MOLECULAR MECHANISMS INVOLVED IN THE IN VITRO MODULATION OF HUMORAL IMMUNE RESPONSES BY ESTROGEN AND PROGESTERONE.

We recently demonstrated that estrogen (E2) and progesterone (Pg) modulated the asymmetric antibody synthesis by a murine hybridoma, in a dose-dependent manner. Since IL-6 and a progesterone induced blocking factor (PIBF) were previously described to stimulate the asymmetric antibody synthesis by murine hybridomas, here we analyzed whether E2 and Pg were able to modulate IL-6 receptor (IL-6R) signal transduction pathways and also, whether hybridoma cells synthesized PIBF in response to Pg. Three independent experiments were performed in which hybridoma B cells were cultured with different concentrations of E2 and Pg during 48 h and then PIBF was assessed in whole cell extracts by western blot. To investigate IL-6R signal transduction, the hybridoma was cultured in the same conditions, with or without 10 ng/mL IL-6. After 48 h, culture supernatants were discarded and fresh medium plus 20 ng/mL IL-6 was added to cells for 30 minutes. Finally, the cells were harvested and JAK-1 and gp130 molecules were assessed in the whole extracts by western blot. Maximal PIBF expression was observed when the hybridoma was cultured with 10-10 M Pg, compared to the control (p<0.05). Analysis of IL-6R signal transduction pathway showed that while IL-6 treatment induced an increase of gp130 as well as JAK-1 expression by the cells, 10-6 M E2 and Pg diminished gp130 expression (p<0.05) whereas JAK-1 was not significantly affected. This data shows two molecular mechanisms, IL-6R signal transduction modulation and PIBF induction, that might be involved in the E2 and Pg effect on asymmetric antibody synthesis. [ABSTRACT FROM AUTHOR]