Extracellular adenosine triphosphate (ATP) binds to purinergic receptors and, as a danger molecule, promotes inflammatory responses. Here we tested whether periodate-oxidized ATP (oATP), a P2X7 receptor (P2X7R) antagonist can attenuate renal ischemia-reperfusion injury and clarify the related cellular mechanisms. Treatment with oATP prior to ischemia-reperfusion injury decreased blood urea nitrogen, serum creatinine, the tubular injury score, and tubular epithelial cell apoptosis after injury. The infiltration of dendritic cells, neutrophils, macrophages, CD69CD4, and CD44CD4 T cells was attenuated, but renal Foxp3CD4 Treg infiltration was increased by oATP. The levels of IL-6 and CCL2 were reduced in the oATP group. Additionally, oATP treatment following injury improved renal function, decreased the infiltration of innate and adaptive effector cells, and increased the renal infiltration of Foxp3CD4 Tregs. Post-ischemia-reperfusion injury oATP treatment increased tubular cell proliferation and reduced renal fibrosis. oATP treatment attenuated renal functional deterioration after ischemia-reperfusion injury in RAG-1 knockout mice; however, Treg depletion using PC61 abrogated the beneficial effects of oATP in wild-type mice. Furthermore, oATP treatment after transfer of Tregs from wild-type mice improved the beneficial effects of Tregs on ischemia-reperfusion injury, but treatment after transfer of Tregs from P2X7R knockout mice did not. Renal ischemia-reperfusion injury was also attenuated in P2X7R knockout mice. Experiments using bone marrow chimeras established that P2X7R expression on hematopoietic cells rather than non-hematopoietic cells, such as tubular epithelial cells, plays a major role in ischemia-reperfusion injury. Thus, oATP attenuated acute renal damage and facilitated renal recovery in ischemia-reperfusion injury by expansion of Tregs.
Therefore, overexpression of human CD200 in donor pigs could constitute a promising strategy for overcoming xenograft rejection.
BackgroundGranulocyte colony-stimulating factor (G-CSF) can induce regulatory T cells (Tregs) as well as myeloid-derived suppressor cells (MDSCs). Despite the immune modulatory effects of G-CSF, results of G-CSF treatment in systemic lupus erythematosus are still controversial. We therefore investigated whether G-CSF can ameliorate lupus nephritis and studied the underlying mechanisms.MethodsNZB/W F1 female mice were treated with G-CSF or phosphate-buffered saline for 5 consecutive days every week from 24 weeks of age, and were analyzed at 36 weeks of age.ResultsG-CSF treatment decreased proteinuria and serum anti-dsDNA, increased serum complement component 3 (C3), and attenuated renal tissue injury including deposition of IgG and C3. G-CSF treatment also decreased serum levels of BUN and creatinine, and ultimately decreased mortality of NZB/W F1 mice. G-CSF treatment induced expansion of CD4+CD25+Foxp3+ Tregs, with decreased renal infiltration of T cells, B cells, inflammatory granulocytes and monocytes in both kidneys and spleen. G-CSF treatment also decreased expression levels of MCP-1, IL-6, IL-2, and IL-10 in renal tissues as well as serum levels of MCP-1, IL-6, TNF-α, IL-10, and IL-17. When Tregs were depleted by PC61 treatment, G-CSF-mediated protective effects on lupus nephritis were abrogated.ConclusionsG-CSF treatment ameliorated lupus nephritis through the preferential expansion of CD4+CD25+Foxp3+ Tregs. Therefore, G-CSF has a therapeutic potential for lupus nephritis.Electronic supplementary materialThe online version of this article (doi:10.1186/s12882-016-0380-x) contains supplementary material, which is available to authorized users.
Human B-1 cells have been proposed to be CD20+CD27+CD43+CD1c− B cells found in the umbilical cord and adult peripheral blood, but their regulatory mechanisms have not been well elucidated. Previously, we reported that mouse CD49dhigh CD4+ T cells could enhance the secretion of natural antibodies by B-1 cells. In this study, we aimed to investigate the presence and helper functions of the human equivalents of murine CD49dhigh CD4+ T cells. Here, we showed that human CD49dhigh CD4+ T cells found in the peritoneal cavity (PEC), spleen, and peripheral blood can enhance the production of IgM antibodies by B-1 cells. As revealed in mouse, CD49dhigh CD4+ T cells were more abundant in the PEC and showed a higher tendency to form conjugates with B cells than CD49dlow CD4+ T cells. Moreover, CD49dhigh CD4+ T cells showed a Th1-like memory phenotype, characterized by high expression of CD44 and CXCR3; low expression of CD62L and CCR7; rapid production of IFN-γ, tumor necrosis factor-α, and IL-2 upon stimulation with phorbol myristate acetate and ionomycin; and rapid proliferation upon stimulation with anti-CD3 and anti-CD28 antibodies. These cells also expressed high levels of PD-1, ICOS, and CD5, suggesting that they are undergoing chronic stimulation. Remarkably, CD49dhigh CD4+ T cells specifically helped B-1 cells, but not follicular memory B cells (CD27+ CD43−CD1c−) or marginal zone B cells (CD27+CD43−CD1c+), produce IgM and IgG antibodies. In parallel, the titer of human anti-blood group A IgM was positively correlated with the frequency of CD49dhigh CD4+ T cells. In conclusion, we identified human CD49dhigh CD4+ T cells with a Th1-like memory phenotype that secrete Th1 proinflammatory cytokines and help B-1 cells secrete antibodies, thereby aiding in primary defense. We suggest that these CD49dhigh CD4+ T cells are a unique type of B-cell helper T cells distinct from follicular helper T cells.
