Evaluation of Marrow Granulocytic Reserves in Normal and Disease States

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.