Utility of IL-2 Complexes in Promoting the Survival of Murine Orthotopic Forelimb Vascularized Composite Allografts.

Background: Vascularized composite allografts (VCA) are novel, life-enhancing forms of transplantation (Tx). However, host immune responses to the various VCA components, especially those involving skin, are complex and make selection of appropriate therapy challenging. While the interplay between Foxp3+ T regulatory (Treg) cells and CD4 and CD8 effector T cells is of central importance in determining the acceptance or rejection of solid organ allografts, there is little information available concerning the contribution of Tregs to VCA survival. In addition, the effects of therapeutic expansion in vivo of host Treg populations on VCA survival are unknown. Methods: We established a fully MHC-disparate (BALB/c->C57BL/6) murine orthotopic forelimb Tx model to explore the benefits of pre and post-Tx IL-2/anti-IL-2 monoclonal antibody complex (IL-2C) administration to expand the host Treg population and thereby attempt to promote Treg-dependent VCA survival. Results: Both strategies expanded the Treg population in vivo and prolonged VCA survival (p

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