Cellular immune reactivity against donor-antigen correlates with the outcome after clinical islet transplantation: toward a better post-transplant monitoring

S. Lacotte¹, S. Ferrari², S. Borot¹, J. Villard², S. Demuylder-Mischler¹, P. Morel¹, G Mentha¹, T. Berney¹, C. Toso^1
1 Geneva University Hospital, Department of Surgery, Geneva, Switzerland; ² Geneva University Hospital, Divison of Transplant Immunology, Geneva, Switzerland

Improved post-transplant monitoring would improve islet transplantation outcome. The aim of the present study was to highlight the efficiency of immune assays to detect alloreactivity following islet transplantation and to demonstrate a correlation with clinical outcome. Peripheral blood mononuclear cells were isolated from 14 allogeneic islet recipients. Mixed lymphocyte culture used recipient cells (responder), and donor or third party cells (target). The level of immune reactivity was assessed as the release of IFNγ (ELISpot), cell proliferation (FACS analysis) and cytokine quantification (Luminex). Clinical outcome was assessed with the beta-score (Ryan et al, Diabetes Care2005). Clinical outcome correlated with the number of IFNγ-secreting cells following incubation with donor cells(-0.485, p=0.007, Spearman), but not with third party cells (0.6, p=0.84).Similarly, a high number of donor-specific proliferating cells was associated with a low beta-score (-0.505, p=0.006). Both IFNγ-ELISPOT and proliferation were accurate in predicting outcome (ROC curve AUC=0.77 and 0. 83respectively). The cell subset distribution was similar in IFNγ-producing cells than in the whole population of peripheral mononuclear cells. Regarding phenotype of proliferating cells , CD4-expressing Tlymphocytes (CD3⁺CD4⁺) and NKcells (CD3^-CD56⁺) were the main Ki67⁺ cells(24.6% +/- 2.7% and 17.3% +/- 2.1% respectively). The proliferation ofCD8-expressing T lymphocytes was less intense (6.8% +/- 1.2%). Patients with the worse islet function (beta-score<4) showed increased levels CD4⁺Ki67⁺cells(37.6% vs 16.6%, p=0.0001). No significant differences were observed in CD8⁺Ki67⁺ cells and CD56⁺Ki67⁺ cells (9.8% vs 5.1% and 15.6% vs17,5%, p>0.5). This study demonstrates that cellular immune reactivity against donor cells correlates with islet function . Phenotype of cell-subsets and cytokine profile may help to establish immune profile of islet-transplanted patients. These assays have the potential to be of substantial help in the management of islet graft recipients.