Differential effects of hyperthermia on human leukocyte production of interferon-alpha and interferon-gamma

Hyperthermia is being used clinically in the treatment of neoplasms. However, there are insufficient data regarding effects of hyperthermia on leukocyte functions potentially important in antitumor immunity. In order to provide such data, human mononuclear leukocytes were exposed to moderate (40.7 degrees C) and marked (42.7 degrees C) hyperthermia for 2 hr. Leukocyte viability, measured by dye exclusion, was not altered by such exposures. Exposure of the cells to moderate hyperthermia did not alter leukocyte production of interferon-alpha in response to influenza virus or interferon-gamma in response to the mitogen phytohemagglutinin. Exposure of the cells to marked hyperthermia significantly depressed production of interferon-alpha. In contrast, production of interferon-gamma was not altered by exposure of the leukocytes to marked hyperthermia. Many studies support a role for interferons (alpha as well as gamma) in antitumor immunity. The current and other data suggest that marked hyperthermia in cancer therapy should be applied locally whenever possible, rather than to the whole body, in order to limit adverse effects on immunity. The data suggest further that interferon-gamma may be a heat shock (stress) protein for human leukocytes.