Introduction

Mesenchymal Stem Cells (MSC) are an interesting cell therapy for clinical organ transplantation and are usually isolated from bone marrow (BM-MSC) or adipose tissue (A-MSC) 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 BM-MSC and or A-MSC are capable of induction of HLA specific lysis by CD8+ T cells.

Methods

HLA class-I mismatched BM-MSC and A-MSC from healthy individuals were used in parallel experiments (n=5) as stimulators and targets. 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. Target BM-MSC and A-MSC were labeled with Europium and incubated for 4 hours with effector cells. Lysis was determined by measurement of Europium release.

Results

Co-culture of PBMC and BM-MSC induced CD8+ T cells capable of lysing BM-MSC and not the mismatched A-MSC, showing that lysis was HLA class-I specific. The CD8+ mediated lysis 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 5:1) till 75.1% (E:T ratio 40:1) (figure 1).

Using A-MSC in the co-culture resulted in HLA class-I specific CD8+ mediated lysis of A-MSC. Yet, this effect was less prominent than for BM-MSC with a maximal mean lysis of 30.5% (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.

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