Ischemia reperfusion injury (IRI) is a common and important clinical problem in many different organ systems, including kidney, brain, heart, liver, lung, and intestine. IRI occurs during all deceased donor organ transplants. IRI is a highly complex cascade of events that includes interactions between vascular endothelium, interstitial compartments, circulating cells, and numerous biochemical entities. It is well established that the innate immune system, such as complement, neutrophils, cytokines, chemokines, and macrophages participate in IRI. Recent data demonstrates an important role for lymphocytes, particularly T cells but also B cells in IRI. Lymphocytes not only participate in augmenting injury responses after IRI, but could also be playing a protective role depending on the cell type and stage of injury. Furthermore, lymphocytes appear to be participating in the healing response from IRI. These new data open the possibility for lymphocyte targeted therapeutics to improve the short and long term outcomes from IRI.

Multipotent mesenchymal stromal cells from the bone marrow ameliorate acute kidney injury through a mechanism other than transdifferentiation into renal tissue. Stromal cells exert immunoregulatory effects on dendritic and T cells, both of which are important in the pathophysiology of immune-mediated kidney injury. We hypothesized that similar cells with immunoregulatory function exist within the adult kidney. We isolated murine kidney-derived cells with morphologic features, growth properties, and an immunophenotype characteristic of mesenchymal stromal cells. These cells lacked lineage markers and could be differentiated into mesodermal cell lineages, including osteocytes and adipocytes. Furthermore, these kidney-derived cells induced the generation of bone marrow-derived dendritic cells with significantly reduced MHC II expression, increased CD80 expression, increased IL-10 production and the inability to stimulate CD4+ T cell proliferation in allogeneic and nominal antigen-specific cultures. Experiments in mixed and transwell cultures demonstrated that the production of soluble immune modulators, such as IL-6, was responsible for these effects on dendritic cell differentiation and maturation. Contact-dependent mechanisms, however, inhibited mitogenic T cell proliferation. In summary, kidney-derived cells may suppress inflammation in the kidney in vivo; a better understanding of their biology could have therapeutic implications in a wide variety of immune-mediated kidney diseases.

Mouse antithymocyte globulin (mATG) prevents, as well as reverses, type 1 diabetes in NOD mice, through mechanisms involving modulation of the immunoregulatory activities of T lymphocytes. Dendritic cells (DC) play a pivotal role in the generation of T cell responses, including those relevant to the autoreactive T cells enabling type 1 diabetes. As Abs against DC are likely generated during production of mATG, we examined the impact of this preparation on the phenotype and function of DC to elucidate novel mechanisms underlying its beneficial activities. In vivo, mATG treatment transiently induced the trafficking of mature CD8− predominant DC into the pancreatic lymph node of NOD mice. Splenic DC from mATG-treated mice also exhibited a more mature phenotype characterized by reduced CD8 expression and increased IL-10 production. The resultant DC possessed a potent capacity to induce Th2 responses when cultured ex vivo with diabetogenic CD4+ T cells obtained from BDC2.5 TCR transgenic mice. Cotransfer of these Th2-deviated CD4+ T cells with splenic cells from newly diabetic NOD mice into NOD.RAG−/− mice significantly delayed the onset of diabetes. These studies suggest the alteration of DC profile and function by mATG may skew the Th1/Th2 balance in vivo and through such actions, represent an additional novel mechanism by which this agent provides its beneficial activities.

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