Targeting Regulatory T Cells for Transplant Tolerance: New Insights and Future Perspectives

High-throughput CRISPR technology: a novel horizon for solid organ transplantation

Organ transplantation is the gold standard therapy for end-stage organ failure. However, the shortage of available grafts and long-term graft dysfunction remain the primary barriers to organ transplantation. Exploring approaches to solve these issues is urgent, and CRISPR/Cas9-based transcriptome editing provides one potential solution. Furthermore, combining CRISPR/Cas9-based gene editing with an ex vivo organ perfusion system would enable pre-implantation transcriptome editing of grafts. How to determine effective intervention targets becomes a new problem. Fortunately, the advent of high-throughput CRISPR screening has dramatically accelerated the effective targets. This review summarizes the current advancements, utilization, and workflow of CRISPR screening in various immune and non-immune cells. It also discusses the ongoing applications of CRISPR/Cas-based gene editing in transplantation and the prospective applications of CRISPR screening in solid organ transplantation.

HLA class II antibody activation of endothelial cells induces M2 macrophage differentiation in peripheral blood

BACKGROUND

Donor-specific human leukocyte antigen (HLA) class II antibodies (HLA-II Abs) combined with allogeneic endothelial cells (ECs) mediate high-risk rejection in kidney transplant patients. Macrophage accumulation is a significant histological feature of antibody-mediated rejection (AMR) in kidney transplant patients. Here, we further investigated the effect of HLA-II Abs on macrophage phenotypes to provide theoretical basis for clinical treatment of AMR.

METHODS

We prepared an experimental model containing HLA-II Ab-stimulated microvascular ECs and peripheral blood mononuclear cells (PBMCs) co-culture and explored the potential relationship of HLA-II Ab, ECs activation, and macrophage differentiation. Immune phenotype of macrophage subsets was analyzed and quantified by flow cytometry. HLA-II Ab activation of ECs induces M2 macrophage differentiation signal pathways which were investigated by qPCR and western blotting.

RESULTS

The stimulation of ECs by F(ab')₂ fragment of HLA-II Abs led to phosphorylation of PI3K, Akt, and mTOR, which mediated IL-10, ICAM-1, VCAM-1 secretion. The enhanced ICAM-1 and IL-10 promoted the migration of PBMCs and their differentiation into CD68⁺ and CD163⁺ (M2-type) macrophages, respectively, but not CD86⁺ macrophages.

CONCLUSION

These findings revealed the PI3K/Akt/mTOR signal pathways activated by HLA-II Abs in ECs and the immune regulation ability of HLA-II Abs to induce PBMC differentiation.

TIGIT agonism alleviates costimulation blockade-resistant rejection in a regulatory T cell-dependent manner

Belatacept-based immunosuppression in kidney transplantation confers fewer off-target toxicities than calcineurin inhibitors but comes at a cost of increased incidence and severity of acute rejection, potentially due to its deleterious effect on both the number and function of Foxp3+ regulatory T cells (Tregs). TIGIT is a CD28 family coinhibitory receptor expressed on several subsets of immune cells including Tregs. We hypothesized that coinhibition through TIGIT signaling could function to ameliorate costimulation blockade-resistant rejection. The results demonstrate that treatment with an agonistic anti-TIGIT antibody, when combined with costimulation blockade by CTLA-4Ig, can prolong allograft survival in a murine skin graft model compared with CTLA-4Ig alone. Further, this prolongation of graft survival is accompanied by an increase in the frequency and number of graft-infiltrating Tregs and a concomitant reduction in the number of CD8+ T cells in the graft. Through the use of Treg-specific TIGIT conditional knockout animals, we demonstrated that the TIGIT-mediated reduction in the graft-infiltrating CD8+ T cell response is dependent on signaling of TIGIT on Foxp3+ Tregs. Our results highlight both the key functional role of TIGIT on Foxp3+ Tregs under conditions in which CTLA-4 is blocked and the therapeutic potential of TIGIT agonism to optimize costimulation blockade-based immunosuppression.

