Thymus-dependent Areas Research Articles

Developmental Exposure to Endocrine Disrupter DDT Interferes with Age-Related Involution of Thymus.

The impact of endocrine-disrupting chemicals on the development and involution of the immune system is a possible reason for the increased incidence of disorders associated with inappropriate immune function. The thymus is a lymphoid and also an endocrine organ, and, accordingly, its development and functioning may be impaired by endocrine disruptors. The aim was to evaluate age-related thymus involution in mature rats exposed to the endocrine disruptor DDT during prenatal and postnatal ontogeny. Methodology included in vivo experiment on male Wistar rats exposed to low doses of DDT during prenatal and postnatal development and morphological assessment of thymic involution, including the immunohistochemical detection of proliferating thymocytes. The study was carried out at the early stage of involution. Results: DDT-exposed rats exhibited a normal anatomy, and the relative weight of the thymus was within the control ranges. Histological and immunohistochemical examinations revealed increased cellularity of the cortex and the medulla, higher content of lymphoblasts, and more intensive proliferation rate of thymocytes compared to the control. Evaluation of thymic epithelial cells revealed a higher rate of thymic corpuscles formation. Conclusion: The data obtained indicate that endocrine disrupter DDT disturbs postnatal development of the thymus. Low-dose exposure to DDT during ontogeny does not suppress growth rate but violates the developmental program of the thymus by slowing down the onset of age-related involution and maintaining high cell proliferation rate. It may result in excessive formation of thymus-dependent areas in peripheral lymphoid organs and altered immune response.

Maria de Sousa, (1939-2020).

Maria de Sousa, (1939-2020).

Immunohistochemical evidences showing the presence of thymulin containing cells located in involuted thymus and in peripheral lymphoid organs.

Thymulin is a well-characterized thymic hormone that exists as a nonapeptide coupled to equimolar amounts of Zn2+. Thymulin is known to have multiple biological roles, including T cell differentiation, immune regulation, and analgesic functions. It has been shown that thymulin is produced by the reticulo-epithelial cells of the thymus, and it circulates in the blood from the moment of birth, maintain its serum level until puberty diminishing thereafter in life. To study the localization of this hormone, we prepared polyclonal and monoclonal antibodies against the commercial peptide and utilized immunocytochemical techniques for visualization. The results indicate that thymulin stains the thymic reticular cells, the outer layers of Hassall's corpuscles and a large round cellular type, which is keratin-negative and does not show affinity for the common leukocyte antigen (CD-45). In mice, this thymulin-positive cell remains in the thymus throughout life and even appears in relatively increased numbers in old involuted thymi. It also appears in thymus-dependent areas of the spleen and lymph nodes, demonstrating that at least one of the thymus cells containing this peptide can be found in peripheral lymphoid tissue.

Immunohistochemical evidences showing the presence of thymulin containing cells located in involuted thymus and in peripheral lymphoid organs

Thymulin is a well-characterized thymic hormone that exists as a nonapeptide coupled to equimolar amounts of Zn2+. Thymulin is known to have multiple biological roles, including T cell differentiation, immune regulation, and analgesic functions. It has been shown that thymulin is produced by the reticulo-epithelial cells of the thymus, and it circulates in the blood from the moment of birth, maintain its serum level until puberty diminishing thereafter in life. To study the localization of this hormone, we prepared polyclonal and monoclonal antibodies against the commercial peptide and utilized immunocytochemical techniques for visualization. The results indicate that thymulin stains the thymic reticular cells, the outer layers of Hassall's corpuscles and a large round cellular type, which is keratin-negative and does not show affinity for the common leukocyte antigen (CD-45). In mice, this thymulin-positive cell remains in the thymus throughout life and even appears in relatively increased numbers in old involuted thymi. It also appears in thymus-dependent areas of the spleen and lymph nodes, demonstrating that at least one of the thymus cells containing this peptide can be found in peripheral lymphoid tissue.

