Female NSG mice were reconstituted with human Th1 cells (5 million) and human monocytes (3 million). Between day 20 and day 35 post-transplant, mice developed severe x-GVHD (A; left and middle panel). Within 24 hrs of GVHD onset, mice were treated three times with BMSC (2 million) and each injection was separated by four days. Photographs from a representative mouse from each group are shown (A; right panel). Summary of percent weight loss, from three experiments, in control and treated cohorts (B). Cumulative kaplain-meier survival curve from three experiments (C). For weight loss, P value was determined using a two-way anova test. For survival curve, P values were determined using log-rank test. Each experiment had n=5 animals per cohort, experiments were performed in triplicate with 3 different BMSC clinical products. *=P<0.05, **=P<0.01 and ***=P<0.001.