| It has been repeatedly demonstrated that Low dose irradiation could activate the immunologic reaction which involves antigen presenting cell and T lymphocytes. The co-stimulatory molecules and cytokines play an important role in the reaction.There have been a few reports about LDR effects between DC and T lymphocytes. In our study, we discussed it on the basis of our previous work. We observed the secretion changes of co-stimulatory molecules and cytokines in the DC/TLC co-culture system in the different dose radiation and compared them with in-vivo system. Furthermore, we got some preliminary results which can explain the effects of ionization on the reaction between DC and T lymphocyte and the possible mechanism of them. Our finding will enrich the immune excited effect theory induced by low dose ionization.1 The effect of ionizing radiation on DC in the DC/TLC co-culture system1.1 The effect of ionizing radiation on the co-stimulatory molecules of DCFlow cytometry (FCM) was used to detect the expression changes of CD80 and CD40 (percentage of positive cells) of DC after 0.075Gy and 2.0 Gy X-ray. The results showed that:The expression of CD80 and CD40 (percentage of positive cells) increased after 0.075Gy X-ray and reached its peak at 48h (p<0.01), but the expression of CD40 decreased after 48h.While after 2.0 Gy X-rays, the expression of CD40 and CD80 decreased with the passage of time (p<0.01).The data indicated that 0.075Gy X-ray can induced the expression of CD40 and CD80 on DC which can submit antigen better. Also, it can improve the immune surveillance and response. However, the 2.0 Gy dose showed the inverse results.1.2 The effect of ionizing radiation on IL-27 of DC in the DC/TLC co-culture system Enzyme-linked immune-sorbent assay (ELISA) was used to detect the changes of IL-27 after different doses of X-rays and different time. The results showed that:the IL-27 took a transient decreased at 12h,then increased and reached its peak at 72h (p<0.05,p<0.01)after 0.075Gy. After 2.0 Gy, it was decreased at 6-24h, and reached its valley at 24h (p<0.01),then increased and reached its peak at 72h (p<0.01).The dose-effect studies elucidated that IL-27 was decreased following 0.05～0.1Gy radiation and reached its valley at 0.075Gy (p<0.05), and then increased gradually, each dose is higher in test group than that in control group (p<0.01)1.3 The effect of ionizing radiation on IL-12 of DC in the DC/TLC co-culture systemELISA was used to detect the changes of IL-12 after different doses of X-rays and different time. The results showed that:there was no change in the secretion of IL-12 within 12h after radiation. IL-12 was increased at 24h and 72h (p<0.01) after 0.075Gy X-ray. While it decreased with the passage time and reached its valley at 48h(p<0.05) after 2.0 Gy X-ray. The dose-effect studies elucidated that IL-12 decreased after 0-0.5Gy and reached its valley at 0.5Gy (p<0.01) then increased, however there was no significant change versus the control.The result may be caused by the non-optimized time which we chose to analysis after different doses of X-rays. So It can not reflect the dose-effect of IL-12 correctly. In the future, we will observe others time points to perfect the dose-effect reaction.In summary, the results suggested that LDR could induce DC to expression more CD40 and CD80, while higher dose radiation could suppress them. At the same time, LDR could induce DC to secrete aplenty of cytokines to enhance immunologic reaction.2. The effect of ionizing radiation on T lymphocytes in the DC/TLC co-culture system2.1 The effect of ionizing radiation on co-stimulatory molecules ofTlymphocytesFCM was used to detect the changes in the expression of CD28 and CD40L of T lymphocytes after different doses of X-rays. The results showed that the expression of CD28 and CD40L (percentage of positive cells) increased significantly after 0.075Gy radiation. While after 2.0 Gy X-ray the expression of CD28 showed a time-dependent decrease. However, CD40L was remained above the level of control, being statistically significant (p<0.01).we conclude that CD28 played a key role in LDR, while CD40/CD40L did not involve in the reaction2.2 The effect of ionizing radiation on IFN-y of TLC in the DC/TLC co-culture systemELISA was used to detect the changes of IFN-y after different doses of X-rays. The result showed that IFN-y was increased after 0.075Gy and reached its peak at 48h (p<0.01). While 2.0 Gy X-rays led to apparent decrease from 6-24h(p<0.01),then took on a transient increase.The dose-effect studies elucidated that IFN-γwas remained above the level of control after 0.05 Gy,0.2Gy,0.5Gy, being statistically significant(p<0.01,p<0.05),and its decreased following 1-4Gy radiation.These results suggested that IFN-y is positive related with the activation of TLC after low dose radiation, because LDR can induce TLC to express more co-stimulatory molecules. This was completely consistent with the previous reports that LDR can induce the mouse splenocytes to secret IFN-y.2.3 The effect of ionizing radiation on TGF-β1 of TLC in the DC/TLC co-culture systemELISA was used to detect the changes of TGF-β1 after different doses of X-rays. The result showed that TGF-β1 was decreased after 0.075Gy and reached its valley at 72h (p<0.01). While 2.0 Gy X-rays induced increased with the passage of time at 6-48h (p<0.01, p<0.05),and then decreased sharply. The dose-effect studies elucidated that TGF-β1was decreased following 0.050-0.500Gy radiation, and then rapidly rose, at 4Gy (p<0.01) it reached its peak.The mentioned results suggested that the IFN-y played an important role in LDR; while the mechanism of high-dose immune suppression was not only with the down-regulation of CD28, but also with the up-regulation of TGF-(31, which is a negative regulator in the immunologic reaction.3. The effects of ionizing radiation on IFN-γ,TGF-β1 and IL-27 of mouse thymocytes and splenocytes ELISA was used to detect the changes of IFN-γ,TGF-β1 and IL-27 after different doses of X-rays.The result showed that IL-27 and IFN-y were increased after 0.075Gy in thymocytes, but TGF-β1 was decreased (p<0.01), IFN-γ,TGF-β1 and IL-27 were increased after 2.0 Gy in thymocytes(p<0.01). However, IFN-γ,TGF-β1 and IL-27 did not change significantly after 0075Gy in splenocytes. After 2.0 Gy IFN-y, TGF-β1 expression increased(p<0.01), but the expression of IL-27 decreased in splenocytes(p<0.01).In summary, we found that LDR can induced CD80/CD28 andCD40/CD40L on DC/TLC and stimulate IFN-y secretion, but inhibit TGF-β1 expression. Combined with our previous results, we conclude that excitatory effect of low doses of immune mechanisms was closely with the co-stimulatory molecules and cytokines on APC/TLC.
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