The Toll-IL-1R Member Tir8 Modulates Post-Transplant Kidney Ischemia/reperfusion Injury By Inhibiting Resident F4/80+CX3CR1+ Cell Expansion.

Post-transplant (tx) ischemia/reperfusion injury (IRI) activates TLR/IL-1R on inflammatory leukocytes initiating innate immune response.In a mouse model of renal artery clamp deficiency of Tir8, aTLR/IL-1R negative regulator, aggravated post-ischemic acute renal failure and intrarenal leukocyte accumulation (Lech M, JI, 2009). We investigated the role of TIR8 in modulating post-tx IRI and inflammatory response in a mouse syngeneic kidney tx model. Donor and recipient C57BL/6 mice were congenic for CD45 to discriminate between intragraft recipient (CD45.1+) and donor (CD45.2+) leukocytes. Wild-type (wt, n=5) or Tir8-/- (Tir8-/-, n=5) donor kidneys were exposed to 30 min cold ischemia before tx. Transient impairment of graft function was found at 1day post-tx in wt (BUN: 1day 53±19, 10day 44±15, 30day 27±3mg/dl). At variance, the Tir8-/--group showed irreversible severe graft dysfunction (BUN: 1day 95±23, 10day 87±25, 30day 67±23 mg/dl, P<0.05 vs wt-group). Recipient intragraft leukocytes increased post-tx over time both in wt and in Tir8-/- groups, with no difference between the two groups (table). At variance, donor renal leukocytes significantly expanded post-tx only in the Tir8-/- group.Table: No Caption available.*p<0.05 vs naïve and 10d post-tx. **p<0.05 vs naïve and corresponding wt.By triple immunofluorescence analysis, at 10 days post-tx, only few expanding donor leukocytes were CD11c+ cells (CD45.2+/CD45.1-/CD11c+ wt: 3±1/field, Tir8-/- 7±1/field). At variance, the majority of donor expanding leukocytes were F4/80+ (CD45.2+/CD45.1-/F4/80+) cells both in wt (27±7/field) and in Tir8-/- groups (67±14/field, P<0.05 vs wt). A significant percentage of F4/80+ cells were also CX3CR1+ (50±7%) in the Tir8-/- group, at variance with wt-group (9±1%). The high percentage of F4/80+CX3CR1+ cells in ischemic Tir8-/- transplanted kidneys was associated with increased oxidative stress (N-Tyr staining semiquantitative score 0-3, Tir8-/- 1.4±0.5, vs wt 0.5±0.1, P<0.05) and tissue damage (cumulative score 0-12, Tir8-/- 3.2±1, wt 0.75±0.3, P<0.05).Thus, TIR8 modulates post-tx IRI possibly by suppressing expansion and activation of resident intragraft F4/80+CX3CR1+ cells. Limiting such expansion might be clinically relevant.