中华鳖胸腺显微和亚显微结构及其在进化上的意义

应用透射电子显微镜观察了中华鳖胸腺的显微和亚显微结构。发现中华鳖胸腺从结构上可分为皮质和髓质,皮质富含淋巴细胞,髓质富含上皮性网状细胞。在各发育期中华鳖胸腺皮质、髓质交界处和髓质区有明显的囊状胸腺小体和交错突细胞。在２００ｇ以上的成年鳖胸腺内发现有同心圆状胸腺小体。电镜下,胸腺内淋巴细胞分为大、中、小３型。上皮性网状细胞从亚显微结构上分为支持型和分泌型。胸腺囊包括细胞内囊和细胞间囊,以细胞内囊居多     

胸腺及性激素对大鼠肝脏药物代谢酶活力和抗氧化功能调节作用的研究

胸腺是机体发育成熟最早的器官,在胚胎晚期胸腺的皮质和髓质已经形成,出生后胸腺小体数目增多,性成熟时胸腺的结构和功能发育到高峰,此后胸腺开始退化,分泌胸腺激素的能力随年龄的增长逐渐降低。由于胸腺的退化,导致T淋巴细胞的分化、成熟障碍,机体免疫功能衰退,因而有人提出胸腺是控制衰老过程中免疫功能变化的生物钟。     

斜带石斑鱼胸腺的显微和超微结构

本文通过解剖及组织切片技术、光学显微镜、透射和扫描电子显微镜技术,对斜带石斑鱼(Epinephelus coioides)胸腺器官组织进行了观察研究。结果表明:斜带石斑鱼胸腺实质主要由胸腺细胞(淋巴细胞)和网状上皮细胞构成。鱼体从Ⅰ龄之后,其胸腺发生明显的变化,与幼鱼有所不同,主要是胸腺可明显区分为三个区域:胸腺外皮质区、内皮质区和髓质区。外皮质区主要由网状上皮细胞、黏液细胞、成纤维细胞和少量淋巴细胞构成,细胞排列疏松;内皮质区主要由密集的淋巴细胞和网状上皮细胞组成,以含有大量的淋巴细胞为特征;髓质区主要由淋巴细胞和较多的网状上皮细胞构成,总体特征是淋巴细胞数量比内皮质区的少,且细胞排列较疏松。外皮质区、内皮质区相当于高等脊椎动物的皮质;髓质区相当于高等脊椎动物的髓质。髓质区之下有结缔组织,在Ⅱ龄以上的成体出现胸腺小体(Hassall's corpuscles)或类似胸腺小体的结构,而且随着年龄的增加,胸腺外皮质区增厚,结缔组织增加,还表现在内皮质区和髓质区组织逐渐萎缩变薄,胸腺的细胞组成类型和淋巴细胞数量上有所变化等等。这些现象在Ⅱ龄鱼开始出现,即胸腺呈现退化迹象,在Ⅲ龄以上鱼体呈现明显的退化和萎缩。胸腺表面扫描电镜结果表明:其上皮细胞表面具有微嵴以及由微嵴组成的指纹状结构,有一些微孔分布。透射和断面扫描电镜的结果进一步表明:胸腺组织内的细胞成分复杂,除了淋巴细胞和网状上皮细胞外,还具有巨噬细胞、肥大细胞、肌样细胞、浆细胞、指状镶嵌细胞和纤维细胞等。     

