T cell receptor excision circles as a tool for evaluating thymic function in young children

The thymus is a primary lymphoid organ responsible for the maturation of T cells as well as the immunological central tolerance. It is in the antenatal period and infancy that it plays its major role. In clinical practice, T cell receptor excision circles (TRECs) are considered a direct and reliable measure of the thymic function. TRECs are a by-product of DNA formation in gene rearrangement of T cell receptors. They are stable and they do not duplicate during mitosis, representing the recent emigrant T cells from the thymus. Despite their importance, TRECs have been neglected by physicians and there is a lack of data regarding thymic function during infancy of healthy children. In order to evaluate thymic function in the first years of life, we propose measuring TRECs as a valuable tool. One hundred and three blood samples from children and adolescents between 3 months and 20 years of age were analyzed. The mean TRECs count was 136.77±96.7 copies of TRECs/μL of DNA. The individuals between 0 and 5 years of age had significantly higher TRECs values than those between 10 and 20 years of age. No significant difference was observed in TRECs values among age groups below 5 years of age. An inverse correlation between TRECs and age was found (r=0.3 P=0.003). These data highlight and validate the evidence of decreased thymus function with age, even during infancy. Awareness should be raised with this important albeit ignored organ.

Growth hormone in the presence of laminin modulates interaction of human thymic epithelial cells and thymocytes in vitro

BACKGROUND: Several evidences indicate that hormones and neuropeptides function as immunomodulators. Among these, growth hormone (GH) is known to act on the thymic microenvironment, supporting its role in thymocyte differentiation. The aim of this study was to evaluate the effect of GH on human thymocytes and thymic epithelial cells (TEC) in the presence of laminin. RESULTS: GH increased thymocyte adhesion on BSA-coated and further on laminin-coated surfaces. The number of migrating cells in laminin-coated membrane was higher in GH-treated thymocyte group. In both results, VLA-6 expression on thymocytes was constant. Also, treatment with GH enhanced laminin production by TEC after 24 h in culture. However, VLA-6 integrin expression on TEC remained unchanged. Finally, TEC/thymocyte co-culture model demonstrated that GH elevated absolute number of double-negative (CD4-CD8-) and single-positive CD4+ and CD8+ thymocytes. A decrease in cell number was noted in double-positive (CD4+CD8+) thymocytes. CONCLUSIONS: The results of this study demonstrate that GH is capable of enhancing the migratory capacity of human thymocytes in the presence of laminin and promotes modulation of thymocyte subsets after co-culture with TEC.

Fibronectin modulates thymocyte-thymic epithelial cell interactions following Trypanosoma cruzi infection

Developing thymocytes interact with thymic epithelial cells (TECs) through cell-cell interactions, TEC-derived secretory moieties and extracellular matrix (ECM)-mediated interactions. These physiological interactions are crucial for normal thymocyte differentiation, but can be disrupted in pathological situations. Indeed, there is severe thymic atrophy in animals acutely infected with Trypanosoma cruzi due to CD4+CD8+ thymocyte depletion secondary to caspase-mediated apoptosis, together with changes in ECM deposition and thymocyte migration. We studied an in vitro model of TEC infection by T. cruzi and found that infected TEC cultures show a reduced number of cells, which was likely associated with decreased proliferative capacity, but not with increased cell death, as demonstrated by bromodeoxyuridine and annexin-V labelling. The infected TEC cultures exhibited increased expression of fibronectin (FN), laminin (LM) and type IV collagen. Importantly, treatment with FN increased the relative number of infected cells, whereas treatment with anti-FN or anti-LM antibodies resulted in lower infection rates. Consistent with these data, we observed increased thymocyte adhesion to infected TEC cultures. Overall, these results suggest that ECM molecules, particularly FN, facilitate infection of the thymic epithelium and that the consequent enhancement of ECM expression might be associated with changes in TEC-thymocyte interactions.

