Decreased immunosuppressive effect of cortisol on natural killer cytotoxic activity in senile dementia of the Alzheimer type.

Former studies have indicated alterations of the cytotoxic activity of natural killer (NK) cells in senile dementia of the Alzheimer type (SDAT). These changes may be related to the increased reactivity of NK cells with cytokines, even if an impairment of the immunosuppressive effect of glucocorticoids cannot be excluded. In the present study we have demonstrated a lower immunosuppressive effect of cortisol on NK cytolytic function in patients with SDAT than in healthy elders and in patients with dementia of multi-infarct origin (MID). This suppression is completely lacking when cortisol is employed at low concentrations (10(-7) M) and is significantly reduced after incubation at physiological (10(-6) M; p < 0.001) and supraphysiological concentrations (10(-5) M; p < 0.001). The addition of IL-2 (50 and 100 IU/ml/cells) significantly antagonizes the effects of cortisol in SDAT, whereas the cortisol-dependent immunosuppression is partially maintained in healthy elders and in patients with MID. Our data indicate that the defect of the immunosuppressive effect of cortisol may play a role in NK dysregulation in SDAT, contributing to the cytokine-mediated NK overactivity in this disease.