Role of the programmed death-1 pathway in regulation of alloimmune responses in vivo

SE Sandner, MR Clarkson, AD Salama… - The Journal of …, 2005 - journals.aai.org
SE Sandner, MR Clarkson, AD Salama, A Sanchez-Fueyo, C Domenig, A Habicht…
The Journal of Immunology, 2005journals.aai.org
Abstract Programmed death-1 (PD-1), an inhibitory receptor up-regulated on activated T
cells, has been shown to play a critical immunoregulatory role in peripheral tolerance, but its
role in alloimmune responses is poorly understood. Using a novel alloreactive TCR-
transgenic model system, we examined the functions of this pathway in the regulation of
alloreactive CD4+ T cell responses in vivo. PD-L1, but not PD-1 or PD-L2, blockade
accelerated MHC class II-mismatched skin graft (bm12 (IA bm12) into B6 (IA b)) rejection in …
Abstract
Programmed death-1 (PD-1), an inhibitory receptor up-regulated on activated T cells, has been shown to play a critical immunoregulatory role in peripheral tolerance, but its role in alloimmune responses is poorly understood. Using a novel alloreactive TCR-transgenic model system, we examined the functions of this pathway in the regulation of alloreactive CD4+ T cell responses in vivo. PD-L1, but not PD-1 or PD-L2, blockade accelerated MHC class II-mismatched skin graft (bm12 (IA bm12) into B6 (IA b)) rejection in a similar manner to CTLA-4 blockade. In an adoptive transfer model system using the recently described anti-bm12 (ABM) TCR-transgenic mice directly reactive to IA bm12, PD-1 and PD-L1 blockade enhanced T cell proliferation early in the immune response. In contrast, at a later time point preceding accelerated allograft rejection, only PD-L1 blockade enhanced T cell proliferation. In addition, PD-L1 blockade enhanced alloreactive Th1 cell differentiation. Apoptosis of alloantigen-specific T cells was inhibited significantly by PD-L1 but not PD-1 blockade, indicating that PD-1 may not be the receptor for the apoptotic effect of the PD-L1-signaling pathway. Interestingly, the effect of PD-L1 blockade was dependent on the presence of CD4+ CD25+ regulatory T cells in vivo. These data demonstrate a critical role for the PD-1 pathway, particularly PD-1/PD-L1 interactions, in the regulation of alloimmune responses in vivo.
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