Many of the studies selected reported an inhibitory effect in the proliferation of both B (55) and T (35, 36, 69, 72) cells after treatment with hMSCs. Some of the studies selected described a decrease in the proliferation of both CD8+ (50, 72) and CD4+ (38, 39, 50, 59) T cells after treatment of GvHD with hMSCs. However, an increase in the CD4+/CD8+ T cell ratio was also commonly observed (36, 50, 53). Specifically, some studies reported that the administration of hMSCs suppressed the clonal expansion of CD4+IFN-γ+ Th1 (40, 72) and CD4+IL-17+ Th17 (40, 50, 59, 72) cells while exhibiting an opposite effect on CD4+IL-4+ Th2 (40) and CD4+CD25+Foxp3+ Treg (40, 50, 53, 55, 58, 59, 65, 72) cells. In addition, a study conducted by Weng et al. (42) demonstrated that the administration of hMSCs stimulated the generation of CD8+CD28− T cells, which may regulate the balance between Th1 and Th2 responses. Regarding the effects of hMSCs administration in the proliferation and differentiation of B cells, a study conducted by Zhang et al. (55) demonstrated that the treatment with hMSCs inhibited the proliferation of CD19+ B cells and increased the proportion of CD5+IL-10+Breg cells within the CD19+ B cell population. On the other hand, Gao et al. (65) reported an increase in the proliferation of CD27+ memory B lymphocytes after the administration of hMSCs. Effects in the proliferation of NK cells following the administration of hMSCs were also observed in some studies. For instance, a study conducted by Jitschin et al. (50) found that the proportion of activated CD56bright NK-cells was significantly lower in patients treated with hMSCs compared to untreated patients while Gao et al. (65) described a decrease in the total number of NK cells following hMSCs administration. Some studies also reported effects in the infiltration of immune cells in organs typically affected by GvHD after treatment with hMSCs. For instance, Gregoire-Gauthier et al. (38) described that the infiltration of CD4+ T helper cells was found to be decreased in the liver and increased in spleen of acute GvHD mice after hMSCs administration. On the other hand, in a study conducted by Luz-Crawford et al. (72), infiltration of CD8+ cytotoxic T cells in spleen was found to be either decreased or increased after hMSCs administration, depending on the source of hMSCs used. Furthermore, according to Girdlestone et al. (61), administration of hMSCs previously treated with rapamycin significantly inhibited the infiltration of CD45+ cells in the spleen of acute GvHD mice.