Park Hae-Ran, Jo Sung-Kee, Paik Sang-Gi
Radiation Food and Biotechnology Team, Korea Atomic Energy Research Institute (KAERI), Yusong, Daejeon, Korea.
Int J Radiat Biol. 2005 Mar;81(3):221-31. doi: 10.1080/09553000500077088.
Ionizing radiation is known to reduce the helper T (Th) 1-like function, but not the Th2-like function, resulting in a Th1/Th2 imbalance. While this has been known for some time, the mechanism behind the preferential suppression of the Th1 cell activation has not yet been explained. The aim is to elucidate the mechanism in the Th cell imbalance after ionizing irradiation. C57BL/6 mice, 7 weeks old, received whole-body gamma-irradiation (WBI) of 5 Gy. In all instances, the spleen and peritoneal cells were obtained from mice 7 weeks after irradiation. To distinguish Th1 and Th2 cell function, interferon (IFN)-gamma and interleukin (IL)-4 produced by these cells were analysed by an enzyme-linked immunosorbent assay (ELISA). To isolate the primary T cells, the anti-CD90.2 microbead-conjugated antibody was used and the labelled cells were separated by magnetic cell sorting (MACS). To investigate the influence of the IL-12p70 secreted by the antigen-presenting cells, ovalbumin (OVA)-primed peritoneal adherent cells (PAC) were fixed by 1% paraformaldehyde and co-cultured with OVA-specific Th cells in the presence of supernatant of PAC culture with OVA for 16 h. IL-12 receptor, signal transducers and activators of transcription 4 (STAT4) and IFN-gamma expression in the T cells of the WBI mice were detected by reverse transcriptase-polymerase chain reaction (RT-PCR). The spleen lymphocytes of WBI mice showed a depression of IFN-gamma production against OVA, although the total IL-12 was highly secreted. However, the heterodimer IL-12, biologically active protein, was induced less in WBI mice. Although the OVA-specific Th cells were co-cultured with fixed OVA-primed PAC obtained from normal mice, the OVA-specific Th cells showed a decreased IFN-gamma secretion in the presence of the culture supernatant of the activated PAC from the WBI mice. In addition, recombinant IL-12p70 restored the cytokine balance of the OVA-specific Th cells. However the cytokine balance of primary T cells from WBI mice was not completely restored by the normal antigen-presenting cells that abundantly secrete IL-12p70. It was assumed that after WBI, the regenerated T cells also have some problems. It was then observed that the IL-12 receptor expression and intracellular levels of the STAT4 were much lower in the T cells of the WBI mice. The results suggest that the shifted response of the helper T cells after WBI exposure is due not only due to a significant suppression of the secretion of the IL-12p70 in the antigen-presenting cells, but also to the lower expression of the IL-12 receptor on T cells.
已知电离辐射会降低辅助性T（Th）1样功能，但不会降低Th2样功能，从而导致Th1/Th2失衡。虽然这一现象已为人所知有一段时间了，但Th1细胞激活受到优先抑制背后的机制尚未得到解释。目的是阐明电离辐射后Th细胞失衡的机制。7周龄的C57BL/6小鼠接受了5 Gy的全身γ射线照射（WBI）。在所有情况下，照射后7周从小鼠获取脾脏和腹膜细胞。为区分Th1和Th2细胞功能，通过酶联免疫吸附测定（ELISA）分析这些细胞产生的干扰素（IFN）-γ和白细胞介素（IL）-4。为分离原代T细胞，使用抗CD90.2微珠偶联抗体，并通过磁性细胞分选（MACS）分离标记细胞。为研究抗原呈递细胞分泌的IL-12p70的影响，用1%多聚甲醛固定卵清蛋白（OVA）致敏的腹膜黏附细胞（PAC），并在OVA特异性Th细胞存在的情况下，与OVA培养的PAC培养上清共同培养16小时。通过逆转录聚合酶链反应（RT-PCR）检测WBI小鼠T细胞中IL-12受体、信号转导和转录激活因子4（STAT4）以及IFN-γ的表达。WBI小鼠的脾脏淋巴细胞对OVA产生的IFN-γ分泌减少，尽管总的IL-12分泌量很高。然而，具有生物活性的异二聚体IL-12在WBI小鼠中诱导较少。尽管OVA特异性Th细胞与从正常小鼠获得的固定的OVA致敏PAC共同培养，但在来自WBI小鼠的活化PAC的培养上清存在的情况下，OVA特异性Th细胞显示出IFN-γ分泌减少。此外，重组IL-12p70恢复了OVA特异性Th细胞的细胞因子平衡。然而，来自WBI小鼠的原代T细胞的细胞因子平衡并未被大量分泌IL-12p70的正常抗原呈递细胞完全恢复。据推测，WBI后再生的T细胞也存在一些问题。随后观察到，WBI小鼠的T细胞中IL-12受体表达和STAT4的细胞内水平要低得多。结果表明，WBI暴露后辅助性T细胞反应的改变不仅是由于抗原呈递细胞中IL-12p70分泌的显著抑制，还由于T细胞上IL-12受体的低表达。
