Figure 1: Paracrine and immunomodulatory effects as possible mechanisms of action of mesenchymal stem cells (MSCs) in autism spectrum disorder (ASD) treatment. In humans, ASDs are associated with immune alterations and pro-inflammatory cytokines (i.e., IL-1β) over-production. These cytokines are able to trigger pro-inflammatory cellular events. Data from in vitro models show that MSCs are able to affect not only T cells, but also other cells of the immune system (i.e., NK cells). Immunoregulatory properties of MSCs are through secretion of large amounts of several bioactive molecules (paracrine activity), that is, PGE-2, IL-10. These molecules cause the inhibition or the unresponsiveness of T-cell mediated responses.