186: CD4+ T-cell maturation and activation state dictate the impact of STAT3 mediated IL-6 induced changes in the transcriptome

Abstract

Interleukin-6 (IL-6) plays a pivotal role in essential inflammatory events in both innate and acquired immunity including T cell recruitment, differentiation, activation and survival. This importance is highlighted by the central role of IL-6 in driving debilitating chronic human inflammatory diseases such as Rheumatoid Arthritis (RA), multiple myeloma, peritonitis, Crohn’s and Castleman’s disease. Despite its importance, our knowledge of how IL-6 mediates these diverse events remains very primitive. Dissection of the molecular gene targets and pathways driven by IL-6 is essential for the early diagnosis, treatment and improved prognosis of human disease. In this study, we use an ‘analysis of transcriptome’ approach to identify clinically relevant predictive biomarkers present in CD4+ T-cells responding to IL-6 via STAT3 signalling. Purified resting and activated CD4+ T-cell populations in a series of differentiation states were examined from both WT and IL6R-deficient mice. Affymetrix Mouse GeneChip® 2.0ST Array analysis of mRNA samples was performed and differential transcript expression amongst T-cell populations validated by RT-PCR. IL-6 driven protein expression, phosphorylation and activation were also measured directly by flow cytometry. Using this simple approach, we show that the gene-expression pattern in response to IL-6 is highly dynamic and tightly linked to T-cell maturation and experience. Whilst the gene-repertoire induced by IL-6 signalling in T-cells appears enriched in Stat3-induced and RA-associated genes, we also observed the modified transcription of several unique potential biomarker genes. Intriguingly, IL-6 stimulation was also found to modify the expression of a number of key genes suggesting a novel mechanism by which this cytokine can promote cell proliferation and survival. Our results suggest that IL-6 mediated transcription changes may be exploited for the diagnosis and/or stratification of human disease.