GENOMICS AND BIOMARKERS

B. Lu¹, S. Pommey², S. Robson³, A. D'apice¹, P. Cowan⁴, K. Dwyer^1
1Immunology Research Centre, St Vincent's Hospital, Melbourne, Fitzroy/VIC/AUSTRALIA, ², St Vincent's Hospital, Fitzroy/AUSTRALIA, ³Beth Israel Deaconess Medical Centre, Harvard Medical school, 02115/MA/UNITED STATES OF AMERICA, ⁴Dept Of Immunology, St Vincent's Hospital, Fitzroy/VIC/AUSTRALIA

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Background. Adenosine signalling protects in models of warm hepatic ischemia reperfusion injury (IRI) through a targeted action on CD4⁺ T cells and/or NKT cells. In transplantation, both warm and cold ischemia contribute to IRI. Warm ischemic times are relatively short. However, cold ischemia can be prolonged and adversely affects subsequent graft function. CD39, in concert with CD73, hydrolyses extracellular nucleotides to adenosine. Our data showed that human CD39 transgenic (hCD39tg) mice have an increased capacity to produce adenosine and are deficient in CD4⁺ and NKT cells. We hypothesized the over-expression of human CD39 should protect against cold preservation/ cold IRI. Aims. To examine the impact of hCD39 transgene expression on a cold hepatic IRI model. Methods. The absolute numbers of CD4⁺ T cells and NKT cells were determined in hCD39tg C57BL/6 mice and wild type (WT) C57BL/6 litter mates using flow cytometric analysis (n=9, respectively). Cold IRI was examined using a mouse orthotopic liver transplantation model: Livers from hCD39tg mice (n=6), WT mice (n=6), and invariant NKT (iNKT) cell deficient mice (Japha281^-/- C57BL/6, n=6) were transplanted into WT recipients after 18hrs of cold storage in UW solution. Following 6 hours reperfusion, serum alanine transaminase (ALT) and interleukin-6 (IL-6) were measured and the grafts were removed for histological analysis. Results. Livers from hCD39tg mice are deficient in CD4⁺ T cells (hCD39tg spleen 13.6x10⁶ cells versus WT 20.4x10⁶, p<0.001) and NKT cells (hCD39tg spleen 0.18x10⁶ cells versus WT 0.56x10⁶, p<0.01). Following cold storage and syngeneic transplantation, hCD39tg liver grafts functioned significantly better than WT grafts (ALT 10018 ± 653U/L versus 15638 ± 1513 U/L, p<0.01), in accordance with histological findings of less extensive necrosis. Systemic IL-6 was also significantly lower in recipients of hCD39tg grafts (2396±438 pg/mL versus 4336±647 pg/mL, p<0.05). Liver grafts from iNKT cell deficient donors were as susceptible to cold storage and IRI as wild type donor grafts. Conclusions. hCD39tg expression protects against cold IRI in a model of liver transplantation. This is unlikely to be due to fewer passenger NKT cells but may be attributable to increased adenosine generation within the graft, conferring anti-inflammatory and anti-coagulant effects.

Disclosure: All authors have declared no conflicts of interest.