The impact of osteogenic, chondrogenic and myocardial differentiation on immunogenicity of allogeneic mesenchymal stem cells. Changes and responses to allogeneic mesenchymal stem cells (MSCs) as they differentiate in vitro (blue shaded areas) or in vivo (green shaded areas) are represented. General immunological characteristics of MSCs are represented along with documented changes that take place as they differentiate into osteogenic, chondrogenic and cardiomyocyte lineages. Changes to relevant molecules are indicated with up arrows representing an increase, down arrows representing a decrease and an equals sign representing no change in the indicated parameter. CTL, cytotoxic T lymphocyte; DC, dendritic cell; dMSC, differentiated MSC; Ig, immunoglobulin; MHCI, major histocompatibility complex class I; MHCII, major histocompatibility complex class II; MSC, mesenchymal stem cell; NO, nitric oxide; PBL, peripheral blood leukocyte; PGE2, prostaglandin E2.