Search

Proinflammatory, cytotoxic CD4+CD28nullT cells can be substantially expanded in patients with end‐stage renal disease. These cells have been associated with the risk for rejection, but their alloreactive potential is unknown. CD4+CD28nullT cells were stimulated with HLA‐mismatched antigen presenting cells in the absence/presence of exogenous cytokines. Alloreactive potential was evaluated based on proliferation, degranulation, cytotoxicity, and cytokine production. Further, their suppressive capacity was assessed by measuring inhibition of proliferating alloreactive CD28+T cells. CD4+CD28nullT cells contained alloreactive (CD137+) T cells but did not proliferate in response to allogeneic stimulation, unless interleukin (IL)‐15 was added. However, they could proliferate on stimulation with cytomegalovirusantigen without exogenous cytokines. IL‐15 increased the frequency of proliferating alloreactive CD4+CD28nullT cells to 30.5% without inducing CD28 expression (P< .05). After allogeneic stimulation together with IL‐15 and IL‐21, frequency of degranulating CD107a+CD4+CD28nullT cells increased significantly from 0.6% to 5.8% (P< .001). Granzyme B and perforin positivity remained similar, but production of interferon‐γ and tumor necrosis factor‐α increased by the combination of IL‐15 and IL‐21 (P< .001 and P< .05, respectively). Finally, CD4+CD28nullT cells did not show significant suppression. Thus, CD4+CD28nullT cells represent a population with absent alloreactivity unless IL‐15 is present. CD4+CD28null T cells can become alloreactive when the proper conditions are met, especially in the presence of IL‐15, and IL‐21 can enhance the cytotoxic potential of CD4+CD28null T cells.

Proinflammatory, cytotoxic CD4+CD28nullT cells can be substantially expanded in patients with end-stage renal disease. These cells have been associated with the risk for rejection, but their alloreactive potential is unknown. CD4+CD28nullT cells were stimulated with HLA-mismatched antigen presenting cells in the absence/presence of exogenous cytokines. Alloreactive potential was evaluated based on proliferation, degranulation, cytotoxicity, and cytokine production. Further, their suppressive capacity was assessed by measuring inhibition of proliferating alloreactive CD28+T cells. CD4+CD28nullT cells contained alloreactive (CD137+) T cells but did not proliferate in response to allogeneic stimulation, unless interleukin (IL)-15 was added. However, they could proliferate on stimulation with cytomegalovirus antigen without exogenous cytokines. IL-15 increased the frequency of proliferating alloreactive CD4+CD28nullT cells to 30.5% without inducing CD28 expression (P< .05). After allogeneic stimulation together with IL-15 and IL-21, frequency of degranulating CD107a+CD4+CD28nullT cells increased significantly from 0.6% to 5.8% (P< .001). Granzyme B and perforin positivity remained similar, but production of interferon-γ and tumor necrosis factor-α increased by the combination of IL-15 and IL-21 (P< .001 and P< .05, respectively). Finally, CD4+CD28nullT cells did not show significant suppression. Thus, CD4+CD28nullT cells represent a population with absent alloreactivity unless IL-15 is present.

Acute rejection is one of the major immunological determinants of kidney graft function and survival. Early biomarkers to predict rejection are lacking. Emerging evidence reveals a crucial role for the monocyte/macrophage lineage cells in the pathogenesis of rejection. We hypothesized that higher pretransplant numbers of proinflammatory CD16+ monocytes can predict rejection. The study cohort consisted of 104 kidney transplant recipients (58 with no rejection and 46 with biopsy‐proven rejection) and 33 healthy persons. Posttransplant median follow‐up time was 14.7 mo (interquartile range 0.3–34 mo). Pretransplantation blood samples were analyzed by flow cytometry for monocyte immunophenotypes. Groups were compared by Cox regression models for the occurrence of acute rejection. We documented a significantly increased absolute number of pretransplant CD16+ monocytes in patients who developed biopsy‐proven rejection after transplantation compared with those with no rejection (hazard ratio [HR] 1.60, 95% CI1.28–2.00, p < 0.001) and healthy persons (HR1.47, 95% CI1.18–1.82, p < 0.001). In parallel, significantly fewer absolute numbers of CD16− monocytes were observed at pretransplant time points in rejectors versus nonrejectors (HR0.74, 95% CI0.58–0.94, p < 0,014). A higher pretransplant number of CD16+ monocytes is significantly associated with a higher risk of acute rejection after kidney transplantation. Pretransplant numbers of CD16+monocytes can serve as a novel biomarker to predict acute rejection after kidney transplantation.