Human Regulatory T Cells: Understanding the Role of Tregs in Select Autoimmune Skin Diseases and Post-Transplant Nonmelanoma Skin Cancers

Regulatory T cells (Tregs) play an important role in maintaining immune tolerance and homeostasis by modulating how the immune system is activated. Several studies have documented the critical role of Tregs in suppressing the functions of effector T cells and antigen-presenting cells. Under certain conditions, Tregs can lose their suppressive capability, leading to a compromised immune system. For example, mutations in the Treg transcription factor, Forkhead box P3 (FOXP3), can drive the development of autoimmune diseases in multiple organs within the body. Furthermore, mutations leading to a reduction in the numbers of Tregs or a change in their function facilitate autoimmunity, whereas an overabundance can inhibit anti-tumor and anti-pathogen immunity. This review discusses the characteristics of Tregs and their mechanism of action in select autoimmune skin diseases, transplantation, and skin cancer. We also examine the potential of Tregs-based cellular therapies in autoimmunity.

Classic and Current Opinions in Human Organ and Tissue Transplantation

Graft tolerance is a pathophysiological condition heavily reliant on the dynamic interaction of the innate and adaptive immune systems. Genetic polymorphism determines immune responses to tissue/organ transplantation, and intricate humoral and cell-mediated mechanisms control these responses. In transplantation, the clinician's goal is to achieve a delicate equilibrium between the allogeneic immune response, undesired effects of the immunosuppressive drugs, and the existing morbidities that are potentially life-threatening. Transplant immunopathology involves sensitization, effector, and apoptosis phases which recruit and engages immunological cells like natural killer cells, lymphocytes, neutrophils, and monocytes. Similarly, these cells are involved in the transfer of normal or genetically engineered T cells. Advances in tissue transplantation would involve a profound knowledge of the molecular mechanisms that underpin the respective immunopathology involved and the design of precision medicines that are safe and effective.

Six Decades of History of Hypertension Research at the University of Toledo: Highlighting Pioneering Contributions in Biochemistry, Genetics, and Host-Microbiota Interactions

PURPOSE OF REVIEW

The study aims to capture the history and lineage of hypertension researchers from the University of Toledo in Ohio and showcase their collective scientific contributions dating from their initial discoveries of the physiology of adrenal and renal systems and genetics regulating blood pressure (BP) to its more contemporary contributions including microbiota and metabolomic links to BP regulation.

RECENT FINDINGS

The University of Toledo College of Medicine and Life Sciences (UTCOMLS), previously known as the Medical College of Ohio, has contributed significantly to our understanding of the etiology of hypertension. Two of the scientists, Patrick Mulrow and John Rapp from UTCOMLS, have been recognized with the highest honor, the Excellence in Hypertension award from the American Heart Association for their pioneering work on the physiology and genetics of hypertension, respectively. More recently, Bina Joe has continued their legacy in the basic sciences by uncovering previously unknown novel links between microbiota and metabolites to the etiology of hypertension, work that has been recognized by the American Heart Association with multiple awards. On the clinical research front, Christopher Cooper and colleagues lead the CORAL trials and contributed importantly to the investigations on renal artery stenosis treatment paradigms. Hypertension research at this institution has not only provided these pioneering insights, but also grown careers of scientists as leaders in academia as University Presidents and Deans of Medical Schools. Through the last decade, the university has expanded its commitment to Hypertension research as evident through the development of the Center for Hypertension and Precision Medicine led by Bina Joe as its founding Director. Hypertension being the top risk factor for cardiovascular diseases, which is the leading cause of human mortality, is an important area of research in multiple international universities. The UTCOMLS is one such university which, for the last 6 decades, has made significant contributions to our current understanding of hypertension. This review is a synthesis of this rich history. Additionally, it also serves as a collection of audio archives by more recent faculty who are also prominent leaders in the field of hypertension research, including John Rapp, Bina Joe, and Christopher Cooper, which are cataloged at Interviews .

T-Lymphocyte Subsets Alteration, Infection and Renal Outcome in Advanced Chronic Kidney Disease

Background: T-lymphocyte subsets reflect patients' immune status and are associated with adverse outcomes in various diseases. However, the association between T-lymphocyte subsets and major infection and renal outcome in chronic kidney disease (CKD) patients has not been well-addressed.