人胸腺内交错突细胞的免疫组织化学研究

本文用免疫组织化学方法检测胎儿期,儿童以及成人胸腺内交错突细胞的分布和ＨＬＡＤＲ抗原的表达．结果表明：Ｓ－１００抗体能够清楚显示胸腺内交错突细胞,这些细胞主要分布在皮,髓质交界处和髓质内,在皮质内的交错突细胞大都单个存在,偶而看到交错突细胞成团存在．交错突细胞的周围,常见有淋巴细胞形成玫瑰花结．出生后随年龄的增长,交错突细胞逐渐减少。ＨＬＡ－ＤＲ抗体能与胸腺内多种细胞反应,如皮,髓质内上皮细胞,巨噬细胞和交错突细胞,但它们染色强度不等．交错突细胞ＨＬＡ－ＤＲ抗体的阳性反应位于质膜和突起部,染色强阳性,巨噬细胞反应不尽一致一般多为阳性,胞质内未见有吞噬淋巴细胞碎片．上皮细胞染色一般由弱阳性到阳性,核阴性,仅有质膜呈阳性反应,有关ＨＬＡ－ＤＲ抗原表达的可能意义进行了讨论．     

人胎胸腺基质细胞的免疫组织化学观察

用免疫组织化学法观察了六种单克隆抗体在１４例２１～３８周胎儿胸腺基质细胞中的反应。结果表明,三种ＭＨＣ－Ⅱ类抗原的表达有差异。ＨＬＡ－ＤＲ＋和ＨＬＡ－ＤＱ＋细胞多,主要分布于髓质,皮质中较少。ＨＬＡ－ＤＰ＋细胞少,几乎只见于髓质。抗表皮角蛋白抗体阳性的上皮细胞见于部分髓质与少数皮质上皮细胞,被膜及小叶间隔下上皮细胞和胸腺小体。Ｓ－１００＋的交错突细胞主要分布于髓质,皮质中较少。ＭＯ＋２的巨噬细胞见于整个胸腺实质,皮质深层最多。     

自然衰老过程中SD大鼠免疫系统结构功能的变化

目的 观察自然衰老SD大鼠免疫系统结构和功能的改变,并探讨其可能的机制。方法 SD大鼠60只,饲养于SPF环境中。分别在6、12、18、24月龄安乐10只动物,以淋巴细胞转化实验和NK细胞杀伤实验判断淋巴细胞功能;用免疫荧光法测定外周血淋巴细胞亚群。CBA法检测血清中细胞因子含量,比色法检测血清中超氧化物歧化酶(SOD)和丙二醛(MDA)。并对胸腺、脾进行组织病理学观察。结果 随年龄增长大鼠淋巴细胞转化能力降低。CD8阳性T细胞数减少。脾细胞对NK靶细胞杀伤能力降低。血清中IL-2的量减少,IL-6、IL-10含量升高,SOD减少,MDA增多。胸腺脏器系数降低。胸腺萎缩,脾髓窦扩张,淋巴滤泡萎缩,髓外造血增多。脾中8-OHd G+细胞主要位于红髓区,成簇分布。胸腺中阳性细胞主要存在于髓质中,从皮质到髓质阳性细胞逐渐增多。结论 提示免疫系统的增龄性退化与其氧化损伤的累积有一定关系,为衰老免疫损伤学说提供了实验依据。     

不同月龄近交系五指山小型猪免疫器官的组织形态学

目的对不同月龄近交系五指山小型猪免疫器官组织特点进行观察,为其用于建立人类免疫相关疾病模型提供基础形态学资料。方法2、4和12月龄小型猪免疫器官被分别固定,常规石蜡切片、HE染色,光镜观察。结果4月龄前,胸腺内胸腺细胞和胸腺小体的数量均随年龄的增长逐渐增多;12月龄时,胸腺细胞数量有所减少,排列比较疏松,胸腺小体的数量和体积基本没有变化;2月龄时胸腺小体周围可见许多大小不同的空泡状细胞和细胞碎片。4月龄前,脾白髓动脉周围组织淋巴鞘和脾小结在也随年龄增长而逐渐增多增大,但12月龄时有所减少并维持在一定水平,其变化与大鼠和鸡的基本一致。2月龄淋巴结皮质靠内,髓质靠外,4月龄两者分界不明显,12月龄淋巴小结较大,淋巴细胞排列疏松,髓质内淋巴细胞较少,毛细血管增多。结论从整体结构上观察,近交系五指山小型猪免疫器官的组织学结构与人和其它哺乳动物之间没有明显的差异。     

