Electron microscopic study of involuting thymus of “lethargic” mutant mice

The thymus, which undergoes spontaneous involution three weeks after birth in “lethargic” mutant mice, was studied by electron microscopy. Ultrastructural alterations observed in the involuting thymus of “lethargic” mice resemble those of acute thymic involution induced by the administration of adrenal corticosteroids. The responsive cells in thymic involution of “lethargic” mice were cortical thymocytes, macrophages, and epithelial cells. The first indication of the involution was the appearance of a large number of degenerating thymocytes in the cortex. Pyknotic nuclei of degenerating thymocytes were observed within the macrophages. Macrophages of the involuting thymus were characterized by their content of thymocyte pyknotic nuclei as well as a variety of cytoplasmic inclusions. Cytoplasmic inclusions were also found in the epithelial cells. The inclusions were of two different types: (a) tonofibrils in markedly increased numbers in relation to a non-involuted thymus, and (b) large vacuoles with dense bodies and/or myelin figures, as found in a normal cell, but several times the number one would expect to find. A large number of lipid-laden cells were found in the involuted thymus. This type of cell was not seen in the normal thymus. Numerous Hassall's corpuscles were also found in the involuted thymus of “lethargic” mice.     

Nerve growth factor prevents apoptosis of cord blood-derived human cultured mast cells synergistically with stem cell factor

BACKGROUND: Stem cell factor (SCF) has been identified as a critical survival factor of human mast cells. Other cytokines which possess survival promotion activity on human mast cells are less known. OBJECTIVE: We examined the survival promotion activity of nerve growth factor (NGF) on cord blood-derived human cultured mast cells. METHODS: Expression and function of NGF receptors on the mast cells were examined by RT PCR, flowcytometric analysis, immunoprecipitaion and western blotting. The survival promotion activity of NGF to the mast cells was examined. To evaluate the proliferating activity of NGF on the human cultured mast cells, flow cytometric analysis with propidium iodide staining was applied. To confirm whether the human mast cell growth activity of NGF was caused by a suppression of apoptosis, the proportion of the cells containing in situ DNA fragmentation was counted. RESULTS: The human cultured mast cells expressed the high affinity receptor p140trk but not the low affinity receptor p75LNGFR. NGF induced the phosphorylation of p140trk. NGF alone could not support the survival of the mast cells, however, the addition of NGF to the culture medium containing recombinant SCF led to a significant increase of the number of survival mast cells. No significant changes of the cell cycle from G0/G1 phase to the S/G2 + M phases were observed by NGF. In contrast, the addition of NGF to the medium with SCF showed a significant inhibitory effect on the apoptosis of the mast cells. CONCLUSION: NGF may act as a key factor to promote the survival of human mast cells synergistically with SCF through the prevention of apoptosis.     

Molecular control over thymic involution: from cytokines and microRNA to aging and adipose tissue

The thymus is the primary organ for T ‐cell differentiation and maturation. Unlike other major organs, the thymus is highly dynamic, capable of undergoing multiple rounds of almost complete atrophy followed by rapid restoration. The process of thymic atrophy, or involution, results in decreased thymopoiesis and emigration of naïve T cells to the periphery. Multiple processes can trigger transient thymic involution, including bacterial and viral infection(s), aging, pregnancy and stress. Intense investigations into the mechanisms that underlie thymic involution have revealed diverse cellular and molecular mediators, with elaborate control mechanisms. This review outlines the disparate pathways through which involution can be mediated, from the transient infection‐mediated pathway, tightly controlled by micro RNA , to the chronic changes that occur through aging.     

