Enhancement of in vitro hsp72 expression by placental IL-6

To give an approach in order to elucidate the mechanism by which placental IL-6 induce modifications in the glycosylation status of immunoglobulins, in the present work, we investigate a putative relationship between a stimulus by placental IL-6 and expression of cytoplasmic "hsp70 family proteins" in an in vitro model.

Supernatants of cultures of placentae obtained from primiparous and multiparous AKR/J x AKR/J and AKR/J x BALB/c mouse crossbreedings were added to mouse IgGI hybridoma cultures which produced symmetric and asymmetric anti-dinitrophenol (anti-DNP) antibodies. Analyses of the expression of inducible hsp72/constitutive hsp73 in cellular lysates obtained from hybridomas cultured, in the presence of rmIL-6 or crude murine placental culture supernatants, followed by neutralization assays with anti IL-6, were performed. In addition, the level of IL-6 present in the employed placental culture supernatants was determined and compared with the placental hsp70-inducing effect.

These experiments showed that mouse placentae were able to release IL-6 in vitro. In addition, mouse placental supernatants (PS) containing over 1,000 pg/mL of IL-6 enhanced the expression of the inducible isoform hsp72 in the employed hybridomas. This effect was abolished when the hsp70-inducing PS were previously incubated with anti-mIL6 antibody.

These observations indicate that mouse placentae produce different titers of IL-6 and suggest that IL-6 appears to be the unique mouse placental factor able to induce in vitro hsp72 synthesis. A relationship with the increased synthesis of anti-paternal antigen asymmetric antibodies, previously observed during pregnancy, is discussed.