电磁脉冲辐照后小鼠红细胞形态和电泳率的改变

目的 研究不同场强的电磁脉冲(EMP)对红细胞形态和电泳率的改变,以探讨其量效关系.方法 BALB/c雄性小鼠50只,随机分为5组即50、100、200、400kV/m组和对照组,每组10只.用EMP辐照小鼠,EMP参数为场强0～400kV/m,前沿3ns,脉冲次数200个,脉冲间隔4s.照后小鼠尾部取全血,采用扫描电镜观察受照小鼠红细胞膜表面的形态改变;用显微细胞电泳法,观察红细胞电泳率和胞膜带电性的变化,研究其场强与效应的关系.结果 200kV/m辐照后扫描电镜观察红细胞胞膜上出现多个棘突小泡;各组红细胞膜带电特性均为负电,随着EMP场强(0～400kV/m)的增加,受照小鼠的红细胞电泳率逐渐降低,以照后2h时最为显著,200kV/m、400kV/m组电泳率降低最为显著(P＜0.01),0kV/m组电泳率为0.917±0.040μm·s-1/V·cm-1,这两组电泳率分别降低至(0.600±0.076)μm·s-1/V·cm-1和(0.484±0.064)μm·s-1/V·cm-1.随着照后时间的延长,辐照组细胞电泳率逐渐恢复,照后2天已恢复至正常水平.结论 EMP可引起受照小鼠红细胞膜棘突改变和电泳率降低,EMP场强与红细胞电泳率之间存在一定的量效关系.     

艾氏腹水癌对免疫系统的影响 Ⅲ.宿主免疫器官的组织学变化(摘要)

本文采用了计量组织学的方法来探讨艾氐腹水癌(EAC)带瘤小鼠的胸腺、脾脏和淋巴结的组织学变化。结果发现随着肿瘤的急剧增长,ICR/JCL近交系小鼠的胸腺发生进行性萎缩,皮质日趋变薄,胸腺细胞逐渐排空,但胸腺细胞的有丝分裂指数却是早期升高,晚期下降;上皮性网状细胞相互聚集成团,继而变性坏死;胸腺淋巴管扩张,Hassall′s小体增多。脾脏白髓区的范围和淋巴结胸腺依赖(TD)区中淋巴细胞的数量也出现先增加,后减少的现象。根据上述结果,     

曲酸对辐射损伤小鼠免疫系统的影响

目的：探讨曲酸对辐照后小鼠免疫系统的影响。方法将20只雄性C57小鼠随机分为正常组、模型照射组、曲酸低、高剂量组。正常组动物不做任何处理,其他3组动物在照前27 h分别单次皮下注射无菌蒸馏水、75及300 mg/kg的曲酸溶液,注射体积为0．2 ml/20 g体质量。3组动物经4 Gy 60 Coγ射线单次照射。照后第2天及第8天分两批处死小鼠,分别测定小鼠的脾淋巴细胞转化能力及脾脏和胸腺指数,并制作组织病理学切片观察其形态学变化。结果与模型照射组比较,300 mg/kg曲酸给药组小鼠的脾淋巴细胞转化能力、脾脏和胸腺指数均显著提高（P＜0．01）,而且脾脏和胸腺的组织形态学变化改善明显;与正常组比较,模型照射组小鼠的上述指标均显著受损。结论急性辐射可明显损伤小鼠的免疫系统;曲酸能够增强淋巴细胞的增殖能力,对辐照后小鼠的免疫系统有显著的保护作用。     

自体骨髓在受致死照射小鼠淋巴器官重建中的作用

本文报告了小鼠屏蔽两侧后肢受1000和1200rad照射后周身淋巴组织重建的动态变化.至照后45天,1000rad组外周血T、B淋巴细胞的含量分别相当于对照组的69%和55%;1200rad组在照后30天分别相当于对照组的40.5%和18%.胸腺、淋巴结(肠系膜和腋窝)以及脾脏的白髓都处于重建不良状态.文中对保留大量自体骨髓而淋巴器官重建不良的原因进行了分析. 周围淋巴器官在照后重建过程中出现短期的髓外造血.在照后14～45天,肠系膜淋巴结内出现持续的浆细胞过度增生.文中强调研究肠粘膜免疫辐射损伤的重要性.     

