Chemokines and Their Receptors in Islet Allograft Rejection and as Targets for Tolerance Induction

Induction of Immune Tolerance in Islet Transplantation Using Apoptotic Donor Leukocytes

Allogeneic islet transplantation has become an effective treatment option for severe Type 1 diabetes with intractable impaired awareness due to hypoglycemic events. Although current immunosuppressive protocols effectively prevent the acute rejection associated with initial T cell activation in recipients, chronic rejection has remained an obstacle for achieving long-term allogeneic islet engraftment. The development of donor-specific immune tolerance to the allograft is the ultimate goal given its potential ability to overcome chronic rejection and disregard the need for maintenance immunosuppression, which may be toxic to islet grafts. Recently, a breakthrough in tolerance induction during allogeneic islet transplantation using apoptotic donor lymphocytes (ADLs) in a non-human primate model had been reported. Several studies have suggested that the clonal depletion, anergy, and expansion of the antigen-specific regulatory immune network are the mechanisms for donor-specific tolerance with ADLs, which act synergistically to induce robust transplant tolerance. This achievement represents a huge step forward toward the clinical application of immune tolerance induction. We herein summarize the reported operational induction therapies in islet transplantation using the ADLs. Moreover, a few obstacles for the engraftment of transplanted islets, such as islet immunogenicity and instant blood-mediated response, which need to be resolved in the future, are also discussed.

Comprehensive analysis of gene expression of isolated pancreatic islets during pretransplant culture

Background:

The aim of this study was to investigate the effect of pretransplant culture on the survival of pancreatic islet grafts, and to determine the biological characteristics of isolated islets during pretransplant culture.

Methods:

The survival of islets from Wistar rats, transplanted to diabetic C57BL/B6 mice, was compared between fresh islets and cultured islets. A comprehensive gene expression analysis was employed to investigate biological processes during pretransplant culture, and in vitro validation studies were performed.

Results:

Survival of cultured xenografts was significantly prolonged as compared to that of fresh islets (fresh: 12.5 ± 1.9 days, 1-day cultured: 16.0 ± 1.3 days (p= 0.017), 3-day cultured: 17.0 ± 2.6 days (p= 0.014)). Comprehensive gene expression analysis identified significant upregulation of annotated functions associated with inflammation in cultured groups. Six proinflammatory genes, including heme oxygenase 1 (HO-1) and IL-6, were significantly upregulated during culture. Validation studies revealed significantly higher levels of IL-6 in the supernatant of cultured islets and HO-1 in the cultured islets when compared with fresh islets.

Conclusion:

Transplantation of cultured islets induced significant but minimal prolongation of graft survival in xenogeneic combinations. Comprehensive analysis of gene expression in cultured islets showed biological processes associated with proinflammation during culture.

Mitomycin C treatment improves pancreatic islet graft longevity in intraportal islet transplantation by suppressing proinflammatory response

The in vitro culture period prior to cell transplantation (i.e. pancreatic islet transplantation) enables cell modification and is thus advantageous. However, the islet preconditioning method has not been fully explored. Here we present a simple approach for islet preconditioning that uses the antibiotic mitomycin C (MMC), which has antitumor activity, to reduce islet immunogenicity and prevent proinflammatory events in an intraportal islet transplantation model. Freshly isolated mice islets were treated for 30 min with 10 μg/mL MMC or not, cultured for 20 h and transplanted into the livers of syngeneic or allogeneic diabetic mouse recipients. In the allogeneic model, MMC preconditioning significantly prolonged graft survival without requiring immunosuppressants. In vitro, MMC treatment suppressed the expression of proinflammatory cytokines in islet allografts, while immunohistochemical studies revealed the suppression of inflammatory cell infiltration into MMC-treated allografts relative to untreated allografts. Furthermore, MMC preconditioning significantly suppressed the mRNA expression of proinflammatory cytokines into the transplant site and induced the differentiation of regulatory T cells with the ability to suppress CD4⁺ T cell-mediated immune responses. In conclusion, islet preconditioning with MMC prolonged graft survival in an intraportal islet transplantation model by suppressing proinflammatory events and inducing potentially regulatory lymphocytes.

