Results of pancreas transplantation after steroid withdrawal under tacrolimus immunosuppression

Purpose. The results of steroid withdrawal in pancreas transplant recipients under tacrolimus immunosuppression were analyzed. Methods. From July 4, 1994 until April 30, 1998, 147 pancreas transplantations were performed in 141 patients, including 126 simultaneous pancreas-kidney transplantations, 13 pancreas after kidney transplantation, and 8 pancreas transplantations alone. Baseline immunosuppression consisted of tacrolimus and steroids without antilymphocyte induction. Twenty-three patients were excluded from analysis because of early graft loss in 17 cases, retransplantation in 5 cases, and simultaneous pancreas-kidney transplantation after heart transplantation in 1 patient. Results. With a mean follow-up of 2.8±1.1 years (range 1.0 to 4.8 years), complete steroid withdrawal was achieved in 58 (47%) patients with a mean time to steroid withdrawal of 15.2±8 months (range 4 to 40 months after transplantation). Of the entire cohort of 141 patients, overall 1-, 2-, and 4-year patient survival rates were 98%, 95.5%, and 86%, respectively. Overall 1-, 2-, and 4- year graft survival rates were 83%, 80%, and 71% (pancreas) and 95%, 91%, and 84% (kidney), respectively. Of the 124 patients analyzed for steroid withdrawal, 1-, 2-, and 4-year patient survival rates were 98%, 97%, and 92%, respectively. Overall 1-, 2-, and 4-year graft survival rates were 98%, 91.5%, 83% (pancreas) and 97%, 95%, and 91% (kidney). Patient, pancreas, and kidney survival rates at 1 year were 100%, 100%, and 98% (off steroids) versus 97%, 91%, and 96% (on steroids, all NS) and at 4 years were 100%, 94%, and 95% (off steroids) versus 78%, 68%, and 85% (on steroids, P=0.01, 0.002, and NS, respectively). The cumulative risk of rejection at the time of follow-up was 76% for patients on steroids versus 74% for patients off steroids (P=NS). Seven patients originally tapered off steroids were treated for subsequent rejection episodes, which were all steroid sensitive, and two of these seven patients are currently off steroids. Thirteen patients received antilymphocyte therapy for steroid-resistant rejection, five of whom are now off steroids. Tacrolimus trough levels were 9.3±2.4 ng/ml (off steroids) and 9.7±4.3 (on steroids, P=NS). Mean fasting glucose levels were 98±34 mg/dl (off steroids) and 110±41 mg/dl (on steroids, P=NS). Mean glycosylated hemoglobin levels were 5.2±0.9% (off steroids) and 6.2±2.1% (on steroids, P=0.02), and mean serum creatinine levels were 1.4±0.8 mg/dl (off steroids) and 1.7±1.0 mg/dl (on steroids, P=0.02). Conclusion. These data show for the first time that steroid withdrawal can be safely accomplished in pancreas transplant recipients maintained on tacrolimus-based immunosuppression. Steroid withdrawal is associated with excellent patient and graft survival with no increase in the cumulative risk of rejection

Cardiosphere-derived cells suppress allogeneic lymphocytes by production of PGE2 acting via the EP4 receptor

derived cells (CDCs) are a cardiac progenitor cell population, which have been shown to possess cardiac regenerative properties and can improve heart function in a variety of cardiac diseases. Studies in large animal models have predominantly focussed on using autologous cells for safety, however allogeneic cell banks would allow for a practical, cost-effective and efficient use in a clinical setting. The aim of this work was to determine the immunomodulatory status of these cells using CDCs and lymphocytes from 5 dogs. CDCs expressed MHC I but not MHC II molecules and in mixed lymphocyte reactions demonstrated a lack of lymphocyte proliferation in response to MHC-mismatched CDCs. Furthermore, MHC-mismatched CDCs suppressed lymphocyte proliferation and activation in response to Concanavalin A. Transwell experiments demonstrated that this was predominantly due to direct cell-cell contact in addition to soluble mediators whereby CDCs produced high levels of PGE2 under inflammatory conditions. This led to down-regulation of CD25 expression on lymphocytes via the EP4 receptor. Blocking prostaglandin synthesis restored both, proliferation and activation (measured via CD25 expression) of stimulated lymphocytes. We demonstrated for the first time in a large animal model that CDCs inhibit proliferation in allo-reactive lymphocytes and have potent immunosuppressive activity mediated via PGE2