Human mast cells express functional TrkA and are a source of nerve growth factor

Mast cells are the principal effector cells in IgE-dependent hypersensitivity reactions. Despite reports that rodent mast cells proliferate in the presence of nerve growth factor (NGF), human mast cells reportedly do not respond to this factor. To determine if human mast cells express the NGF receptors, TrkA tyrosine receptor and the low affinity NGF receptor (LNGFR), we first analyzed the mRNA expression by RT-PCR of TrkA and LNGFR in a human mast cell line (HMC-1) and in human mast cells cultured in the presence of stem cell factor. Both HMC-1 and cultured human mast cells were found to express TrkA but not LNGFR. TrkA protein was demonstrated by Western blot analysis of HMC-1 lysates. Using flow cytometric analysis and mast cell tryptase as a mast cell marker, both HMC-1 cells and cultured human mast cells were shown to co-express tryptase and TrkA. Treatment of mast cells with NGF resulted in phosphorylation of TrkA on tyrosine residues as detected by immunoblotting with an antiphosphotyrosine antibody. Furthermore, NGF induced the immediate early gene c-fos in HMC-1 cells. HMC-1 cells and cultured human mast cells were also found to express NGF mRNA, and conditioned medium from HMC-1 cells stimulated neurite outgrowth from chicken embryonic sensory ganglia in culture. This effect was blocked by anti-NGF. Thus, mast cells express functional TrkA and synthesize NGF, suggesting a mechanism by which NGF may act as an autocrine factor for human mast cells, and by which mast cells and nerves may interact.     

Allometric growth of the rat peritoneal mast cell mass and of the granular constituents: heparin, histamine and 5-hydroxytryptamine

This paper reports an attempt to measure the normal growth of connective tissue mast cells in rats aged 6 to 24 weeks. We used peritoneal mast cells as a model, and calculated the total mast cell mass and the mass of its components from total peritoneal mast cell numbers and their content of protein, heparin, histamine and 5-hydroxytryptamine (5-HT). The growth process was analysed with the aid of allometric, log-log plots of mast cell quantities versus body weight and linear regression, in order to facilitate comparisons with other systems, notably the lymphoid apparatus. We found that the growth of peritoneal mast cells conformed to the allometric principle (r = 0.91 to 0.93). There were no deviations from linearity or changes in the slope (growth rate constant, k) of the allometric lines within the studied growth interval. K ranged from 1.3 to 1.7, indicating that the mast cell mass and its different components grew at a faster rate than the body as a whole, typical of a late maturing cell system. The mode of growth of the peritoneal mast cells is thus distinctly different from that of the lymphoid system, and neither thymus involution nor sexual maturation appears to influence the growth of these cells.     

Mast cells and eosinophils are involved in activation of ulcerative colitis

PurposeThe intestinal mucosal immune cells such as the mast cells and eosinophils play an important role in the pathogenesis of ulcerative colitis (UC). The aim of present study was to compare the number of mast cells and eosinophils in patients with active and non-active ulcerative colitis. Another purpose was to found whether the number of eosinophils could correlate with number of mast cells in both tested groups.Material and MethodsThe twenty-five of formalin-fixed, paraffin-embedded tissue specimens of active ulcerative colitis, the twenty of non-active ulcerative colitis and the ten of controls were retrieved from archival material. Tryptase and chymase immunopositive cells were detected using immunohistochemical method. Additionally, the number of mast cells and eosinophils were detected using the most common histochemical methods.ResultsThe number of eosinophils and toluidine blue stained and tryptase immunopositive mast cells was significantly increased in active UC compared to non-active UC. In active stage of UC positive correlation between the number of mast cells stained with toluidine blue and the number of chymase and tryptase immunopositive mast cells were observed. Moreover, the number of eosinophils was significantly correlated with number of mast cells stained with toluidine blue and number of tryptase- and chymase immunopositive mast cells. In non-active stage of UC positive correlation was observed only between the number of mast cells stained with toluidine blue and chymase immunopositive cells and eosinophils.ConclusionsIn conclusion, our findings confirmed that mast cells and eosinophils are functionally involved in the course of UC.     

