Since pregnancy influences serum OPG and sRANKL and the disturbance of the sRANKL to OPG ratio rather than alterations in their absolute levels, has been associated with many disorders including autoimmune diseases [22,27] we considered the sRANKL/OPG ratio in pregnant and non-pregnant women with or without MS (Figure 1E) as a marker of sRANKL bioavailability. This evidence concerns the gene TNFRSF11B and autoimmune disease.