豚鼠胸腺含P物质、降钙素基因相关肽和神经肽Y神经的定位研究

为研究神经肽调节胸腺生理功能的作用途径,作者采用免疫组织化学ＡＢＣ法结合ＧＤＮ增强技术,以３０μｍ厚恒冷箱切片光镜下观察了豚鼠胸腺内含ＳＰ、ＣＧＲＰ和ＮＰＹ神经纤维的定位与分布。结果发现,ＳＰ和ＣＧＲＰ免疫反应神经纤维在胸腺内分布广泛,呈线状或串珠状,可见于血管周围,小叶间结缔组织和胸腺实质。实质中以皮髓质交界区和髓质区纤维分布较密集,而走行于皮质淋巴组织的神经纤维相对稀疏,胸腺小体附近亦可见含ＣＧＲＰ神经分布。含ＮＰＹ神经纤维主要分布于血管周围、小叶间隔和皮髓质交界区,仅少数分支穿行于皮质胸腺细胞之间。胸腺被膜中有上述３种肽能神经纤维分布。本研究结果表明,胸腺内有丰富的肽能神经分布,这可能是神经肽调节胸腺生理功能的重要方式之一。     

关于鸡法氏囊淋巴滤泡皮质部形成的研究

初生雏鸡孵出后立即结扎法氏囊管,使外界抗原进入法氏囊腔通路受阻,法氏囊髓质部细胞未见增殖分化,从而没有淋巴细胞穿过基膜形成皮质部。结扎法氏囊管后喂养半个月的雏鸡,再拆除结扎线,恢复泄殖腔与法氏囊的通道,外界抗原又可进入法氏囊腔,刺激滤泡髓部细胞分裂增殖,并穿过基膜形成皮质部。但由于曾结扎半月,所以迁移到皮质部的细胞与对照组比较相对减少。结扎法氏囊管后同时注射枯草杆菌(Bs)和四球菌(Mt),法氏囊滤泡皮质部与正常对照组相似,有的甚至比对照组更为发达。电镜观察皮质部具有不同成熟度的浆细胞。孵出的雏鸡用睾酮(TP)处理后法氏囊滤泡虽有皮质部,但不是正常的皮质部淋巴细胞。实验结果表明滤泡皮质部的形成与孵化后外界抗原的刺激有关,法氏囊作为鸟类特有的体液免疫的中枢淋巴器官,可能仅指胚胎时期发育的淋巴滤泡髓质部,而法氏囊皮质部则可能相当于外周淋巴器官。它的形成必须依赖于外界抗原的刺激。     

草鱼胸腺组织学的研究

草鱼胸腺位于鳃腔背上角,紧贴在鳃腔膜之下,突起部分伸入到下颞凹,整个胸腺形态形似菱角。其组织结构可分为外区、中区和内区。中区和内区主要由淋巴细胞和网状上皮细胞构成,在组织结构上分别类似于高等脊椎动物胸腺的皮质和髓质区。胸腺淋巴细胞可分大、中、小三型,小淋巴细胞约占78％,中淋巴细胞约占15％,大淋巴细胞约占4％。在Ⅰ龄草鱼,每毫克胸腺约有3.6×106个胸腺淋巴细胞,Ⅱ龄草鱼约为2×106。Ⅰ至Ⅱ龄草鱼胸腺重量明显地随鱼龄增加,Ⅱ龄以上草鱼胸腺重量变化无规律,成鱼胸腺表现出明显的退化。草鱼胸腺除年龄性退化外,还存在环境因素引起的非年龄性退化。       

