Abstract 3516: Evaluation of whole body hyperthermia system: changes of core body temperature and their effects on immune system

We have recently introduced a whole-body hyperthermia (WBH) system (Heckel ht3000) which is a specific device for WBH consisting of four water-filtered infrared-A (wIRA) irradiators and synthetic leather tent for heat-retention. We are now studying how this system should be used in combination with cancer immune-cell therapy such as DC-based vaccination and adoptive T cell therapy. The aim of this study is to examine the effects of increase in core body temperature on the number and function of peripheral blood leukocytes. Heat treatment was applied to healthy volunteers with this system; rectal temperature which was used as a representative of core body temperature, and axillary temperature were monitored simultaneously. During the irradiation phase, the volunteers were exposed to wIRA until their rectal temperature reached at 38.5°C, and they were then wrapped in synthetic leather tent for 60 min (heat retention phase) in order to maintain rectal temperature within fever range (38.5-40.5°C). Peripheral blood was taken from the each volunteer 3 times; before irradiation, at the time when rectal temperature reached at 38.5°C, and when elevated rectal temperature returned to 38.5°C after the completion of heat retention. Blood samples were analyzed by using flow cytometry to examine the number of leukocytes, lymphocytes subsets and NK cells-killing activities. During the irradiation phase, rectal temperature of every volunteer was gradually elevated, and it reached at 38.5°C after 60-90 min irradiation. Moderate but continuous elevation of rectal temperatures was observed even after irradiation, and they were kept at 39.0-39.5°C during the heat retention phase. After the volunteers got out of the heat retention tent, rectal temperatures were gradually decreased, and 30-60 min later, it returned to below 38.5°C. Regarding the number of peripheral leukocytes, NK cells showed the most striking change. In fact, they showed rapid increase in number at the time when rectal temperature reached at 38.5°C, on the other hand, the number of NK cells sharply decreased to approximately 50-60% of the one in pre-irradiation phase when the elevated rectal temperature retuned to 38.5°C. We also examined how NK cells changed their functions and phenotypes in some volunteers, and found that killing activity significantly enhanced after heat-treatment in fever range. Regarding the number of other types of cells, monocytes and granulocytes showed gradual increase during and aft