电磁脉冲致大鼠睾丸组织急性损伤的超微结构研究

目的 :通过观察电磁脉冲 (EMP)辐照大鼠后其睾丸组织学及超微结构的急性改变 ,初步探讨EMP致睾丸损伤的特点。方法 :雄性二级Wistar大鼠 2 4只 ,随机分为 6组 ,每组 4只。其中 1组为对照组 ,其余 5组为辐照组。辐照组在高场强电磁脉冲模拟源下 ,以场强为 6× 10 4 V·m-1,脉冲上升时间为 2 0ns,脉宽为 30 μs的条件下 ,在 2min内辐照大鼠 5次 ,对照组不做任何处理 ,辐照后于 1、6、12、2 4和 48h活杀动物 ,电镜制片 ,PHILIPS -CM12 0电镜下观察、拍片。结果 :被辐射组大鼠睾丸精原细胞和间质细胞超微结构 6h后变化明显 ,线粒体水肿、空化、髓样体形成 ;内质网扩张 ;糖原颗粒减少。睾丸间质细胞的内分泌颗粒排空明显。结论 :EMP辐照后早期即可引起大鼠睾丸精原细胞及间质细胞损伤 ,细胞膜系统的损伤及应激反应可能参与了其超微结构损伤过程 ,睾丸间质细胞可能为电磁脉冲损伤的敏感细胞之一     

电磁脉冲对眼辐射损伤的研究

目的 :通过电磁脉冲 (EMP)辐照成年犬 ,长期动态观察角膜、晶状体及视网膜的病理变化 ,探讨EMP对视觉系统的影响。方法 :高场强 (2～ 12 )× 10 4V/m的EMP、1～ 30次辐照实验犬 ,采用Feulgen ,AgNOR和PI染色方法 ,以激光扫描共聚焦显微镜 (LSCM)和图像分析技术进行检测。结果 :EMP辐射可使晶状体上皮细胞AgNOR和DNA含量下降 ,前皮质水肿 ,白内障发生。对EMP损伤敏感程度依次为 :晶状体 >角膜 >视网膜。损伤具有剂量 效应相关性。结论 :高场强EMP可引起犬晶状体前皮质混浊、白内障发生 ,损伤具有剂量 效应相关性。     

慢性长期微波辐照对大鼠外周血T、B淋巴细胞亚群的影响

目的 观察慢性低剂量微波辐照对大鼠外周血T、B淋巴细胞亚群的影响,探讨微波辐射致免疫组织损伤的效应和机制.方法 清洁级雄性Wistar大鼠,按照微波辐照平均功率密度随机分为0(对照)、2.5、5、10mW/cm24组,每天辐照6min,每周5d,连续辐照1个月,于辐照14d后以及连续辐照1个月后的1、30、60、180d活杀大鼠取材.采用血细胞自动分析仪进行外周血白细胞(WBC)计数,流式细胞仪检测胸腺组织中活性氧自由基(ROS)水平,以及大鼠外周血CD3+、CD4+、CD8+T细胞亚群和CD45RA+B细胞亚群的变化.结果 ①连续辐照结束后60d,外周血WBC在2.5mW/cm2组较对照组明显升高(P<0.05),在10mW/cm2组明显降低(P<0.01).辐照后180d,各辐照组WBC较对照组明显降低(P<0.05).②连续辐照14d后,胸腺组织内ROS水平随辐照剂量增加而持续升高,呈较好的剂量-效应关系.辐照1个月结束后的60d,5mW/cm2组ROS水平明显低于对照组(P<0.05).③辐照1个月结束后的1～60d,外周血T细胞亚群变化不明显,但辐照后180d,2.5mW/cm2组CD3+和CD4+T细胞较对照组明显升高(P<0.05),而5mw/cm2组CD8+T细胞较对照组明显降低(P<0.05).各辐照组CD4+/CD8+比值虽然在辐照后180d出现升高趋势,但与对照组比较未见统计学差异.④辐照后60d,5mW/cm2组外周血CD45RA+B淋巴细胞较对照组明显增加(P<0.01),而辐照后180d,各辐照组CD45RA+B细胞却明显低于对照组(P<0.05,P<0.01).结论 大鼠经长期低剂量微波辐照后,免疫功能在早期改变不明显,晚期损伤较为明显,外周血WBC和CD45RA+B淋巴细胞在辐照后180d明显减少.     

