It has been suggested that maladaptation of the maternal immune response during pregnancy might be a causal factor for preeclampsia. This study was designed to examine the systemic immune status at both the innate level and the adaptive level in pregnancies complicated by preeclampsia (n=15) and normal pregnancies (n=15). Spontaneous and in vitro-induced secretion of IL-5, IL-6, IL-10, IL-12, IL-13 and TNF-alpha, in response to paternal blood cells and the vaccination antigens purified protein derivate of tuberculin (PPD) and tetanus toxoid (TT), was detected in cell culture supernatants from blood mononuclear cells by ELISA. Preeclamptic women showed reduced numbers of basophil granulocytes in the blood (p=0.004) and lower spontaneous secretion of IL-5 from blood mononuclear cells (p=0.016). In addition, paternal antigen-induced secretion of IL-10 was decreased in preeclampsia compared with normal pregnancy (p=0.012). No further differences between preeclampsia and normal pregnancy were found for any stimuli or cytokines. The present findings of reduced basophil numbers and lower spontaneous in vitro secretion of IL-5 in preeclampsia compared with normal pregnancy indicate a decrease in systemic Th2 immunity in preeclampsia. Furthermore, the decrease in paternal antigen-induced secretion of the immunosuppressive cytokine IL-10 in preeclampsia indicates a fetus-specific decrease in immunosuppression mediated by blood mononuclear cells. Whether these systemic changes are a cause or a consequence of preeclampsia remains to be elucidated.