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 (E-2) affect asymmetric antibody synthesis by modulating IL-6 production in hybridoma cells. METHOD OF STUDY: Hybridoma 112D5 B cells were cultured with E-2, Pg or recombinant IL-6. Cell proliferation was assessed by 3 H-thymidine incorporation, and asymmetric antibodies were measured in culture supernatants by Con A fixation and enzyme-linked immunusorbant assay (ELISA). E-2 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: 112135 expressed both PR and ER, which were differentially regulated. At 48 hr, Pg and E-2 slightly decreased cell proliferation whereas IL-6 did not. As well as IL-6, 10(-10) m Pg but not E-2 induced asymmetric antibody production. Interestingly, Pg at 10(-6) m decreased asymmetric antibody synthesis by hybridoma cells. Finally, mainly Pg but also E-2 increased. IL-6 synthesis, although IL-6 levels did not correlate with asymmetric antibodies synthesized in the presence of E-2 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.