The Role of the Thymus and Recent Thymic Migrants in the Maintenance of the Adult Peripheral Lymphocyte Pool

The thymus is essential for the initial seeding of T cells to the periphery, but its role in maintaining the adult T cell pool remains poorly defined. We investigated whether changes to the rate of T cell export could form part of the mechanism(s) controlling the homeostatic regulation of the size and composition of the peripheral T cell pool. Using neonatal thymi grafted under the kidney capsule, we found that irrespective of whether the pool was oversupplied (by thymic grafts) or undersupplied (due to neonatal thymectomy), the thymic export rate was constant from both the host and graft thymus, and the periphery remained constant in size. Recent thymic emigrants (RTE) were also tracked to determine the extent of their acceptance into the T cell pool of a normal mouse. As a population, RTE are phenotypically mature, but were distinct from resident T cells in the periphery, being released in a CD4/CD8 ratio approximately twice that of established peripheral T cells. This export ratio is similar to that of T cells in the mature thymic compartment, but soon after entry into the periphery, the ratio falls, indicating separate thymic and peripheral regulation of the CD4/CD8 ratio. RTE may also be preferentially incorporated into the periphery, causing displacement of resident T cells, thus maintaining the size of the peripheral pool. Although not vital for the maintenance of a functional T cell pool, the acceptance of RTE in a “full” peripheral pool would ensure that the T cell receptor repertoire is kept diverse and that the T cell population encompasses a broad range of naive as well as memory T cells.     

胸腺肿块的影像学诊断

本文从影像学包括胸部平片、断层及CT和MRI的综合方法对37例胸腺肿物的诊断及鉴别诊断作全面探讨,提出胸腺肿仂的特征及其诊断思维,首先由于其胚胎发生的关系而定位,本组94.6％病例基底紧贴并位于升主动脉前方;其次良性肿物包膜完整,密度均匀,恶性出现包膜破坏,浸润生长和坏死;最后结合其他征象和临床资料作出定性诊断及鉴别诊断。还对这些影像学方法在诊断方面的价值作出评估。     

T cell homeostasis: thymus regeneration and peripheral T cell restoration in mice with a reduced fraction of competent precursors

We developed a novel experimental strategy to study T cell regeneration after bone marrow transplantation. We assessed the fraction of competent precursors required to repopulate the thymus and quantified the relationship between the size of the different T cell compartments during T cell maturation in the thymus. The contribution of the thymus to the establishment and maintenance of the peripheral T cell pools was also quantified. We found that the degree of thymus restoration is determined by the availability of competent precursors and that the number of double-positive thymus cells is not under homeostatic control. In contrast, the sizes of the peripheral CD4 and CD8 T cell pools are largely independent of the number of precursors and of the number of thymus cells. Peripheral "homeostatic" proliferation and increased export and/or survival of recent thymus emigrants compensate for reduced T cell production in the thymus. In spite of these reparatory processes, mice with a reduced number of mature T cells in the thymus have an increased probability of peripheral T cell deficiency, mainly in the naive compartment.     

Natural antibodies in sera of patients with systemic lupus erythematosus

Sera obtained from fifty-five patients with active systemic lupus erythematosus (SLE) and from four patients with mixed connective tissue disease (MCTD) previously shown by immunofluorescence and by double immunodiffusion to possess antinuclear antibodies, were tested for the presence of natural antibodies of IgG, IgA, and IgM isotypes. Antibody activity to actin, myosin, DNA, TNP, albumin, and tubulin was examined, using an enzyme-linked immunosorbent assay (ELISA). It was found that, in comparison with the antibody titers in normal sera, most of the SLE and MCTD sera possessed statistically greater amounts of IgG, IgA, and IgM antibodies directed against all the antigens tested. Furthermore, the IgG, IgA, and IgM antibody activity to DNA and TNP, compared to that found with all the other antigens, was significantly higher. Antibodies reacting with a saline extract of calf thymus (ECT) were studied by ELISA and by immunodiffusion. No correlation was observed between the natural antibody titers and the serum antibody levels to ECT detected either by ELISA or by immunodiffusion.     

