Effect of ionizing radiation on gene expression in CD4+ T lymphocytes and in Jurkat cells: Unraveling novel pathways in radiation response

To better understand at the molecular level the effect of ionizing radiation in leukocytes, the global transcriptional response to X-ray irradiation was studied in human CD4+ T lymphocytes and in Jurkat cells. Microarray analysis performed on freshly isolated human CD4+ T lymphocytes 8 h after an LD50 irradiation dose of 1 Gy revealed that out of 13,825 genes, 1084 were modulated more than 1.5-fold. The most strongly up-regulated genes were predominantly p53 targets. In contrast, exposure of the CD4+ T lymphocyte-derived Jurkat leukemic cell line (with no functional p53 gene) to an equivalent LD50 dose (0.5 Gy) induced a partly different and more limited set of genes. Interestingly, this set of genes belonged to the Rho and cytokine signaling pathways, suggesting the existence of novel pathways regulated by low-dose ionizing radiation.