The expanding role of nerve growth factor: from neurotrophic activity to immunologic diseases

Numerous studies published in the last 10–15 years have shown that nerve growth factor (NGF), a polypeptide originally discovered in connection with its neurotrophic activity, also acts on cells of the immune system. NGF has been found in various immune organs including the spleen, lymph nodes, and thymus, and cells such as mast cells, eosinophils, and B and T cells. The circulating levels of NGF increase in inflammatory responses, in various autoimmune diseases, in parasitic infections, and in allergic diseases. Stress-related events both in animal models and in man also result in an increase of NGF, suggesting that this molecule is involved in neuroendocrine functions. The rapid release of NGF is part of an alerting signal in response to either psychologically stressful or anxiogenic conditions in response to homeostatic alteration. Thus, the inflammation and stress-induced increase in NGF might alone or in association with other biologic mediators induce the activation of immune cells during immunologic insults. A clearer understanding of the role of NGF in these events may be useful to identify the mechanisms implicated in certain neuroimmune and immune dysfunctions.     

The production of immunomodulating polypeptides by the thymus during its acute (accidental) involution in children

The content of the thymalin polypeptides in the thymus is studied in the course of the 1st to 4th stages of the acute thymus involution in children dying from noninfectious and infectious disease. The results obtained were compared to the level of the circulating thymic factor and the number of T- and 'O' lymphocytes in the circulating blood of children with identical diseases and control group of the same age. It is concluded that the acute involution of the thymus in children with non-infectious and acute infectious diseases results in the progressive decrease of the production by the thymus of the immunomodulating polypeptides (thymic hormones) which is restored in the period of recovery.     

Response of intestinal globule leucocytes in the mouse during a Trichinella spiralis infection and its independence of intestinal mast cells.

We have previously reported that intestinal mast cells represent a separate population of mast cells which is thymus- (T-) dependent. In this paper we examine whether the appearance of these cells is dependent on thymus-dependent antibodies or thymus serum factor(s). The response of intestinal mast cells and globule leucocytes to a Trichinella spiralis infection was therefore studied in congenitally athymic (nude) mice after treatment with specific anti-T. spiralis hyperimmune serum or normal mouse serum from thymus-bearing litter-mates. However, transfer of both types of serum did not lead to an intestinal mast cell response. It was concluded that the presence of an intact thymus or T-dependent cellular reactions and/or their products are essential for appearance of intestinal mast cells. In contrast infected athymic mice reacted with a minor reponse of globule leucocytes irrespective of the serum transfer. Occasionally metachromatic intra-epithelially located cells with toluidine-blue-positive granules, believed to be globule leucocytes, showed mitotic figures. Metachromatic cells were observed occasionally within the lumen of the gut. These data were interpreted as supporting the idea that the globule leucocyte is a cell sui generis and independent of the intestinal mast cell.     

The human thymus

The human thymus is a lymphoepithelial organ in which T cells develop during fetal life. After maturation and selection in the fetal thymic microenvironment, T cells emigrate to peripheral lymphoid tissues such as the spleen, gut, and lymph nodes, and establish the peripheral T cell repertoire. Although the thymus has enormous regenerative capacity during fetal development, the regenerative capacity of the human postnatal thymus decreases over time. With the advent of intensive chemotherapy regimens for a variety of cancer syndromes, and the discovery that infection with the Human Immunodeficiency Virus (HIV) leads to severe loss of CD4⁺ T cells, has come the need to understand the role of the human thymus in reconstitution of the immune system in adults. During a recent study of the thymus in HIV infection, we observed many CD8⁺ T cells in AIDS thymuses that had markers consistent with those of mature effector cytotoxic T cells usually found in peripheral immune tissues, and noted these CD8⁺ effector T cells were predominately located in a thymic zone termed the thymic perivascular space. This article reviews our own work on the thymus in HIV-1 infection, and discusses the work of others that, taken together, suggest that the thymus contains peripheral immune cell components not only in the setting of HIV infection, but also in myasthenia gravis, as well as throughout normal life during the process of thymus involution. Thus, the human thymus can be thought of as a chimeric organ comprised of both central and peripheral lymphoid tissues. These observations have led us to postulate that the thymic epithelial atrophy and decrease in thymopoiesis that occurs in myasthenia gravis, HIV-1 infection, and thymic involution may in part derive from cytokines or other factors produced by peripheral immune cells within the thymic perivascular space. An erratum to this article is available at .     