Histogenesis of the rat thymic medulla during first stages of development

We investigated first stages of thymic medulla organisation in foetuses of Wistar strain rats. between 13th and 17th days of foetal life (GD). Medullary cells were identified by immunocytochemical localisation of neuron-specific enolase (NSE) as well as by traits of ultrastructure. The first thymic medullary precursor cells which were reactive for NSE were at first spread all over the thymic primordium. In the period of thymus colonisation by lymphoid cells, the following stages were distinguished in medulla organisation: (1) migration of NSE+ cells to the central portion of the thymus (GD 14-15), (2) small medullary epithelial patches, distributed within the thymus (GD 16), and (3) expansion of medullary patches into medullary compartment (GD 17). At the second and third stages of the medulla organisation, an increase in the number of NSE+ cells, followed by differentiation of their ultrastructure and increase in their biological activity were observed. We conclude that formation of medullary architectural pattern is controlled by interactions between maturing epithelial cells and developing lymphoid cells and by angiogenesis in the region.     

Thymocyte subpopulations during early fetal development in sheep

Phenotypic analysis of thymocytes during fetal development may identify subpopulations which are either absent or difficult to detect in postnatal thymus. A panel of monoclonal antibodies specific for sheep lymphocyte antigens (SBU-T1, -T4, -T8, -T6) was used to identify thymocyte subpopulations in postnatal and fetal sheep. Thymuses were analyzed by two-color immunofluorescence and flow cytometry or by immunohistology. Two-color immunofluorescent staining of postnatal sheep thymus with anti-SBU-T4 and anti-SBU-T8 revealed four relatively distinct subpopulations with particular localizations: a) SBU-T4-T8-, predominantly outer cortex (12%); b) SBU-T4+T8+, inner cortex (74%); c) SBU-T4+T8-, medulla (10%), and d) SBU-T4-T8+, medulla (4%). One- and two-color immunofluorescent analysis of cells from early fetal thymuses demonstrated the appearance of SBU-T8+ cells well before SBU-T4+ cells. Immunohistologic staining of fetal sheep thymus at various stages of gestation (term = 150 days) revealed that lymphoid cells and MHC class II-positive dendritic cells first appeared at 35 days, at which stage the thymic epithelium was weakly positive for class I MHC antigens but negative for class II MHC antigens. The earliest lymphocyte antigens detectable on fetal sheep thymocytes were SBU-LCA and SBU-T1. By 40 days, the antigens SBU-T6, SBU-T4, and SBU-T8 were detectable on a small number of thymocytes; SBU-T8 preceded SBU-T4, and the number of SBU-T8+ thymocytes always exceeded the number of SBU-T4+ thymocytes throughout early gestation. At 50 days, a thymic medulla appeared and thereafter grew rapidly in size. Immunoperoxidase staining of serial sections of the fetal neck revealed cortical-type thymocytes outside the thymus from 40 days onward, before the appearance of a thymic medulla. However, by 60 days, only medullary-type thymocytes were observed either extrathymically or within the interlobular septa of the thymus, indicating that only thymocytes with a medullary phenotype leave the thymus from this stage of gestation.     

The human thymic microenvironment: Thymic epithelium contains specific keratins associated with early and late stages of epidermal keratinocyte maturation

