First, the effects of d7EB cells on sepsis-induced lung inflammatory injury and death induced via CLP were determined. Because the studies involved transplantation of human progenitor cells in mice, the question of xenotransplantation was considered. In mice treated with CsA, transplantation of human d7EB cells (500,000 cells in 200 L of PBS) reduced mortality after lethal CLP, from 10% in control mice receiving mitomycin-blocked mouse embryonic fibroblasts (MEFs) to approximately 40% in the transplant group ( Figure 1A ). Although the CsA-immunosuppressed septic model proved useful in establishing a therapeutic role for human cells, there remained the important bias of pharmacologic immunosuppression in the sepsis model. Based on findings that ESCs and adult bone marrow stromal cells 19 -22 might not be strongly immunogenic because they generally lack major histocompatibility complex class II antigens, 23 the effectiveness of these cells in immunocompetent septic mice without the complicating effects of previous immunosuppression was evaluated. Human d7EB cells in these mice were as protective against CLP-induced death as demonstrated in CsA-treated mice; that is, survival improved from less than 10% at 48 hours after CLP in control mice to 50% in the transplant group ( Figure 1B) . Also investigated were alterations in lung vascular permeability and edema formation at 24 hours after CLP. d7EB cell transplantation significantly reduced neutrophilic lung inflammation and lung edema and prevented lung endothelial barrier dysfunction in treated mice compared with the control group (Figure 2, A-D) . The improvement in lung injury and survival was associated with decreased production of TNF-␣ and IFN-␥ in septic lungs, whereas there was no change in IL-10 production ( Figure 2E ). Despite the absence of immunosuppression, d7EB cells were not immediately rejected, and their presence in recipient mouse lungs was verified up to 24 hours after cell transplantation. Increased numbers of cells were observed in the recipient lungs at 1 and 3 hours after transplantation, as demonstrated by human-specific laminin staining ( Figure 3A ). The number of cells in the lungs gradually decreased, but cells were still detectable during the first 24 hours ( Figure 3B) ; however, no cells were visible at 48 hours after administration (data not shown).