FOXP3 and systemic sclerosis: In addition to S1P being able to “disarm” Foxp3 Tregs mentioned above, S1P and LPA regulate the function, migration, and trafficking of all lymphoid cells and monocyte/macrophage/dendritic cells with S1P also being able to sequester T cells in the thymus and peripheral lymphoid organs, resulting in some instances in lymphopenia, which is frequently found in patients with SSc (225–227).