Dolca Thomas

The Abundant NK Cells in Human Secondary Lymphoid Tissues Require Activation to Express Killer Cell Ig-Like Receptors and Become Cytolytic

Natural killer cells are important cytolytic cells in innate immunity. We have characterized human NK cells of spleen, lymph nodes, and tonsils. More than 95% of peripheral blood and 85% of spleen NK cells are CD56dimCD16+ and express perforin, the natural cytotoxicity receptors (NCRs) NKp30 and NKp46, as well as in part killer cell Ig-like receptors (KIRs). In contrast, NK cells in lymph nodes have mainly a CD56brightCD16− phenotype and lack perforin. In addition, they lack KIRs and all NCR expression, except low levels of NKp46. The NK cells of tonsils also lack perforin, KIRs, NKp30, and CD16, but partially express NKp44 and NKp46. Upon IL-2 stimulation, however, lymph node and tonsilar NK cells up-regulate NCRs, express perforin, and acquire cytolytic activity for NK-sensitive target cells. In addition, they express CD16 and KIRs upon IL-2 activation, and therefore display a phenotype similar to peripheral blood NK cells. We hypothesize that IL-2 can mobilize the NK cells of secondary lymphoid tissues to mediate natural killing during immune responses. Because lymph nodes harbor 40% and peripheral blood only 2% of all lymphocytes in humans, this newly characterized perforin− NK cell compartment in lymph nodes and related tissues probably outnumbers perforin+ NK cells. These results also suggest secondary lymphoid organs as a possible site of NK cell differentiation and self-tolerance acquisition.

Switching from Calcineurin Inhibitor-based Regimens to a Belatacept-based Regimen in Renal Transplant Recipients: A Randomized Phase II Study

BACKGROUND AND OBJECTIVES Prolonged use of calcineurin inhibitors (CNIs) in kidney transplant recipients is associated with renal and nonrenal toxicity and an increase in cardiovascular risk factors. Belatacept-based regimens may provide a treatment option for patients who switch from CNI-based maintenance immunosuppression. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS This is a randomized, open-label Phase II trial in renal transplant patients with stable graft function and receiving a CNI-based regimen. Patients who were ≥6 months but ≤36 months after transplantation were randomized to either switch to belatacept or continue CNI treatment. All patients received background maintenance immunosuppression. The primary end point was the change in calculated GFR (cGFR) from baseline to month 12. RESULTS Patients were randomized either to switch to belatacept (n=84) or to remain on a CNI-based regimen (n=89). At month 12, the mean (SD) change from baseline in cGFR was higher in the belatacept group versus the CNI group. Six patients in the belatacept group had acute rejection episodes, all within the first 6 months; all resolved with no allograft loss. By month 12, one patient in the CNI group died with a functioning graft, whereas no patients in the belatacept group had graft loss. The overall safety profile was similar between groups. CONCLUSIONS The study identifies a potentially safe and feasible method for switching stable renal transplant patients from a cyclosporine- or tacrolimus-based regimen to a belatacept-based regimen, which may allow improved renal function in patients currently treated with CNIs.

An Integrated Safety Profile Analysis of Belatacept in Kidney Transplant Recipients

Background. Belatacept is associated with better renal function and an improved cardiovascular/metabolic risk profile versus cyclosporine in kidney transplant recipients. The current analysis examined pooled safety data for belatacept versus cyclosporine used in combination with basiliximab, mycophenolate mofetil, and steroids. Methods. Patients enrolled in three core studies in de novo kidney transplantation were randomized to a more intensive (MI) or less intensive (LI) regimen of belatacept or cyclosporine. The pooled analysis included 1425 patients (MI: 477; LI: 472; cyclosporine: 476). Median follow-up was approximately 2.4 years. Results. Belatacept was generally well tolerated. The frequency of deaths (MI: 7%; LI: 5%; cyclosporine: 7%) and serious infections (MI: 37%; LI: 32%; cyclosporine: 36%) were lower in the LI group versus cyclosporine. The frequency of malignancies was 10%, 6%, and 7% in the MI, LI, and cyclosporine groups, respectively. Sixteen cases of posttransplant lymphoproliferative disorder (PTLD) occurred (n=8 MI; n=6 LI; n=2 cyclosporine), including nine cases involving the central nervous system (CNS) (n=6 MI; n=3 LI). The risk of CNS PTLD was highest in Epstein-Barr virus(−) recipients; more CNS PTLD cases occurred in the MI group. One case of progressive multifocal leukoencephalopathy was reported in the MI group. Conclusions. Treatment with belatacept-based regimens was generally safe for a period of at least 2 years. There was a greater risk of PTLD—specifically CNS PTLD—in the belatacept groups versus cyclosporine, especially in Epstein-Barr virus(−) patients and with the MI dose. The number of deaths and serious infections was lower in the LI regimen versus MI and cyclosporine. The overall safety profile favored the LI over the MI regimen.