Multiple Dendritic Cell Populations Activate CD4+ T Cells after Viral Stimulation

Dendritic cells (DC) are a heterogeneous cell population that bridge the innate and adaptive immune systems. CD8α DC play a prominent, and sometimes exclusive, role in driving amplification of CD8+ T cells during a viral infection. Whether this reliance on a single subset of DC also applies for CD4+ T cell activation is unknown. We used a direct ex vivo antigen presentation assay to probe the capacity of flow cytometrically purified DC populations to drive amplification of CD4+ and CD8+ T cells following infection with influenza virus by different routes. This study examined the contributions of non-CD8α DC populations in the amplification of CD8+ and CD4+ T cells in cutaneous and systemic influenza viral infections. We confirmed that in vivo, effective immune responses for CD8+ T cells are dominated by presentation of antigen by CD8α DC but can involve non-CD8α DC. In contrast, CD4+ T cell responses relied more heavily on the contributions of dermal DC migrating from peripheral lymphoid tissues following cutaneous infection, and CD4 DC in the spleen after systemic infection. CD4+ T cell priming by DC subsets that is dependent upon the route of administration raises the possibility that vaccination approaches could be tailored to prime helper T cell immunity

Killing of Targets by CD8+ T Cells in the Mouse Spleen Follows the Law of Mass Action

It has been difficult to correlate the quality of CD8 T cell responses with protection against viral infections. To investigate the relationship between efficacy and magnitude of T cell responses, we quantify the rate at which individual CD8 effector and memory T cells kill target cells in the mouse spleen. Using mathematical modeling, we analyze recent data on the loss of target cells pulsed with three different peptides from the mouse lymphocytic choriomeningitis virus (LCMV) in mouse spleens with varying numbers of epitope-specific CD8 T cells. We find that the killing of targets follows the law of mass-action, i.e., the death rate of individual target cells remains proportional to the frequency (or the total number) of specific CD8 T cells in the spleen despite the fact that effector cell densities and effector to target ratios vary about a 1000-fold. The killing rate of LCMV-specific CD8 T cells is largely independent of T cell specificity and differentiation stage. Our results thus allow one to calculate the critical T cell concentration at which growth of a virus with a given replication rate can be prevented from the start of infection by memory CD8 T cell response

Therapeutic approach to FSGS in children

Therapy of primary focal segmental glomerulosclerosis (FSGS) in children incorporates conservative management and immunosuppression regimens to control proteinuria and preserve kidney function. In long-term cohort studies in adults and children with primary FSGS, renal survival has been directly associated with degree of proteinuria control. This educational article reviews the current therapeutic approach toward children with primary FSGS

Mechanism of cellular rejection in transplantation

The explosion of new discoveries in the field of immunology has provided new insights into mechanisms that promote an immune response directed against a transplanted organ. Central to the allograft response are T lymphocytes. This review summarizes the current literature on allorecognition, costimulation, memory T cells, T cell migration, and their role in both acute and chronic graft destruction. An in depth understanding of the cellular mechanisms that result in both acute and chronic allograft rejection will provide new strategies and targeted therapeutics capable of inducing long-lasting, allograft-specific tolerance

A genome-wide CRISPR screen identifies a restricted set of HIV host dependency factors

Host proteins are essential for HIV entry and replication and can be important nonviral therapeutic targets. Large-scale RNA interference (RNAi)-based screens have identified nearly a thousand candidate host factors, but there is little agreement among studies and few factors have been validated. Here we demonstrate that a genome-wide CRISPR-based screen identifies host factors in a physiologically relevant cell system. We identify five factors, including the HIV co-receptors CD4 and CCR5, that are required for HIV infection yet are dispensable for cellular proliferation and viability. Tyrosylprotein sulfotransferase 2 (TPST2) and solute carrier family 35 member B2 (SLC35B2) function in a common pathway to sulfate CCR5 on extracellular tyrosine residues, facilitating CCR5 recognition by the HIV envelope. Activated leukocyte cell adhesion molecule (ALCAM) mediates cell aggregation, which is required for cell-to-cell HIV transmission. We validated these pathways in primary human CD4 + T cells through Cas9-mediated knockout and antibody blockade. Our findings indicate that HIV infection and replication rely on a limited set of host-dispensable genes and suggest that these pathways can be studied for therapeutic intervention