Immunomodulatory effects of ionizing radiation on peripheral blood mononuclear cells

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 INFγ, IL-2 and TNFα, 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.

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, TNFα 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.

Here we show that IR exposure induces necrotic cell death in PBMCs as the main response. IR exposure significantly induced secretions of Granzyme B, TNFα, IL2, and INFγ 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.

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.