Acute rejection is one of the major immunological determinants of kidney graft function and survival. Early biomarkers to predict rejection are lacking. Emerging evidence reveals a crucial role for the monocyte/macrophage lineage cells in the pathogenesis of rejection. We hypothesized that higher pretransplant numbers of proinflammatory CD16+ monocytes can predict rejection. The study cohort consisted of 104 kidney transplant recipients (58 with no rejection and 46 with biopsy-proven rejection) and 33 healthy persons. Posttransplant median follow-up time was 14.7 mo (interquartile range 0.3–34 mo). Pretransplantation blood samples were analyzed by flow cytometry for monocyte immunophenotypes. Groups were compared by Cox regression models for the occurrence of acute rejection. We documented a significantly increased absolute number of pretransplant CD16+ monocytes in patients who developed biopsy-proven rejection after transplantation compared with those with no rejection (hazard ratio [HR] 1.60, 95% CI 1.28–2.00, p < 0.001) and healthy persons (HR 1.47, 95% CI 1.18–1.82, p < 0.001). In parallel, significantly fewer absolute numbers of CD16− monocytes were observed at pretransplant time points in rejectors versus nonrejectors (HR 0.74, 95% CI 0.58–0.94, p < 0,014). A higher pretransplant number of CD16+ monocytes is significantly associated with a higher risk of acute rejection after kidney transplantation.

The Jak inhibitor CP-690,550 inhibits alloreactivity and is currently being investigated for prevention of allograft rejection after transplantation. In this study, we examined the effect of CP-690,550 on IL-2-mediated JakSTAT5 phosphorylation by CD4CD25brightFoxP3CD127?lowT cells (Treg) and CD4CD25negeffector T cells (Teff) in kidney transplant (KTx) patients. Phosphospecific flow cytometry was used to study the effect of CP-690,550 on IL-2-induced intracellular STAT5-phosphorylation. IL-2-induced phosphorylation of STAT5 (P-STAT5) in both Treg and Teff, which was significantly higher for CD4CD25brightTreg (increased by 71, mean) than for CD4CD25negTeff (increased by 42). In the presence of 100 ngmL CP-690,550, a clinically relevant exposure, IL-2-induced P-STAT5 was partially inhibited in CD4CD25brightTreg ( inhibition; 51), while almost completely blocked in Teff (inhibition; 84, p 0.03). The IC50was 2-3 times higher for Treg (104 ngmL) than for Teff (40 ngmL, p 0.02). In the presence of CP-690,550, Treg exhibited additional suppressive activities on the alloactivated proliferation of Teff (56, mean). In addition, CD4CD25brightTreg from KTx-patients receiving CP-690,550 vigorously suppressed the proliferation of Teff (87, mean). Our findings show that CP-690,550 effectively inhibits Teff function but preserves the suppressive activity of CD4CD25brightregulatory T cells.

The Jak inhibitor CP-690,550 inhibits alloreactivity and is currently being investigated for prevention of allograft rejection after transplantation. In this study, we examined the effect of CP-690,550 on IL-2-mediated Jak/STAT5 phosphorylation by CD4+CD25brightFoxP3+CD127−/lowT cells (Treg) and CD4+CD25negeffector T cells (Teff) in kidney transplant (KTx) patients. Phosphospecific flow cytometry was used to study the effect of CP-690,550 on IL-2-induced intracellular STAT5-phosphorylation. IL-2-induced phosphorylation of STAT5 (P-STAT5) in both Treg and Teff, which was significantly higher for CD4+CD25brightTreg (increased by 71%, mean) than for CD4+CD25negTeff (increased by 42%). In the presence of 100 ng/mL CP-690,550, a clinically relevant exposure, IL-2-induced P-STAT5 was partially inhibited in CD4+CD25brightTreg (% inhibition; 51%), while almost completely blocked in Teff (%inhibition; 84%, p = 0.03). The IC50was 2–3 times higher for Treg (104 ng/mL) than for Teff (40 ng/mL, p = 0.02). In the presence of CP-690,550, Treg exhibited additional suppressive activities on the alloactivated proliferation of Teff (56%, mean). In addition, CD4+CD25brightTreg from KTx-patients receiving CP-690,550 vigorously suppressed the proliferation of Teff (87%, mean). Our findings show that CP-690,550 effectively inhibits Teff function but preserves the suppressive activity of CD4+CD25brightregulatory T cells.