血红素氧合酶-1在早期腹主动脉瘤中的动态表达

目的探讨早期腹主动脉瘤(AAA)的发病机制。方法建立大鼠腹主动脉瘤模型,于术后3、7、14、28d取材,观察主动脉的扩张情况,弹力纤维染色观察弹力纤维的损伤;原位分子杂交检测动脉壁中血红素氧合酶(HO)1mRNA的动态表达,免疫组织化学染色检测细胞间黏附分子(ICAM)-1及巨噬细胞特异性抗原CD68的蛋白表达。结果在AAA组织中,HO1mRNA表达于3d出现,14d达到高峰,为(33.9±6.9)%,与其他时段相比,差异有统计学意义(P<0.01)。ICAM1及CD68蛋白表达分别于7、14d达到高峰(P<0.01)。结论HO-1在早期腹主动脉瘤组织中表达增强,伴随着弹力纤维损伤和炎性细胞浸润。     

单核细胞趋化蛋白-1基因表达在实验性腹主动脉瘤发病过程中的意义

目的　探讨实验性腹主动脉瘤 (abdominalaorticaneurysm ,AAA)不同阶段 ,动脉壁中单核细胞趋化蛋白 1(monocytechemotacticprotein 1,MCP 1)基因的表达及意义。方法　经腔内导管灌注制成大鼠AAA模型 ,分别于 3d、1、2、4周切取腹主动脉 ,应用原位杂交、Western蛋白质印迹、CD6 8免疫组织化学染色观察AAA发病不同时期动脉壁中MCP 1基因表达情况及巨噬细胞的浸润程度。结果　MCP 1mRNA表达于灌注后 1周达高峰 ,阳性率为 39 5 %± 7 5 % ;CD6 8、MCP 1蛋白表达均于灌注后 2周达高峰 ,与其他时段相比 ,差异有非常显著意义 (P <0 0 1)。结论　动脉壁中MCP 1基因做为AAA发病过程中的一种早期表达基因 ,诱导了单核巨噬细胞在动脉壁的黏附、浸润 ,对AAA的发生、发展起着重要的促进作用。     

二甲双胍对血管紧张素Ⅱ诱导的ApoE~(-/-)小鼠腹主动脉瘤形成的影响

目的:研究二甲双胍对血管紧张素Ⅱ诱导的ApoE基因敲除小鼠腹主动脉瘤形成的炎性机制的影响。方法:8~10周龄雄性ApoE~(-/-)小鼠随机分为Control组,AAA组,AAA+MET3组,采用皮下埋置AngⅡ胶囊渗透压泵的方式构建小鼠腹主动脉瘤动物模型。28d后取材,检测腹主动脉最大直径以及AAA发生率。HE以及免疫组织化学染色分析炎症细胞浸润情况,qPCR技术检测腹主动脉中ICAM-1表达,WesternBlot技术检测腹主动脉中NF-κB表达变化。结果:AAA+MET组腹主动脉最大直径以及AAA发生率均低于AAA组;AAA+MET组炎症细胞以及巨噬细胞浸润少于AAA组;应用二甲双胍后,小鼠腹主动脉瘤动物模型中ICAM-1表达以及NF-κB表达均显著降低。结论:二甲双胍可以抑制组织中NF-κB信号通路激活,下调ICAM-1的表达,并进一步抑制巨噬细胞聚集,减轻血管壁炎症反应,从而抑制AAA发展。     

氯血红素对腹主动脉瘤形成的抑制作用的实验研究

目的探讨血红素氧合酶-1（HO-1）基因在大鼠腹主动脉瘤（AAA）形成中的作用及机制。方法大鼠随机分成氯血红素组（实验组）和生理盐水组（对照组），建立腹主动脉瘤模型，于术后7d取材，观察主动脉的扩张情况，免疫组化染色检测细胞间黏附分子（ICAM）-1及HO-1的蛋白表达。原位分子杂交检测动脉壁中HO-1mRNA的表达。结果实验组动脉扩张受到抑制，未形成AAA（P〈0．01）；其HO-1mRNA和HO-1的蛋白表达增强（P〈0．05）；ICAM-1蛋白表达受到抑制（P〈0．01）。结论氯血红素通过促进HO-1过表达，抑制ICAM-1蛋白表达，从而抑制腹主动脉瘤的形成．     

