Natural glucocorticoids (Gc) produced during stress have profound effects on the immune system. It is well known that Gc induce apoptosis in precursor T and B cells, markedly altering lymphopoiesis. However, it has been noted that marrow myeloid cells expanded both in proportion and absolute numbers in the mouse after Gc exposure. Mice were implanted with a corticosterone (CS) tablet that increased serum Gc and caused atrophied thymuses, both classic signs of activation of the stress axis. Blood neutrophil counts were elevated (4.8؋), whereas lymphocyte counts declined. Flow cytometric analysis of the marrow revealed that the phenotypic distribution of the various major classes of cells was shifted by Gc exposure. As expected, marrow lymphocyte numbers declined >40% after 3 days of exposure to Gc. Conversely, in the myeloid compartment, both monocytes and granulocytes increased in number by >40%. Further, all granulocyte developmental stages showed large increases in both total number and percentage of cells. To investigate the functional capacity of mature granulocytes from Gc-treated mice, an improved granulocyte isolation method was developed. Gc exposure had little effect on the ability of granulocytes to produce superoxide or undergo chemotaxis or phagocytose bacteria. These results indicate that Gc treatment shifts bone marrow composition and provides evidence that granulocytes and their progenitors are selectively preserved under stressful conditions without losing function.granulopoiesis ͉ lymphopoiesis
Natural glucocorticoids (Gc) produced during stress have profound effects on cells of the immune system. It is known that Gc induce apoptosis in precursor T and B cells markedly altering lymphopoiesis; however, it has been noted that bone marrow myeloid cells expanded both in proportion and absolute numbers in the mouse marrow after Gc treatment. In this study, increased serum Gc and atrophied thymus were observed in mice implanted with corticosterone tablets compared to sham operated mice. Additionally, blood neutrophil counts were elevated dramatically, while lymphocyte counts sharply declined. In the bone marrow, nucleated cell number was unchanged, however the distribution of cell type was dramatically shifted. As expected, marrow lymphocytes declined more than 40% after 3 days, while monocytes and granulocytes increased in number by at least 40%. Further, all granulocyte developmental stages showed dramatic increases in both total number and percent of nucleated marrow. Gc‐exposure had little to no effect on the ability of granulocytes to produce superoxide, undergo chemotaxis or phagocytose bacteria. These results indicated that Gc treatment drastically shifted bone marrow composition and provided evidence that granulocytes and their progenitors were selectively preserved under stressful conditions without losing function.This research was supported by NIH grant DK 52289‐29.
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