The adaptation model of immunity: allograft rejection versus allograft adaptation

Abstract

Abstract Rejection of allografts and acceptance of grafts between identical twins appear to be associated with allogeneity or nonself entity of allografts as suggested by the self-nonself (SNS) model of immunity. Nevertheless, such guilt by association does not necessarily follow a cause-effect direction. The adaptation model proposes that graft rejection or tolerance is determined by the expression of the tissue-specific adaptation receptors (AdRs) which are linked to anti-apoptotic pathways for tolerating the recipient’s alloreactive immune response induced by surgical procedure during organ transplantation. A better engraftment of less matched living-donor organs compared with matched cadaver-donor organs is because of a severely altered AdRs in the latter. To this end, tissue adaptation to an anti-graft immune response suggests that AdRs can be restored in allografts if treated properly. Re-transplantation studies demonstrated that second fresh skin allograft rejection while the first adapted allograft from the same donor remaining viable in the presence of all-reactive T cells. Also, constitutive expression of a bidirectional AdR, B7-H1 linked to Bcl-xL anti-apoptotic pathway, in the cornea and retina protects them from rejection while block-ade of B7-H1 accelerates allograft rejection. Also, severe GVHD following autologous stem cell transplantation could be due to chemotherapy-induced alterations in the AdRs in target tissues. This is supported by demonstrating that autologous T RMcells that are involved in local tissue homeostasis but not alloreactive T EMcells are involved in GVHD. Interestingly, restoration of the putative AdR, B7-H1, expression by parenchymal tissues could prevent or ameliorate GVHD in humans. This work was supported by the Office of the Assistant Secretary of Defense for Health Affairs through the Breast Cancer Research Program under Award No. W81XWH2210793. Opinions, interpretations, conclusions, and recommendations are those of the authors and are not necessarily endorsed by the U.S. Department of Defense. This work was also supported by multi-investigator pilot funding from the VCU Massey Cancer Centre, supported in part with funding from NIH/NCI Cancer Centre support grants P30 CA016059.