小鼠脾脏树突状细胞的分布与形态学观察

目的:认识脾脏树突状细胞的含量、分布及形态特征.方法:运用光镜、电镜观察,免疫组化标记(CD11c、CD205、CD80与CD86、I-Ab)与免疫荧光标记方法,观察小鼠脾脏树突状细胞的含量、分布与形态结构.结果:小鼠脾脏白髓与红髓中散在分布着体积较大的不规则形树突状细胞,含量以白髓边缘区最多,依次为白髓和红髓脾索.CD11c DC约占脾脏细胞总数的3%,而CD205 DC约占脾脏细胞总数的2‰.脾脏树突状细胞表面形成数个胞浆突起.胞核略长多有凹陷.胞浆低电子密度,细胞器不发达,无溶酶体和吞噬体.结论:多种树突状细胞标志物联合标记,结合光、电镜形态学观察,能够较全面反映小鼠脾脏内树突状细胞的形态分布特征,为树突状细胞研究提供了形态学依据.     

长期微波辐照对大鼠脾脏淋巴细胞的影响

目的 观察不同强度微波长期辐照对大鼠脾脏淋巴细胞的影响,探讨长期微波辐照对脾脏淋巴细胞的损伤效应及其机制.方法 雄性清洁级Wistar大鼠90只,按平均微波辐照功率密度随机均分为0(对照)、2.5、5、10mW/cm2四组(n=25),连续辐照1个月(6min/d,5d/周).于辐照结束后1、30、60、180d取材,观察大鼠体重、脾脏指数及脾脏T、B淋巴细胞亚群的变化.结果 辐照后7～180d各辐照组大鼠体重明显低于对照组.辐照后1d,2.5和5mW/cm2组脾脏系数均显著升高(P<0.05),辐照后30d 5mW/cm2组脾脏系数显著降低(P<0.05),至辐照后60d和180d各辐照组脾脏系数基本恢复到对照组水平.辐照后1、30、60d,各组大鼠脾脏T细胞亚群均无明显改变;辐照后180d,各辐照组大鼠脾脏T细胞亚群明显降低,其中2.5mW/cm2组CD3+T细胞明显减少,SmW/cm2组CD3+、CD4+、CD8+T细胞明显减少,10mW/cm2组CD4+和CD8+T细胞明显减少、CD4+/CD8+比值明显降低(P<0.05或P<0.01).CD45RA+B细胞未见明显改变.结论 大鼠经长期低剂量微波辐照后早期脾脏淋巴细胞亚群改变不明显,晚期(辐照后180d)脾脏T淋巴细胞各亚群均显著降低,表现为明显的免疫抑制.     

分割照射对肝癌移植瘤小鼠脾脏免疫细胞的影响

目的探讨肝癌皮下移植瘤小鼠的分割照射对远端脾脏组织的影响。方法构建荷瘤C57BL/6 J小鼠模型,取对数期生长的小鼠肝癌细胞Hepa 1-6接种于小鼠右侧皮下(1×10^7/只),荷瘤小鼠按随机数表法分为荷瘤对照组和照射组,每组20只。另设10只健康小鼠作为健康对照组。照射组皮下肿瘤给予8 Gy×3次X射线局部照射,剂量率为0.883 Gy/min。照射后第7、14天检测小鼠肿瘤脏器指数、脾脏脏器指数、脾脏病理学改变,以及脾脏T淋巴细胞亚群、B淋巴细胞亚群、NK细胞的变化。结果与荷瘤对照组相比,照后7、14 d,照射组小鼠肿瘤脏器指数显著降低(t=4.649、26.34,P<0.05),脾脏中NK细胞显著升高(t=3.952、3.633,P<0.05),CD3+、CD4+、CD3+CD4+淋巴细胞以及CD4+/CD8+比值在照后7 d显著降低(t=3.193、3.656、3.219、2.641,P<0.05),CD3+淋巴细胞在照后14 d显著降低(t=3.031,P<0.05),其余指标脾脏脏器指数、B淋巴细胞、CD3+CD4+淋巴细胞、CD8+淋巴细胞变化不显著。结论肿瘤局部照射可引起远隔器官内淋巴细胞比例失衡,导致机体免疫力下降,为放疗免疫损伤提供了新的诠释。     