Increased expression of the peroxisome proliferator-activated receptor γ in the immune system of weaned pigs after Escherichia coli lipopolysaccharide injection

Peroxisome proliferator-activated receptor γ (PPARγ), a member of the nuclear hormone receptor superfamily, has been implicated in regulation of immunity and inflammation in rodents and humans. The objective of the current study was to investigate whether the expression of PPARγ was altered in the immune system of weaned pigs after Escherichia coli lipopolysaccharide (LPS) injection. PPARγ expression was investigated in the thymus, spleen, mesenteric lymph node and peripheral white blood cells of weaned pigs (8.54 ± 0.24 kg BW) after LPS injection (100 μg/kg BW, n = 6) and controls (sterile saline, n = 6), by using real-time polymerase chain reaction, Western blot analysis, and immunohistochemistry. Plasma pro-inflammatory cytokines and hormones were also assessed. LPS triggered PPARγ mRNA and protein expression in the thymus ( P < 0.05, 4.24-fold; P < 0.10, 1.46-fold), spleen ( P < 0.10, 2.75-fold; P < 0.05, 1.84-fold), mesenteric lymph node ( P < 0.05, 4.32-fold; P < 0.05, 1.96-fold) and peripheral white blood cells ( P < 0.001, 24.44-fold; P < 0.001, 1.58-fold). The LPS-injected pigs showed an increase in PPARγ staining in splenic corpuscle and periarterial lymphatic sheath of white pulp ( P < 0.05) and red pulp ( P < 0.001) of spleen, and in medullas of thymus lobule of thymus ( P < 0.05), and in thymus-dependent area of mesenteric lymph node ( P < 0.05) compared to the control pigs. Concurrent with up-regulation of PPARγ expression, LPS induced increases in plasma interleukin-6 ( P < 0.001), tumor necrosis factor-α ( P < 0.001), cortisol ( P < 0.001), prostaglandin E 2 ( P < 0.01) and 15-deoxy-Δ 12,14-prostaglandin J 2 (15d-PGJ 2) ( P < 0.05), and decreases in plasma insulin ( P < 0.10) and insulin-like growth factor-1 ( P < 0.001). These results suggest that induction of PPARγ expression in immune system may be associated with the release of the natural PPARγ activating ligand 15d-PGJ 2, and play an important role in host response to immunological stress. Additionally, it is possible that PPARγ would be a new therapeutic target in treatment of immunological stress of livestock.

De novo expression of MECA‐79 glycoprotein‐determinant on developing B lymphocytes in gut‐associated lymphoid tissues

Rabbit is one of several species that depend on development of B lymphocytes in gut-associated lymphoid tissues for primary immunoglobulin-repertoire diversification. The rabbit appendix is an important site of early B-lymphocyte development. We previously reported that peripheral lymph node addressin detected by monoclonal antibody (mAb) MECA-79 played a role in recruitment of immature blood-borne B cells into neonatal rabbit appendix. Here, we report expression of an approximately 127 000 MW O-linked sulphated proteoglycan on developing B cells in appendix and Peyer's patches recognized by the mAb MECA-79. Binding of the mAb to B lymphocytes was sensitive to enzyme treatment with O-sialoglycoprotease and expression was partially inhibited by sodium chlorate, a metabolic inhibitor of sulphation. The proportions of MECA-79(+) B lymphocytes gradually increased from < 0.5% at 3 days to > 70% at 6 weeks in appendix and Peyer's patches. The proportions of MECA-79(+) B lymphocytes in spleen and peripheral blood were very low (0.5-2%). However, the MECA-79 determinant was detected on B cells in splenic germinal centres after immunization. In situ labelling of appendix cells showed that the MECA-79 determinant was expressed on fluorescein-labelled B lymphocytes that migrated from appendix into mesenteric lymph nodes. B-cell MECA-79 may be involved in interactions with T cells and/or dendritic cells. Alternatively, because we found that lymphatic endothelium in the thymus-dependent area of appendix, a site for lymphocyte exit, expressed P-selectin (CD62P), interaction of the MECA-79 determinant on B cells with CD62P may have a role in the exit of B lymphocytes from rabbit appendix.

Anatomical and cellular basis of immunity and tolerance in the intestine.

Anatomical and cellular basis of immunity and tolerance in the intestine.

X-linked lymphoproliferative disease: clinical, diagnostic and molecular perspective.

X-linked lymphoproliferative disease: clinical, diagnostic and molecular perspective.

Mice lacking expression of the chemokines CCL21-ser and CCL19 (plt mice) demonstrate delayed but enhanced T cell immune responses.

The paucity of lymph node T cells (plt) mutation leads to a loss of CCL21 and CCL19 expression in secondary lymphoid organs. plt mice have defects in the migration of naive T cells and activated dendritic cells into the T cell zones of lymphoid organs, suggesting that they would have defects in T cell immune responses. We now demonstrate T cell responses in plt mice are delayed but ultimately enhanced. Responses to contact sensitization are decreased at day 2 after priming but increased at day 6. After subcutaneous immunization, antigen-specific T cell proliferation and cytokine production in plt mice are increased and remain markedly elevated for at least 8 wk. Compared with wild-type mice, a proportion of T cell response in plt mice are shifted to the spleen, and prior splenectomy reduces the T cell response in draining lymph nodes. After immunization of plt mice, T cells and dendritic cells colocalize in the superficial cortex of lymph nodes and in splenic bridging channels, but not in T cell zones. These results demonstrate that plt mice mount robust T cell responses despite the failure of naive T cells and activated dendritic cells to enter the thymus dependent areas of secondary lymphoid organs.