Methods: Patients diagnosed with stage 3–5 of non-dialysis CKD were recruited, and healthy subjects were selected as the controls. T-lymphocyte subsets (CD3⁺, CD4⁺, CD8⁺) were detected by flow cytometry, and the CD4⁺/CD8⁺ T cell ratio was then calculated. Patients were divided into the normal-level group and the low-level group according to the clinical reference value. The primary outcomes were the major infection and renal outcome.

Results: A total of 410 CKD patients were enrolled; the average age was 47.25 years. Compared to the healthy controls, the level of CD3⁺, CD4⁺, CD8⁺ T cells, and the CD4⁺/CD8⁺ T cell ratio were significantly decreased in CKD patients (p < 0.05). During the median follow-up of 2.56 (quartile interval 1.24–3.46) years, major infections occurred in 15.10% of the CKD patients. The incidence of infection was significantly higher in the low-level group of CD3⁺, CD4⁺ T cells, and CD4⁺/CD8⁺ T cell ratio compared with the normal level groups. Kaplan-Meier analysis showed that the lower level of CD3⁺, CD4⁺ T cells, and CD4⁺/CD8⁺T cell ratio is associated with a greater risk of infection. Cox regression analysis further confirmed that low CD3⁺, CD4⁺ T cells, and CD4⁺/CD8⁺ T cell ratio were independent risk factors of infection in CKD patients. Moreover, during the follow-up, renal events occurred in 37.50% of patients. Kaplan-Meier analysis indicated that low levels of CD3⁺, CD4⁺, and CD8⁺ T cells are significantly associated with renal outcome in CKD patients. Cox regression analysis showed that low level of CD3⁺ T cells (HR = 2.407, 95% CI: 1.664–3.482, p < 0.001), CD4⁺ T cells (HR = 2.397, 95% CI: 1.633–3.518, p < 0.001) and CD8⁺ T cells (HR = 2.416, 95% CI: 1.476–3.955, p < 0.001) were independent risk factors for renal outcome after multivariable-adjusted.

Conclusion: CKD patients had a defect in T-lymphocyte subpopulation. T-lymphocyte subsets were closely associated with infection and renal outcome in CKD patients. Suggesting T-lymphocyte subsets are independent predictors of infection and renal outcome in CKD patients.

Tissue Treg Secretomes and Transcription Factors Shared With Stem Cells Contribute to a Treg Niche to Maintain Treg-Ness With 80% Innate Immune Pathways, and Functions of Immunosuppression and Tissue Repair

We used functional -omics angles and examined transcriptomic heterogeneity in CD4⁺Foxp3⁺ regulatory T cells (Treg) from spleen (s-Treg), lymph nodes (LN-Treg), intestine (int-Treg), and visceral adipose tissue (VAT-Treg), and made significant findings: 1) Five new shared Treg genes including NIBAN, TNFRSF1b, DUSP4,VAV2, and KLRG1, and 68 new signatures are identified. Among 27 signaling pathways shared in four tissue Treg, 22 pathways are innate immune pathways (81.5%); 2) s-Treg, LN-Treg, int-Treg, and VAT-Treg have zero, 49, 45, and 116 upregulated pathways, respectively; 3) 12, 7, and 15 out of 373 CD markers are identified as specific for LN-Treg, int-Treg, and VAT-Treg, respectively, which may initiate innate immune signaling; 4) 7, 49, 44, and 79 increased cytokines out of 1176 cytokines are identified for four Treg, respectively, suggesting that Treg have much more secretory proteins/cytokines than IL-10, TGF-β, and IL-35; 5) LN-Treg, int-Treg, and VAT-Treg have 13 additional secretory functions more than s-Treg, found by analyzing 1,706 secretomic genes; 6) 2, 20, 25, and 43 increased transcription factors (TFs) out of 1,496 TFs are identified four Treg, respectively; 7) LN-Treg and int-Treg have increased pyroptosis regulators but VAT-Treg have increased apoptosis regulators; 8) 1, 15, 19, and 31 increased kinases out of 661 kinome are identified for s-Treg, LN-Treg, int-Treg, and VAT-Treg, respectively; 9) comparing with that of s-Treg, LN-Treg, int-Treg, and VAT-Treg increase activated cluster (clusters 1–3) markers; and decrease resting cluster (clusters 4–6) markers; and 10) Treg promote tissue repair by sharing secretomes and TFs AHR, ETV5, EGR1, and KLF4 with stem cells, which partially promote upregulation of all the groups of Treg genes. These results suggest that stem cell-shared master genes make tissue Treg as the first T cell type using a Treg niche to maintain their Treg-ness with 80% innate immune pathways, and triple functions of immunosuppression, tissue repair, and homeostasis maintenance. Our results have provided novel insights on the roles of innate immune pathways on Treg heterogeneity and new therapeutic targets for immunosuppression, tissue repair, cardiovascular diseases, chronic kidney disease, autoimmune diseases, transplantation, and cancers.

