Background.To further delineate the cytokine involvement in human acute graft-versus-host disease (GVHD), we analyzed cytokine expression in peripheral blood mononuclear cells (PBMC) from patients who developed acute GVHD after allogeneic bone marrow transplantation and from those who did not.Methods.We used a highly quantitative and sensitive polymerase chain reaction assay based on the coamplification of an internal standard, with the cDNA derived from the mRNA of interest. Results are expressed in copy numbers, after normalization to a fixed amount of actin, allowing comparison between different samples. After a myeloablative regimen, 22 patients with hematological diseases received an unmanipulated allograft from a matched sibling. They were subsequently submitted to prophylactic immunosuppression. We examined the transcription of genes encoding cytokines in PBMC and skin biopsies. We selected T helper 1 (interferon ([IFN]γ, interleukin [IL]-2), T helper 2 (IL-4, IL-10), and inflammatory (IL-1, IL-6) cytokines.Results.Four weeks after bone marrow transplantation, the bulk of the PBMC population exhibited an increased expression of IL-1 and IL-6, with no major difference between GVHD+and GVHD-patients. In addition, although IL-2 expression was not detected, increased levels of IFNγ mRNA were observed in allografted patients, with higher levels in GVHD+patients. In skin biopsies sampled at the beginning of GVHD, although low expression of IL-1 and IL-6 could be observed, neither type 1 (IL-2, IFNγ) nor type 2 (IL-4, IL-10) cytokines could be detected.Conclusions.These studies suggest that the occurrence of human GVHD does not seem to be clearly associated with a T helper 1-type cytokine pattern.