Immunologic properties of human fetal mesenchymal stem cells

Objective: Mesenchymal stem cells (MSCs) can be isolated from adult bone marrow and fetal liver. We investigated the immunologic properties of undifferentiated and differentiated human fetal MSCs. Study design: Expression of HLA class I and II was investigated by flow cytometry and Western blot on undifferentiated fetal MSC and after in vitro differentiation to adipocytes and osteocytes. Alloreactivity was studied after adding fetal MSCs to allogeneic, lymphocytes in mixed lymphocyte cultures. Results: Fetal MSCs expressed HLA class I but not HLA class II. The presence of interferon gamma (IFN-gamma) in the growth medium for 2 days initiated the intracellular synthesis of HLA class II, but 7 days of exposure was required for cell surface expression. Neither undifferentiated nor differentiated fetal MSCs induced proliferation of allogenic lymphocytes. Fetal MSCs treated with IFN-gamma suppressed alloreactive lymphocytes. Conclusion: Undifferentiated and differentiated fetal MSCs do not elicit alloreactive lymphocyte proliferation. The results suggest that fetal MSCs have potentials for allogenic transplantation. (C) 2004 Elsevier Inc. All rights reserved.