Modulation of interferon secretion by concanavalin A and interleukin-2 in first trimester placental explants in vitro

The human placenta has been demonstrated to be a site of interferon (IFN) production. We report here that early human placental explants in vitro release both type I (IFN-alpha and -beta) and type II (IFN-gamma) immunoreactive IFN. The mitogen concanavalin A (Con A) stimulated immunoreactive (ir-) IFN-gamma secretion in both a dose- and time-dependent manner, but had no significant effect on either ir-IFN-alpha or -beta release. The enhancement of ir-IFN-gamma secretion by Con A, at 2-20 micrograms/ml, was significant at 1 h and persisted until 24 h, but was not significant at 48 h. A high dose of recombinant human interleukin-2 (IL-2) stimulates the release of all three types of ir-IFNs, suggesting that interaction of IL-2 with its receptor might be one cause of the constitutive production of placental IFNs. The patterns of response to Con A and IL-2 were different from those of lymphocytes, providing indirect evidence suggesting that the source of these IFNs might not be lymphocytic. Taken together, these results indicate that first trimester human placental explants in vitro produce both type I and type II IFNs, the major IFN produced depending on the inducer. IL-2 may be one of the physiological inducers of placental IFNs.