Apoptosis as an index of stress related accidental involution in the human thymus

Abstract

Stress related accidental involution of the thymus has as one of its features an increased rate of Cortisol mediated apoptosls of cortical lymphocytes. Glucocorticord injection of animals causes an elevation of apoptosis counts with a time span of approximately 3 to 72 hours. We counted apoptotic lymphocytes in semithin plastic sections from 266 human autopsy thymuses. Based on the results obtained in the animal experiments, we tested the following hypotheses: <ul><li>1)Apoptotic counts in individuals dying less than three hours after the onset of their fatal condition (sudden deaths) would be low as they would be unaffected by any elevation in their serum Cortisol level occasioned by the stress of their condition.</li><li>2)Apoptotic counts in individuals dying between three and seventy two hours after the onset of the condition causing death (delayed deaths) would reflect any elevation in their serum Cortisol level.</li></ul> The sudden death group did have very low apoptotic counts (N-208; Mean 0.24±0.03 SEM) and the majority of the delayed death group did have high counts (N-58; Mean 17.94±3.38 SEM). However, there were a significant number of cases in the latter group with low counts (N=19). The reason for this unexpected result is at present unclear. However, it is possible that in these individuals the condition causing death may have in some way interfered with the stress pathway (Stress factor → Central nervous system → Pituitary → Adrenal cortex) and that Cortisol levels were thus not elevated.