Ex vivo Pretreatment of Islets with Mitomycin C: Reduction in Immunogenic Potential of Islets by Suppressing Secretion of Multiple Chemotactic Factors

Strategies to reduce the immunogenicity of pancreatic islets and to prevent the activation of proinflammatory events are essential for successful islet engraftment. Pretransplant islet culture presents an opportunity for preconditioning to improve outcomes of islet transplantation. We previously demonstrated that ex vivo mitomycin C (MMC) pretreatment and subsequent culture significantly prolonged graft survival. Fully understanding the biological process of pretreatment could result in the development of a protocol to improve the survival of islet grafts. Microarrays were employed to conduct a comprehensive analysis of genes expressed in untreated or MMC-treated rat islets that were subsequently cultured for 3 d. A bioinformatics software was used to identify biological processes that were most affected by MMC pretreatment, and validation studies, including in vivo and in vitro assay, were performed. The gene expression analysis identified significant downregulation of annotated functions associated with cellular movement and revealed significant downregulation of multiple genes encoding proinflammatory mediators with chemotactic activity. Validation studies revealed significantly decreased levels of interleukin 6 (IL-6), monocyte chemoattractant protein 3 (MCP-3), and matrix metallopeptidase 2 (MMP2) in culture supernatants of MMC-treated islets compared with controls. Moreover, we showed the suppression of leukocyte chemotactic activity of MMC-treated islets in vitro. We also showed that MMC-treated islets secreted lower levels of chemoattractants that synergistically reduced the immunogenic potential of islets. Histological and immunohistochemical analyses of the implant site revealed that infiltration of monocytes, CD3-positive T cells, and B cells was decreased in MMC-treated islets. In conclusion, the ex vivo pretreatment of islets with MMC and subsequent culture can reduce the immunogenic potential and prolong the survival of islet grafts by inducing the suppression of multiple leukocyte chemotactic factors.

Multifunctional Pancreatic Islet Encapsulation Barriers Achieved via Multilayer PEG Hydrogels

The diverse requirements for a successful islet encapsulation barrier suggest the benefit of a barrier system that presents differing functionalities to encapsulated cells and host cells. Initially, multifunctional hydrogels were synthesized via the sequential photopolymerization of PEG hydrogel layers, each with different isolated functionalities. The ability to achieve localized biological functionalities was confirmed by immunostaining of different entrapped antibodies within each hydrogel layer. Survival of murine islets macroencapsulated within the interior gel of two-layer hydrogel constructs was then assessed. Maintenance of encapsulated islet survival and function was observed within multilayer hydrogels over 28 days in culture. Additionally, the functionalization of the islet-containing interior PEG gel layer with cell–matrix moieties, with either 100 μg/ml laminin or 5 mM of the adhesive peptide IKVAV found in laminin, resulted in increased insulin secretion from encapsulated islets similar to that in gels without an exterior hydrogel layer. Finally, through cell seeding experiments, the ability of an unmodified, exterior PEG layer to prevent interactions, and thus attachment, between nonencapsulated fibroblasts and entrapped ECM components within the interior PEG layer was demonstrated. Together the presented results support the potential of multilayer hydrogels for use as multifunctional islet encapsulation barriers that provide a localized biologically active islet microenvironment, while presenting an inert, immunoprotective exterior surface to the host environment, to minimize graft–host interactions.

The TIM Family of Cosignaling Receptors: Emerging Targets for the Regulation of Autoimmune Disease and Transplantation Tolerance

Currently, lifelong immune suppression regimens are required for solid organ and cellular transplantation and carry significant increased risk of infection, malignancy, and toxicity. For non-life-saving procedures such as islet transplantation, the risk/benefit ratio of lifelong immunosuppression versus benefit from transplantation requires even more careful balance. The search for specific agents to modulate the immune system without chronic immunosuppression is important for the broad application of islet transplantation. The T-cell immunoglobulin mucin (TIM) family is a distinct group of coreceptors that are differentially expressed on TH1 and TH2 cells, and have the potential to regulate both cytotoxic and humoral immune responses. Completed murine studies demonstrate Tim pathways may be important in the regulation of tolerance to self (auto), harmless (allergic), and transplant (allo) antigen; however, the potential impact of targeting Tim coreceptors has yet to be fully explored in transplantation tolerance induction or autoimmune disease. The current review examines the impact of Tim coreceptor targeting as an emerging therapeutic option for regulating autoimmune diseases and prevention of allograft rejection.

