Gene expression signature of naïve and in vitro activated CD8 T cells in response to IL-12 and Type I IFN

Differentiation of naive CD8 T cells into cytotoxic effector cells requires three distinct signals- antigen (signal 1), costimulation -B7-1 (signal 2) and cytokine, either interleukin-12 or interferon-a/b (signal 3). Interaction of naive CD8 T cells with antigen and B7-1 programs cell division and proliferation whereas the presence of cytokines- IL-12 or IFNa/b promote survival, differentiation and memory establishment. In the absence of signal 3, the cells interacting with antigen/B7-1 undergo tolerance induction. The objective of this study was to elucidate the mechanisms how the provision of signal 3 promotes differentiation and averts tolerance induction in CD8 T cells. Trichostatin A is a pharmacological agent that inhibits histone deacetylase activity, hence regulating chromatin structure and gene expression and differentiation in many cell types. Gene signature profiles of IL-12, IFNa/b and trichostatin A stimulated cells were compared to elucidate the molecular mechanisms of gene regulation. Oligonucleotide microarray analysis is carried out to determine the extent and molecular nature of the CD8 T cell differentiation program induced by IL-12 or IFNa/b in concert with antigen and B7-1 signal. The programming for development of function and memory in presence of signal 3 occurs over three days of initial stimulation, and antigen-B7 and IL-12 or IFNa/b must be present for most of this period to achieve maximal responses. We analyzed gene expression in highly purified naive CD8 T cells at 0, 24, 48 and 72h of in vitro culture stimulated with antigen-B7 and with or without IL-12 or IFNa/b to tease apart gene expression profiles of naive, 2-signal and 3-signal stimulated cells over the course of 3-days. Gene expression of cells stimulated with trichostatin A for 72hr were compared with IL-12 or IFNa/b stimulated cells. 20 arrays.