趋化因子RANTES在腹主动脉瘤形成中的作用

目的探讨调节活化正常T细胞表达和趋化因子RANTES在腹主动脉瘤(AAA)形成中的作用。方法将Wistar大鼠56只随机分成7组,灌注法建立AAA模型。A组不灌注。E、F、G组腹腔注射吡咯烷二硫代氨基甲酸酯(PDTC)。分别在术后4、7、14d取标本。用苏木素伊红(HE)及免疫组织化学染色观察动脉壁炎性细胞浸润及RANTES的表达,并用逆转录聚合酶链反应(RTPCR)观察RANTESmRNA的表达。结果术后7d,RANTES及RANTESmRNA的表达最高,分别为(44.73±6.81)%和(81.58±5.73)%。术后14d形成AAA,动脉扩张率为(113.73±5.75)%。在E、F、G组,RANTES的表达受到抑制(P<0.05),且术后14d没形成AAA。结论RANTES在AAA形成之前表达升高,促进了AAA的形成。     

一氧化氮、诱导性一氧化氮合酶在实验性大鼠腹主动脉瘤中的作用

目的:探讨一氧化氮(NO)和诱导性一氧化氮合酶(iNOS)在实验性大鼠腹主动脉瘤形成中的作用和机制.方法:建立大鼠腹主动脉瘤灌注模型,对照组予以生理盐水腹主动脉灌注,余下予以猪胰弹性蛋白酶灌注制作腹主动脉瘤模型,并分为实验组(术后腹腔注射生理盐水)、药物组(术后腹腔注射氨基胍),观察各组大鼠血清NO、腹主动脉瘤壁组织学和基质金属蛋白酶-9(MMP-9)、iNOS的变化.结果:生理盐水灌注组大鼠术前术后血清NO无明显变化,iNOS、MMP-9表达弱阳性或阴性,动脉壁炎性细胞浸润轻、弹性蛋白降解少;实验组血清NO显著升高,iNOS及MMP-9表达强阳性,炎性细胞浸润重、弹性蛋白几乎完全降解;应用氨基胍后iNOS变化不明显,而NO显著降低,MMP-9表达显著减弱,炎性细胞浸润和弹性蛋白降解明显减轻.结论:iNOS、MMP-9的表达和血清NO水平在实验组均显著升高.iNOS及其合成的NO能促进腹主动脉壁炎性细胞的浸润、中膜基质的降解和MMPs的表达,从而导致了腹主动脉瘤的生成.     

巨噬细胞浸润在腹主动脉瘤发病中的作用

腹主动脉瘤(abdominal aortic aneurysm，AAA)是一种主动脉局限性扩张性疾病。虽然临床上能通过主动脉重建手术或腔内隔绝术对其进行有效治疗，但因为其发病机制尚未完全清楚，将直接影响对AAA的早期防治效果。目前在AAA的病因学研究中，炎性细胞浸润与AAA发病的关系正受到国内外学者的广泛重视。本文对炎性细胞中的一种主要成分——巨噬细胞参与AAA形成的各种作用作一概述。     

改良腹主动脉瘤大鼠模型的制作方法

目的 介绍一种改良腹主动脉腔内灌注猪胰蛋白酶（PPE）制作腹主动脉瘤（AAA）大鼠模型的方法。方法 将20只SD大鼠随机为两组,分别是改良腹主动脉腔内灌注PPE组和传统腹主动脉腔内灌注PPE组,每组10只。通过超声测量腹主动脉直径,比较两组大鼠的手术相关指标,大鼠存活率,术后7、14d的AAA成瘤率和腹主动脉扩张率。通过弹性纤维染色和免疫组织化学染色（IHC）染色法观察腹主动脉弹性纤维情况和炎性细胞浸润情况。结果 改良腹主动脉腔内灌注PPE组的手术时间明显短于传统腹主动脉腔内灌注PPE组,每只大鼠的PPE用量明显少于传统腹主动脉腔内灌注PPE组,差异均有统计学意义（P﹤0.01）。术后14 d,两组的大鼠存活率比较,差异无统计学意义（P﹥0.05）。术后7 d,改良腹主动脉腔内灌注PPE组的腹主动脉扩张率、AAA成瘤率均高于传统腹主动脉腔内灌注PPE组,差异均有统计学意义（P﹤0.05）;术后14 d,改良腹主动脉腔内灌注PPE组的腹主动脉扩张率明显高于传统腹主动脉腔内灌注PPE组,差异有统计学意义（P﹤0.01）,但两组的AAA成瘤率比较,差异无统计学意义（P﹥0.05）。改良腹主动...     