Pancreatic β-Cell production of CXCR3 ligands precedes diabetes onset

Type 1 diabetes mellitus (T1DM) results from immune cell-mediated reductions in function and mass of the insulin-producing β-cells within the pancreatic islets. While the initial trigger(s) that initiates the autoimmune process is unknown, there is a leukocytic infiltration that precedes islet β-cell death and dysfunction. Herein, we demonstrate that genes encoding the chemokines CXCL9, 10, and 11 are primary response genes in pancreatic β-cells and are also elevated as part of the inflammatory response in mouse, rat, and human islets. We further established that STAT1 participates in the transcriptional control of these genes in response to the pro-inflammatory cytokines IL-1β and IFN-γ. STAT1 is phosphorylated within five minutes after β-cell exposure to IFN-γ, with subsequent occupancy at proximal and distal response elements within the Cxcl9 and Cxcl11 gene promoters. This increase in STAT1 binding is coupled to the rapid appearance of chemokine transcript. Moreover, circulating levels of chemokines that activate CXCR3 are elevated in non-obese diabetic (NOD) mice, consistent with clinical findings in human diabetes. We also report herein that mice with genetic deletion of CXCR3 (receptor for ligands CXCL9, 10, and 11) exhibit a delay in diabetes development after being injected with multiple low doses of streptozotocin. Therefore, we conclude that production of CXCL9, 10, and 11 from islet β-cells controls leukocyte migration and activity into pancreatic tissue, which ultimately influences islet β-cell mass and function. © 2016 BioFactors, 42(6):703-715, 2016.

Transcriptional regulation of chemokine genes: a link to pancreatic islet inflammation?

Enhanced expression of chemotactic cytokines (aka chemokines) within pancreatic islets likely contributes to islet inflammation by regulating the recruitment and activation of various leukocyte populations, including macrophages, neutrophils, and T-lymphocytes. Because of the powerful actions of these chemokines, precise transcriptional control is required. In this review, we highlight what is known about the signals and mechanisms that govern the transcription of genes encoding specific chemokine proteins in pancreatic islet β-cells, which include contributions from the NF-κB and STAT1 pathways. We further discuss increased chemokine expression in pancreatic islets during autoimmune-mediated and obesity-related development of diabetes.

CCL20 is elevated during obesity and differentially regulated by NF-κB subunits in pancreatic β-cells

Enhanced leukocytic infiltration into pancreatic islets contributes to inflammation-based diminutions in functional β-cell mass. Insulitis (aka islet inflammation), which can be present in both T1DM and T2DM, is one factor influencing pancreatic β-cell death and dysfunction. IL-1β, an inflammatory mediator in both T1DM and T2DM, acutely (within 1h) induced expression of the CCL20 gene in rat and human islets and clonal β-cell lines. Transcriptional induction of CCL20 required the p65 subunit of NF-κB to replace the p50 subunit at two functional κB sites within the CCL20 proximal gene promoter. The NF-κB p50 subunit prevents CCL20 gene expression during unstimulated conditions and overexpression of p50 reduces CCL20, but enhances cyclooxygenase-2 (COX-2), transcript accumulation after exposure to IL-1β. We also identified differential recruitment of specific co-activator molecules to the CCL20 gene promoter, when compared with the CCL2 and COX2 genes, revealing distinct transcriptional requirements for individual NF-κB responsive genes. Moreover, IL-1β, TNF-α and IFN-γ individually increased the expression of CCR6, the receptor for CCL20, on the surface of human neutrophils. We further found that the chemokine CCL20 is elevated in serum from both genetically obese db/db mice and in C57BL6/J mice fed a high-fat diet. Taken together, these results are consistent with a possible activation of the CCL20-CCR6 axis in diseases with inflammatory components. Thus, interfering with this signaling pathway, either at the level of NF-κB-mediated chemokine production, or downstream receptor activation, could be a potential therapeutic target to offset inflammation-associated tissue dysfunction in obesity and diabetes.

