NIV Congres

Introduction Mesenchymal Stem Cells (MSC) are of interest as cell therapy for clinical organ transplantation and are commonly isolated from bone marrow or adipose tissue of either autologous or allogeneic origin. Allogeneic cell use seems convenient but might harbor the risk of sensitization against foreign HLA. Therefore, we evaluated whether bone marrow and or adipose tissue derived MSC are capable of induction of HLA specific lysis by CD8+ T cells.

Methods MSC were isolated from bone marrow (BM-MSC) or adipose tissue (A-MSC) of healthy individuals. HLA class I mismatched BM-MSC and A-MSC were used in parallel experiments (n=5) as stimulators and as targets for CD8+ T cells. MSC were either stimulated with 50ng/ml IFNγ or unstimulated before co-culture with IL-2 activated HLA class-I mismatched PBMC. Effector CD3+CD8+ T cells were obtained from these co-cultures via FACS sorting. Unstimulated and IFNγ-stimulated target BM-MSC and A-MSC were labeled with Europium and incubated for 4 hours with effector cells. Lysis of MSC was determined by spectrophotometric measurement of Europium release.

Results Co-culture of PBMC and BM-MSC resulted in the induction of CD8+ T cells capable of lysing this BM-MSC and not of the mismatched A-MSC, demonstrating that lysis occured in a HLA class I specific manner. The CD8+ mediated lysis was increased when stimulator MSC and/or target MSC were IFNγ-stimulated, which augmented HLA class I expression, and ranged from a mean of 10.9% (effector: target (E:T) ratio of 5:1) till 75.1% (E:T ratio 40:1) if both stimulator and target were IFNγ-stimulated. Using A-MSC in the co-culture resulted in CD8+ mediated lysis of A-MSC in an HLA class I specific manner. Yet, this effect was less prominent than for BM-MSC with a maximal lysis of 30.5% (mean, E:T ratio 40:1) using IFNγ-stimulated stimulator and target MSC.

Conclusion Both BM-MSC and A-MSC can induce HLA class I specific lysis by CD8+ T cells. These results indicate a potential risk of allogeneic MSC use of sensitization against HLA and plea in favor of autologous cell usage for clinical application.