Tonsilar NK cells restrict B cell transformation by the epstein-barr virus via IFN-γ

Cells of the innate immune system act in synergy to provide a first line of defense against pathogens. Here we describe that dendritic cells (DCs), matured with viral products or mimics thereof, including Epstein-Barr virus (EBV), activated natural killer (NK) cells more efficiently than other mature DC preparations. CD56(bright)CD16(-) NK cells, which are enriched in human secondary lymphoid tissues, responded primarily to this DC activation. DCs elicited 50-fold stronger interferon-gamma (IFN-gamma) secretion from tonsilar NK cells than from peripheral blood NK cells, reaching levels that inhibited B cell transformation by EBV. In fact, 100- to 1,000-fold less tonsilar than peripheral blood NK cells were required to achieve the same protection in vitro, indicating that innate immune control of EBV by NK cells is most efficient at this primary site of EBV infection. The high IFN-gamma concentrations, produced by tonsilar NK cells, delayed latent EBV antigen expression, resulting in decreased B cell proliferation during the first week after EBV infection in vitro. These results suggest that NK cell activation by DCs can limit primary EBV infection in tonsils until adaptive immunity establishes immune control of this persistent and oncogenic human pathogen.

Systemic transforming growth factor-β1 gene therapy induces Foxp3+ regulatory cells, restores self-tolerance, and facilitates regeneration of beta cell function in overtly diabetic nonobese diabetic mice

Background. Type 1 diabetes results from auto-aggressive T–cell-mediated destruction of beta cells of the pancreas. Recent data suggest that restoration of self-tolerance may facilitate islet-cell regeneration/recovery. In view of the immunoregulatory activity of transforming growth factor (TGF)-&bgr;1, we investigated whether systemic TGF-&bgr;1 gene therapy blocks islet destructive autoimmunity and facilitates regeneration of beta-cell function in overtly diabetic nonobese diabetic (NOD) mice. Methods. We used site-directed mutagenesis to create cysteine to serine mutation at sites 224 and 226 and constructed a replication deficient adenovirus (Ad) vector encoding active form of human TGF-&bgr;1 (Ad-hTGF-&bgr;1). Overtly diabetic NOD mice received intravenous injection of Ad-hTGF-&bgr;1. Seven to 14 days after the injection, the mice received transplants with 500 syngeneic islets under the kidney capsule. Islet-graft survival and regeneration of endogenous beta-cell function were examined. Results. Syngeneic islet grafts failed by day 17 in all untreated mice, whereas Ad-hTGF-&bgr;1 therapy prolonged survival of islet grafts. Islet grafts from treated mice showed well-preserved islets with a peri-islet infiltrate primarily of CD4+ T cells and expression of CD25 and Foxp3. Systemic TGF-&bgr;1 gene therapy was associated with islet regeneration in the native pancreas. Native pancreas of treated mice revealed islets staining strongly for insulin. Similar to what was found in the syngeneic islet graft, there were well-demarcated peri-islet infiltrates that were positive for CD4, TGF-&bgr;1, and Foxp3. Conclusions. Our data demonstrate that systemic TGF-&bgr;1 gene therapy blocks islet destructive autoimmunity, facilitates islet regeneration, and cures diabetes in diabetic NOD mice.