Extracellular matrix proteins in organ transplantation.

Extracellular matrix proteins in organ transplantation.

Trypanosoma cruzi:T Cell Subpopulations in the Peyer's Patches of BALB/c Infected Mice

The changes in the T cell subsets of the Peyer's patches and the thymus were analyzed in BALB/c mice infected withTrypanosoma cruzi,Tulahuén strain. During the acute stage of the infection both lymphoid organs drastically reduced their cellularity. This was mainly due to the decrease in the immature CD4+CD8+T cell population in the thymus and in both T and B cells in the Peyer's patches. In the acute infection, few Peyer's patches were found and the histological studies revealed a depletion of the thymic-dependent areas, paralleling the decreased number of cells expressing CD4 and αβ T cell receptor. After 14 weeks, in the late stage of the infection, the cellularity and the levels of the T cell subsets studied returned to values similar to those of noninfected mice.

Lymphatic tissue changes in rats flown on Spacelab Life Sciences-2.

Thymus, spleen, inguinal lymph node, and bone marrow specimens from rats flown on the 14-day Spacelab Life Sciences-2 mission were examined after staining of tissue sections. The primary observation was a transient retrogressive change in lymphatic tissues in the rats within a few hours after landing. There was a diffuse increase in tingible body-containing macrophages in the cortex of the thymus, thymus-dependent areas of the splenic white pulp, and inguinal lymph node. This was not observed 9 days after recovery. The in situ labeling of fragmented DNA strands catalyzed by exogenous terminal deoxynucleotidyltransferase (TdT) with ApopTag reagents (Oncor, Gaithersburg, MD) inside the tingible body-containing macrophages indicated that the process was one of apoptosis. No increase in tingible body macrophage activity was noted in thymus and spleen tissue obtained from rats in flight on flight day 13. The reaction to gravitational stress from readaptation to 1 G is the most likely explanation of the transient retrogressive change in lymphatic tissues.

A life stage of particle-laden rat dendritic cells in vivo: their terminal division, active phagocytosis, and translocation from the liver to the draining lymph.

Initiation of an adoptive immune response against pathogenic organisms, such as bacteria and fungi, may involve phagocytic activity of dendritic cells (DC) or their immature precursors as a prelude to antigen processing and presentation. After intravenous injection of rats with particulate matter, particle-laden cells were detected in the peripheral hepatic lymph. Since it has been known there is a constant efflux of DC from nonlymphoid organs into the draining peripheral lymph, we examined whether these particle-laden cells belonged to the DC or macrophage lineage. The majority of particle-laden cells in lymph showed immature monocyte-like cytology, and the amount of ingested particles was small relative to typical macrophages. We identified these particle-laden cells as DC based on a number of established criteria: (a) they had a phenotype characteristic of rat DC, that is, major histocompatibility complex class Ihigh+ and IIhigh+, intercellular adhesion molecule 1+ and 80% positive with the rat DC-specific mAb OX62; (b) they showed strong stimulating capacity in primary allogeneic mixed leukocyte reaction; (c) in vitro, they had little phagocytic activity; and (d) the kinetics of translocation was similar to that of lymph DC in that they migrated to the thymus-dependent area of the regional nodes. Furthermore, bromodeoxyuridine feeding studies revealed that most of the particle-laden DC were recently produced by the terminal division of precursor cells, at least 45% of them being <5.5 d old. The particle-laden DC, defined as OX62+ latex-laden cells, were first found in the sinusoidal area of the liver, in the liver perfusate, and in spleen cell suspensions, suggesting that the site of particle capture was mainly in the blood marginating pool. It is concluded that the particle-laden cells in the hepatic lymph are recently produced immature DC that manifest a temporary phagocytic activity for intravascular particles during or after the terminal division and that the phagocytic activity is downregulated at a migratory stage when they translocate from the sinusoidal area to the hepatic lymph.

Age associated changes in the distribution of lpr gene-induced B220-positive T cells in lymphoid organs of MRL/Mp-lpr/lpr mice using dual exposure microphotographs of double immunofluorescence staining.

