What is graft rejection?4 answersGraft rejection refers to the immune response in which the recipient's immune system recognizes the transplanted organ or tissue as foreign and attacks it, leading to the destruction of the graft and subsequent rejection. Graft rejection can occur in various types of transplantation, such as keratoplasty and hematopoietic cell transplantation. In keratoplasty, failed grafts are commonly caused by endothelial rejection, which is the major cause of graft failure. In hematopoietic cell transplantation, graft rejection can manifest as the absence of initial engraftment or the disappearance of donor hematopoiesis. The rejection process involves both adaptive immune responses mediated by T cells and B cells, as well as innate immune responses mediated by natural killer cells. To prevent graft rejection, immunosuppressive drugs can be used, and HLA matching is an important method for preventing rejection of allografts.
What is the role of Granzyme expression in tumor rejection?4 answersGranzyme expression plays a crucial role in tumor rejection. Granzyme F is highly upregulated in the tumor microenvironment (TME) and is expressed by a subset of antigen-experienced and exhausted T cells. Granzyme B is expressed by cytotoxic T cells (Tc) and Natural Killer cells and aids in killing affected cells. Granzyme B expression positively correlates with the response of patients with mesothelioma to immune checkpoint inhibitor immunotherapy. Granzyme K is associated with improved prognosis in solid tumors and is predominantly expressed by innate-like lymphocytes and a population of CD8+ T cells. The overall expression of granzyme B within the tumor microenvironment is a prognostic marker indicative of priming immunity. These findings suggest that different granzymes have distinct roles in cytotoxicity and immune responses against tumors.
What are the effects of rejection sensitivity on ADHD symptoms over time?4 answersRejection sensitivity has been found to have effects on ADHD symptoms over time. Individuals with ADHD symptoms tend to have higher victim justice sensitivity, more perceptions of injustice, and higher anxious and angry rejection sensitivity, but lower perpetrator justice sensitivity compared to controls. Heightened rejection sensitivity is associated with increased internalizing symptoms, including anxiety and depression, in adolescents and young adults. This association is mediated by emotion dysregulation, expressive suppression, and social avoidance. While individuals with ADHD may not have elevated rejection sensitivity compared to controls, low rejection sensitivity predicts negative relational outcomes in adults with ADHD. Both ADHD-Combined Type and ADHD-Primarily Inattentive Type are associated with lower general self-esteem and negative relational outcomes, with ADHD-IA reporting more negative outcomes than ADHD-C. Attachment style, ADHD symptoms, and rejection sensitivity are interconnected in adolescents, with attachment security being indirectly linked to better adjustment outcomes via an ADHD latent factor. Rejection sensitivity is associated with various subclinical syndromes and mental disorders, including borderline symptoms, depressive symptoms, social anxiety, and aggressive behavior.
What is Acute cellular Rejection?3 answersAcute cellular rejection (ACR) is a T cell-mediated immune response to transplanted tissue that can lead to chronic allograft dysfunction and loss. ACR primarily involves CD4+ and CD8+ T cells, but there is significant heterogeneity within these cell compartments. Naïve CD4+ T cells are activated and differentiate into specific T helper subsets under the influence of local cytokines. These subsets have distinct phenotypic and functional characteristics, with reported differences in their contribution to rejection responses. Regulatory T cell subsets have the potential to promote tolerance of allografts. Understanding the specific contributions of these cell subsets in the context of transplantation may reveal new avenues for therapeutic intervention to prevent rejection. Late ACR, associated with donor-specific antibodies and chronic rejection, can also involve B cells and plasma cells. ACR is a major complication after lung transplantation and is considered a major cause of chronic lung allograft dysfunction.
T cells involved in rejection?4 answersT-cell allorecognition in transplant rejection involves three distinct mechanisms: the direct pathway, the indirect pathway, and the semidirect pathway. CD4 T cells, in addition to CD8 T cells, play a crucial role in cancer immunotherapy. They can directly recognize cancer cells if they express MHC II and also have various other functions such as inducing tumoricidal macrophages, destroying tumor vasculature, and helping CD8 T cells in the effector phase. Alloreactive memory T cells are a major barrier to tolerance induction in clinical transplantation. They can be generated through direct exposure to allogeneic MHC molecules or through microbial infections. Alloreactive memory T cells are involved in the rejection process and are resistant to conventional immunosuppression and costimulation blockade. Skin tissue-resident T cells have been found to contribute to allograft rejection, exhibiting a Th17 program that can be inhibited to prolong graft survival.
Do B cells oversee humoral immunity?4 answers