Lymphokine expression profile of resting and stimulated CD4⁺ CTL clones specific for the glycoprotein of vesicular stomatitis virus

A panel of long-term murine T lymphocyte clones specific for the glycoprotein of vesicular stomatitis virus (VSV) in association with either H-2I-A^d or I-E^d was tested for the production of cytokines in both resting and poststimulation states using both in situ hybridization and bioassay. All but one of the clones showed antigen-specific cytolytic activity in a 4-hr ⁵¹Cr release assay. Unexpectedly, the clones did not appear to be typical Th1 cells. Five of these T cell clones produced both IL-2 and IFN-γ but not IL-4 after stimulation with either phorbol 12-myristate 13-acetate (PMA) or concanavalin A (Con A). Some clones constitutively expressed mRNA for IL-2 and INF-γ. The proliferation of these clones was factor independent, suggesting an autocrine growth mechanism. Three clones produced variable levels of IL-4 mRNA and some, to significant quantities, of IL-2 mRNA. One cytolytic clone produced neither IL-2 nor IL-4 mRNA to detectable levels, although mRNA for IFN-γ was observed. A noncytolytic, Ag-specific clone produced IL-6, tumor necrosis factor (TNF), and lymphotoxin (LT), but no IL-2, IL-4, or IFN-γ mRNA. There was a strong quantitative correlation between the expression of IL-2-, INF-γ-, and LT-specific mRNAs by the clones. All the T cell clones tested which secreted INF-γ and LT expressed no measurable IL-4 mRNA. We examined expression of several other genes in the panel of clones. These included TNF, met-enkephalin (met-enk), IL-1 and IL-6. IL-1 m-RNA synthesis was not observed in any of the T cell clones. Almost all clones produced TNF mRNA. Parallel bioassays showed that secreted IL-2/IL-4 activity levels and mRNA levels correlated well for all clones. Thus, we observed a great degree of heterogeneity among CD4⁺ cytolytic T lymphocyte clones.