B-cell response in solid organ transplantation

Chronic rejection models for vascularized composite tissue allotransplantation

Vascularized composite tissue allotransplantation (VCA) has transformed patients' lives by enabling limb, face, abdominal wall, and penile transplants. Despite advancements in screening and immunosuppression, chronic rejection continues to limit the success of VCA. Lack of reliable preclinical models exacerbates this challenge. Here, we report on new mouse models of chronic rejection following heterotopic hind limb VCA. We employed different levels of MHC mismatch using CD8 knockout C57BL/6 mice as recipients along with BALB/c or B6 H2-Ab1bm12 mice as donors. Transient CD4 T cell depletion was induced to allow graft maturation. Evaluation included gross findings, changes in immune status changes, production of donor-specific antibodies (DSA), C4d levels, and histopathological alterations. Two chronic rejection models displayed common features of clinical chronic graft rejection, such as skin stricture, hair loss, adnexal atrophy, extensive fibrosis and mast cell infiltration without widespread necrotic changes common in acute rejection. Similar to chronic rejection patients, large populations of activated B and plasma cells were detected in the recipient's immune system as well as increased DSA and C4d production. Collectively, our models closely replicate the immunological and histopathological aspects of chronic graft rejection post-VCA, and could provide a new platform for evaluation of novel therapeutic interventions prior to clinical evaluation.

The effects of interleukin-21 in the biology of transplant rejection

Interleukin-21 (IL-21) is a cytokine that plays a crucial role in regulating immune responses, affecting various immune cell types, including T cells, B cells, natural killer (NK) cells, and dendritic cells. IL-21 is primarily produced by CD4+ T cells, particularly follicular helper T (Tfh) cells and Th17 cells, and has been shown to be extensively involved in regulating both innate and adaptive immunity. IL-21 is particularly significant in the differentiation, proliferation, and effector functions of T cells and B cells. In the context of organ transplantation, IL-21 contributes to the promotion of acute transplant rejection and the development of chronic rejection, which is primarily antibody-mediated. This review summarizes relevant studies on IL-21 and discusses its multifaceted roles in transplant immune rejection, providing insights into therapeutic strategies for either inhibiting graft rejection or promoting tolerance. It also explores the feasibility of blocking the IL-21 signaling pathway within current immunosuppressive regimens, aiming to provide further clinical references.

Drug delivery strategies for local immunomodulation in transplantation: Bridging the translational gap

Drug delivery strategies for local immunomodulation hold tremendous promise compared to current clinical gold-standard systemic immunosuppression as they could improve the benefit to risk ratio of life-saving or life-enhancing transplants. Such strategies have facilitated prolonged graft survival in animal models at lower drug doses while minimizing off-target effects. Despite the promising outcomes in preclinical animal studies, progression of these strategies to clinical trials has faced challenges. A comprehensive understanding of the translational barriers is a critical first step towards clinical validation of effective immunomodulatory drug delivery protocols proven for safety and tolerability in pre-clinical animal models. This review overviews the current state-of-the-art in local immunomodulatory strategies for transplantation and outlines the key challenges hindering their clinical translation.

Past and present discovery of the BAFF/APRIL system - A bibliometric study from 1999 to 2023

Cytokines from the Tumour Necrosis Factor (TNF) family are important regulators of both physiological and pathological processes. The discovery of novel TNF ligands and receptors, BAFF and APRIL, have opened up new possibilities for scientists to explore the effect of these cytokines on the human immune system. The role of BAFF/APRIL system in B lymphocytes is particularly important for survival and maintenance of homeostasis. Aberrant expression of the system is associated with various immunological disorders. Hence, this study provides a comprehensive overview of the past and present BAFF/APRIL system research development in a bibliometric perspective. To our best knowledge, this is the first ever bibliometric analysis conducted focusing on the BAFF/APRIL system. A total of 1055 relevant documents were retrieved from WoSCC. Microsoft Excel, VOSviewer, and Biblioshiny of R studio were bibliometric tools used to analyse the scientific literature. From 1999, the annual publications showed an upward trend, with Journal of Immunology being the most productive journal. USA leads the race for BAFF/APRIL system research developments. Pascal Schneider, a senior researcher affiliated with University of Lausanne, Switzerland was recognised as the most productive author and institution in the BAFF/APRIL system research field. The research focus transitioned from focusing on the role of the system in B cell biology, to immunological disorders and finally to development of BAFF/APRIL targeting drugs. Despite several studies elucidating briefly the pathway mechanism of BAFF/APRIL system in B-cell selection, substantial research on the mechanism of action in disease models and T cell activation and development of immunomodulating drugs from natural origins remains largely unexplored. Therefore, future research focusing on these areas are crucial for the deeper understanding of the system in disease manifestations and progression allowing a better treatment management for various immunological disorders.

Challenges and opportunities in the islet transplantation microenvironment: a comprehensive summary of inflammatory cytokine, immune cells, and vascular endothelial cells

It is now understood that islet transplantation serves as a β-cell replacement therapy for type 1 diabetes. Many factors impact the survival of transplanted islets, especially those related to the microenvironment. This review explored microenvironmental components, including vascular endothelial cells, inflammatory cytokines, and immune cells, and their profound effects on post-islet transplantation survival rates. Furthermore, it revealed therapeutic strategies aimed at targeting these elements. Current evidence suggests that vascular endothelial cells are pivotal in facilitating vascularization and nutrient supply and establishing a new microcirculation network for transplanted islets. Consequently, preserving the functionality of vascular endothelial cells emerges as a crucial strategy to enhance the survival of islet transplantation. Release of cytokines will lead to activation of immune cells and production and release of further cytokines. While immune cells hold undeniable significance in regulating immune responses, their activation can result in rejection reactions. Thus, establishing immunological tolerance within the recipient's body is essential for sustaining graft functionality. Indeed, future research endeavors should be directed toward developing precise strategies for modulating the microenvironment to achieve higher survival rates and more sustained transplantation outcomes. While acknowledging certain limitations inherent to this review, it provides valuable insights that can guide further exploration in the field of islet transplantation. In conclusion, the microenvironment plays a paramount role in islet transplantation. Importantly, we discuss novel perspectives that could lead to broader clinical applications and improved patient outcomes in islet transplantation.