Normal T-cell development is dependent on interactions with the thymic microenvironment; thymic epithelial cells are thought to play a key role in the induction of thymocyte maturation, both through direct contact and, indirectly, via thymic hormone secretion. It has been postulated that thymic epithelial cells progress through an antigenically defined pathway of differentiation similar to that of epidermal keratinocytes. As keratins vary according to epithelial cell type and the stage of epithelial cell maturation, we used a panel of monoclonal antibodies against keratins to study specific types of keratin intermediate filaments within human thymic epithelium. The demonstration in human thymus of keratins previously shown to be associated with distinct stages of epidermal keratinocytic maturation would support the hypothesis that thymic epithelial cells undergo sequential stages of differentiation. Two-dimensional immunoblot analysis of cytoskeletal extracts from human thymus revealed that thymic epithelium contains the following keratins: 1-2, 5, 6, 7, 8, 10, 13, 14, 15, 16, and 17 (molecular masses, 65-67, 58, 56, 54, 52, 56.5, 51, 50, 50', 48, and 46 kilodaltons, respectively). Thus, in thymic epithelium, we found keratins previously observed in epidermal basal cells (5, 14, 15), as well as keratins specific for terminally differentiated keratinocytes in supra-basal epidermis (1-2, 10). Indirect immunofluorescence (IF) performed on fetal and postnatal human thymus demonstrated that keratin epitopes recognized by antibodies AE-3, 35 beta H11, and RTE-23 are present on epithelial cells of the subcapsular cortex, the cortex, the medulla, and Hassall's bodies. In contrast, antibodies AE-1 and RTE-22 reacted primarily with neuroendocrine thymic epithelium (subcapsular cortex, medulla, Hassall's bodies). The epithelial reactivity of antibody AE-2 was limited to epithelial cells in Hassall's bodies and did not appear until 16 weeks of fetal gestation i.e., when Hassall's bodies first formed. Two-dimensional gel analysis of thymic keratins demonstrated that antibody AE-2 identified only the keratins with molecular masses of 56.6 and 65-67 kilodaltons (10 and 1-2 respectively) in thymus. These data, together with the selective reactivity of AE-2 with Hassall's bodies in fluorescence assays, demonstrate the localization in Hassall's bodies of the high-molecular-weight keratins associated with the late stages of epidermal cell maturation. In summary, we demonstrated that human thymic epithelium contains specific keratins found in multiple epithelial types as well as keratins associated with both early and late stages of epidermal cell differentiation.(ABSTRACT TRUNCATED AT 400 WORDS)     

The human thymic microenvironment. Phenotypic characterization of Hassall's bodies with the use of monoclonal antibodies

The human thymic microenvironment is important in promotion of T cell maturation, particularly during early stages of thymic ontogeny. Hassall's bodies (HB) are epithelial swirls in the human thymic medulla that are thought to be derived from endocrine medullary thymic epithelium. To study the ontogeny and function of various components of the human thymic microenvironment, we have produced four monoclonal antibodies (TE-8, TE-15, TE-16, and TE-19) that selectively reacted in thymus with HB. Antibodies TE-8 and TE-16 reacted with the cells forming the outer rim of the HB swirl. Antibody TE-19 reacted with the entire cellular portion of HB and with epithelial cells immediately surrounding HB. Granular foci in the cellular swirls of greater than 90% of HB reacted with antibody TE-15. During thymic ontogeny, the antigens defined by antibodies TE-8, TE-15, TE-16, and TE-19 were first detected in fetal thymus on HB beginning at 16 wk gestation, the age when HB morphologically appear in the thymus. Aberrant expression of the antigens corresponding to antibodies TE-8, TE-15, TE-16, and TE-19 was observed on thymic tissue from individuals with severe cellular immunodeficiency disease. In human skin, antibodies TE-8, TE-16, and TE-19 reacted with the stratum granulosum; antibody TE-15 reacted with the stratum corneum. Thus, with the use of antibodies TE-8, TE-15, TE-16, and TE-19, we have identified HB as antigenically distinct regions of endocrine thymic epithelium. Furthermore, we have shown that these anti-HB reagents also selectively react with epidermal keratinocytes in the terminal stages of keratinocyte maturation.     

Metallophilic macrophages are lacking in the thymus of lymphotoxin-β receptor-deficient mice

Lymphotoxin-β receptor (LTβR) axis plays a crucial role in development and compartmentalization of peripheral lymphatic organs. But, it is also required for the appropriate function and maintenance of structural integrity of the thymus: in LTβR-deficient animals the clonal deletion of autoreactive lymphocytes is impaired and differentiation of thymic medullary epithelial cells is disturbed. In this study, using several markers, we showed that thymic metallophilic macrophages were lacking in LTβR-deficient mice. In tumor necrosis factor receptor-I (p55)-deficient mice (which we used as positive control) thymic metallophilic cells were located, similarly as in normal mice, in the thymic cortico-medullary zone at the junction of cortex and medulla. These findings show that LTβR is necessary for maintenance of metallophilic macrophages in the thymus and provide further evidence that these cells may represent a factor involved in thymic negative selection.     

