T and B lymphocytes have been implicated in the pathogenesis of renal ischemia reperfusion injury (IRI). The trafficking of lymphocytes into kidneys during IRI has been postulated to underlie this effect, but has not been rigorously studied. We therefore characterized the lymphocyte populations infiltrating into mouse kidneys 3 and 24 h after renal IRI. Immunohistochemistry and flow cytometry staining of kidney lymphocytes showed increased trafficking of CD3+ T cells and CD19+ B cells in both sham-operated and IRI mice 3 h after renal IRI. In the IRI mice, increased infiltration of NK1.1+ and CD4+NK1.1+ cells compared with normal and sham-operated mice was observed 3 and 24 h after renal IRI, respectively. After 24 h of renal IRI, the decreased percentages of CD3+, CD19+, and NK1.1+ populations in the IRI mice compared with control groups were observed. Increased TNF-α and IFN-γ production of kidney infiltration CD3+ T cells in IRI mice but not sham-operated mice was found. Unexpectedly, isolation and transfer of kidney-infiltrating lymphocytes 24 h after renal IRI into T cell-deficient mice reduced their functional and histological injury after renal IRI, suggesting that kidney-infiltrating lymphocytes could have a protective function. These quantitative, qualitative, and functional changes in kidney lymphocytes provide mechanistic insight into how lymphocytes modulate IRI, as well as demonstrating that abdominal surgery alone leads to lymphocyte changes in kidney.

Recent data have demonstrated a role for CD4+ cells in the pathogenesis of renal ischemia reperfusion injury (IRI). Identifying engagement of adaptive immune cells in IRI suggests that the other major cell of the adaptive immune response, B cells, may also mediate renal IRI. An established model of renal IRI was used: 30 min of renal pedicle clamping was followed by reperfusion in B cell-deficient (μMT) and wild-type mice. Renal function was significantly improved in μMT mice compared with wild-type mice at 24, 48, and 72 h postischemia. μMT mice also had significantly reduced tubular injury. Both groups of mice had similar renal phagocyte infiltration postischemia assessed by myeloperoxidase levels and similar levels of CD4+ T cell infiltration postischemia. Peritubular complement C3d staining was also similar in both groups. To identify the contribution of cellular vs soluble mechanism of action, serum transfer into μMT mice partially restored ischemic phenotype, but B cell transfers did not. These data are the first demonstration of a pathogenic role for B cells in ischemic acute renal failure, with a serum factor as a potential underlying mechanism of action.

It is well-established that significant ischemia-reperfusion injury during kidney transplantation results in increased incidence of long-term fibrosis and rejection. To test for a role of T cell infiltration and activation following ischemic injury, we induced both bilateral and unilateral renal ischemia in mice, followed by reperfusion, and then isolated mononuclear cells. Analysis of these cells by flow cytometry showed that 2 weeks after bilateral ischemia there was a significant increase of CD8 + T cells. Furthermore, both CD4 + and CD8 + T cells infiltrated the injured kidney 6 weeks after unilateral ischemia. These T cells had increased expression of CD69 + and CD44hiCD62L −, markers of activation and effector-memory, respectively. CD4 + NK1.1 + and CD19 + B cells were decreased in percentage both 6 and 11 weeks after bilateral or unilateral injury. There was a significant upregulation of IL-1β, IL-6, TNF-α, IFN-γ, MIP-2, and RANTES expression, measured by real-time PCR, 6 weeks after unilateral renal ischemia, further indicating T cell activation. Depletion of CD4 + and CD8 + T cells before ischemia caused less medullary damage and reduced kidney IFN-γ expression, whereas their depletion following ischemia increased kidney IL-1β; however, depletion of these cells had no effect on histological damage to the kidney. Our study demonstrates that moderate or severe kidney ischemia induces long-term T lymphocyte infiltration and cytokine/chemokine upregulation, leading to kidney structural changes.