Major histocompatibility complex class II antigen expression in rejecting cardiac allografts: detection using in vivo imaging with radiolabeled monoclonal antibody

Evaluation of 131I-anti-MIF mAb as a reporter for allograft rejection

Finding a specific agent will be useful for monitoring allorejection in clinic. The macrophage migration inhibitory factor (MIF) was reported to be one of the major cytokines involved in allorejection. In this study, we evaluated whether (131)I-anti-MIF mAb could be an efficient imaging reporter for monitoring allorejection. (131)I-anti-MIF mAb or control (131)I-IgG was injected to skin allotransplantation mice and T/NT ratios were evaluated. The imaging changes of grafts were dynamically displayed by whole-body images. The results showed that up-regulation of MIF expression was found in allografts but not in isografts. During the whole progression of rejection, the T/NT ratio in the (131)I-anti-MIF mAb group was significantly higher than that in the (131)I-IgG group and markedly increased on the top of rejection. The graft-rejection could also be shown more clearly in the (131)I-anti-MIF mAb group by whole-body imaging. These results implied that (131)I-anti-MIF mAb may be a valid method for facilitating the development of protocols to monitor allorejection.

Molecular imaging in transplantation: basic concepts and strategies for potential application

BACKGROUND

The potential applications of molecular imaging in the clinical arena are diverse and expanding rapidly. One such area of application is transplantation. Currently, biopsy is the gold standard for monitoring allograft well-being after transplantation of organs or tissues. However, biopsies are invasive, associated with morbidity if performed on a routine basis and can potentially miss focal rejection.

AIM

It is notable that none of the existing studies in the literature have examined the possible role of molecular imaging in transplantation-related indications. In this direction, this paper aims to discuss imaging strategies that could be of pertinence in monitoring immune events and improving long-term outcomes after solid organ or tissue transplantation.

METHODS

This paper discusses the currently available direct/surrogate imaging techniques/agents that can be used to detect chemokine receptors/ligands, leucocyte endothelial events and ischaemia-reperfusion injury in transplantation.

CONCLUSION

Molecular imaging methods can non-invasively detect, quantify and monitor immune phenomena, such as rejection or graft-versus-host disease, after transplantation. Molecular imaging could help in targeted biopsy and could improve graft survival by allowing for early intervention with tailored immunosuppressive regimens. Given the unprecedented progress in the field, the potential benefits of molecular imaging to the speciality of organ and tissue transplantation cannot be underestimated.

Targeted ultrasound imaging using microbubbles

Targeted ultrasound imaging uses acoustically active contrast agents bearing a ligand on the surface that binds to a function-specific molecule. These ultrasound contrast agents are typically gas-filled microbubbles, nongaseous liposomes, or lipid-encapsulated perfluorocarbon emulsions. Binding of the contrast agent to the target results in persistent contrast enhancement during ultrasound imaging. This approach has been applied to the ultrasound imaging of pathophysiologic processes such as inflammation associated with ischemia reperfusion, heart transplant rejection, atherosclerotic plaque, thrombus, and apoptosis.

Chronic allograft rejection. Do the Th2 cells preferentially induced by indirect alloantigen recognition play a dominant role?

Chronic rejection has been the major obstacle to the long-term allograft survival in the clinic. Although the etiology of this rejection reaction is multifactorial, alloantigen-specific immune activation plays the most critical role. We herein hypothesize that CD4+ Th2 cells that are preferentially induced by the indirect recognition of allogeneic histocompatibility antigens late in transplantation may play the most critical role in the initiation and/or maintenance of chronic allograft rejection. Immunosuppression used to prevent acute rejection and the nature of antigen-presenting cells and alloligands in the graft may all contribute to immune deviation to the Th2 response. This response may be further perpetuated by type 2 cytokines conceivably produced by activated macrophages, NK cells, and CD8+ T cells in the graft. Cytokines and growth factors induced by this type 2 response, in turn, allow for activation of B, endothelial, and smooth muscle cells that collectively contribute to the pathogenesis of chronic allograft rejection by producing alloantibodies and growth hormones required for interstitial fibrosis, extracellular matrix deposition, and vascular neointimal hyperplasia.

Microneurovascular allotransplantation of the canine tongue

INTRODUCTION

Reconstruction of the tongue with existing methods of tissue transfer often leaves glossectomy patients with significant deficits in speech and swallowing. The critical role of the tongue is implied by its unique structure and function. This paper reports the development of an animal model of hemitongue allotransplantation and documents functional and anatomic outcomes of this procedure.

METHODS

Ten pairs of unmatched dogs underwent reciprocal exchange of the left hemitongue with microneurovascular replantation. The unoperated hemitongue acted as the control. Under cyclosporine immunosuppression, animals surviving long term underwent clinical observation, before electromyography, force transduction studies, and histological evaluation being euthanized.

RESULTS

Five animals survived between 6 and 13 months for long-term evaluation. The remaining group were euthanized because of or died of overwhelming infection or uncontrollable transplant rejection. The latter sometimes resulted from difficulty in the delivery of the cyclosporine. Clinical recovery of tongue function was observed, as well as resumption of motor unit potential activity on electromyography. Contractile force recovery of the transplanted tongue averaged 68% of control (range, 47%-97%), and histological study of the hypoglossal and lingual nerves demonstrated anatomic evidence of reinnervation. Preservation of muscle, mucosal, and stromal ultrastructure was seen with light microscopy of the transplanted tongue.

CONCLUSIONS

Allotransplantation of the hemitongue and associated neurovascular apparatus is possible in a large mammalian model, with long-term survival of tissue being accompanied by partial recovery of contractile properties. Anatomical and clinical evidence also points to sensory recovery. These data support the future possibility of employing a similar technique in glossectomy patients.