BackgroundAnti-carbohydrate antibody responses, including those of anti-blood group ABO antibodies, are yet to be thoroughly studied in humans. Because anti-ABO antibody-mediated rejection is a key hurdle in ABO-incompatible transplantation, it is important to understand the cellular mechanism of anti-ABO responses. We aimed to identify the main human B cell subsets that produce anti-ABO antibodies by analyzing the correlation between B cell subsets and anti-ABO antibody titers.MethodsBlood group A-binding B cells were analyzed in peritoneal fluid and peripheral blood samples from 43 patients undergoing peritoneal dialysis and 18 healthy volunteers with blood group B or O. The correlation between each blood group A-specific B cell subset and anti-A antibody titer was then analyzed using Pearson's correlation analysis.ResultsBlood group A-binding B cells were enriched in CD27+CD43+CD1c− B1, CD5+ B1, CD11b+ B1, and CD27+CD43+CD1c+ marginal zone-B1 cells in peripheral blood. Blood group A-specific B1 cells (P=0.029 and R=0.356 for IgM; P=0.049 and R=0.325 for IgG) and marginal zone-B1 cells (P=0.011 and R=0.410 for IgM) were positively correlated with anti-A antibody titer. Further analysis of peritoneal B cells confirmed B1 cell enrichment in the peritoneal cavity but showed no difference in blood group A-specific B1 cell enrichment between the peritoneal cavity and peripheral blood.ConclusionsHuman B1 cells are the key blood group A-specific B cells that have a moderate correlation with anti-A antibody titer and therefore constitute a potential therapeutic target for successful ABO-incompatible transplantation.
Background. Plasmapheresis in combination with immunoglobulin and rituximab is often used to induce accommodation in ABO-incompatible (ABOi) living-donor transplantation; however, this regimen cannot be applied to cases of ABOi deceased-donor transplantation. Here, we investigated whether an anti–complement component 5 (C5) antibody-based regimen can induce accommodation in ABOi heart transplantation. Methods. Both IgM and IgG anti-blood type A antibodies were induced in wild-type mice by sensitization using human blood type A antigen. Heterotopic ABOi heart transplantation was performed from human blood type A-transgenic C57BL/6J mice to sensitized wild-type DBA/2 mice. Results. Either anti-C5 antibody or conventional triple immunosuppressants (corticosteroid, tacrolimus, mycophenolate mofetil) alone did not induce accommodation in majority of ABOi heart allografts, whereas their combination induced accommodation in more than 70% of cases despite the presence of anti-A antibodies. The combination therapy markedly suppressed the infiltration of T cells and macrophages into ABOi allografts, despite mild deposition of IgG and C4d. T-cell activation and differentiation into Th1, Th2, and Th17 cells were suppressed along with CD49dhighCD4+ T and follicular helper T cells in the combination treatment group. CD24+ B cells, including both CD24+CD23+ marginal zone B cells and CD24+CD23− T2-marginal zone B cells, were increased in the accommodation group. Conclusions. C5 inhibitor-based immunosuppression induced accommodation in murine ABOi heart transplantation, presenting a promising strategy for ABOi deceased-donor transplantation.
Objectives: Regulatory B cells (Bregs) are a new B cell subset that suppresses immune responses. Recently, both anti-CD45RB and anti-Tim-1 treatments have been found to regulate immune responses by inducing Bregs; however, the role of Bregs in renal ischemia-reperfusion injury (IRI) has not been shown. Methods: We investigated impacts of Bregs and anti-CD45RB on IRI and its mechanisms using mouse models of bilateral renal IRI. Results: Adoptive transfer of Bregs prior to or following IRI attenuated renal IRI. Anti-CD45RB treatment with or without anti-Tim-1 prior to IRI increased the renal infiltration of CD19 + Tim-1 + Bregs and regulatory T cells. Anti-CD45RB decreased serum creatinine levels, pathologic injury score, and tubular apoptosis. Levels of IL-1β, IL-6, MCP-1, IFN-γ, and IL-17 were decreased, whereas IL-10 was increased in the CD45RB group. Following IRI, anti-CD45RB with or without anti-Tim-1 also induced Bregs, thereby improving renal function and tubular regeneration. In RAG1 knockout mice with B cell transfer, TCRα knockout mice, and wild-type mice with T cell depletion, anti-CD45RB increased Bregs and attenuated IRI. However, anti-CD45RB did not attenuate IRI in RAG1 knockout mice with T cell transfer or μMT mice and induced only mild improvement in wild-type mice with B cell depletion. Furthermore, B cells from IL-10 knockout mice did not show anti-CD45RB-mediated renal protection against IRI, in contrast to those from wild-type mice. Conclusions: Anti-CD45RB treatment attenuated acute renal injury and facilitated renal recovery after IRI through induction of IL-10 + Bregs. The present study suggests anti-CD45RB as a potential therapeutic strategy in renal IRI.
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