Induction of apoptotic cell death in rat thymus and spleen after a bolus injection of methamphetamine

We examined whether methamphetamine (MAP) induced apoptotic cell death in vivo. Male Wistar rats were injected intraperitoneally with 25 mg MAP/Kg body weight and were sacrificed at 4, 8 and 24 h. As early as 4 h after a single dose of MAP, DNA ladder bands representing DNA fragmentation into multiples of the internucleosomal DNA length of about 180 by were observed by gel electrophoresis in thymic and splenic DNA. DNA from control rats injected with 1 ml physiological saline/Kg body weight showed no ladder band patterns. The proportion of fragmented DNA from the thymus increased in a time-dependent manner up to 8 h and faint ladder band patterns were observed at 24 h, indicating that cell death via apoptosis occurred at an early stage and then apoptotic bodies were scavenged. DNA fragmentation in the thymus and spleen induced with MAP was also confirmed by the terminal deoxynucleotidyl transferase-mediated dUTPbiotin nick end labeling (TUNEL) method in situ. In control thymus samples, stained cells were numerous in the cortex but sparse in the medulla. At the boundary area between the cortex and medulla, stained cells were seen as a layer. In the MAP-treated rats, stained cells were increased and dispersed equally in the cortex and medulla. In control spleen samples, stained cells were numerous in all areas excluding the germinal centers. Cells at the germinal centers were stained intensively in MAP-treated rat spleen. Light microscopical analyses allowed us to identify lymphocytes during the course of apoptotic cell death. Electron microscopic studies showed morphological landmarks for the process of cellular apoptosis in both organs e.g. lymphocytes with chromatin condensed into crescents at the periphery of the nuclei and apoptotic bodies. These results indicate that MAP induced cell death of the thymic and splenic lymphocytes via apoptosis.     

Radiation and Hormone Effects Upon Lymphocyte Release from Isolated Perfused Dog Spleens

Summary

Studies on lymphocyte release from isolated perfused dog spleens following administration of adrenal extracts and irradiation indicate that the rate of cell release was proportional to the perfusion flow-rate and independent of hormone dosage. The hormone-induced cell release into the perfusate was eliminated by 100 r of x-irradiation to the spleen during perfusion, causing lymphocytolysis in situ; but 200 r of whole-body ⁶⁰Co irradiation two to four days prior to splenectomy did not prevent lymphocyte release under the influence of adrenal cortex extract.

Treatment with A.C.E. caused white-pulp hypoplasia. Marked pyknosis of white pulp and perfusate lymphocytes was observed within two hours following 100 r or x-irradiation. A synergism of effect upon the spleen was noted when irradiation and steroid hormones were administered within short intervals of each other. The lymphocytes released into the perfusate appeared to originate in the bands of medium-sized lymphocytes in the splenic white pulp. Perfusion did not impair reticulo-endothelial efficiency.     

多器官衰竭早期免疫器官细胞凋亡的检测及意义

用大鼠腹腔注射酵母多糖的方法复制出多器官衰竭（ＭＯＦ）实验模型，动用透射电镜与原位细胞ＤＮＡ末端标记方法（ＴＵＮＥＬ），研究ＭＯＦ大鼠细胞凋亡现象与规律。结果表明：ＭＯＦ早期大鼠细胞凋亡异常增多且以免疫器官细胞凋亡为主，电镜所见之细胞及凋亡小体与ＴＵＮＥＬ标记性细胞主要分布于胸腺皮质、脾白髓和淋巴结副皮质区。提示：ＭＯＦ早期免疫器官大规模淋巴细胞凋亡与ＭＯＦ启动机制有重要关系。     

Release and retention of labelled DNA in the thymus and spleen of irradiated mice.

The process of release and retention of labelled DNA in thymus and spleen of normal and irradiated (60Co) mice has been studied after administration of 3H-thymidine. The results indicate that the dividing fraction of lymphoid cells is more resistant to radiation than the fraction of nondividing lymphocytes. The time courses of the specific activities of DNA in thymus and spleen were different especially after irradiation with lethal doses. It is suggested that the process of depletion in the lymphoid series is probably similar for both thymus and spleen but, the different cellular composition of these organs led to apparently unrelated results.     

