In murine cardiac allografts, targeting BTLA accelerated rejection of partially MHC-mismatched grafts, whereas targeting PD-1 accelerated rejection of fully MHC-mismatched grafts.
Does targeting BTLA or PD-1 alter the survival of partially versus fully MHC-mismatched cardiac allografts in murine models?
BTLA and PD-1 exert distinct inhibitory actions in vivo, with the BTLA pathway dominating in regulating responses against restricted allogeneic mismatch in cardiac allografts.
Although fully MHC-mismatched murine cardiac allografts are rapidly rejected, allografts mismatched at only MHC class I or class II alleles survive long term; the immunologic basis for the long-term survival of MHC class I- or II-mismatched allografts is unknown. We examined the roles of two recently described inhibitory receptors, B and T lymphocyte attenuator (BTLA) and programmed death-1 (PD-1), in the survival of partially or fully MHC-mismatched allografts using gene-deficient recipients as well as through use of blocking mAbs in wild-type hosts. Partially MHC-mismatched allografts showed strong induction of BTLA, but not PD-1 mRNA and survived long term in wild-type recipients, whereas targeting of BTLA or its ligand, herpesvirus entry mediator, but not PD-1, prompted their rapid rejection. By contrast, fully MHC-mismatched cardiac allografts were acutely rejected in wild-type recipients despite the induction of both BTLA and PD-1. Targeting of PD-1 in several fully MHC-mismatched models accelerated rejection, whereas targeting of BTLA unexpectedly enhanced PD-1 induction by alloreactive CD4 and CD8 T cells and prolonged allograft survival. In vitro studies using allogeneic dendritic cells and T cells showed that at low levels of T cell activation, BTLA expression was primarily induced, but that with increasing degrees of T cell activation, the expression of PD-1 was strongly up-regulated. These data suggest that BTLA and PD-1 exert distinct inhibitory actions in vivo, with the BTLA/herpesvirus entry mediator pathway appearing to dominate in regulating responses against a restricted degree of allogeneic mismatch.
Tao et al. (Tue,) conducted a other in Cardiac allograft rejection. Targeting of BTLA or PD-1 (via gene deficiency or blocking mAbs) vs. Wild-type/untreated controls was evaluated on Allograft survival and rejection. In murine cardiac allografts, targeting BTLA accelerated rejection of partially MHC-mismatched grafts, whereas targeting PD-1 accelerated rejection of fully MHC-mismatched grafts.