Career Development Awardee of the National Institutes of Health, United States Public Health Service
Involution and regeneration of the thymus in mice, induced by bacterial endotoxin and studied by quantitative histology and electron microscopy†
Version of Record online: 3 FEB 2005
Copyright © 1968 Wiley-Liss, Inc.
American Journal of Anatomy
Volume 122, Issue 3, pages 573–605, May 1968
How to Cite
Gad, P. and Clark, S. L. (1968), Involution and regeneration of the thymus in mice, induced by bacterial endotoxin and studied by quantitative histology and electron microscopy. Am. J. Anat., 122: 573–605. doi: 10.1002/aja.1001220310
Supported in part by grants GM 3784 and GM AM 7176 from the National Institutes of Health, United States Public Health Service, grant GB 4788 from the National Science Foundation, and a grant from P. Carl Petersen's Foundation, Denmark.
- Issue online: 3 FEB 2005
- Version of Record online: 3 FEB 2005
Lipopolysaccharide from S. typhosa, injected intraperitoneally into Swiss albino mice, produced acute thymic involution—maximal at 48 hours after injection, followed by regeneration that was complete within 5 to 7 days. Using tissues fixed and embedded for electron microscopy, cell counts were made with the light microscope and cytological details were examined in electron micrographs. The cellular events of involution and regeneration were similar to those produced by injection of adrenal glucocorticoids, but it remains to be determined whether or not endotoxin acts on the thymus by inciting adrenal cortical secretion.
Involution appeared to be the result of both the death of small lymphocytes and reduced lymphopoiesis in the thymus. Within 48 hours, macrophages had cleared away the cellular debris and medullary epithelial cells showed signs of hypertrophy and increased putative secretory activity. Subsequently, large lymphocytes proliferated at an accelerated rate in the subcapsular cortex, the cortex grew in width by the accumulation of small lymphocytes, and regeneration ceased when the thymus had reached its former size.
These observations provide circumstantial evidence for the hypothesis that in regeneration, medullary epithelial cells increase their production of a lymphopoietic hormone which stimulates mitotic proliferaton of cortical lymphocytes.