新分离呼肠病毒BYD1株实验感染食蟹猴的病理学改变及发病机制

目的：系统观察新分离呼肠病毒感染食蟹猴的病理学变化，探讨其发病机制。方法：用从SARS患者分离的呼肠病毒BYD1株通过滴鼻和静脉注射两种途径，感染4只食蟹猴(每组2只)。每组分别在感染后7d和33d各处死1只，进行肺脏、心肌、肝脏、脾脏、肾脏、肠、脑和淋巴等组织病理学检查。结果：肉眼观察感染猴肺组织可见水肿和红白相间的实变。病理组织学变化主要集中在肺脏、脾脏、淋巴结和全身小静脉。肺脏表现局部肺泡腔出血，并有蛋白液渗出。肺泡间隔充血、淤血、水肿，导致肺泡壁增厚。支气管上皮细胞和黏膜纤毛脱落，支气管周围单核细胞浸润。脾脏、淋巴结白髓减少，红髓淤血，发生中心淋巴细胞数量减少。全身组织器官小静脉明显淤血。结论：食蟹猴实验感染呼肠病毒BYD1株后，出现间质性肺炎，脾脏、淋巴结萎缩和全身小静脉淤血等一系列组织病理学特征。病毒感染后，受侵害肺脏出现血氧交换障碍和免疫器官功能下降是导致食蟹猴发病的内在机制。新分离的呼肠病毒感染食蟹猴出现的病理学变化提示可以作为严重呼吸综合征的病理学模型。     

Long-term exposure of Sprague Dawley rats to 20 kHz triangular magnetic fields

PURPOSE: There are only a few reports on harmful effects of 20 kHz sine waves; however, it is essential to comprehensively evaluate the potentially harmful effect of triangular signals at the same frequency. Therefore, in this study, effects of long-term exposure to 20 kHz magnetic fields was examined. MATERIALS AND METHODS: Eighty Sprague Dawley rats were divided into two groups (half male and female in each sham and exposed groups), and they were exposed to 20 kHz triangular magnetic fields at 6.25 microT rms for 8 h/day for 12 or 18 months. Urinalysis [pH, glucose, protein, ketone bodies, red blood cells (RBC), nitrogen, bilirubin, urobilinogen, and specific gravity], hematological analysis (RBC, hemoglobin, hematocrit, thrombocyte count, and leucocyte count), blood biochemistry (total protein, blood urea nitrogen, creatinine, glucose, total bilirubin, total cholesterol, aspartate aminotransferase, alanine aminotransferase, and alkaline phosphatase), and histopathological analysis of organs (thymus, stomach, intestine, liver, kidney, testis, ovary, spleen, brain, heart, and lung) were performed. RESULTS: No significant differences were seen between 20 kHz magnetic-fields exposed rats and sham-exposed rats in body and organ weights, hematological analysis, blood biochemistry, urinalysis data, and histopathological examination, except for the numbers of neutrophiles and lymphocytes in female rats. The number of neutrophiles was significantly increased in female rats on the 12th month after exposure, and the number of lymphocytes in female rats was significantly decreased on the 18th month. CONCLUSION: Long-term exposure of rats to 20 kHz triangular magnetic fields did not induce any significantly harmful effects, except changes in neutrophiles at 12 months and lymphocytes at 18 months of exposure in female rats. These hematological changes need to be investigated again at a higher intensity of 20 kHz magnetic fields.     

EPR study of mouse tissues in search for adaptive responses to low level whole-body X-irradiation.

