重症肌无力患者胸腺肥大细胞的形态数量和超微结构研究

为探讨研究重症肌无力（ＭＧ）患者胸腺内肥大细胞的形态数量和其超微结构变化与ＭＧ发病的关系。方法对２８例ＭＧ患者作胸腺肥大细胞的形态半定量分析和光镜观察，其中１６例的胸腺进行电镜检查。结果ＭＧ胸腺不仅表现组织学异常，且肥大细胞数量明显增多，尤其是在非增生胸腺内出现大量肥大细胞，而在增生的髓质和生发中心区几乎见不到。电镜观察提示肥大细胞与上皮细胞、Ｔ淋巴细胞和毛细血管关系密切，且含多种形态的分泌颗粒。结论肥大细胞对胸腺细胞的分化成熟、胸腺屏障和胸腺功能，以及ＭＧ发病均起到一定的重要作用。     

The afferent innervation of the thymus gland in the rat

The afferent nervous supply to the thymus gland has been investigated by means of the retrograde transport of horseradish peroxidase. It has been shown that the thymus receives an afferent supply from the nodose ganglia of the vagus and from the dorsal root ganglia C₁–C₇. The afferent innervation of the right and left thymic lobes is bilaterally organized; the fibers of a small celled population of nodose ganglion neurons cross outside the thymus and those of a larger celled population cross within the thymus gland. The functional implications of these findings are discussed in the context of central nervous system-immune system interactions.     

Split tolerance in chimeric GVH mice

Abstract The i.v. inoculation of parental spleen cells into unirradiated adult F1 hybrid mice results in a graft-versus-host reaction (GVHR). In the strain combination B10D2±(B10.BRx B10.D2) F1, this reaction is associated with thymic injury and transient but profound cellular immune deficiency. We further analysed the immune status of these mice 60 days after GVHR induction. Phenotypic studies of spleen cells showed that these mice were re-populated with parental lymphocytes resulting in a high degree of chimerism (85%). At this time, the mice looked healthy and recovered a normal cytotoxic T cell response (CTL) against allogeneic cells. GVH chimeric splenocytes were unresponsive against F 1 hybrid cells in mixed lymphocyte culture (MLC), but exhibited anti-F1 CTL reactivity. We also analysed the anti-F 1 reactivity of these mice in vivo. GVH chimeric splenocytes were unable to induce GVHR after injection into a new F1 hybrid and F1 GVH mice specifically rejected F1 bone marrow (BM) cells after lethal irradiation. Grafting a neonatal parental thymus prevented the rejection of F1 BM cells and restored CTL alloreactivity. It is concluded that the chimeric state induced by GVHR is associated with a split tolerance and that a radiosensitive thymic-dependent mechanism is involved in maintaining self-tolerance in these mice.     

Thymus in myasthenia gravis: a light and electron microscopic study of a case with thymic follicular hyperplasia

The present study has focused mainly on microenvironmental aspects of the thymus from a 17-year-old female patient suffering from myasthenia gravis. The most striking lightmicroscopic feature was again the well known presence of lymphoid follicular hyperplasia. Ultrastructurally, the configuration, cellular composition and fine structure were to a large extent the same as in other, peripheral lymphoid organs. Cells showing the typical morphologic characteristics of fibroblastic reticulum cells, which are most probably precursors of dendritic reticulum cells, were observed within germinal centers. Additionally the morphology of the unaffected medulla and corticomedullary region was studied, thereby paying particular attention to the structural changes of interdigitating cells. These contained frequently Birbeck granules, which have not been described before in human thymus.     