Expression of cytokines and proteases in mast cells in the lesion of subcapsular cell hyperplasia in mouse adrenal glands

To examine the possible roles of mast cells in the pathogenesis of subcapsular cell hyperplasia (SCH) in the adrenal glands of mice, we investigated the expression of certain cytokines, including stem cell factor (SCF), tumor necrosis factor-alpha (TNF-alpha), nerve growth factor (NGF), and basic fibroblast growth factor (bFGF), and mast cell-specific proteases, such as mouse mast cell protease (mMCP)-2 and mMCP-7. The mRNAs of c-kit (SCF receptor), bFGF, TNF-alpha, mMCP-2, and mMCP-7 were expressed in both the adrenal glands and the mouse bone marrow-derived mast cells (mBMMCs). Immunoreactivities for cytokines (SCF, NGF, TNF-alpha) and proteases (mMCP-2, mMCP-7) were exclusively located in the mast cells in SCH lesions. The immature mBMMCs did not express the mRNAs of SCF and NGF, whereas the mast cells in the SCH lesions showed the expression of SCF and NGF. These findings suggest that SCH may provide a favorable microenvironment for functional maturation of mast cells to produce SCF and NGF, and the mast cells in SCH lesions synthesize SCF and NGF and may, in part, use them in autocrine fashion for their survival and differentiation. Therefore, mast cells may contribute to SCH pathogenesis by producing a range of multifunctional cytokines and proteases.     

电针对脑梗塞大鼠海马结构内GFAP免疫阳性细胞的形态学影响

目的观察电针对脑梗塞大鼠海马结构内胶质纤维酸性蛋白(GFAP)免疫阳性细胞形态学的影响,为探讨针刺治病机制的胶质细胞机制提供实验依据。方法线栓法建立大鼠脑梗塞模型,用免疫细胞化学方法显示针刺对大鼠海马结构内GFAP免疫阳性细胞的形态、分布及数量,并与非针刺组、假手术组和对照组的比较,电针对大鼠海马结构GFAP阳性细胞的形态。结果①对照组大鼠海马结构内可见散在多角形和椭圆形的GFAP阳性细胞。前者分布多见于CA4区,胞体较大,突起少而短,GFAP免疫反应产物沉积胞膜和胞体一侧;后者多见与CA1区,胞体较小,突起多而长,GFAP免疫产物充满胞体。假手术组大鼠海马结构内GFAP免疫反应阳性细胞的分布和形态与对照组的比未见明显组间差异。非电针组大鼠海马结构内可见大量GFAP免疫阳性细胞,GFAP免疫反应较对照组明显增强。但其形态和分布与对照组的比未见明显差异。电针组大鼠海马结构内GFAP免疫阳性细胞的数量、体积和免疫反应的程度均比非电针组的增多、增大和增强。②对照组大鼠海马结构内GFAP阳性细胞数量与假手术组的差异无统计学意义(P0.05);非电针组的GFAP阳性细胞比对照组的明显增加,差异有统计学意义(P0.01);电针组的GFAP阳性细胞比非电针组的增加,差异有统计学意义(P0.01)。③大鼠海马结构内GFAP免疫产物的相对量在对照组与假手术组的比较差异无统计学意义(P0.05);非电针组的比对照组的明显增加,差异有统计学意义(P0.01);电针组的比非电针组的增加,差异有统计学意义(P0.01)。结论1～2mA强度的电刺激"曲池"和"足三里"穴位能影响大鼠海马结构内星形胶质细胞的激活并上调GFAP的表达,参与缺血性神经元生存或死亡归宿的调节过程。     

Thymic pseudotumorous enlargement due to follicular hyperplasia in a human immunodeficiency virus sero-positive patient. Immunohistochemical and molecular biological study of viral infected cells.

