The effects of in vitro hyperthermia on natural killer activity from lung, blood and spleen

The in vitro effects of hyperthermia on natural killer (NK) activity from rat lung, peripheral blood and spleen were assessed. NK activity of all three compartments was very sensitive to heat shock. Exposure at 42.5 degrees C for 30 min resulted in more than 95% inhibition of NK activity. Conjugate-formation assays revealed that the mechanisms of hyperthermic NK inactivation are associated with post-binding lytic events. However, hyperthermia treated NK cells could partially recover their cytotoxic activity. Unheated lung lymphocytes (LL) were more sensitive to hyperthermic inhibition than spleen (SL) and blood (PBL) lymphocytes but they were also able to recover to a greater extent from such inactivation. Moreover, the responsiveness of NK cells from lung, blood and spleen to interleukin-2 (IL-2) and interferon (IFN-alpha/beta) was altered differently by heat shock. Hyperthermia treatment increased the ability of NK cells from blood to respond to IL-2 or IFN-alpha/beta. Similarly hyperthermia treated NK cells from spleen were more responsive to IFN-alpha/beta. By contrast such treatment did not change significantly the responsiveness of lung NK cells to these agents. Taken together, our findings indicate that NK cells from various compartments behave differently in response to hyperthermia treatment. Moreover, it suggests that hyperthermia treatment does not irreversibly comprise the host natural killer response and may even in some cases increase NK cell responsiveness to biological response modifiers (BRM).