Effect of a low dose of whole-body X-irradiation (D1 = 0.075 Gy) of mice on some biochemical changes induced in the spleen and thymus by a subsequent challenge dose (D2 = 1.5 Gy) was studied by electron paramagnetic resonance (EPR). Kunming and SHK mice were used. Concentration of ribonucleotide reductase (RR) in the spleen and thymus of unirradiated Kunming mice was 0.70 and 0.46 microM respectively, and of unirradiated SKH mice--0.37 and 0.21 microM respectively (systematic error 45%). For mice exposed only to the low dose (D1 group), a stimulating effect on RR activity in spleen and thymus was found, while in mice subjected only to the D2 dose (D2 group) activity of the enzyme in the organs decreased considerably 18 h after irradiation. The group of mice irradiated with D1 and D2 doses, given at a 6-h interval (D1 plus D2 group), showed a RR activity in the organs lower than D1 and higher than D2 groups. This finding indicates that there exists an adaptation-like response to a low-dose whole-body irradiation in murine spleen and thymus. This low 'inductive' dose makes the organs' RR less susceptible to inhibition induced by a subsequent challenge dose. Preliminary results showed that the same kind of response is probably a characteristic of the RR content of splenocytes as well as of the rate of thymidine incorporation into splenocytes. 5-Thyml radicals of DNA (TH radicals) induced in whole tissues by gamma-irradiation in vitro at 77 K were also studied. Radiochemical yield of these radicals (4.0 and 5.3 nmol j-1), for spleen and thymus respectively of unirradiated Kunming mice, and 2.3 and 2.6 nmol J-1, for spleen and thymus respectively of unirradiated SHK mice (systematic error 30%), decreased significantly in both organs upon D2 irradiation. This decrease, however, was the consequence of DNA content diminishing upon D2 irradiation rather than change of DNA radiosensitivity: the beta value of TH radicals, i.e. yield of radicals per unit mass of DNA in each organ was equal for the mice from all D1, D1 plus D2, D2 and control groups. The beta values of TH radicals in mouse spleen and thymus were of the same order of magnitude compared with the yield of the single-strand breaks of DNA measured previously in rat organs just after whole-body irradiation, i.e. about 1 x 10(2) (Gy x 10(12) Da)-1.     

Alterations of immune functions induced by 12C6+ ion irradiation in mice

PURPOSE: To estimate the biological risks to the immune system of the type of space radiation, 12C6+, encountered by cosmonauts during long-term travel in space. MATERIALS AND METHODS: The Kun-Ming strain mice were whole-body irradiated by 12C6+ ion with 0, 0.01, 0.05, 0.075, 0.2, 0.3, 0.5, 0.75, 1 or 2 Gy, at a dose rate of 1 Gy/min. At 35 days after irradiation, the thymus and spleen weights were measured, the natural killer (NK) cells activity of spleen was determined by 3-(4, 5-dimethylthiazol-2-yl)- 2, 5-diphenyl tetrazolium bromide (MTT), and the interferon-gamma (IFN-gamma) levels in serum and thymus were detected with enzyme-linked immunosorbent assays (ELISA). RESULTS: The results showed that the thymus weight, IFN-gamma levels in serum and the activity of splenic NK-cells had significantly increased at a dose of 0.05 Gy. With further dose increase, the weight of spleen continued to increase but the weight of thymus, IFN-gamma level and NK-cells activity declined. CONCLUSIONS: These results suggest that the dose of 0.05 Gy irradiation has a stimulatory effect on mouse immunity; this effect declined with increasing dose.     

小鼠胸腺树突状细胞的分布与形态学观察

目的研究小鼠胸腺树突状细胞的分布与形态。方法运用光镜、电镜和树突状细胞标志物(CD205、CDla与MIDC-8)免疫组化标记方法观察小鼠胸腺树突状细胞的分布、含量与形态。结果小鼠胸腺树突状细胞在皮髓交界区分布最多，然后依次为皮质区和髓质区。树突状细胞约占胸腺细胞总数的2％。胸腺树突状细胞表面形成胞浆突起向，周围包绕的淋巴细胞间延伸，核不规则，多有凹陷，胞浆低电子密度，细胞器稀少且不含溶酶体。结论多种树突状细胞标志物联合标记，结合光镜、电镜形态学观察，可以有效地计数并显示胸腺树突状细胞的形态特征。     

Flt3配体联合其他细胞因子对受照射小鼠免疫系统的作用研究

目的：研究Flt3配体（FL）在受照射小鼠免疫系统恢复中的作用。方法：采用F－800血细胞自动计数仪行外周血细胞计数及血细胞分类计数，流式细胞仪分析外周血淋巴细胞表型。结果：照射前应用FL或照射后联合应用FL，IL－11，EPO和G－CSF等细胞因子，能有效地促进受照小鼠外周血白细胞和淋巴细胞的恢复，对CD8^ 细胞的恢复作用尤为明显，同时使CD4^ /CD8^ 细胞比值较早恢复正常，提高受照射小鼠的生存率，结论：FL不但能促进辐射损伤机体造血功能的恢复，对免疫系统的亦具有重要的作用，FL单独或与其他细胞因子联合应用，对辐射损伤动物具有明显的防护和治疗效应。