Epstein-Barr virus (EBV) transformed human B cells proliferate indefinitely in vitro, and it has been proposed that cytokine-mediated autocrine loops contribute to the maintenance of the lymphoblastoid phenotype. We used a novel multiprobe RNase protection assay to quantify cytokine mRNA species expressed by EBV-transformed lymphoblastoid cell lines (LCL), derived either by the transformation of B cells with B95-8 or wild-type EBV or by the in vitro outgrowth of EBV-associated B cell lymphomas to identify cytokines that are commonly expressed in all LCL and thus more likely to be essential for immortalization of B cells. All 16 LCL expressed high levels of tumor necrosis factor (TNF)alpha, TNFbeta, and transforming growth factor (TGF)beta1 mRNA, while interleukin (IL)-10 transcripts were detected in most LCL but at a lower level. Expression of IL-1alpha, IL-1beta, IL-6, IL-12p35, IL-12p40, IL-13 and IFNgamma mRNA was variable among the LCL tested. Granulocyte-macrophage colony-stimulating factor (GM-CSF), IL-2, IL-4, and IL-5 mRNA were undetectable in all LCL. Furthermore, we found that IL-10, TNFalpha, and TNFbeta mRNA were induced in EBV-negative B cell lines after infection with EBV. These data define common versus idiosyncratic patterns of cytokine expression by LCL and, in the former case, such cytokines as TNFalpha, TNFbeta, and IL-10 emerge as strong candidates that are essential for the autocrine regulation of EBV-immortalized B cells.