LMP-420, a small molecular inhibitor of TNF-α, prolongs islet allograft survival by induction of suppressor of cytokine signaling-1: synergistic effect with cyclosporin-A

Inflammatory insults following islet transplantation (ITx) hinders engraftment and long-term function of the transplanted (Tx) islets. Using a murine model of ITx, we determined the role of LMP-420, a novel TNF-α inhibitor, both individually and in combination with the immunosuppressant cyclosporine A (CSA) in islet engraftment and survival. Diabetic C57BL/6 mice were Tx with 500 BALB/c islets under the kidney capsule. Four cohorts were used: LMP-420 only, CSA only, combination of LMP-420 and CSA (LMP+CSA), and control (n = 12 per cohort). Serial monitoring of blood glucose levels revealed that LMP+CSA (35 ± 5 days) prolonged stable blood insulin levels compared to control (6 ± 4 days). Immunohistology demonstrated that coadministration (LMP+CSA) results in a significant decrease in CD8(+) T-cell infiltration (LMP+CSA: 31 ± 18 vs. control: 224 ± 51 cells, p < 0.001). Serum cytokine analysis revealed that LMP-420 administration resulted in an increase in the anti-inflammatory cytokine IL-10 (2.5-fold), and a decrease in TNF-α (threefold) with no change in IL-2. However, coadministration resulted in a marked decrease in both IL-2 and TNF-α (threefold) along with increase in IL-10 (threefold). Coadministration also demonstrated increase of antiapoptotic SOCS-1 and Mn-SOD expression and significant reduction of donor-specific antibodies (p < 0.005). In conclusion, LMP-420 administration with CSA results in the upregulation of anti-inflammatory and antiapoptotic mechanisms which facilitate islet allograft engraftment and survival.

Evolution of β-Cell Replacement Therapy in Diabetes Mellitus: Islet Cell Transplantation

Diabetes mellitus remains one of the leading causes of morbidity and mortality worldwide. According to the Centers for Disease Control and Prevention, approximately 23.6 million people in the United States are affected. Of these individuals, 5 to 10% have been diagnosed with Type 1 diabetes mellitus (T1DM), an autoimmune disease. Although it often appears in childhood, T1DM may manifest at any age, leading to significant morbidity and decreased quality of life. Since the 1960s, the surgical treatment for diabetes mellitus has evolved to become a viable alternative to insulin administration, beginning with pancreatic transplantation. While islet cell transplantation has emerged as another potential alternative, its role in the treatment of T1DM remains to be solidified as research continues to establish it as a truly viable alternative for achieving insulin independence. In this paper, the historical evolution, procurement, current status, benefits, risks, and ongoing research of islet cell transplantation are explored.

Conditional and specific inhibition of NF-κB in mouse pancreatic β cells prevents cytokine-induced deleterious effects and improves islet survival posttransplant

BACKGROUND

Islets are susceptible to damage by proinflammatory cytokines via activation of transcription factor NF-κB. We hypothesized that inhibition of NF-κB activity will decrease cytokine-mediated β-cell injury and improve islet transplant functional outcome.

METHODS

We created a transgenic mouse expressing a degradation resistant N-terminally deleted IκBα (ΔNIκBα) under the control of a commercially available tetracycline-controlled transcriptional activation system using a rat insulin promoter. Isolated islets from transgenic and control mouse strains were exposed to cytokines in vitro and assayed or transplanted.

RESULTS

Western blot analysis showed that ΔNIκBα was significantly increased with doxycycline treatment. Cytokine-induced NF-κB activation was significantly decreased in transgenic (0.065 ± 0.013 absorbance value/μg protein) vs control islets (0.128 ± 0.006; P < .05). Suppression of cytokine-mediated NF-κB activity decreased expression of inducible nitric oxide synthase, monocyte chemoattractant protein-1, and interferon-γ inducible protein-10 RNA transcripts, and significantly decreased nitric oxide production in transgenic islets (0.084 ± 0.043 μM/μg protein) vs. controls (0.594 ± 0.174; P < .01). The insulin stimulation index in islets exposed to cytokines was higher in transgenic vs controls (1.500 ± 0.106 vs 0.800 ± 0.098; P < .01). Syngeneic transplants of a marginal mass of intraportally infused transgenic islets resulted in a reversion to euglycemia in 69.2% of diabetic recipients at a mean of 7.8 ± 1.1 days vs. 35.7% of control islet recipients reverting at a mean of 15.8 ± 2.9 days (P < .05).

CONCLUSION

Conditional and specific suppression of NF-κB activity in β cells protected islets from cytokine-induced dysfunction in vitro and in vivo. These results provide a proof of principle that inhibition of NF-κB activity in donor islets enhances function and improves the outcome of islet transplantation.

Association of polymorphisms of interleukin-8, CXCR1, CXCR2, and selectin with allograft outcomes in kidney transplantation

BACKGROUND

Both chemokines and adhesion molecules mediate allograft rejection by recruiting leukocytes into the allograft. We investigated the association of six single nucleotide polymorphisms (SNPs) located in interleukin (IL)-8, CXCR1, CXCR2, and selectin with kidney allograft outcomes.

