Temporal sequence and cellular origin of interleukin-2 stimulated cytokine gene expression.

A study of activation of the cytokine network by interleukin 2, IL-2, may provide a rationale for devising cytokine combination and cytokine antagonist treatments with increased anti-tumour efficacy and decreased toxicity. We have investigated the expression of mRNA for 13 cytokines and three transcription factors during in vitro culture of peripheral blood mononuclear cells, PBMC, with IL-2. A consistent pattern of induction was seen in nine individuals, with early (2-24 h) induction of IL-1 beta, IL-6, tumour necrosis factor, TNF, lymphotoxin, LT, and gro. TNF and LT mRNA was expressed continually throughout culture, but levels of mRNA for IL-1 beta, IL-6, and gro declined by 24-48 h. After 48 h, PBMC began to express mRNA for IFN-gamma, IL-5, GM-CSF, and M-CSF. At 15 min to 1 h post IL-2 mRNA for c-fos, c-jun, and c-myc, and TNF was induced in three individuals studied. IL-4, IFN-alpha, and IL-1 alpha mRNA was not detected. Only a minority of cells expressed mRNA for TNF, IL-1 beta, IL-6 and IFN-gamma, and monocytes were the main source. Levels of cytokine protein in culture supernatants mirrored the pattern of mRNA induction. This in vitro model shows clear parallels with the reported in vivo production of cytokines during IL-2 therapy, and may prove useful in designing new therapeutic strategies.