Ricardo Camprodon¹, Matthew Bowles², Graham Pockley¹

¹Medical School, Sheffield University, Sheffield, United Kingdom; ²Department of Surgery, Derriford Hospital, Plymouth, United Kingdom

Introduction: Ischemia/reperfusion injury (IRI) promotes acute intestinal graft rejection and effective approaches for protecting intestinal grafts are required. Ischemic pre-conditioning (IPc) ameliorates the deleterious effects of IRI and cold preservation and it might also influence graft rejection.

Aims: To determine the influence of graft IPc on alloantibody (AlloAb) levels, the deposition of immunoglobulins in graft tissue, the induction of stress protein (Hsp60, Hsp70) and ICAM-1 expression in graft tissue and serum Hsp60 and Hsp70 antibody levels.

Methodology: Lewis rats received full-length pre-conditioned or non-pre-conditioned heterotopic Brown Norway intestinal allografts. Isografts acted as controls. Blood and graft tissue were collected pre-sacrifice. Tissue Hsp60, Hsp70 and ICAM-1 expression and IgG₁, IgG₂ and IgM deposition were determined by immunohistochemistry. Area of staining (mm²) was quantified using image analysis. Serum IgG₁, IgG₂ and IgM binding to donor CD3⁺ T cells was determined by flow cytometry and the intensity of staining (FI) used as a measure of MHC class I-specific AlloAbs. Serum Hsp60 and Hsp70 antibodies were determined by ELISA.

Results: (1) Rejection induced IgG₁, IgG₂ and IgM AlloAbs, and IPc decreased circulating levels of donor-specific IgG₁ (FI: 90 vs 75) and intragraft deposition of IgG₁ (0.21 v 0.17 mm²). (2) There was a significant linear correlation between tissue and serum levels of IgG₁ AlloAbs. (3) IPc attenuated rejection-induced tissue expression of Hsp60 and Hsp70 (Hsp60: 0.65 v 0.95 mm^2, Hsp70: 0.65 v 1.15 mm²) and this expression was inversely proportional to serum IgG₁ and IgG₂ Hsp60 and Hsp70 antibody levels. (4) ICAM-1 expression was significantly lower in IPc grafts (1.05 v 2.06 mm²).

Conclusions: IPc ameliorates anti-graft humoral responses and might protect intestinal allografts. Serum AlloAb measurements could be a useful index of AlloAb-mediated rejection. The reduction in ICAM-1 expression induced by IPc might suggest an effect on the cellular response to intestinal allografts.