腹主动脉瘤发病中低氧诱导因子-1α介导血管平滑肌细胞凋亡的研究

目的　研究腹主动脉瘤 (AAA)发病不同时期动脉壁中低氧诱导因子 (HIF) 1α的表达及与血管平滑肌细胞 (SMC)凋亡的关系。方法　将 60只Wistar大鼠制成AAA模型 ,分别于术后 1、3、7、14、2 1d切取腹主动脉 ,应用原位DNA片段末端标记 (TUNEL)检测SMC中的凋亡信号 ,用免疫组织化学方法检测HIF 1α及凋亡相关基因p5 3、bcl 2的蛋白表达。结果　HIF 1α的表达于术后 3d达表达高峰 ,为 (18.4± 3 .5 ) % ;术后 7d左右是TUNEL染色及p5 3蛋白表达的高峰时段 ,分别为(19.8± 3 .8) %、(17.6± 3 .3 ) % ;bcl 2蛋白在术后 1d时表达较强烈 ,为 (14 .1± 2 .9) %。结论　HIF 1α参与了腹主动脉缺血缺氧状态下的继发损害过程 ,并可通过调节动脉壁中p5 3、bcl 2的蛋白表达水平促进SMC的凋亡 ,是AAA发病过程中一个重要的中间因子。     

腹主动脉瘤动脉壁血管平滑肌细胞增殖及凋亡的研究

目的研究腹主动脉瘤 (abdominalaorticaneurysm ,AAA)在发病不同时期动脉壁平滑肌细胞 (smoothmusclecells,SMC)增殖与凋亡的改变。方法建立大鼠AAA模型 ,分别于术后 3d、1、2、3、4周切取腹主动脉 ,应用原位DNA片段末端标记 (TUNEL)和免疫组织化学方法检测腹主动脉壁中SMC凋亡和相关基因bcl 2、bax蛋白以及增殖细胞核抗原 (PCNA)、α 血管平滑肌肌动蛋白(α actin)的表达。结果TUNEL及PCNA表达高峰时段分别为术后 2～ 3周和 1周 ;术后 3d至 1周凋亡细胞少于PCNA阳性SMC ,2～ 4周多于PCNA阳性SMC且SMC数量明显减少 ;bcl 2与bax蛋白表达分别于术后 1、3周达到峰值 (P <0 0 1)。结论动脉壁SMC增殖和凋亡的失衡与AAA发病密切相关 ;bcl 2与bax基因参与了对AAA动脉壁中SMC凋亡的调控。     

硫酸寡聚糖复合物对实验性腹主动脉瘤的抑制作用

目的 观察乙酰肝素酶抑制剂PI-88对腹主动脉瘤形成的抑制作用。方法 利用豚鼠-SD大鼠异种移植腹主动脉瘤模型，于移植术后4周内连续PI-88治疗；术后4周利用Northem blot杂交和免疫组化技术，检测移植腹主动脉直径、乙酰肝素酶表达、微血管增生及炎性细胞浸润程度。结果 与非治疗组相比，治疗组腹主动脉乙酰肝素酶表达、移植血管直径、微血管增生及炎性细胞浸润程度均显著降低，但仍高于阴性对照组。结论 PI-88可通过抑制乙酰肝素酶作用，控制腹主动脉瘤形成。     

Tamoxifen up-regulates catalase production, inhibits vessel wall neutrophil infiltration, and attenuates development of experimental abdominal aortic aneurysms

