In vitro modulation of protective antibody responses by estrogen, progesterone and interleukin-6.

PROBLEM: We have previously demonstrated that the addition of placental interleukin-6 (IL-6) to murine hybridomas increased asymmetric antibody synthesis. Here we analyze whether progesterone (Pg) and estrogen (E2) affect asymmetric antibody synthesis by modulating IL-6 production in hybridoma cells.

METHOD OF STUDY: Hybridoma 112D5 B cells were cultured with E2, Pg or recombinant IL-6. Cell proliferation was assessed by 3H-thymidine incorporation, and asymmetric antibodies were measured in culture supernatants by Con A fixation and enzyme-linked immunusorbant assay (ELISA). E2 and Pg-receptors (ER and PR) were evaluated in whole cell extracts by Western blot. IL-6 was measured in culture supernatants by ELISA.

RESULTS

112D5 expressed both PR and ER, which were differentially regulated. At 48 hr, Pg and E2 slightly decreased cell proliferation whereas IL-6 did not. As well as IL-6, 10(-10) M Pg but not E2 induced asymmetric antibody production. Interestingly, Pg at 10(-6) M decreased asymmetric antibody synthesis by hybridoma cells. Finally, mainly Pg but also E2 increased IL-6 synthesis, although IL-6 levels did not correlate with asymmetric antibodies synthesized in the presence of E2 or Pg.

CONCLUSIONS

In cells expressing both ER and PR, we could demonstrate that steroids participate in humoral immune responses by modulating asymmetric antibody synthesis. IL-6 proved to be only partially involved. Other possible mechanisms involved in the effect of Pg on blocking antibody responses and their contribution to a successful pregnancy are discussed in the paper.