Adoptive transfer of Tregs: A novel strategy for cell-based immunotherapy in spontaneous abortion: Lessons from experimental models

Since half of the genes are inherited from the paternal side, the maternal immune system has to tolerate the presence of foreign paternal antigens. Regulatory T cells facilitate the development and maintenance of peripheral tissue tolerance of the fetus during pregnancy. Reduction in regulatory T cells is associated with complications of pregnancy, including spontaneous abortion. Recent studies in mouse models have shown that the adoptive transfer of Tregs can prevent spontaneous abortion in mouse models through improving maternal tolerance. Thus, adoptive cell therapy using autologous Tregs could potentially be a novel therapeutic approach for cell-based immunotherapy in women with unexplained spontaneous abortion. Besides, strategies for activating and expanding antigen-specific Tregs ex vivo and in vivo based on pharmacological agents can pave the foundation for an approach incorporating immunotherapy and pharmacotherapy. This review aims to elaborate on the current understanding of the therapeutic potential of the adoptive transfer of Tregs in the treatment of spontaneous abortion disease.

Listing Malignant Melanoma Patients for Renal Transplantation

BACKGROUND

Melanoma is an immune responsive malignancy and the need for immunosuppression for successful transplantation may lead to recurrent disease. The recommended waiting time is unknown with various groups recommending anywhere from no wait to 5 years.

METHODS

In this single-center, retrospective observational study all kidney transplant recipients' charts from 1991 to 2015 were reviewed for a diagnosis of melanoma before transplantation. The charts were reviewed for the clinical characteristics of melanoma pre transplantation, induction immunosuppression, maintenance immunosuppression, graft function, death, and recurrence of melanoma.

RESULTS

Thirteen patients with a history of melanoma underwent kidney transplantation during this period. Recipients had been in remission for an average of 7.0 years (range, 10 months to 20 years, median 6 years). Approximately 61.5% received a living donor transplant, antithymocyte globulin was administered in 23.1% of recipients, and the remaining 76.9% received basiliximab. Melanoma recurred in 1 patient (7.7%). Maintenance immunosuppression varied, but only 2 patients remained on standard triple therapy with prednisone, calcineurin inhibitor, and antimetabolite therapy. Average follow-up time since transplant was 7.5 years, with 1 patient death 9 years post transplant from sepsis.

CONCLUSION

In conclusion, with our center demonstrates safety of kidney transplantation in patients with a prior history of localized melanoma and shorter waiting time. In malignant melanoma stage 0 and 1, waiting the recommended 5 years from the time of remission to kidney transplantation should be reconsidered.

Applications of CRISPR technologies in transplantation

In transplantation, the ever-increasing number of an organ's demand and long-term graft dysfunction constitute some of the major problems. Therefore, alternative solutions to increase the quantity and quality of the organ supply for transplantation are desired. On this subject, revolutionary Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) technology holds enormous potential for the scientific community with its expanding toolbox. In this minireview, we summarize the history and mechanism of CRISPR/Cas9 systems and explore its potential applications in cellular- and organ-level transplantation. The last part of this review includes future opportunities as well as the challenges in the transplantation field.

