Overall, based on our study, we propose a model (Figure 5) in which pregnancy thanks to the placenta promotes the production of a dimeric form of OPG that creates a conducive environment able to mitigate, acting on the sRANKL/OPG ratio, the excessive presence of sRANKL in peripheral blood of MS mothers with effects that can extend up to CNS on maternal astrocytes and their interaction with immune cells. The gene discussed is TNFRSF11B; the disease is myeloid sarcoma.