BACKGROUND: Selective estrogen receptor modulators (SERMs), similar to estrogens, possess vasoprotective effects by reducing release of reactive oxygen species. Little is known about the potential effects of SERMs on the pathogenesis of abdominal aortic aneurysms (AAAs). This study's objective was to investigate the growth of experimental AAAs in the setting of the SERM tamoxifen. METHODS: In the first set of experiments, adult male rats underwent subcutaneous tamoxifen pellet (delivering 10 mg/kg/day) implantation (n = 14) or sham operation (n = 16). Seven days later, all animals underwent pancreatic elastase perfusion of the abdominal aorta. Aortic diameters were determined at that time, and aortas were harvested 7 and 14 days after elastase perfusion for immunohistochemistry, real-time polymerase chain reaction, Western blot analysis, and zymography. In the second set of experiments, a direct irreversible catalase inhibitor, 3-amino-1,2,4-triazole (AT), was administered intraperitoneally (1 mg/kg) daily to tamoxifen-treated (n = 6) and control rats (n = 6), starting on day 7 after elastase perfusion. Aortic diameters were measured on day 14. In a third set of experiments, rats were perfused with catalase (150 mg/kg) after the elastase (n = 5), followed by daily intravenous injections of catalase (150 mg/kg/day) administered for 10 days. A control group of rats (n = 7) received 0.9% NaCl instead of catalase. RESULTS: Mean AAA diameters were approximately 50% smaller in tamoxifen-treated rats compared with sham rats 14 days after elastase perfusion (P = .002). The tamoxifen-treated group's aortas had a five-fold increase in catalase mRNA expression (P = .02) on day 7 and an eight-fold increase in catalase protein on day 14 (P = .04). Matrix metalloprotroteinase-9 activity was 2.4-fold higher (P = .01) on day 7 in the aortas of the controls compared to the tamoxifen-treated group's aortas. Tamoxifen-treated rats had approximately 40% fewer aortic polymorphonuclear neutrophils compared to controls on day 7 (P = .05). Administration of the direct catalase inhibitor AT to tamoxifen-treated rats partially reversed the aneurysm inhibitory effect of tamoxifen by nearly 30% (P = .02). In contrast, catalase administration inhibited AAA formation by 44% (P = .002). CONCLUSIONS: The selective estrogen receptor modulator tamoxifen inhibits the development of AAAs in male rats in association with an up-regulation of catalase and inhibition of aortic wall neutrophil infiltration.     

Aortic wall cell proliferation via basic fibroblast growth factor gene transfer limits progression of experimental abdominal aortic aneurysm

OBJECTIVE: Our previous study demonstrated that high flow conditions stimulated cell proliferation in the aortic wall in a rat model of abdominal aortic aneurysm (AAA), and we speculated that there is a possible relation between medial cell density and aortic wall integrity. In the present study we delivered the basic fibroblast growth factor (bFGF) gene to the aortic wall of a rat AAA model and evaluated the effects of growth factor-enhanced smooth muscle cell (SMC) proliferation on aneurysm progression. METHODS: AAA was induced in rats by means of infusion of porcine pancreatic elastase. Immediately after elastase infusion the abdominal aorta was filled with an expression plasmid vector containing the bFGF gene (bFGF group) or LacZ gene (control group); then gene transfer to the aortic wall was carried out with an in vivo electroporation method. The animals were killed 7 days after treatment, and the aneurysm was measured. The numbers of SMCs, macrophages, and endothelial cells were counted with immunostaining, and cell replication was evaluated with bromodeoxyuridine (BrdU) staining. RESULTS: Aneurysm diameter in the bFGF group was significantly smaller than that in the control group (4.6 +/- 0.3 mm vs 6.5 +/- 1.4 mm; P <.01). The numbers of medial SMCs and BrdU-incorporated cells in the bFGF group were significantly greater than those in the control group (SMC, 101 +/- 34 per high-power field [hpf] vs 80 +/- 31/hpf; P <.05, BrdU, 107 +/- 63/hpf vs 50 +/- 33/hpf; P <.05), whereas no difference was detected in the numbers of macrophages and endothelial cells between the 2 groups. CONCLUSIONS: Delivery of bFGF to the aortic wall induced significant enhancement of medial SMC proliferation, without an increase in inflammatory infiltration, then successfully limited aneurysm enlargement. These findings suggest that increased medial cellularity inhibits aneurysm formation, which possibly offers a clue for developing a new strategy for treatment of AAAs.     

Inflammatory abdominal aortic aneurysm: close relationship to IgG4-related periaortitis

Inflammatory abdominal aortic aneurysm (AAA) is a member of a family of disorders referred to as "chronic periaortitis" together with retroperitoneal fibrosis. Retroperitoneal fibrosis is included in IgG4-related disease, which is characterized by numerous infiltrating IgG4-positive plasma cells and high serum IgG4 concentrations. However, the relationship between IgG4-related disease and inflammatory AAA has not been documented. In this study, we examined the clinicopathologic characteristics of inflammatory (10 cases) and atherosclerotic (22 cases) AAAs, based on the hypothesis that inflammatory AAA might be related to IgG4-related disease. Cases of inflammatory AAA could be classified into 2 groups based on immunostaining of IgG4. Four patients showed diffuse infiltration of abundant IgG4-positive plasma cells (IgG4-related cases), whereas the remaining 6 cases of inflammatory AAA and all cases of atherosclerotic AAA had only a few IgG4-positive plasma cells (non-IgG4-related cases). IgG4-related inflammatory AAA was pathologically characterized by the frequent infiltration of eosinophils, lymph follicle formation, perineural inflammatory extension, and inconspicuous infiltration of neutrophils compared with non-IgG4-related inflammatory AAA. Obliterative phlebitis, which is venous occlusion with inflammatory cell infiltration, is observed in all IgG4-related cases. In addition, serum IgG4 concentrations were significantly higher in IgG4-related inflammatory AAA (109 to 559 mg/dL, normal range: 4 to 110 mg/dL) than non-IgG4-related inflammatory AAA (32 to 59 mg/dL) and all atherosclerotic AAA (12 to 83 mg/dL). In conclusion, inflammatory AAAs might be classified into 2 groups: IgG4-related or nonrelated. The former might be one of the IgG4-related diseases, and could be included in IgG4-related periaortitis together with retroperitoneal fibrosis.     

