Anti-interleukin 2 receptor monoclonal antibodies spare phenotypically distinct T suppressor cells in vivo and exert synergistic biological effects.

The therapeutic efficacies of ART-18, ART-65, and OX-39, mouse antibodies of IgG1 isotype recognizing distinct epitopes of the p55 beta chain of the rat IL-2-R molecule, were probed in LEW rat recipients of (LEW X BN)F1 heterotopic cardiac allografts (acute rejection in untreated hosts occurs within 8 d). A 10-d course with ART-18 prolongs graft survival to approximately 21 d (p less than 0.001). Therapy with ART-65, but not with OX-39, was effective (graft survival approximately 16 and 8 d, respectively). Anti-IL-2-R mAb treatment selectively spared T cells with donor-specific suppressor functions; the CD8+ (OX8+ W3/25-) fraction from ART-18-modified recipients, and primarily the CD4+ (W3/25+ OX8-) subset from ART-65-treated hosts conferred unresponsiveness to naive syngeneic rats after adoptive transfer, increasing test graft survival to approximately 16 and 45 d, respectively. Concomitant administration of ART-18 and ART-65 to recipient animals in relatively low doses exerted a strikingly synergistic effect, with 30% of the transplants surviving indefinitely and 50% undergoing late rejection over 50 d. These studies provide evidence that anti-IL-2-R mAbs selectively spare phenotypically distinct T cells with suppressor functions. The data also suggest that in vivo targeting of functionally different IL-2-R epitopes may produce synergistic biological effects

Alternative Splicing of CEACAM1 by Hypoxia-Inducible Factor-1α Enhances Tolerance to Hepatic Ischemia in Mice and Humans

Although alternative splicing (AS) drives transcriptional responses and cellular adaptation to environmental stresses, its contributions in organ transplantation have not been appreciated. We have shown that carcinoembryonic antigen-related cell adhesion molecule (Ceacam1; CD66a), a transmembrane biliary glycoprotein expressed in epithelial, endothelial, and immune cells, determines donor liver transplant quality. Here, we studied how AS of Ceacam1 affects ischemia-reperfusion injury (IRI) in mouse and human livers. We found that the short cytoplasmic isoform Ceacam1-S increased during early acute and late resolution phases of warm IRI injury in mice. Transfection of Ceacam1-deficient mouse hepatocytes with adenoviral Ceacam1-S mitigated hypoxia-induced loss of cellular adhesion by repressing the Ask1/p-p38 cell death pathway. Nucleic acid-blocking morpholinos, designed to selectively induce Ceacam1-S, protected hepatocyte cultures against temperature-induced stress in vitro. Luciferase and chromatin immunoprecipitation assays identified direct binding of hypoxia-inducible factor-1α (Hif-1α) to the mouse polypyrimidine tract binding protein 1 (Ptbp1) promoter region. Dimethyloxalylglycine protected mouse livers from warm IR stress and hepatocellular damage by inhibiting prolyl hydroxylase domain-containing protein 1 and promoting AS of Ceacam1-S. Last, analysis of 46 human donor liver grafts revealed that CEACAM1-S positively correlated with pretransplant HIF1A expression. This also correlated with better transplant outcomes, including reduced TIMP1, total bilirubin, proinflammatory MCP1, CXCL10 cytokines, immune activation markers IL17A, and incidence of delayed complications from biliary anastomosis. This translational study identified mouse Hif-1α-controlled AS of Ceacam1, through transcriptional regulation of Ptbp1 promoter region, as a functional underpinning of hepatoprotection against IR stress and tissue damage in liver transplantation