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pubmed:abstractText |
Rejection of solid organ allograft involves alloreactive T-cell expansion. The importance of NF-?B and NFAT in this process is underscored by the therapeutic efficacy of immunosuppressive agents, which target the two transcription factors. Since calpains, calcium-activated proteases, are involved in the activation of NF-?B and NFAT, we investigated the role of calpains in allograft rejection. In human transplant kidneys undergoing acute or chronic rejection, we show an increased expression of CAPN 1 gene encoding ?-calpain, associated with a marked expression of ?-calpain, mainly in infiltrating T cells. To address the role of calpain in rejection, we used a skin transplant model in transgenic mice expressing high levels of calpastatin, a calpain-specific inhibitor. We show that calpain inhibition extended skin allograft survival, from 11 to 20 days. This delay was associated with a limitation in allograft infiltration by T cells. In vitro, calpain inhibition by calpastatin transgene expression limited dramatically T-cell migration but, unexpectedly, increased slightly T-cell proliferation. Amplification of IL-2 signaling via the stabilization of IL-2R common ?-chain provided an explanation for the proliferation response. This is the first study establishing that calpain inhibition delays allograft rejection by slowing down T-cell migration rather than proliferation.
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