Expression of preprotachykinin-A and neuropeptide-Y messenger RNA in the thymus.

The preprotachykinin-A gene, the common gene of mRNAs encoding both substance-P (SP) and neurokinin-A (NKA), was shown to be expressed in Sprague-Dawley rat thymus by detection of specific mRNA in gel-blot analyses. In situ hybridization revealed dispersed PPT-A-labeled cells in sections from rat thymus, with a concentration of grains over a subpopulation of cells in the thymic medulla. Also, neuropeptide-Y mRNA-expressing cells were found in the rat thymus, primarily in the thymic medulla. Rat thymic extracts contained SP-like immunoreactivity (SP-LI), and the major part of the immunoreactivity coeluted with authentic SP and SP sulfoxide standards. SP-LI was also detected in human thymus, which contained between 0.09-0.88 ng SP-LI/g wet wt. Evidence for translation of preprotachykinin-A mRNA in the rat thymus was obtained from the demonstration of NKA-LI in thymic cells with an epithelial-like cell morphology. Combined with previous observations on the immunoregulatory roles of tachykinin peptides and the existence of specific receptors on immunocompetent cells, the demonstration of intrathymic synthesis of NKA suggests a role for NKA-LI peptides in T-cell differentiation in the thymus.     

Role of CCL19/21 and its possible signaling through CXCR3 in development of metallophilic macrophages in the mouse thymus

We have already shown that metallophilic macrophages, which represent an important component in the thymus physiology, are lacking in lymphotoxin-β receptor-deficient mice. However, further molecular requirements for the development and correct tissue positioning of these cells are unknown. To this end, we studied a panel of mice deficient in different chemokine ligand or receptor genes. In contrast to normal mice, which have these cells localized in the thymic cortico-medullary zone (CMZ) as a distinct row positioned between the cortex and medulla, in plt/plt (paucity of lymph node T cells) mice lacking the functional CCL19/CCL21 chemokines, metallophilic macrophages are not present in the thymic tissue. Interestingly, in contrast to the CCL19/21-deficient thymus, metallophilic macrophages are present in the CCR7-deficient thymus. However, these cells are not appropriately located in the CMZ, but are mostly crowded in central parts of thymic medulla. The double staining revealed that these metallophilic macrophages are CCR7-negative and CXCR3-positive. In the CXCL13-deficient thymus the number, morphology and localization of metallophilic macrophages are normal. Thus, our study shows that CCL19/21 and its possible signaling through CXCR3 are required for the development of thymic metallophilic macrophages, whereas the CXCL13–CXCR5 signaling is not necessary.     

Transcriptional and Histological Analyses of the Thymic Developmental Process in the Fetal Pig

The humanized pig model, in which human cells or tissues can be functionally maintained in pigs, can be an invaluable tool for human medical research. Although the recent development of immunodeficient pigs has opened the door for the development of such a model, the efficient engraftment and differentiation of human cells may be difficult to achieve. The transplantation of human cells into fetal pigs, whose immune system is immature, will ameliorate this problem. Therefore, we examined the development of porcine fetal thymus, which is critical for the establishment of the immune system. We first analyzed the levels of mRNA expression of genes that are relevant to the function of thymic epithelial cells or thymocytes in whole thymi from 35 to 85 days of gestation (DG) and at 2 days postpartum (DP) by quantitative RT-PCR. In addition, immunohistochemical analyses of thymic epithelial cells from DG35 to DG55 and DP2 were performed. These analyses showed that the thymic cortex was formed as early as DG35, and thymic medulla gradually developed from DG45 to DG55. These findings suggested that, at least before DG45, the thymus do not differentiate to form fully functional T cells.