Mesenchymal stromal cells (MSCs) are utilized in cell-based therapies. In this study we compared bone marrow derived MSCs from a healthy 6 month old infant (iMSC) and multimorbid donors above 70 years (sMSC).Cells were characterized by morphology, FACS, and mesenchymal lineage differentiation to confirm their similarity. Their proliferative and migratory potential was compared using the MTT assays and novel living cell imaging. Immunogenicity of MSCs was assessed by flow cytometry for surface molecules, in vivo ELISPOT assays using Balb/C mice, and demonstration of donor specific antibodies.Both groups of MSCs showed typical spindle shaped morphology, plastic adherence, and the same potential to differentiate into cells of the mesenchymal lineage. Both iMSC and sMSC expressed cell typical surface markers, such as CD90, CD105, as well as CD44 and were negative for CD45, CD34, CD31 and CD117. Differences were noted in the biology of cells: iMSCs showed higher proliferation (p<0.001) and migration (p<0.001) rates compared to sMSC. No significant differences were observed between iMSCs and sMSCs for HLA class I-, β2 microglobulin-, HLA class II-, and costimulatory molecule expression. Immunological relevant molecules as well as immunomodulatory molecules were increased in the presence of IFNγ. Both iMSCs as well as sMSCs provoked similar low T H 1 and T H 2 responses in unidirectional ELISPOT assays in vivo (spot frequencies IFNγ:106±49 vs. 80±73 and for IL-4: 108±70 vs. 105±107, respectively). Also no differences between groups were observed for IgM donorspecific antibodies (iMSC: 145.8±31.1 vs sMSC: 113.2±27.6; p= ns).Our results suggest that donor age does not seem to influence the immunogenicity and immunomodulatory properties of bone marrow derived MSCs. Their clinical use, however, might be limited by their significant lower proliferation capacity compared to younger cell sources.