Immunotherapies, although promising in preclinical studies, have not yet enhanced the survival of patients with glioblastomas. To further understand the immunobiology of glioblastomas in clinical settings, we examined 53 cytokine or cytokine receptor transcripts in 12 human glioblastomas and 6 human glioblastoma cell lines and correlated the findings with the degree of inflammation. Multi-probe RNase protection assays were used to examine Th1, Th2, and Th3 cytokine and cytokine receptor expression. Th2 [interleukin (IL)-6, leukemia inhibitory factor and oncostatin M] and Th3 (transforming growth factor-beta1, 2, 3) cytokine and their receptor transcripts were strongly expressed in almost all glioblastomas and glioma cell lines. Two other Th2 cytokine receptor subunit transcripts (IL-4Ralpha and IL-13Ralpha) were also commonly detected. In contrast, although Th1 cytokine receptors tumor necrosis factor (TNF) RI, interferon (IFN)-gammaRalpha, IFN-gammaRbeta, were detected, their cytokines (IFN-gamma, TNF-alpha, lymphotoxin-alpha) were not. Transcripts for IL-2 family cytokine (IL-2, IL-7, IL-9, IL-15) and receptors (IL-2Ralpha, IL-2Rbeta, gammac, IL-7Ralpha, IL-9Ralpha, IL15Ralpha) and IL-12 family cytokine (IL-12p40) and receptors (IL-12Rbeta1 and IL-12beta2) were essentially absent in both tumors and cell lines. Immunohistochemical methods showed sparse T lymphocyte infiltrates and numerous microglia in the glioblastomas. This pattern indicates an 'immunosuppressive status' in glioblastomas and could account for the failure of immunotherapy in such tumors.