Prognostic value of immunological profile based on CD8+ and FoxP3+ T lymphocytes in the peritumoral and intratumoral subsites for renal cell carcinoma

PURPOSE

We aimed to assess an "Immunological Profile (IP)" including CD8+ and FoxP3+ T lymphocytes for renal cell carcinoma (RCC) to evaluate its effects on tumor pathological characteristics, disease progression, and survival.

METHODS

Adjacent normal and intratumoral specimens from 42 patients who had undergone radical nephrectomy for RCC were analyzed for counts of CD8+ and FoxP3+ T lymphocytes by immunohistochemistry. Tissue from both sites were evaluated and scored separately according to low (0) or high (1) expression of CD8 and FoxP3. A total score (min: 0, max: 4) was assigned to each patient. Thereafter, patients were divided into two groups for clinicopathologic and survival stratification based on score (IP_Weak 0-2; and IP_Strong 3-4). Survival curves were constructed using the Kaplan-Meier method, and a multivariable Cox regression model was used for overall survival (OS) and progression-free survival (PFS).

RESULTS

The mean follow-up was 54.73 ± 21.34 months. Poor RCC characteristics including pT3-T4, tumor necrosis, lymphovascular invasion, lymph node involvement, and larger tumor size were significantly more common in the IP_Weak patients compared to IP_Strong (p < 0.05). Kaplan-Meier analysis showed that IP_Weak patients had worse OS (62.5 vs. 100%; p = 0.006) and PFS (50 vs. 94.4%; p = 0.002) compared to IP_Strong patients. In multivariable analysis, IP_Weak (HR 8.64; 95% CI 1.09-68.05, p = 0.042) and high tumor node metastasis stage (HR 45.33; 95% CI 4.69-437.68, p < 0.001) were significant independent predictors of poor PFS.

CONCLUSION

Assessment of IP including CD8+ and FoxP3+ T lymphocytes in adjacent normal and intratumoral sites in RCC may serve as a good predictive marker for PFS.

Limited efficacy of rapamycin monotherapy in vascularized composite allotransplantation

BACKGROUND

Vascularized composite allotransplantation (VCA) is a novel and life-enhancing procedure to restore a patient's function and/or appearance. Current immunosuppression in VCA recipients is based on calcineurin inhibitor (CNI) therapy that can lead to severe complications, such that inducing immune tolerance is a major goal of VCA research. In contrast to CNI, rapamycin (RPM) is thought to be beneficial to the development of immune tolerance by suppressing T-effector cells (Teffs) and expanding T-regulatory (Treg) cells. However, we found high dose RPM monotherapy prolonged VCA survival by only a few days, leading us to explore the mechanisms responsible.

METHODS

A mouse orthotopic forelimb transplantation model (BALB/c- > C57BL/6) was established using WT mice, as well as C57BL/6 recipients with conditional deletion of T-bet within their Treg cells. Events in untreated VCA recipients or those receiving RPM or FK506 therapy were analyzed by flow-cytometry, histopathology and real-time qPCR.

RESULTS

Therapy with RPM (2 mg/kg/d, p < .005) or FK506 (2 mg/kg/d, p < .005) each prolonged VCA survival. In contrast to FK506, RPM increased the ratio of splenic Treg to Teff cells (p < .05) by suppressing Teff and expanding Treg cells. While the proportion of activated splenic CD4 + Foxp3- T cells expressing IFN-γ were similar in control and RPM-treated groups, RPM decreased the proportions ICOS+ and CD8+ IFN-γ + splenic T cells. However, RPM also downregulated CXCR3+ expression by Tregs, and forelimb allografts had reduced infiltration by CXCR3+ Treg cells. In addition, allograft recipients whose Tregs lacked T-bet underwent accelerated rejection compared to WT mice despite RPM therapy.

CONCLUSIONS

We demonstrate that while RPM increased the ratio of Treg to Teff cells and suppressed CD8+ T cell allo-activation, it failed to prevent CD4 Teff cell activation and impaired CXCR3-dependent Treg graft homing, thereby limiting the efficacy of RPM in VCA recipients.