We have used the reverse transcriptase polymerase chain reaction (RT-PCR) technique to assess the expression of cytokine genes in various T cell subsets of autoimmune-prone mice. Our study confirmed the previously described features in lpr mice that IFN-γ, TNF-α, and TNF-βwere transcribed by various T cell subsets. We in this study demonstrated that double negative (DN) T cells, the major cell population in lpr mice, failed to express interleukin-3 (IL-3), IL-4, IL-5, and IL-6 genes that influence B cell growth and activation. In contrast, DN T cells expressed Eta-1 gene that is shown to augment polyclonal activation of B cells and immunoglobulin production. Thus, it is conceivable that T cell-derived B cell-stimulatory activities in MRL/lpr mice can be attributed to Eta-1, rather than IL-3, IL-4, IL-5 or IL-6. We also demonstrated that CD4+T cells infiltrating into kidney tissues of MRL/Ipr mice expressed various cytokine genes such as IL-1, IL-5, IL-6, IFN-γ, TNF-α, TNF-βand TGF-p.