Selective Reconstitution by GM-CSF of the Immune Response in Human Immunosuppressed Cells

Abstract

Background: Since infection remains the major complication of immunosuppressive therapy in organ transplantation, reconstitution of the innate immunity against infections, without activation of the acquired immune response, in order to prevent graft rejection, is a clinically desirable status in transplant recipients. This study investigates the reconstitution potential of GM-CSF in immunosuppressed blood from liver transplant patients.Methods: In vitro and ex vivo immunosuppressed whole blood or PBMC from 10 healthy donors and from 10 liver transplant patients, whose blood was drawn post liver transplantation, was stimulated with LPS or Con A after incubation with GM-CSF. ELISA, RPA, Western-blot and gene array were used to compare ex vivo the cytokine release, mRNA, protein expression and the gene expression profile, altered by GM-CSF under immunosuppression.Results: GM-CSF restored TNF mRNA and protein expression to the stimulated non-suppression control levels, without inducing IL-2 production and T-cell proliferation in immunosuppressed blood in vitro and ex vivo. In contrast, GM-CSF did not restore the expression of IL-1beta mRNA and protein, but rather enhanced the release of IL-1 receptor antagonist. In contrast to GM-CSF, exogenous IL-1beta restored an IL-2-independent Con A-stimulated proliferation of immunosuppressed lymphocytes to the Con A stimulated control levels, characterized by down-regulation of p27kip1 and up-regulation of Cdk2 and Jab1. This might explain why GM-CSF does not reactivate the lymphocyte response under immunosuppression. Furthermore, gene expression profiling indicated that many genes encoding for the innate immune response were essentially completely restored, while important markers for LPS-responses of lymphocytes were not restored.Conclusions: The selective restoration of innate immune defense suggests a therapeutic potential of GM-CSF in fighting against infections upon organ transplantation.