An enlargement of the thymus suggesting a tumor was discovered in a 28-year-old man who had early-stage acquired immune deficiency syndrome. A biopsy was performed. The adipose involuted thymus, with persistence of many Hassall's corpuscles, was judged to be a large lymphoid follicular hyperplasia. This follicular hyperplasia was similar to that previously described for lymph nodes, spleen, and other lymphoid tissues at earlier stages of human immunodeficiency virus infection, before the development of acquired immune deficiency syndrome. Human immunodeficiency virus RNA and p24 human immunodeficiency virus protein were detected in the hyperplastic germinal centers (lymphocytes and follicular dendritic infected cells), and also in many cells that may have been either lymphocytes and/or epithelial cells in the interfollicular areas. The tissue was negative for Epstein-Barr virus DNA sequences, as determined by the polymerase chain reaction. These observations identify the first state of infection of the thymus in a human immune deficiency virus-infected adult, preceding the severe involution with lymphoid depletion observed in all fatal cases of acquired immunodeficiency syndrome in which the thymus has been analyzed.     

The role of mast cells in inflammatory processes: evidence for nerve/mast cell interactions

In the rat, there is considerable evidence of mast cell/nerve interaction both in the normal and infected intestine. Between 67 and 87% of all mast cells in the intestinal lamina propria of rats infected 22-35 days earlier with Nippostrongylus brasiliensis were touching nerves. These membrane contacts were between subepithelial mast cells and nonmyelinated nerves containing substance P, calcitonin gene-related peptide and neurone specific enolase. 2.5S nerve growth factor (NGF) has a significant enhancement effect on antigen-induced histamine release without addition of phosphatidylserine, and the in vivo administration of NGF to rats causes both connective tissue and mucosal mast cells to dramatically increase in number. All of these effects are both dose dependent and NGF specific, as evidenced by inhibition with anti-NGF. 2.5S NGF also causes in vitro increase of colonies in methylcellulose cultures of human peripheral blood. The effects of NGF in this system are synergistic with other T cell-derived growth factors and relatively specific for metachromatic cell growth. These observations support the conclusions that nerves and mast cells may constantly communicate and provide a structural and conceptual framework whereby the central nervous system may communicate with inflammatory events.     

Alterations in mast cell frequency and relationship to angiogenesis in the rat mammary gland during windows of physiologic tissue remodeling

Background: The mammary epithelium undergoes proliferation and regression accompanied by remodeling of the fibrocellular and vascular stroma. Mast cells are abundant in these compartments and have been implicated in remodeling during wound healing and cancer progression. The purpose of this study was to test the hypothesis that mast cell abundance correlates with physiologic mammary tissue remodeling during estrous cycling, lactogenesis (pregnancy and lactation) and involution. Results: Mast cell and capillary frequency were quantified in the stroma surrounding ducts and lobules from mammary glands of rats. During estrous cycling, periductal mast cell numbers were unchanged, but lobule‐associated mast cells significantly increased in the regressive phase of diestrus II. During lactogenesis, lobular stroma mast cells peaked early in pregnancy, at D2, followed by a significant decrease throughout lactation. Involution was associated with a rapid return in mast cell numbers, similar to diestrus II. Lobular vascularization peaked during the state of metestrus, when limited secretory differentiation occurs. Lobular angiogenesis peaked at D7 of pregnancy, regressed, and then returned to high levels during lactation and early involution, when secretory differentiation is high. Conclusions: These results suggest mast cells are predominantly associated with regressive lobular remodeling during cycling and involution, whereas angiogenesis is predominantly associated with secretory differentiation. Developmental Dynamics 241:890–900, 2012. © 2012 Wiley Periodicals, Inc.