ABSTRACT: Tumor necrosis factor alpha (TNFalpha) plays an important role in immune regulation, inflammation, and autoimmunity. Chronic TNFalpha exposure has been shown to down-modulate T cell responses. In a mouse T cell hybridoma model, TNFalpha attenuated T cell receptor (TCR) signaling. We have confirmed that chronic TNFalpha and anti-TNFalpha exposure suppressed and increased T cell responses in BDC2.5 CD4+ T cells, respectively. The goal of this study is to analyze global transcriptional alterations resulting from TNFalpha treatment on TCR signaling pathways using cDNA microarrays. We found that genes involved in functional categories including T cell signaling, cell cycle, proliferation, ubiquitination, cytokine synthesis, calcium signaling, and apoptosis were modulated. Genes such as ubiquitin family genes, cytokine inducible SH2-containing genes, cyclin-dependent kinase inhibitors p21, p57, calmodulin family genes (calmodulin -V1, -V2, and ?V3) and calcium channel voltage- dependent, N type alpha1B subunit (CaV2.2) were induced by TNFalpha, while Vav2, Rho GTPase activating protein, calcium channel voltage dependent, L type alpha 1C subunit (CaV1.2), interleukin-1 (IL) receptor-associated kinase 1, and -V2 (IRAK-1and -2) and IL enhancer binding factor 3 were reduced by TNFalpha. Genes such as CaV1.2 and proliferating cell nuclear antigen, repressed by TNFalpha, were induced by anti-TNF treatment. Further, we showed that chronic TNFalpha exposure impaired NF-kappaB and AP-1 transactivation activity, leading to T cell unresponsiveness. Thus, our results present a detailed picture of transcriptional programs affected by chronic TNFalpha exposure, and provide candidate target genes, which may function to mediate TNFalpha induced T cell unresponsiveness. Set of arrays that are part of repeated experiments Keywords: Biological Replicate