Recent concepts of the relationship of the blood granulocyte mass to the marrow reserve of granulocytes have been reviewed. Evidence has been presented to show that the marrow is the chief area of granulocyte "reserves" or "stores." The development of acute leukocytosis in response to a stimulus such as the intravenous injection of bacterial endotoxin depends upon release of cells from the intramedullary pool of granulocytes.
The turnover of the marrow granulocyte reserve (MGR) is an orderly process in the steady state, and determines the form of the curve of DNA-labeled granulocytes in the peripheral blood. From estimates of the turnover time of the MGR it appears that the granulocyte spends an average time of about 10 hours in the peripheral blood. Granulocytes do not appear to recirculate once they have left the peripheral blood and have entered the tissues. However, granulocytes may be sequestered within capillary beds for variable periods, and may re-enter the circulating blood from such areas. Such cells are not to be considered as having re-entered the blood from the tissues.
The intravenous injection of a purified bacterial lipopolysaccharide as a stimulus to acute leukocytosis is described. The possbile usefulness of this procedure in assessing the MGR is discussed.
1. Lymphocytes in dogs have been labeled by means of the DNA-P32 incorporation technic.
2. In the thoracic duct, a high level of lymphocyte DNA-P32 specific activity is reached within two hours. After 24 to 30 hours, the activity falls to a lower level which is then maintained for at least 160 hours.
3. Lymphocyte-granulocyte separations on the blood revealed that DNA-P32 specific activity reached a peak on the fourth day for both lymphocytes and granulocytes.
4. These findings are consistent with a short maturation time for the lymphocyte and a short intravascular time.
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