Aims: Mesenchymal stromal cells (MSC) derived from adult bone marrow or adipose tissue offer the potential to open a new frontier in medicine. MSC are involved in modulating immune response and tissue repair in vitro and in vivo. Experimental evidence and preliminary clinical studies have demonstrated that MSC exhibit an important immunomodulatory function in patients with graft versus host disease (GVHD) following allogeneic hematopoietic stem cell transplantation. The immunosuppressive properties of MSC have already been exploited in the clinical setting. However the precise mechanisms are being still investigated.
Methods: We examined the immunosuppressive function of MSC by coculturing them with stimulated HLA incompatible allogeneic lymphocytes in a mixed lymphocyte culture test. The metabolic and proliferative activity of lymphocytes was determined by MTT test.
Results: After stimulation with alloantigens the presence of MSC caused significant decrease of absorbance levels by 62% (P<0.01), 26% (P<0.01) and 6% (P=0.0437) in comparison to positive control depending on the MSC/lymphocyte ratio (1:5, 1:50, 1:500). The mitogenic stimulation of lymphocytes with fMLP or PHA was also significantly reduced during MSC cocultivation. The absorbance was reduced by 42% (P<0.001) and 67% (P<0.001).
Conclusions: Allogeneic bone marrow is an ideal source of MSC for clinical application. The experiments confirmed the dose-dependent inhibitory effect of MSC on lymphocyte proliferation triggered by cellular or mitogenic stimulation. The mixed lymphocyte culture test offers a simple method for characterization and verification of the immunosuppressive potential of MSC, being prepared for clinical use.
Keywords: GVHD; allogeneic; immunosuppression; mesenchymal stromal cells.