Immunological effects of in vitro hyperthermia.

The effect of in vitro hyperthermia treatment on the immunological function of human peripheral blood mononuclear cells (PBMC) was investigated to evaluate the immunosuppressive effect of hyperthermia, which has been successfully used for the treatment of cancer. The viability was slightly reduced after the treatment in a temperature dependent manner, however, it was statistically insignificant. Both natural killer (NK) activity and phytohaemagglutinin (PHA)-induced blastogenesis were temperature-dependently reduced after the treatment. After the treatment at 44 degrees C, NK activity was only 4.3% and no PHA-induced blastogenesis was observed. The reduced NK activity after the treatment may be in part due to a decreased number of subpopulations of highly active NK cells. Leu 7-1, 11+ cells and Leu 7+, 11+ cells. Therefore, the possibility of hyperthermia-induced inhibition of the host immune system must be considered when we use hyperthermia clinically for cancer treatment.