Pregnancy itself does not affect the integrity of the BBB [55], on the contrary, a breakdown of the barrier has been reported in MS patients [56]; so it is possible that during MS pregnancy, factors produced by a fully functional placenta such as the placental OPG may be active on tissues and cells of the pregnant mothers with effects either on immune cells of adaptive and innate immunity, cells within the CNS and/or on their reciprocal interaction. Here, TNFRSF11B is linked to myeloid sarcoma.