Regarding the mechanisms proposed for the action of hMSCs, most studies demonstrated that the administration of hMSCs increased the levels of immunoregulatory cytokines such as IL-10 (82, 159) and IL-4 (82, 159) and reduced the levels of pro-inflammatory ckytokines such as IFN-γ (82), TNF-α (82, 160), IL-2 (82), IL-6 (82, 160), IL-12 (81, 82), and IL-17 (84, 162). A decrease in the proliferation of T lymphocytes (81, 82) and splenocytes (82) following the use of hMSCs was also observed. In particular, some studies reported that the treatment with hMSCs resulted in the inhibition in the clonal expansion of CD4+IL-17+ Th17 (83, 84), CD4+IFN-γ+ Th1 (83), and CD4+ICOS+CD44+ Tfh (161) cells and in the stimulation in the proliferation of CD4+CD25+FoxP3+ Treg (81, 83, 160) cells. Furthermore, effects in the proliferation and differentiation of B cells were also observed. For instance, Park et al. (83) reported the occurrence of a stimulatory effect on the expansion CD1dhiCD5+and CD1dhiCD5+IL-10+Breg cells mediated by hMSCs. This study also described that the administration of hMSCs inhibited the proliferation of both B220+CD23highCD21low FOB cells and B220−CD138+IgD− plasma cells and stimulated the expansion of B220+CD23lowCD21high MZB cells. Park et al. (83) also demonstrated that mice treated with human hMSCs showed significantly decrease in the size and number of germinal centers. Additionally, a study conducted by Jang et al. (161) demonstrated that the administration of hMSCs decreased the proportions of B220+GL7+GC B cells and B220loCD138+ plasma cells, and inhibited the infiltration of these plasma cells into the kidneys. As a consequence of the suppression in both the development of Tfh cells and the subsequent activation of humoral immune components, a decrease in the levels of the autoantibodies to components of the cell nucleus that are usually associated with the development of systemic lupus erythematosus was observed by the majority of the studies selected. Finally, a study by Kimbrel et al. (81) demonstrated that hMSCs suppressed the expression of CD83 in dendritic cells and their secretion of IL-12, both of which are involved in the maturation and activation process of this cell type and are crucial to their ability to properly deliver signals to T cells.