Published in:
01-04-2017 | Article
Targeted deletion of Traf2 allows immunosuppression-free islet allograft survival in mice
Authors:
Jeanette E. Villanueva, Stacey N. Walters, Mitsuru Saito, Elisabeth K. Malle, Nathan W. Zammit, Katherine A. Watson, Robert Brink, Nicole L. La Gruta, Stephen I. Alexander, Shane T. Grey
Published in:
Diabetologia
|
Issue 4/2017
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Abstract
Aims/hypothesis
Administration of anti-CD40 ligand (CD40L) antibodies has been reported to allow long-term islet allograft survival in non-human primates without the need for exogenous immunosuppression. However, the use of anti-CD40L antibodies was associated with thromboembolic complications. Targeting downstream intracellular components shared between CD40 and other TNF family co-stimulatory molecules could bypass these complications. TNF receptor associated factor 2 (TRAF2) integrates multiple TNF receptor family signalling pathways that are critical for T cell activation and may be a central node of alloimmune responses.
Methods
T cell-specific Traf2-deficient mice (Traf2TKO) were generated to define the role of TRAF2 in CD4+ T cell effector responses that mediate islet allograft rejection in vivo. In vitro allograft responses were tested using mixed lymphocyte reactions and analysis of IFN-γ and granzyme B effector molecule expression. T cell function was assessed using anti-CD3/CD28-mediated proliferation and T cell polarisation studies.
Results
Traf2TKO mice exhibited permanent survival of full MHC-mismatched pancreatic islet allografts without exogenous immunosuppression. Traf2TKO CD4+ T cells exhibited reduced proliferation, activation and acquisition of effector function following T cell receptor stimulation; however, both Traf2TKO CD4+ and CD8+ T cells exhibited impaired alloantigen-mediated proliferation and acquisition of effector function. In polarisation studies, Traf2TKO CD4+ T cells preferentially converted to a T helper (Th)2 phenotype, but exhibited impaired Th17 differentiation. Without TRAF2, thymocytes exhibited dysregulated TNF-mediated induction of c-Jun N-terminal kinase (JNK) and canonical NFκB pathways. Critically, targeting TRAF2 in T cells did not impair the acute phase of CD8-dependent viral immunity. These data highlight a specific requirement for a TRAF2–NFκB and TRAF2–JNK signalling cascade in T cell activation and effector function in rejecting islet allografts.
Conclusion/interpretation
Targeting TRAF2 may be useful as a therapeutic approach for immunosuppression-free islet allograft survival that avoids the thromboembolic complications associated with the use of anti-CD40L antibodies.