Neutralising IL-12 Activity as a Strategy for Prolonging Allograft Survival and Preventing Graft-Versus-Host Disease
Interleukin-12 (IL-12) is a key immunoregulatory cytokine which promotes the development of Thl-dependent, cell-mediated immune responses. Acute allograft rejection after organ transplantation and acute graft-versus-host disease (G VHD) after bone-marrow transplantation are generally attributed to cell-mediated immune mechanisms and, therefore, potentially susceptible to immunological intervention at the level of IL-12. Recent data from murine models of transplantation have highlighted the potential of IL-12 as a selective target for immunotherapy. Neutralising endogenous IL-12 for a brief period at the time of transplant promotes long-term deviation from a Thl to a polarised Th2 alloimmune response. This confers lasting protection from GVHD but is less effective at preventing acute rejection, possibly because Th2-dependent immune responses are also capable of effecting graft rejection.