Since increasing evidence has indicated that adipose-derived stem cells (ASCs) can function across the species barrier, the use of xenogeneic ASCs may be a practical alternative to the autotransplantation and allotransplantation. Before animal ASCs can be used clinically, evidence needs to be provided to indicate whether they will survive in a human host. In the present study, we investigated whether rat ASCs (rASCs) could resist human xeno-antibody and complement-mediated lysis as well as investigated the possible mechanisms involved. We found that rASCs could significantly resist human natural antibody and complement-mediated cytotoxicity when incubated with 20% or 50% normal human serum (NHS) in vitro, as compared with rat lymphocytes (rLCs). Mechanistically, rASCs expressed lower level of xenoantigen Gal alpha 1-3Gal beta 1-4GlcNAc (alpha-Gal), which was correlated with decreased binding of human xenoreactive IgG and IgM and reduced deposition of complement C3c and C4c. More interestingly, rASCs had minimal deposition of human membrane attack complex (C5b-9). When the expression of CD55 and CD59 was analyzed by flow cytometry, we found that rASCs expressed very weak CD55 but expressed much higher level of CD59 than rLCs. Moreover, the knockdown of CD59 expression by siRNA largely reversed the resistance of rASCs to the human serum-mediated lysis. Taken together, these data have demonstrated for the first time that rat ASCs are capable to protect themselves from human xenoantibody and complement-mediated lysis, which is dependent on CD59 and is correlated with low expression of alpha-Gal. Xenogenic ASCs may have the potential to treat patients in the future.