微小胸腺瘤

１２例重症肌无力（ＭＧ）胸腺内微小胸腺瘤的临床病理观察，结果提示：微小胸腺瘤平均发病年龄３７岁，１０％ＭＧ患者胸腺内有微小胸腺瘤存在。该肿瘤临床表现为ＭＧ的症状体征；病理形态提示该肿瘤可发生于胸腺皮质、髓质及皮髓质交界区。因肿瘤微小，病灶多发，Ｘ线和ＣＴ检查不能发现，确诊只能依赖病理组织学检查，其病理形态与胸腺瘤相似。本文提出了正确认识微小胸腺瘤的临床病理特征，对ＭＧ治疗、判断预后具有指导意义，并主张对ＭＧ患者无论伴或不伴胸腺瘤，均应采取胸腺切除术，以清除微小胸腺瘤病灶，提高手术疗效。     

18F-FDG PET/CT代谢参数预测胸腺上皮肿瘤恶性程度

目的 观察¹⁸F-FDG PET/CT代谢参数对预测胸腺上皮肿瘤(TET)恶性程度的价值。方法 回顾性分析95例经病理诊断的TET患者,根据病理结果进行组织学分型(低危型胸腺瘤、高危型胸腺瘤、胸腺癌)及临床分期(Ⅰ~Ⅳ期)。基于¹⁸F-FDG PET/CT获取原发灶最大标准摄取值(SUV_max)、峰值标准摄取值(SUV_peak)、原发灶SUV_max与纵隔血池平均标准摄取值的比值,即靶区本底比值(TBR),分别以SUV=2.5及40%SUV_max为阈值,获得病灶糖酵解总量(TLG_2.5、TLG_40%)及肿瘤代谢体积(MTV_2.5、MTV_40%)。比较不同类型及临床分期TET各代谢参数的差异。针对两两比较差异均有统计学意义的代谢参数绘制受试者工作特征(ROC)曲线,计算曲线下面积(AUC),评估其预测不同组织学分型TET的效能。结果 95例中,27例低危型胸腺瘤、15例高危型胸腺瘤、53例胸腺癌;临床分期Ⅰ期28例、Ⅱ期8例、Ⅲ期12例、Ⅳ期47例。不同类型TET间SUV_max、SUV_peak及TBR差异均有统计学意义(P均<0.05),高危型胸腺瘤及胸腺癌TLG_2.5和MTV_2.5均高于低危型胸腺瘤(P均＜0.05),胸腺癌TLG_40%高于低危型胸腺瘤(P＜0.05);其他代谢参数差异均无统计学意义(P均＞0.05)。临床Ⅳ期TET的SUV_max、SUV_peak、TBR、TLG_2.5、TLG_40%、MTV_2.5均高于Ⅰ期(P均＜0.05),Ⅲ期TET的TLG_2.5高于Ⅰ期(P＜0.05),不同临床分期TET其余代谢参数差异均无统计学意义(P均＞0.05)。以SUV_max、SUV_peak及TBR预测低危型与高危型胸腺瘤的AUC分别为0.857、0.840及0.857,预测高危型胸腺瘤与胸腺癌的AUC分别为0.769、0.758及0.755。结论 ¹⁸F-FDG PET/CT代谢参数可有效预测TET恶性程度。     

产前超声于左无名静脉切面测量孕20~38周胎儿胸腺参数

目的 观察产前超声于左无名静脉切面测量孕20~38周胎儿胸腺参数的价值。方法 前瞻性纳入661名孕20~38周健康单胎妊娠孕妇,采用超声分别于三血管切面和左无名静脉切面测量胎儿胸腺参数,包括胸腺横径、前后径、周长及横断面积,分析各参数与孕周的相关性,观察并对比于两切面测量胸腺参数的价值。结果 超声于三血管切面所测孕35~38周胎儿胸腺横径及孕20~38周胎儿胸腺前后径、周长和横断面积均小于左无名静脉切面（P均<0.05）;且相同切面所测胎儿胸腺参数均随孕周增长而增高（P均<0.05）。三血管切面（r=0.873、0.793、0.839、0.858,P均<0.001）和左无名静脉切面（r=0.901、0.796、0.866、0.904,P均<0.001）胸腺横径、前后径、周长及横断面积测值均与孕周呈正相关。观察者间及观察者内测量胸腺参数的一致性均好（ICC均>0.75,P均<0.001）,于左无名静脉切面测量的ICC略高。结论 产前超声于左无名静脉切面测量孕20~38周胎儿胸腺各参数可减小测量误差,在一定程度上弥补三血管切面测量的不足。     

Establishment of a sensitive radioimmunoassay for serum thymic factor with a special reference to extraction procedures.