METHODS

The promoter regions of CXCR1 and CXCR2 were sequenced directly to find SNPs. Reporter gene assay was performed to determine the transcriptional activity of CXCR2 promoter polymorphisms. The association of SNPs in IL-8, CXCR1, CXCR2, and selectin with both acute rejection and estimated glomerular filtration rate at 1-year posttransplant was analyzed in 216 donor-recipient pairs of kidney transplantation.

RESULTS

The donor GA/AA genotypes of CXCR1 -2668G/A (rs2671222) were associated with increased risk for acute rejection even after adjusting for covariates such as gender, diabetes, preemptive transplantation, immunosuppressive regimen, relationship with the donor, and human leukocyte antigen mismatch (adjusted odds ratio 3.56; 95% confidence interval 1.37-9.27; P=0.009). Although the transcriptional activity of the CXCR2 variant promoter was 2.6-fold higher than that of the wild-type promoter (P=0.039), no significant association was observed between CXCR2 polymorphisms and kidney allograft outcomes. SNPs of IL-8, L-selectin, and E-selectin were not associated with kidney allograft outcomes.

CONCLUSION

The donor CXCR1 -2668 GA/AA genotypes were an independent risk factor for acute rejection in kidney transplantation.

Interferon regulatory factor-1 is a key transcription factor in murine beta cells under immune attack

AIMS/HYPOTHESIS

IFN-gamma, together with other inflammatory cytokines such as IL-1beta and TNF-alpha, contributes to beta cell death in type 1 diabetes. We analysed the role of the transcription factor interferon regulatory factor (IRF)-1, a downstream target of IFN-gamma/signal transducer and activator of transcription (STAT)-1, in immune-mediated beta cell destruction.

METHODS

Islets from mice lacking Irf-1 (Irf-1 (-/-)) and control C57BL/6 mice were transplanted in overtly diabetic NOD mice. Viability and functionality of islets were evaluated in vitro. Chemokine expression by Irf-1 (-/-) islets and INS-1E cells transfected with Irf-1 short interfering RNA (siRNA) was measured by real-time PCR as well as in functional assays in vitro.

RESULTS

IRF-1 deletion in islets was associated with higher prevalence of primary non-function (63% vs 25%, p <or= 0.05) and shorter functioning graft survival (6.0 +/- 2.6 vs 10.4 +/- 4.8 days, p <or= 0.05) in contrast to similar skin graft survival. Although Irf-1 (-/-) islets were resistant to cytokine-induced cell death, insulin secretion by them was lower than that of control C57BL/6 islets under medium and cytokine conditions. IL-1 receptor antagonist partly restored the cytokine-induced secretory defect in vitro and completely prevented primary non-function in vivo. Cytokine-exposed Irf-1 (-/-) islets and INS-1E cells transfected with Irf-1 siRNA showed increased expression of Mcp-1 (also known as Ccl2), Ip-10 (also known as Cxcl10), Mip-3alpha (also known as Ccl20) and Inos (also known as Nos2) mRNA and elevated production of monocyte chemoattractant protein-1 (MCP-1) and nitrite compared with controls. In vivo, Irf-1 (-/-) islets displayed a higher potential to attract immune cells, reflected by more aggressive immune infiltration in the grafted islets.

CONCLUSIONS/INTERPRETATION

These data indicate a key regulatory role for IRF-1 in insulin and chemokine secretion by pancreatic islets under inflammatory attack.