Homozygous MRL/Mp-lpr/lpr [MRL/lpr] mice, which have an autosomal recessive mutant lpr gene and exhibit defects in Fas antigen, spontaneously develop autoimmune disease with progressive expansion and accumulation of characteristic abnormal CD4-CD8-double negative T cells that express B220 surface antigen, a B cell-specific surface marker in normal mice. We analyzed the distribution and age related changes of lpr gene-induced abnormal T cells (B220-positive lpr T cells) in the lymphoid organs of MRL/lpr mice. We studied cryostat sections of the spleen, peripheral lymph nodes, mesenteric lymph nodes, and Peyer's patches at different stages using FITC [fluorescein isothiocyanate)-conjugated monoclonal antibodies directed against B220 (RA3-6B2) and PE (phycoerythrin)-conjugated anti-mouse CD3 (2C11) monoclonal antibody, examining dual-exposure microphotographs of double-immunofluorescence stained preparations. We observed that in aged MRL/lpr mice, B220-positive abnormal lpr T cells were not present in the thymus-dependent area, and the majority of the follicular area cells were displaced by lpr T cells. These findings suggest that the cellular trafficking of B220-positive lpr T cells differs from that of conventional T cells and that these lpr-derived T cells play a role in the follicle.

The microepidemiology of wasting syndrome, a common link to diarrheal disease, cancer, rabies, animal models of AIDS, and HIV-AIDS YHAIDS). The feline leukemia virus and rabies virus models.

Infant cats were inoculated intracranially with rabies or feline leukemia viruses in an experimental study of wasting syndrome. The daily pre- and postinoculation body weights were recorded until kittens were moribund. Affected animals in both groups manifested growth failure or wasting syndrome. Immunodepression, manifested by a conspicuous depletion of thymic cortex, the thymus dependent areas of the spleen, and growth hormone producing-alpha adenopituicytes was significantly (p less than 0.01) related to the wasting status of the animals. The ability of pituitary glands from these animals to produce growth hormone was studied by in situ immunoperoxidase staining and showed a significant (p less than 0.01) difference between healthy and wasted animals. Rabies and feline leukemia viruses were each found responsible for the low immunoreactivity of growth hormone producing alpha adenopituicytes. Because the hypothalamus and the hypophysis were both found infected, it was concluded that regardless of the triggering agent in primary wasting, the hypothalamic-hypophyseal-thymic axis was always involved through a decrease in growth hormone production.

Immunostimulatory Activity of Prothymosin‐Alpha in Senescencea

In this study we evaluated the immunorestorative activity of prothymosin-alpha (ProT-alpha) in senescence. Aged rats were repeatedly injected with ProT-alpha after antigen challenge. Both humoral and cell-mediated immune reactions were tested. The results show that ProT-alpha exerted a marked immunopotentiating effect in aged rats. Moreover, ProT-alpha induced enhancement of PFC response, and skin hypersensitivity reactions were more pronounced in senescent rats than in young adult controls. ProT-alpha treatment increased thymus and spleen weights in aged rats, and induced qualitative and quantitative improvements of the cellular make-up of the thymus and thymus-dependent areas of the spleen. The results imply that "restoring" thymus endocrine function by exogenous administration of ProT-alpha may improve immune system homeostasis in senescence.

Enkephalin‐Induced Stimulation of Humoral and Cellular Immune Reactions in Aged Ratsa

Twenty-month-old Wistar rats received intraperitoneal injections of the opioid pentapeptide, methionine-enkephalin (Met-Enk) in periods before and after immunization with cellular and soluble antigens. Animals were treated with 0.2 mg of Met-Enk/kg b.w., a dose previously found to increase immune capacity in young adult rats. Saline-treated 20-month-old, and Met-Enk-treated rats and saline-treated 8-week-old controls were set up for each experimental group. Immune performance was evaluated by plaque-forming cell response, antibody production and various immunoinflammatory reactions. At autopsy, thymus and spleen were weighed and processed for histological examination. The results showed that 0.2 mg dose of Met-Enk produced significant enhancement of both humoral and cellular immune responses in senescent rats. Methionine-enkephalin treatment also induced a significant increase in thymus and spleen weights in these animals. Analysis of the cellular make up of these organs revealed the enlargement of cortical and medullary areas, and pronounced pyroninophilia in the subcortical zone of the thymus and thymus-dependent areas of the spleen. The results suggest that Met-Enk exerts an immunorestorative activity in aged animals, and that changes in the opioid system may play an important role in the maintenance of immune functions during senescence.

