Immunomodulatory effects of ionizing radiation on peripheral blood mononuclear cells

Background: Avoiding exposure to ionizing radiation due to environmental factors is almost inevitable in daily life. Here, we aimed to investigate the possible immunomodulatory effects of ionizing radiation on NK and T cell activation using Peripheral Blood Mononuclear Cells (PBMC). We measured the pro-inflammatory cytokines INF., IL-2 and TNFa, as well as Granzyme B. In addition, we determined the expression levels of CD28, NKG2D (CD314) receptors, which play a key role in the activation of T and NK cells, respectively. Materials and Methods: 20 ml peripheral blood samples were taken from healthy volunteer donors and exposed to radiation doses of 0, 1, 3 and 5 Gy. ELISA analysis was used to measure Granzyme B, INFy, TNFa and IL2. Expression of CD28, NKG2D (CD314) receptors was measured by qRT-PCR analysis. Apoptosis and necrosis were measured by AnnexinV/7AAD analysis. Catalase activity was measured using hemolysates from irradiated blood samples. Results: Here we show that IR exposure induces necrotic cell death in PBMCs as the main response. IR exposure significantly induced secretions of Granzyme B, TNFa, IL2, and INF. in a dose-dependent manner. In addition, mRNA levels of CD28 and NKG2D expressions were increased by 3 Gy IR exposure, but decreased by 5 Gy, while catalase activity increases with 1 Gy IR treatment, 3 and 5 Gy decreases. Conclusions: Our results suggest that not only high doses but even low doses of radiation can modulate the immune response through cytokine secretion and activation of T and NK cell receptors.