Interleukin-10 dose-dependent regulation of CD4+ and CD8+ T cell-mediated graft-versus-host disease

Background. Endogenous interleukin (IL)-10 production has been associated with the lack of graft-versus-host disease (GVHD) in human recipients of MHC-disparate donor grafts. Paradoxically, we have shown that the exogenous administration of high doses (80 mu g/dose) of IL-10 to murine recipients of MHC-disparate grafts accelerates GVHD lethality. Methods. The effects of IL-10 on GVHD mediated by either CD4(+) or CD8(+) T cells was examined in studies involving exogenous IL-IO administration or the infusion of T cells from IL-10-deficient (-/-) donor mice. The role of interferon (IFN)-gamma on IL-10-induced GVHD acceleration was studied using IFN-gamma-deficient (-/-) donor mice or neutralizing monoclonal antibody. Results. IL-10 was found to have a dose-dependent effect on the GVHD lethality mediated by either CD4(+) or CD8(+) T cells. High doses of exogenous IL-10 accelerated GVHD lethality. IFN-gamma release was not responsible for the IL-10 facilitation of GVHD lethality, Paradoxically, low doses of IL-10 protected mice against GVHD lethality. The GVHD protective effect of the bioavailability of small amounts of IL-10 was confirmed by demonstrating that the infusion of T cells from IL-10 -/- donors accelerated GVHD lethality. Conclusions. The results suggest that IL-10 has a dose-dependent effect on the GVHD lethality mediated by CD4(+) or CD8(+) T cells, such that high doses accelerate lethality, while low amounts of bioavailable IL-10 are protective.