The athymic nude rat Immunobiological characteristics with special reference to establishment of non‐antigen‐specific T‐cell reactivity and induction of antigen‐specific immunity

The aim of the present review has been to describe some immunobiological characteristics of the athymic nude rat and on the basis of these to describe the possibilities of establishing non-antigen-specific T-cell reactivity and inducing antigen-specific immunity. After a brief introduction, some general characteristics of the autosomal recessive rnu/rnu rat are outlined. This athymic mutant normally has a longer lifespan than athymic nude mice and is easier to breed. Inbred nude rats are now available with several rat strain backgrounds. Since the rnu/rnu rat is athymic, the morphology and function of the thymus are briefly described. The thymus has two main functions: production of T lymphocytes and production of thymic hormones. The intrathymic T-cell ontogeny is described along with the two thymocyte selection mechanisms, positive and negative selection. Different thymic hormones are mentioned and their possible function outlined. However, thymic hormones still do not play an important role in immunotherapy. There are some striking differences in the morphology of lymphatic tissues of athymic and euthymic rats. The thymic area in nude rats consists only of fat and clusters of epithelial cells. Little research has been performed on bone marrow of athymic nude rats but morphologically there seems to be no difference from findings in normal animals. The thymus-dependent areas of peripheral lymphoid organs, i.e. the paracortical area of lymph nodes, the periarteriolar sheet of the splenic white pulp, and the interfollicular areas of Peyer's patches, are severely cell-depleted in the athymic nude rat. The lower lymphocyte content of these organs is not reflected in the lymphocyte counts of peripheral blood, but the lymphocyte counts of thoracic duct lymph are much lower than those found in euthymic animals. Few T-lymphocyte marker-positive cells are found in the athymic nude rat, and in the epithelium of the intestine there are also lymphocytes bearing neither T nor B markers. These cells probably represent the tau delta receptor-bearing cells. Immunologically the athymic nude rat reflects the thymic aplasia. Normal B-lymphocyte function has been found in both in vitro and in vivo tests, whereas the T-cell function is virtually absent both in vitro and in vivo. Non-MHC-restricted cells with killer activity like NK cells are present in the nude rat, and these cells function normally both in vitro and in vivo.(ABSTRACT TRUNCATED AT 400 WORDS)

ヘアレス犬の皮膚およびリンパ器官の組織学的観察

The skin and lymphoid organs of Mexican hairless dogs and their hairless offspring were examined histologically. The hairless dogs lacked most hairs except for sparse hairs on the head, tail and feet. The skin of newborn pups consisted of a thick epidermis with epidermal ingrowths forming the rudiments of hair follicles. In older dogs more than 2 months of age, however, the epidermis was thin and the ingrowths were few. Neither hair follicles nor skin glands were present. The hairy skin of the head and tail had hair follicles with sebaceous glands. Regarding the lymphoid organs, the newborn pups possessed a thymus like haired pups. But in the older dogs more than 2 months of age, the thymus was atrophied and the lymphocyte population was too sparse to demarcate the cortex and the medulla. Lymphocyte accumulation in older dogs was also poor in the spleen and mesenteric lymph nodes. The present findings indicate that the hairlessness of the Mexican hairless dogs and their descendants is accompanied by early atrophy of the thymus after birth, and is followed by poor accumulation of lymphocytes in the thymus-dependent area of the spleen and the mesenteric lymph nodes. The defect of the thymus in the hairless dog seems to be different from that in athymic nude mice and rats. Further studies are needed to elucidate the immunological response and function in hairless dogs.

The arrangement of collagen fibrils in the lymphatic sinus wall of the rabbit appendix.

The lymphatic sinus of the rabbit appendix was examined by scanning and transmission electron microscopy. Luminal surfaces of the sinus were lined by squamous endothelial cells, some of which, however, were blebby in surface relief due to the presence of electron dense granules in the cytoplasm. Many clusters of lymphocytes were present on the endothelial surface, mainly along the blood vessels of the trabeculae and of the sinus wall. Regional differences in collagen fibrillar arrangement of the sinus wall were demonstrated after the removal of the endothelial cells by the NaOH maceration method (OHTANI, 1987). In the upper region of the sinus and the lymphatic plexus of the internodular thymus dependent area (TDA), the fibrillar layer was a delicate network of interwoven thin fibrils. Furthermore, transmission electron microscopy revealed frequent transmural passages of lymphocytes, which suggest the existence of pores or fenestrations in the fibrillar layer of these regions. The fibrillar layer in the lateral and basal sinus was formed by densely interwoven thick bundles or sheets which consisted of thin collagen fibrils. No obvious space was seen between fibrils. These observations suggest that the upper region of the sinus and the lymphatics in the TDA may be active sites of cell migration from the reticular tissue.