Effect of whole-body hyperthermia on delayed cutaneous hypersensitivity to oxazolone in mice

A murine model of delayed cutaneous hypersensitivity has been used to study an effect of microwave whole-body hyperthermia on the immune system. Marked suppression of immune responsiveness was observed in mice exposed to repeated sessions of hyperthermia. Cell proliferation in regional lymph nodes of mice sensitized with oxazolone was significantly impaired as measured by uptake of 125I-iododeoxyuridine (125IUdR). The proportion of theta-positive cells and the total number of lymph node lymphocytes remained unchanged. Inhibition of proliferation of lymph node lymphocytes in vivo was accompanied by a decrease in mitogen-induced stimulation of lymphocytes in vitro. In particular the phytohaemagglutinin (PHA) response of T cells was affected by hyperthermia. It is concluded that whole-body hyperthermia can be a potent immunosuppressive factor.