the leukocyte count began to increase and reached average levels of 165,000 leukocytes per cubic millimeter within 18 days. This represented an increase in mature neutrophils primarily, although other blood leukocytes were modestly increased as well. The total number of neutrophils per humerus was increased but no increase was detected in the number of myloblasts, promyelocytes, or myelocytes. The tritiated thymidine-labeling index of the latter three cells was not significantly changed during tumor growth. The number of progenitor cells forming granulocytic and mononuclear cells in vitro was decreased in the marrow during tumor growth. Colony-stimulating activity in plasma was slightly increased during the early phase of tumor growth and decreased during later phases. Emergence time of blood neutrophils was normal, as measured by labeling with tritiated thymidine, but decline in labeled cells was abnormally slow in tumor-bearing mice. There was a shift of erythropoiesis to the spleen, but total erythropoiesis appeared to be normal in most mice. Surgical excision of the tumor resulted in prompt reversal of the leukemoid reaction. In the aggregate these results are consistent with a hypothesis that the leukemoid reaction was the result of increased blood transit time of neutrophils primarily, rather than increased neutrophil production.

Neutrophilia, produced by bleeding or by parasitic infection, did not result in a larger than normal number of cells migrating into endotoxin-induced peritoneal exudates. These results fail to support but do not disprove the concept that neutrophil loss from the blood may be controlled primarily by changes in the fractional turnover rate rather than by blood pool size. They indicate that the failure of exudate neutrophils to increase in proportion to blood neutrophils in patients with chronic myeloid leukemia may not be an abnormality as interpreted previously.

The mechanism by which adrenocortical steroids induce granulocytosis in man has been investigated using granulocytes labeled with radioactive diisopropylfluorophosphate. After an intravenous injection of 200 mg of cortisol was given to five normal subjects, the mean value for the total blood granulocyte pool increased from 79 to 138 x 10(7) cells per kg of body weight and reflected an increase in the size of both the circulating granulocyte pool and the marginal granulocyte pool. When granulocytes in the circulation were labeled with diisopropylfluorophosphate and granulocytosis was induced later by the intravenous administration of cortisol, the rate of decline of granulocyte specific activity was increased, indicating that the blood pool was being diluted at an accelerated rate by unlabeled cells entering from the bone marrow. The rate of egress of granulocytes from the blood pool to an inflammatory exudate was studied by the "skin window" technique. After the administration of cortisol, there was a mean reduction in the cellularity of induced inflammatory exudates of 75%. However, this reduction in cellularity varied considerably from subject to subject (45-98%). From these studies we can infer that steroids induce an absolute granulocytosis by decreasing the rate of egress of cells from the total blood granulocyte pool as well as by increasing the influx of cells from the bone marrow. By model simulation studies of the non-steady state induced by cortisol injection, it has been possible to quantitate these rate changes. In the present studies cortisol injection resulted in a mean decrease in blood granulocyte egress of 74% (1-99%) and a mean increase in cell inflow of 450% (300-750%).

Neutrophil kinetics of acute experimental infection were studied with diisopropylfluorophosphate-(32)P labeling in 31 dogs inoculated intrabronchially with pneumococci. In vitro neutrophil labeling indicated a rapid transit time through the blood in early infections, with an elevated marginal granulocyte pool sometimes preceding an elevation of the circulating granulocyte pool. 13 hr after infection, the circulating and total blood granulocyte pools were increased but the rate of neutrophil transit through the blood was normal. During the recovery from infection there was a marked prolongation of neutrophil blood transit time, suggesting virtually complete cessation of bone marrow release of neutrophils into the blood. Labeling of neutrophils in vivo indicated an increased rate of emptying of the bone marrow storage pool proportional to the severity of infection as measured by the fever index. The change in the blood ratio of nonsegmented to segmented neutrophils was a much more accurate index of the severity of infection than the blood granulocyte concentration, correlating significantly with the fever index.