The aim of this study is to evaluate the influence of anti (IL-4, IL-10), and pro-inflammatory (IL-2, IL-12 and IL-18) cytokines in the Th1/Th2 polarization developed during an in vitro allogeneic response with peripheral blood (PB) mononuclear cells of healthy donors, in order to contribute to a possible development of novel therapeutic modalities and response to GVHD treatment. The gene discussed is IL18; the disease is graft versus host disease.