Maternal circulating interferon-γ and interleukin-6 as biomarkers of Th1/Th2 immune status throughout pregnancy

Aim: T cells may be classified as T helper type 1 (Th1) cells, which synthesize cytokines inducing cellular immunity, or T helper type 2 (Th2), which synthesize cytokines inducing humoral immunity. According to the Th1/Th2 paradigm, it has been postulated that successful pregnancy induces an immune Th2 bias, but it is not yet clear how Th1 and Th2 systems vary simultaneously throughout the pregnancy. Methods: Using maternal circulating interferon-gamma (IFN-gamma) and interleukin-6 (IL-6) as biomarkers of Th1 and Th2 cytokines, respectively, we examined the variation of circulating Th1/Th2 ratio in 35 healthy pregnant women from 10 to 40 weeks of pregnancy. Results: With increasing gestational age, maternal circulating levels of IFN-gamma decrease, whereas those of IL-6 increase. The IFN-gamma/IL-6 ratio switches around the 19th week of pregnancy. Conclusions: Our results suggest that maternal systemic IFN-gamma and IL-6 concentrations may be biomarkers of Th1/Th2 immune status during pregnancy. Moreover, our findings showed that contrary to the Th1/Th2 paradigm, the Th1 bias may be prevailing at the beginning of pregnancy, balanced in the middle of pregnancy and supplanted by the Th2 bias at the end of pregnancy.