Health risks from exposure to low doses of ionizing radiation (IR) are becoming a concern due to the rapidly growing medical applications of X-rays. Using microarray techniques, this study aims for a better understanding of whole blood response to low and high doses of IR. Functional analysis of genes diff erentially expressed at 0.05 Gy showed the enrichment of chemokine and cytokine signaling. However, responsive genes to 1 Gy were mainly involved in tumor suppressor protein 53 (p53) pathways. In a second approach, GSEA showed a higher statistical ranking of inflammatory and immune-related gene sets that are involved in both responding and/or secretion of growth factors, chemokines, and cytokines. This indicates the activation of the immune response. Whereas, gene sets enriched at 1 Gy were ‘ classical ’ radiation pathways like p53 signaling, apoptosis, DNA damage and repair. Comparative RT-PCR studies showed the signifi cant induction of chemokine-related genes (PF4 , GNG11 and CCR4) at 0.05 Gy and DNA damage and repair genes at 1 Gy (DDB2 , AEN and CDKN1A).