ISOLATION OF SKIN T LYMPHOCYTES FROM HAND TRANSPLANT, AND EVALUATION OF THEIR ALLO-RESPONSE AGAINST DONOR APCS:

O129 Aims: In our experience the two patients who received a bilateral hand transplantation presented a minimal number of graft rejection episodes without overimmunosuppression. This was unexpected since Langerhans cells, which are present at relatively high number in skin, should have facilitated allograft rejection episodes. Consequently, we decided to study the allo-response of T lymphocytes present in the skin of hand allografts. Thus, T cells were isolated either from the skin of the first recipient who has been transplanted since 3 years and who did not present any clinical sign of rejection, or from skin biopsies issued from the second recipient at day 30, 60, 90, 120, and 180 post-transplantation and during rejection episodes. Methods: T cell specificity toward donor APCs was evaluated at the functional level together with analysis of T cell phenotype and V-beta T cell repertoire. Histological analysis of these biopsies were performed in parallel. Results: In the skin graft of the second patient, i.e the recent graft, we observed that T cells infiltrating maculopapular lesions were mostly CD8+ and demonstrated a specific and durable cytotoxicity against donor targets up to day 180. Moreover, we observed that the degree of the cytotoxic allo-response correlated with the appearance of rejection episodes. In contrast, CD4+ T cells specifically proliferated in response to donor allo-Ag at day 26 only, while no histological and clinical signs of rejection were observed. Indeed, CD4+ T cells lost their specificity against donor APCs upon time post-transplantation and even during rejection episodes. Both CD4+ and CD8+ T cells secreted IL-2 and IFN gamma. In the first patient, i.e the old graft, skin T cells were mostly CD4+, and were non responsive toward donor APCs. More interestingly, skin T cells were able to inhibit the allo-response of recipient blood T cells against donor APCs. The V beta T cell repertoire of T cells infiltrating the skin showed a highly restricted pattern with mostly oligoclonal or clonal expansions, in both the old and the recent graft. Conclusions: Altogether, these results suggest, that the donor specific CD4+ T cells present in the recent graft might have initiated the allo-response which severity was dependent on allo-reactive CD8+ T cells. In contrast, in the old graft, our results suggest the presence of putative immunosuppressive or tolerogenic T cells.