Proapoptotic Bax is hyperexpressed in isolated human islets compared with antiapoptotic Bcl-2

Background. Apoptosis is a well-documented pathway for islet cell death. One potential mechanism is overexpression of death-promoting Bax compared with antiapoptotic Bcl-2 in islets. Methods. We isolated islets from 10 human pancreata and measured the expression of Bax mRNA and Bcl-2 mRNA by real-time quantitative polymerase chain reaction; islet and pancreas expression of Bax, Bcl-2, activated caspase-3, and cleaved poly (ADP-ribose) polymerase were also assessed by immunohistochemistry. Islet cell apoptosis was evaluated by terminal deoxynucleotide transferase-mediated dUTP nick-end labeling (TUNEL) assay and by flow cytometry. Results. The mean (±SE) level of Bax mRNA was 336±79 copies per nanogram of total RNA, and the level of Bcl-2 mRNA was 36±10 (P =0.001). A positive correlation existed between islet expression of Bax mRNA and Bcl-2 mRNA (P =0.001). The islet Bax to Bcl-2 ratio was 10.8±1.3 and 1.71±0.3 for the spleens (P =0.0001). Bax mRNA (P =0.04), but not Bcl-2 mRNA, was expressed at a higher level in islets compared with spleens. Human islets contained large numbers of cells expressing Bax protein, whereas only infrequent islet cells expressed Bcl-2 protein, activated caspase-3, and poly (ADP-ribose) polymerase. The apoptotic index was 5% by TUNEL assay, and the percentage of apoptotic islet cells was 9.7±2.5% by flow cytometry. Sections of human pancreas before islet isolation showed islet staining for Bax but not Bcl-2. Conclusions. Our finding that isolated human islets express Bax at a higher level compared with Bcl-2 suggests a molecular mechanism for islet cell death by apoptosis. We hypothesize that reducing islet expression of Bax, or regulating its activation, will help preserve islet cell mass after islet transplantation.

Enforced c-REL deficiency prolongs survival of islet allografts1.

Background. The NF-&kgr;B/Rel family of transcription factors regulates biologic processes ranging from apoptosis to inflammation and innate immunity. Whether c-Rel, a lymphoid-predominant member of the NF-&kgr;B/Rel family, is essential for transplantation immunity is not known. Methods. We explored the role of c-Rel in the anti-allograft repertory using mice with targeted disruption of the c-Rel gene (c-Rel-/-) as recipients of H-2 mismatched islet allografts. Allogeneic DBA/2 (H-2d) islets were transplanted into the renal subcapsular space of diabetic c-Rel-/- C57BL/6 (H-2b) mice or the c-Rel +/+ C57BL/6 wild-type mice. Islet graft survival, cellular traffic into the islet grafts and their phenotype, and intragraft expression of cytokines and cytotoxic attack molecules were determined at the protein (by immunohistochemistry) and mRNA (by real-time quantitative polymerase chain reaction) levels. Results. We found superior islet graft survival in the c-Rel-/- recipients compared to c-Rel+/+ C57BL/6 recipients. Splenocytes from c-Rel-/- mice proliferated poorly compared to splenocytes from the c-Rel+/+ mice on stimulation with anti-CD3 mAbs or Con A. Peri-islet infiltration composed of T lymphocytes and macrophages was found in both c-Rel+/+ recipients and c-Rel-/- recipients, but intra-islet infiltration was observed only in c-Rel+/+ recipients. Immunohistologic and molecular studies showed impaired T helper-type 1 immunity and decreased intragraft expression of cytotoxic attack molecules perforin and granzyme B in c-Rel-/- recipients as compared to wild-type recipients. Conclusions. Our results demonstrate that c-Rel is essential for robust rejection of islet allografts and support the idea that strategies that impair c-Rel function may be of value for constraining alloimmunity and facilitating survival of allogafts.

Improvement in renal function in kidney transplant recipients switched from cyclosporine or tacrolimus to belatacept: 2‐year results from the long‐term extension of a phase II study

Kidney transplant recipients who switched from a calcineurin inhibitor (CNI) to belatacept demonstrated higher calculated glomerular filtration rates (cGFRs) at 1 year in a Phase II study. This report addresses whether improvement was sustained at 2 years in the long‐term extension (LTE). Patients receiving cyclosporine or tacrolimus were randomized to switch to belatacept or continue CNI. Of 173 randomized patients, 162 completed the 12‐month main study and entered the LTE. Two patients (n = 1 each group) had graft loss between Years 1–2. At Year 2, mean cGFR was 62.0 ml/min (belatacept) vs. 55.4 ml/min (CNI). The mean change in cGFR from baseline was +8.8 ml/min (belatacept) and +0.3 ml/min (CNI). Higher cGFR was observed in patients switched from either cyclosporine (+7.8 ml/min) or tacrolimus (+8.9 ml/min). The frequency of acute rejection in the LTE cohort was comparable between the belatacept and CNI groups by Year 2. All acute rejection episodes occurred during Year 1 in the belatacept patients and during Year 2 in the CNI group. There were more non‐serious mucocutaneous fungal infections in the belatacept group. Switching to a belatacept‐based regimen from a CNI‐based regimen resulted in a continued trend toward improved renal function at 2 years after switching.