Antiapoptotic effect of tacrolimus on cytokine-challenged human islets

Our goal was to investigate whether previously related antiapoptotic and anti-inflammatory effects of tacrolimus could be useful in protecting human islets cultured in the presence of several proinflammatory mediators. Human islets obtained from cadaveric donors after intraductal infusion with collagenase, mechanical digestion, and continuous Ficoll gradient purification were cultured in RPMI-1640 medium for 24 h. Escherichia coli lipopolysaccharide (10 microg/ml) or interleukin-1 (50 UI/ml) + gamma-IF (1000 UI/ml) and low-dose tacroliumus (5 ng/ml) were added. Homogenized samples (300 IE) from five different donors where assigned to four different experimental groups (control, treatment, cytokines, and cytokines + treatment). To evaluate islet damage and apoptotic response, nucleosome content, Bcl-2 protein levels, caspase-3, -8, and -9 levels, and insulin concentration were measured. Also, TNF-alpha and IL-6 levels where assessed as indicators of the inflammatory response. All proapoptotic markers, TNF-alpha, and IL-6 levels were augmented after both LPS and cytokine stimulation. Tacrolimus reduced significantly all of them and restored baseline values of nucleosome and caspase-9 in both experiments and Bcl-2 and caspase-3 when IL-1 + gamma-IF was added. Twenty-four-hour insulin concentration diminished when LPS or IL-1 + gamma-IF were present. Tacrolimus treatment restored insulin levels in both experiments. These results suggest that in vitro apoptotic events and media insulin concentration decrease after proinflammatory stimulation can be reverted using low-dose tacrolimus.

Resolving the conundrum of islet transplantation by linking metabolic dysregulation, inflammation, and immune regulation

Although type 1 diabetes cannot be prevented or reversed, replacement of insulin production by transplantation of the pancreas or pancreatic islets represents a definitive solution. At present, transplantation can restore euglycemia, but this restoration is short-lived, requires islets from multiple donors, and necessitates lifelong immunosuppression. An emerging paradigm in transplantation and autoimmunity indicates that systemic inflammation contributes to tissue injury while disrupting immune tolerance. We identify multiple barriers to successful islet transplantation, each of which either contributes to the inflammatory state or is augmented by it. To optimize islet transplantation for diabetes reversal, we suggest that targeting these interacting barriers and the accompanying inflammation may represent an improved approach to achieve successful clinical islet transplantation by enhancing islet survival, regeneration or neogenesis potential, and tolerance induction. Overall, we consider the proinflammatory effects of important technical, immunological, and metabolic barriers including: 1) islet isolation and transplantation, including selection of implantation site; 2) recurrent autoimmunity, alloimmune rejection, and unique features of the autoimmune-prone immune system; and 3) the deranged metabolism of the islet transplant recipient. Consideration of these themes reveals that each is interrelated to and exacerbated by the other and that this connection is mediated by a systemic inflammatory state. This inflammatory state may form the central barrier to successful islet transplantation. Overall, there remains substantial promise in islet transplantation with several avenues of ongoing promising research. This review focuses on interactions between the technical, immunological, and metabolic barriers that must be overcome to optimize the success of this important therapeutic approach.

Allogeneic islet transplantation

Significant progress has been made in the field of beta-cell replacement therapies by islet transplantation in patients with unstable Type 1 diabetes mellitus (T1DM). Recent clinical trials have shown that islet transplantation can reproducibly lead to insulin independence when adequate islet numbers are implanted. Benefits include improvement of glycemic control, prevention of severe hypoglycemia and amelioration of quality of life. Numerous challenges still limit this therapeutic option from becoming the treatment of choice for T1DM. The limitations are primarily associated with the low islet yield of human pancreas isolations and the need for chronic immunosuppressive therapies. Herein the authors present an overview of the historical progress of islet transplantation and outline the recent advances of the field. Cellular therapies offer the potential for a cure for patients with T1DM. The progress in beta-cell replacement treatment by islet transplantation as well as those of emerging immune interventions for the restoration of self tolerance justify great optimism for years to come.

Resolution of severe atopic dermatitis after tacrolimus withdrawal

Tacrolimus is an immunosuppressive agent used in solid organ and islet transplantation. Its topical form has shown benefit in the treatment of inflammatory skin conditions. Although tacrolimus has a wide spectrum of side effects, dermatological complications related to systemic tacrolimus therapy are limited in the literature. Atopic dermatitis (AD) is a chronic pruritic cutaneous condition that usually begins in infancy and is characterized by an increased Th2 response. We report the case of a patient with type 1 diabetes mellitus (T1DM) and history of AD latent for 10 years who developed severe dermatitis and alopecia 5 months after undergoing allogeneic islet transplantation and initiating a steroid-free immunosuppressive regimen with sirolimus and tacrolimus maintenance. After exclusion of other possible causes for the progression and exacerbation of the clinical presentation of AD, discontinuation of tacrolimus and introduction of mycophenolate mofetil resulted in full remission of the symptoms. The beneficial effects of tacrolimus withdrawal suggest a cause-effect relationship between this adverse event and the utilization of the drug. Islet graft function remained stable after modification of the therapeutic regimen (stable glycemic control and unchanged C-peptide).