Thymic stromal cell specialization and the T-cell receptor repertoire

Ten years ago, we proposed a model for thymus function in which thymic epithelial cells are primarily responsible for imprinting major histocompatibility complex (MHC)-restricted specificity, and bone marrow-derived macrophages or dendritic cells are responsible for the induction of self-tolerance. Since then, transgenic and knockout models have allowed for a dissection of thymic stromal components in vivo, leading to a new understanding of their specialized functions. We have determined that with regard to class II-restricted CD4 T-cell development, two distinct subsets of thymic epithelium help shape the repertoire: Cortical epithelium appears solely responsible for positive selection, whereas a fucose-bearing subset of medullary epithelium is specialized for negative selection. This absolute separation of positive and negative selection into two distinct spatial and temporal compartments leads to a much simpler view of the process of repertoire selection. Finally, a novel view of the function of the thymic medulla is discussed.     

Survival versus neglect: redefining thymocyte subsets based on expression of NKG2D ligand(s) and MHC class I

BALB/c thymocytes can be divided into three distinct subsets according to the expression of a ligand for the NK activation receptor NKG2D (NKG2D-L) and the expression of MHC class I (MHC-I). The first subset (MHC-Imid/NKG2D-Lhigh or "N+") is predominately CD4+CD8+ double positive (DP), comprises approximately 35% of thymocytes in a 6-8-week-old adult and contains uncommitted cells that have neither undergone selection nor are committed to death by neglect. The second subset (MHC-Ilow/NKG2D-Llow or "M-"), also mostly DP cells, comprises approximately 50% of thymocytes and consists of cells committed to death by apoptosis, likely due to neglect. By contrast, the third subset (MHC-Ihigh/NKG2D-Llow or "M+") is largely single positive (SP), represents approximately 15% of thymocytes and mostly contains more mature cells that have undergone successful positive selection. The major advantage of the analysis is that it splits DP cells into two subpopulations, one committed to death by apoptosis and the other subjected to selection. The analysis also suggests that NKG2D-L may play a role in thymocyte development.     

Thymus Ontogeny in Frogs: T-Cell Renewal at Metamorphosis

Metamorphosis in amphibians presents a unique problem for the developing immune system. Because tadpoles are free-living, they need an immune system to protect against potential pathogens. However, at metamorphosis, they acquire a variety of new adultspecific molecules to which the tadpole immune system must become tolerant. We hypothesized that Xenopus laevis tadpoles may avoid potentially destructive antiself responses by largely discarding the larval immune system at metamorphosis and acquiring a new one. By implanting triploid (3N) thymuses into diploid (2N) hosts, we examined the influx and expansion of host T-cell precursors in the donor thymus of normally metamorphosing and metamorphosis-inhibited frogs. We observed that donor thymocytes are replaced by host-derived cells during metamorphosis, but inhibition of metamorphosis does not prevent this exchange of cells. The implanted thymuses export T cells to the spleen. This donor-derived pool of cells declines after metamorphosis in normally developing frogs but is retained to a greater extent if metamorphosis is inhibited. These studies confirm previous observations of a metamorphosis-associated wave of expansion of T cells and demonstrate that it is not dependent on the relatively high concentrations of thyroid hormones required for metamorphosis. Although some larval T cells persist through metamorphosis, others may be destroyed or the larval population is significantly diluted by the expanding adult population.     

大鼠胸腺降黑素受体的鉴定及生物学特性

应用放射配体结合法证实大鼠胸腺内存在降黑素特异结合部位，该结合位点可以满足特异结合部位的基本条件：１．低结合容量；２．高亲和力；３．可饱和性；４．可逆性；５．对降黑素高度特异性。此外，该特异结合位点具昼夜节律；亚细胞分布的研究表明以细胞核含量最高，线粒体次之，并具有年龄依赖性降低，以出生时最高。     

CD45 expression by murine B cells and T cells: Alteration of CD45 isoforms in subpopulations of activated B cells

The CD45 family of high molecular weight cell surface glycoproteins is abundantly expressed by virtually all hematopoietic cells. CD45 molecules exist as multiple isoforms whose extracellular portions vary in protein structure and carbohydrate content but whose intracellular portions are highly conserved and possess tyrosine phosphatase activity. In this review we summarize current studies describing CD45 isoform expression on peripheral and thymic lymphocytes. Further, we analyze changes in CD45 isoform expression by selective populations of activated B cells.