腹主动脉瘤发病机理的实验研究 Ⅱ.基质金属蛋白酶-9在大鼠腹主动脉瘤模型中的动态表达

目的 :检测MMP 9在大鼠正常动脉及动脉瘤模型组织中的动态表达 ,以探讨其在腹主动脉瘤发病机制中的作用。方法 :Wistar大鼠 5 4只 ,随机均分为 1组正常对照组、4组灌注对照组和 4组实验组。实验组腹主动脉灌注弹力蛋白酶 (2 5U ml) 2ml,灌注对照组灌注生理盐水 2ml,分别于术前、术后即刻、2d、7d、14d测量腹主动脉直径 ,并采用免疫组织化学和分子原位杂交技术动态检测腹主动脉组织中MMP 9的表达。结果 :正常及灌注对照组腹主动脉组织中均未发现MMP 9,而实验组弹力蛋白酶灌注后2～ 14dMMP 9均有不同程度升高 ,第 7d达到高峰 ,第 14d有所回落。结论 :MMP 9分泌的增加可能与炎症反应有关 ,且为腹主动脉瘤形成中不可或缺的一步。     

中性粒细胞炎性反应在腹主动脉瘤发病机制中的研究进展

腹主动脉瘤（AAA）是成年人主动脉破裂导致死亡的重要原因,其发病机制尚未完全阐明,且缺乏切实有效的药物治疗手段。作为先天免疫系统的首要防线,中性粒细胞在循环系统白细胞中占据70%的比例。中性粒细胞可通过吞噬、脱颗粒、产生活性氧以及形成中性粒细胞胞外诱捕网（NETs）等机制,参与炎症反应。多项研究表明,中性粒细胞参与无菌性炎症和血栓形成,且过度活化的中性粒细胞也可杀伤正常组织和细胞,造成疾病发生,与AAA的发生发展密切相关。本文结合AAA细胞外基质降解、炎性浸润和血管平滑肌细胞功能丧失三大病理特征,深入探讨了中性粒细胞在AAA病程中的多重角色。中性粒细胞通过炎症因子等机制被募集至病变部位,造成炎性浸润,活化后释放杀伤酶类、基质金属蛋白酶等分子,促进AAA的发展;中性粒细胞通过细胞沉积及相关炎性分子的累积,参与AAA腔内血栓形成,加重疾病进展;中性粒细胞形成NETs为近年来新发现的中性粒细胞杀伤形式,已有文献报道NETs从多角度协同加重炎症,且可能通过激活凝血级联、促进血小板聚集等方式形成腔内血栓,导致AAA的病变加剧,对该疾病进展有重要作用。由于相关研究尚处起步,且多数研究结论尚处表层,...     

