• Olivier Thaunat, Lionel Badet, Valérie Dubois, Jean Kanitakis, Palmina Petruzzo, and Emmanuel Morelon.
• aHospices Civils de Lyon, Hôpital Edouard Herriot, Service de Transplantation, Néphrologie et Immunologie Clinique bUniversité de Lyon cINSERM, U1111 dHospices Civils de Lyon, Hôpital Edouard Herriot, Service d'Urologie et Transplantation eEtablissement Français du Sang fHospices Civils de Lyon, Hôpital Edouard Herriot, Service de Dermatologie, Lyon, France.
• Curr Opin Organ Transplant. 2015 Dec 1; 20 (6): 596-601.

Purpose Of ReviewAs both the number of vascularized composite allotransplants (VCAs) recipients and the duration of their follow-up are limited, immunopathology of VCA rejection remains incompletely understood. VCAs have several immunological peculiarities, which make inaccurate a direct extrapolation of all rules established for solid organs.Recent FindingsDespite their bone marrow content, VCA do not induce chimerism in recipient and are therefore not spontaneously tolerated. Skin compartment of VCA contains a high density of antigen-presenting cells (APCs), some with self-renewal capacity. Donor APCs are responsible for continuous direct allosensitization of recipient's T cells that explains the high incidence of skin T-cell-mediated rejection and their occurrence beyond 1 year.Regenerative capability of the skin prevents the development of chronic rejection of this compartment as long as immunosuppression is maintained. In contrast, VCA can develop graft arteriosclerosis, which could be because of T cell and/or chronic antibody-mediated rejection (AMR). VCA recipients can indeed develop donor-specific antibodies (DSA). Whether DSA can also trigger acute AMR of VCA remains to be clarified.SummaryA better understanding of the specificities of the immunopathology of VCA rejection should pave the way for the rationalization of immunosuppressive strategies aiming at optimizing long-term outcome.

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