A radioimmunoassay (RIA) for serum thymic factor (facteur thymique serique) was established. This assay could detect less than 0.5 pg of serum thymic factor without the interference by other thymic hormones, including thymopoietin II and thymosin alpha 1. Both zinc-free and zinc-bound serum thymic factor showed a similar standard curve, indicating that this RIA could detect both forms of serum thymic factor in the same way. We observed that two procedures were required prior to the measurement in order to measure serum thymic factor content in plasmas; the first, the extraction procedure to remove substances interfering with the assay nonspecifically; the second, the storage of the sample with ethylenediamine tetraacetic acid disodium salt to inhibit the proteases in the plasma to degrade serum thymic factor. By employing this assay system, we observed that cord blood plasmas contained significantly higher level of serum thymic factor than did adult blood plasmas.     

胸腺原发不典型类癌影像学表现

目的 观察胸腺原发不典型类癌(pTAC)的影像学表现。方法 回顾性分析经病理证实的8例pTAC胸部CT和MRI资料,观察其影像学表现。结果 8例pTAC 均为前纵隔单发病灶,5个位于偏右、3个偏左,最大径3.5~16.0 cm、中位最大径8.3 cm;7个呈团块状、1个呈分叶状,边界均清晰;CT均表现为不均匀软组织密度影,内见囊变和坏死,2个内见钙化;MR T1WI均呈等信号,T2WI均呈高信号,弥散加权成像见弥散受限,表观弥散系数(ADC)0.23×10^-3~1.12×10^-3 mm²/s,中位ADC为0.64×10^-3 mm²/s;增强后7个病灶不均匀中度强化、1个不均匀轻度强化;4个见瘤内血管。8例中,3例胸腔积液、3例心包积液,5例纵隔淋巴结转移合并或不合并颈部、锁骨上淋巴结转移,4例胸膜转移,4例骨转移(累及邻近肋骨及颈、胸椎),1例肝转移。结论 pTAC影像学表现具有一定特征性,有助于诊断及鉴别诊断。     

30例胸腺肿瘤及肿瘤样病变的CT诊断

目的 探讨各种病理类型的胸腺肿瘤及肿瘤样病变的CT诊断价值。方法 收集30例胸腺肿瘤及肿瘤样病变行螺旋CT扫描,结合病理对其CT表现进行回顾性分析。结果 30例患者中,胸腺瘤14例,异位胸腺瘤1例,侵袭性胸腺瘤8例,胸腺类癌2例,胸腺癌2例,胸腺淋巴瘤2例,颈部胸腺囊肿1例。结论 CT能对良恶性胸腺肿瘤及肿瘤样病变作出诊断;对部分恶性胸腺肿瘤患者结合临床表现能对病理类型作出一定的判断。     

桑色素对二硝基氟苯诱导的迟发型超敏反应的影响

目的研究桑色素（morin）对二硝基氟苯诱导迟发型超敏反应的影响。方法建立二硝基氟苯（dinitroflu-orobenzene,DNFB）诱导迟发型超敏反应（delayed type hypersensitivity,DTH）模型,观察morin对DTH模型小鼠耳组织肿胀、炎性细胞浸润程度和胸腺指数、脾指数的影响,光学显微镜下观察小鼠耳廓组织学变化,噻唑兰（methyl thia-zolyl tetrazolium,MTT）法检测淋巴结细胞和脾脏淋巴细胞增殖情况。结果双耳称重的结果显示,morin（70mg/ml）处理组与DTH组具有显著的差异（P〈0.05）,能明显抑制DNFB引起的炎症反应;耳廓局部组织学检测也表明,morin能够抑制DNFB诱导的DTH,明显减少淋巴细胞的浸润。morin能降低DTH小鼠胸腺指数和脾脏指数,抑制淋巴结淋巴细胞（P〈0.01）和脾脏淋巴细胞的增殖（P〈0.05）。结论 morin可显著抑制DTH小鼠耳组织肿胀和淋巴细胞浸润程度,降低胸腺和脾脏指数,抑制淋巴细胞的增殖可能是其作用机制之一。     