Elastase is not sufficient to induce experimental abdominal aortic aneurysms

PURPOSE: Research investigating abdominal aortic aneurysms (AAAs) commonly uses a rat model dependent on aortic infusion of porcine pancreatic elastase to initiate AAA formation. Unfortunately, the sizes of AAAs generated by this model have varied widely among published studies. This may reflect lot-to-lot variations in commercial elastase preparations. This study was undertaken to investigate the ability of different lots of elastase to induce AAAs and explain the variability identified. METHODS: Four lots of elastase were evaluated in the standard rat AAA model. Saline solution was used as a control. Additional groups of rats were treated with higher concentrations of elastase with or without the macrophage activator thioglycollate medium. Aortic diameters were measured in all rats. Inflammation and elastin degradation was examined histologically. Elastase activity and purity were evaluated for all lots. RESULTS: Of the four lots tested, only one was able to consistently generate AAAs at the standard dose (P <.05). Increasing the amount of elastase infused produced AAAs in some ineffective lots. Infusion of thioglycollate medium in combination with otherwise ineffective elastase produced AAAs (P =.02). However, the elastase with the highest purity failed to generate AAAs, even at the highest dose tested or in combination with thyioglycollate medium. Thioglycollate medium alone failed to result in AAA formation. All elastase lots displayed elastolytic activity in vitro and produced elastin degradation in vivo. Elastin degradation did not correlate with AAA size in elastase-treated rats (P = NS). Aneurysm size correlated with extent of inflammation (P =.005). CONCLUSION: Induction of AAAs does not correlate with elastolytic activity. Infusion of pure elastase alone is not sufficient to induce AAA formation in spite of evidence of elastin degradation. Presumed inflammatory modifiers, which contaminate some elastase preparations, enhance AAA formation. Future use of this rat model will need to take the variability of elastase preparations into account with controls for each new elastase lot.     

Deletion of CCR2 but not CCR5 or CXCR3 inhibits aortic aneurysm formation

BACKGROUND: Microscopic analysis of abdominal aortic aneurysms (AAAs) demonstrates an abundance of infiltrating leukocytes. The chemokine receptors CCR2, CCR5, and CXCR3 are associated with pathways implicated previously in aneurysm pathogenesis. We hypothesized that genetic deletions of CCR2, CCR5, and CXCR3 would limit leukocyte infiltration and aneurysm formation in a mouse model of AAA. METHODS: CCR2(-/-), CCR5(-/-), CXCR3(-/-), and control mice of the same genetic background were subject to periaortic application of calcium chloride. Aortic diameters were measured before aneurysm induction and at harvest 6 weeks later. Diameters were compared using the Mann-Whitney test. Aortas were stained with H&E and trichrome for histologic analysis. Aortic MMP-2 and MMP-9 activities were measured using zymography. RESULTS: Aneurysm formation was attenuated in CCR2(-/-) mice with the final mean aortic diameter less than that of the control mice (P < .01). Histology revealed preservation of the lamellar architecture and decreased inflammatory cells. Aortic MMP-2 and MMP-9 levels were decreased in CCR2(-/-) mice. CCR5(-/-) and CXCR3(-/-) mice demonstrated no protection from aneurysm formation, which was corroborated by the tissue histology showing similar inflammatory cell infiltration and elastin degradation. CONCLUSIONS: The CCR2 receptor is involved directly in AAA formation, whereas the CCR5 and CXCR3 receptors are not.     

IgG4-positive plasma cells in inflammatory abdominal aortic aneurysm: the possibility of an aortic manifestation of IgG4-related sclerosing disease

Inflammatory abdominal aortic aneurysm (IAA) is associated with autoimmune disease. However, the precise mechanism of IAA remains unclear. There is increasing evidence that IgG4 is involved in the autoimmune mechanism of various idiopathic sclerosing lesions, including sclerosing pancreatitis and retroperitoneal fibrosis. The present study investigated the hypothesis that the IgG4-related autoimmune reaction is involved in the formation of IAA. The study group consisted of 11 cases of IAA (69.2 +/- 8.59y) and 12 age-matched cases of atherosclerotic abdominal aortic aneurysm (AAA, 69.6 +/- 5.94y), which were used in the previous report. A clinicopathologic examination of these lesions was performed, including histology and immunohistochemistry, in relation to the involvement of IgG4-positive plasma cells in the formation of IAA. No difference in the incidence of risk factors for atherosclerosis was observed between the patients with IAA and AAA. Autoimmune diseases were diagnosed in 2 patients with IAA, including rheumatoid arthritis and polyarteritis nodosa. A patient with IAA had pulmonary fibrosis. In contrast, autoimmune diseases were absent in patients with AAA. However, there was no significant difference in the incidence of autoimmune diseases between the patients with IAA and AAA. Lymphocyte and plasma cell infiltration and fibrosis were significantly more intense and extensive in IAA than in AAA. In addition, lymph follicle formation and vasculitis of small veins and arteries were frequently found in the affected lesions of IAA. Immunohistochemically, IAA showed a significant increase in the number of infiltrating IgG4-positive plasma cells and the incidence of a disrupted follicular dendritic cell network in lymph follicles, in comparison with AAA. These findings suggest that IAA may be an aortic lesion reflecting the presence of IgG4-related sclerosing disease, and not a simple inflammatory aneurysm of the aorta.