Lymphoproliferative Disorders After Adult Kidney Transplant: Epidemiology and Comparison of Registry Report With Claims-Based Diagnoses

BACKGROUND Posttransplant lymphoproliferative disorder (PTLD) is a major complication of kidney transplant. STUDY DESIGN Retrospective cohort study comparing PTLD incidence rates using US Medicare claims and Organ Procurement and Transplantation Network (OPTN) data, examining risk factors for PTLD in OPTN data, and studying recipient and graft survival after PTLD diagnosis. SETTING & PARTICIPANTS All adult first-transplant patients who underwent deceased or living donor kidney-only transplants in 2000-2006 (n = 89,485) followed up through 3 years posttransplant. PREDICTORS Recipient and donor characteristics, HLA mismatches, viral serologic test results, and initial immunosuppression. OUTCOMES OPTN-reported or Medicare claims-based PTLD diagnosis, recipient and graft survival after OPTN-reported PTLD diagnosis. MEASUREMENTS Adjusted HRs for PTLD diagnosis estimated using a Cox proportional hazards model; probability of survival free of all-cause graft failure estimated using the Kaplan-Meier method. RESULTS The incidence rate of PTLD during the first posttransplant year was 2-fold higher in Medicare claims (0.46/100 patient-years; 95% CI, 0.39-0.53) than in OPTN data (0.22/100 patient-years; 95% CI, 0.17-0.27). Factors associated with increased rates of PTLD included older age, white race (vs African American), induction with T-cell-depleting antibodies, Epstein-Barr virus seronegativity at the time of transplant, and cytomegalovirus seronegativity at the time of transplant. The adjusted risk of death with graft function was 17.5 (95% CI, 14.3-21.4) times higher after a report of PTLD, and the risk of death-censored graft failure was 5.5 (95% CI, 3.9-7.7) times higher. LIMITATIONS Shortcomings inherent in large databases, including inconsistencies in patient follow-up, reporting, and coding practices by transplant centers; insufficient registry data to analyze acute rejection episodes and antirejection treatment; no available data for potential effects of different types of PTLD treatment on patient outcomes. CONCLUSIONS Despite the limitations of data collected by registries, PTLD clearly is an important complication; both mortality and death-censored graft failure increase after PTLD.

Belatacept-versus Cyclosporine-Based Immunosuppression in Renal Transplant Recipients with Pre-existing Diabetes

BACKGROUND AND OBJECTIVES Renal transplant recipients with pre-existing diabetes (PD) have reduced graft survival and increased risk of mortality and ischemic heart disease compared with nondiabetic transplant recipients. To assess the effect of belatacept in this high-risk group, we evaluated outcomes of the subpopulation with PD from previously published BENEFIT and BENEFIT-EXT trials. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS A post hoc analysis evaluated pooled data from BENEFIT (living donors or standard criteria donors) and BENEFIT-EXT (extended criteria donors). Patients were randomized to receive cyclosporine or a more intensive (MI) or less intensive (LI) belatacept regimen. RESULTS Of 1209 intent-to-treat patients, 336 had PD. At 12 months, the belatacept LI arm demonstrated a numerically higher rate of patients surviving with a functioning graft (90.4% MI [103 of 114], 92.8% LI [90 of 97], and 80.8% cyclosporine [101 of 125]), and fewer serious adverse events than cyclosporine or MI patients. Three cases of posttransplant lymphoproliferative disorder were reported in LI patients, one involving the central nervous system. Higher rates (% [95% confidence interval]: 22.8% MI [15.1 to 30.5]; 20.6% LI [12.6 to 28.7]; 14.4% cyclosporine (8.2 to 20.6]) and grades of acute rejection were observed with belatacept. Measured GFR (ml/min per 1.73 m(2), 59.8 MI; 62.5 LI; 45.4 cyclosporine), and cardiovascular risk profile were better for belatacept versus cyclosporine. CONCLUSIONS In post hoc analysis of patients with PD, patient/graft survival and renal function at 12 months were numerically higher with belatacept versus cyclosporine, but not statistically significant. Further study is necessary to confirm the benefits belatacept may provide in these patients.