Ultrastructure of the thymus in diabetes mellitus and starvation

Introduction The purpose of this study was to investigate the ultrastructural change of the thymus under stress conditions created by diabetes accompanied by fasting, and also the effects of insulin therapy. Methods Forty-eight Sprague-Dawley type rats were used in this experiment. Type 1 diabetes symptoms were induced in 24 of the rats by the application of a single dose of intravenous streptozotocin in sodium citrate buffer through the tail vein. A single dose of sodium citrate buffer was given to rats to create a control group. Following the infusions, rats were divided into control, control and fasting, diabetes, diabetes and fasting, and insulin treatment groups. At the end of the experiment tissues from the thymus of the rats were extracted and examined using electron microscopy. Results Severe degeneration was observed in the prolonged fasting (stress) and diabetes groups without insulin treatment. Insulin treatment was found to mostly reverse this degeneration. Conclusion This study demonstrates that the thymus was affected ultrastructurally by diabetes and concomitant fasting, and insulin treatment can reverse these changes.     

Solid Ectopic Cervical Thymus in Neonates With Thyroid Agenesis

We report a series of ectopic thymus glands as detected by sonography in infants with thyroid agenesis. The patients were children who underwent nuclear medicine and sonography for congenital hypothyroidism. Of the 12 patients with a diagnosis of thyroid agenesis over a 5‐year period, 4 (33%) were shown to have ectopic thymic tissue. Although a cervical ectopic thymus has been previously reported, there is very little discussion of it occurring in conjunction with thyroid agenesis. This case series highlights the importance of recognition of ectopic thymic tissue when examining for thyroid tissue in the setting of congenital hypothyroidism.     

超声诊断儿童甲亢合并甲状腺胸腺组织异位1例

<正>患儿女,12岁,因"发现突眼伴心慌1个月"入院。专科体检:甲状腺中度肿大,气管居中,声音无嘶哑。实验室检查:游离三碘甲腺原氨酸31.19ρmol/L,游离四碘甲腺原氨酸111.9ρmol/L,促甲状腺激素0.04μU/L,抗甲状腺过氧化物酶抗体276.3 U/ml,抗甲状腺球蛋白抗体44.9 U/ml。常规超声检查:甲状腺弥漫性肿大,实质回声增粗,分布不均匀,左侧叶中部背侧见一大小约7.7 mm×4.1 mm稍低回声病灶,边界模糊,内部见多个点状强     

Sonographic findings in ectopic cervical thymus in an infant.

We present the case of a 28-day-old boy with ectopic thymic tissue in the neck. Sonography showed a well-delineated, homogeneous lesion in the left submandibular region that was isoechoic relative to the mediastinal thymus. The lesion had angular margins and lacked a mass effect despite its large size (3 x 2 cm). On power Doppler imaging, arteries with an intermediate-impedance flow pattern were seen entering the lesion from the inferior and lateral margins. On both T1- and T2-weighted MR images, the lesion was isointense relative to the mediastinal thymus and had higher and lower signal intensity than muscle and fat, respectively. A sonographically guided needle biopsy confirmed the diagnosis of ectopic thymus.     

Several different cell surface molecules control negative selection of medullary thymocytes.

Repeated attempts to show that costimulation for negative selection is controlled by a single cell surface molecule have been unsuccessful. Thus, negative selection may involve multiple cell surface molecules acting in consort. In support of this idea, we show here that at least three cell surface molecules, namely CD28, CD5, and CD43, contribute to Fas-independent negative selection of the tolerance-susceptible population of heat-stable antigen (HSA)hiCD4+8- cells found in the medulla. The costimulatory function of these three molecules can be blocked by certain cytokines, IL-4 and IL-7, and coinjecting these cytokines with antigen in vivo abolishes negative selection; Fas-dependent negative selection, however, is maintained. The results suggest that efficient negative selection requires the combined functions of at least four cell surface molecules: CD28, CD5, CD43, and Fas.