Certain Endocrine Influences Governing the Leukocytic Response to Fever

A study is reported of the influences exerted on the levels of the circulating eosinophils, lymphocytes and neutrophils of rats in which body temperatures have been elevated for one hour to 41.0 or to 41.5 C. by means of the Raytheon microwave diathermy apparatus. Preliminary studies were made to determine the influence exerted on these blood categories by the restrictions imposed on the animals such as confinement in cages and insertion of rectal thermistors: factors incident to the experimental procedure. Data were assembled on intact animals, trained to cage confinement and to thermistor implacement, and on such animals subjected to the elevated temperatures. Data were also assembled on adrenalectomized animals, hypophysectomized animals, hypophysectomized-adrenalectomized animals and adrenal-demedullated animals. These data warrant the following conclusions:

1. Cage restrictions and the insertion of the thermistor into the rectum resulted in a mild form of stress inducing a slight eosinopenia, a lymphopenia and a mild neutrophilia. The energy of the microwaves, applied for one hour, greatly accentuated those changes, resulting in marked eosinopenia and lymphopenia, with a greatly increased neutrophilia. When temperatures ranging from 41.0 to 41.5 C. were induced for one hour in previously trained rats, the total eosinophil tabulation decreased in four hours from a control level of 171 ± 24 cells per cu. mm. of blood to 41 ± 5 cells, a decline of 76 per cent. The total number of mononuclear leukocytes decreased from a control level of 19,940 ± 1,000 cells to 8,330 ± 810 cells immediately after heating, while the total number of neutrophilic leukocytes increased from a control level of 3,580 ± 650 cells per cu. mm. to 8,770 ± 1,920 cells at two hours after heating.

2. Adrenalectomy altered the hemograms of rats subjected to those elevated temperatures, by abolishing the eosinopenic and the lymphopenic trends but it did not alter the neutrophilia.

3. Removal of the pituitary gland from animals prior to the increases in their temperatures resulted in an average decrease in the number of eosinophils, a decrease which was not considered significant. The number of neutrophilic leukocytes remained high.

4. When animals lacking both pituitary gland amid adrenal glands were subjected to the same energy for one hour no significant alterations in the number of eosinophils, of lymphocytes or of neutrophils were recorded.

5. The adrenal medulla did not appear to play a significant role in the chain of events leading to the characteristic hemogram in animals subjected to fever. In adrenal-demedullated animals an eosinopenia, a lymphopenia and a neutrophilia occurred as in normal intact animals.

6. The conclusion seems warranted that hyperpyrexia has produced pituitary and adrenocortical stimulation.