Mesenchymal stem cells (MSCs) are usually believed to be immune-privileged. However, immunogenic MSCs were also reported. We hypothesize that there are differences between MSC clones from the same individual in terms of their morphology, proliferation, differentiation and immunogenicity. Our goal is to discover immune-privileged stem cells for universal allogenic MSCs transplantation.

Serial dilutions of bone-marrow derived (BMMSCs) and adipose derived mesenchymal stem cells (ADMSCs) from same animal were carried out to isolate single-cell clones. From a single animal we obtained 3 clones from BMMSCs and 3 from ADMSCs. The proliferation rate of each clonal culture and mixed clonal culture were measured. The tri-differentiation potential of the clonal cultures was compared, as well as with the original isolates from bone marrow and fat. The immune-privileged properties were measured by flow cytometry and immuno-staining for the major histocompatibility complex (MHC) antigens. Mixed leucocyte reaction (MLR) were also performed to investigate immunogenicity.

Tri-differentiation was confirmed in all isolates. All clonal cultures revealed significant different morphology and proliferation rates, compared with each other and mixed cultures. All clonal cultures showed different surface markers, inclusive of MHC antigens. One clone from ADMSCs showed lack of MHC antigens. Our MLR and MHC staining disclosed variety of immune properties.

All clones tri-differentiated which indicated a degree of ‘stemness’. MSCs are generally believed not to express MHC II, resulting in immune-privileged. Our results confirmed our hypothesis because clonal cultures isolated from different origins of same animal show differences in morphology, proliferation rate, and surface marker presentation. Individual immune differences highlighted through single-cell clonal cultures may be crucial to find universal immune-privileged MSCs as universal allogeneic donor.