INITIAL SELECTIN BLOCKADE OF T CELL ACTIVATION AND SIGNALLING COMBINED WITH LOW-DOSE SIROLIMUS AND CYCLOSPORINE IMMUNOSUPPRESSION PREVENTS CHRONIC REJECTION OF KIDNEY ALLOGRAFTS

Abstract

P1141 Aims: We examined the efficacy of recombinant soluble P-selectin glycoprotein ligand (rPSGL-Ig) ± sirolimus (SRL) ± cyclosporine (CsA) in treating the accelerated chronic rejection (CR) of renal allografts from brain dead (BD) F344 donors transplanted into LEW recipients. Methods: rPSGL-Ig (50μg, iv) was administered to the donor 3 hrs after BD and immediately to the host after transplantation to inhibit initial cellular activity. As shown previously, this strategy inhibits T cell activation and signalling. SRL ± CsA was given to immunosuppress subsequent antigen-dependent responses. Grafts from all recipient groups (n=8-12/Gp) were examined histologically at 150 days. Activated CD4+CD25+ T lymphocytes and T cell signalling (signal 1 and 2: TCR/MHC class II and CTLA-4/B7-1/B7/2/CD28) were assessed using double immunostaining. Gene expression of IL-2, IL-10, IFN-γ, TNF-α, TGF-β, and ICAM-1 were measured with RNAse protection assay and Real Time PCR. Recipient groups included: Gp1 = isografts; Gp 2 = BD donor allografts in rats treated with CsA 1mg daily, 10days; Gp 3 = SRL 0.4mg daily 21; Gp4 = SRL (as above) + rPSGLIg (as above); Gp5 = SRL + CsA; Gp6 = SRL + CsA + rPSGL-Ig; Gp7 = SRL 0.1mg, 4-13 days + CsA + rPSGL-Ig. Results: At 150 days after transplantation, Gp1 grafts showed only minor (1/4+) signs of CR (tubular atrophy, interstitial fibrosis, and vascular obliteration). CR of Gp 2 allografts was moderate (2/4+) and extensive in Gp 3 allografts (3/4+). The addition of rPSGL-Ig protected the allografts of Gp 4 hosts substantially (1/4+). Severe tubular injury (4/4+) occurred with high dose SRL+CsA treatment (Gp 5), regardless of rPSGL-Ig (Gp 6). However, grafts of Gp 7 (low dose SRL + CsA + rPSGL-Ig) resembled isografts with inhibited gene expression (IL-2, IFN-γ, and TGF-β), sporadic CD4+CD25+ cells, and signal 1 and 2. Conclusions: Organs from recipients treated with high dose SRL ± CsA showed severe chronic changes, regardless of the effects of rPSGL-Ig on initial T cell activity. In contrast, selectin blockade acts synergistically with low dose SRL plus CsA to prevent CR of renal allografts from BD donors over the long-term.