Morphological characteristics of the rat thymus duringperinatal protein deprivation and early refeeding: a qualitative and quantitative study

Protein malnutrition is particularly deleterious in young individuals. An immunodeficient state is a well‑known functional consequence but alterations in thymic morphology remain unknown. Our aim is to analyze morphological characteristics of the rat thymus in a perinatal undernutrition and renutrition model – we hypothesize these morphological alterations are reversible with early refeeding. Ninety-day-old Wistar rats were allowed to mate and divided into three groups: nourished (N – normal 20% protein diet), undernourished (UN – pre- and postnatal 5% protein diet until post-natal day 60 – PND 60) and renourished (RN – as UN but normal diet from PND 21 to 60). The thymi of 10 pups/group were submitted to macroscopic, histology, morphometry and scanning electron microscopy analyses. Body weight was highest in N and lowest in UN animals as expected but the thymic/body weight ratio remained similar in N and UN; this ratio was significantly higher in the RN group. UN thymi had a prevalence of type I collagen fibers, atrophic lobules and absence of a clear corticomedullary boundary. Thymic cortical component was decreased in UN. Apoptotic thymocytes were more frequently visualized in the UN thymi. N and RN thymi exhibited very similar morphology. Perinatal protein malnutrition induces drastic morphological alterations in rat thymi but these could be largely reversed with early renutrition. Functional studies are needed to assess if organ function mimics morphology in its recovery.

Distribution and Quantification of Lymphocytes in the Major Lymphoid Organs of Naturally Gumboro Infected Broilers / Distribución y Cuantificación de Linfocitos en los Órganos Linfoides Principales de Pollos de Engorda Infectados Naturalmente con Gumboro

Gumboro disease is caused by the infectious bursal disease virus (IBDV) which rapidly destroys immature B-lymphocytes of bursa of Fabricious, and causes immune suppression and high mortality in commercial broiler farms in Bangladesh. To investigate the possible effect of IBDV on lymphocytes and its distribution in the major lymphoid organs, bursa of Fabricious including spleen and thymus of naturally Gumboro-infected broilers, a research was conducted in the Department of Anatomy and Histology, collaboration with the Department of Pathology, Bangladesh Agricultural University, Bangladesh. Bursa of Fabricious, spleen and thymus of 21-days-old Gumboro-infected and non-infected broilers of same age (control) were routinely processed and stained by hematoxylin and eosin to examine the distribution of lymphocytes in the major lymphatic organs as well as quantified the number of lymphocytes under high power magnification field and compared with those of control. The number of lymphocytes in bursa of Fabricious, spleen and thymus of Gumboro-infected broilers were 27.20 ± 1.53, 66.50 ± 2.70 and 79.30 ± 3.92 whereas 121 ± 3.82, 89.90 ± 2.09 and 106.30 ± 4.07 were in non-infected control respectively. The numbers of lymphocytes were significantly (p < 0.05) lower in all lymphatic organs of Gumboro-infected broilers than those of non-infected control. The significant numbers of lymphocytes decrease in spleen and thymus suggest that IBVD not only destroy lymphocytes in bursa of Fabricious, but also in spleen and thymus and thus may severely suppress the immune response of IBVD affected broilers.

La enfermedad de Gumboro es causada por el virus de la bursitis infecciosa (VBI), que destruye rápidamente los linfocitos B inmaduros de la bolsa de Fabricio, y causa supresión inmune y la elevada mortalidad en las granjas comerciales de pollos de engorde en Bangladesh. Para investigar el posible efecto del VBI en los linfocitos y su distribución en los órganos linfoides principales, la bolsa de Fabricio, incluyendo el bazo y el timo de pollos de engorde naturalmente infectados con Gumboro, se realizó una investigación en el Departamento de Anatomía e Histología, y el Departamento de Patología, Universidad Agrícola de Bangladesh, Bangladesh. Tanto la bolsa de Fabricio, bazo y el timo de pollos de engorde con 21 días de edad infectados con Gumboro y no infectados de la misma edad (control) se procesaron de forma rutinaria y se tiñeron con H & E para examinar la distribución de los linfocitos en los órganos linfáticos principales, así cuantificar el número de linfocitos bajo campo de alta magnificación y compararlos con los de control. El número de linfocitos en la bolsa de Fabricio, bazo y timo de pollos infectados con Gumboro fue 27,20 ± 1,53, 66,50 ± 2,70 y 79,30 ± 3,92, respectivamente, mientras que en los controles no infectados fue 121 ± 3,82, 89,90 ± 2,09 y 106,30 ± 4,07 respectivamente. El número de linfocitos fue significativamente (p < 0,05) más bajo en todos los órganos linfáticos de pollos de engorde infectados con Gumboro que los no infectados. La disminuición significativa de linfocitos en el bazo y timo, sugiere que el VBI no sólo destruye linfocitos en la bolsa de Fabricio, sino también en el bazo y el timo y, por tanto, puede suprimir severamente la respuesta inmune de pollos de engorde afectados por VBI.

Can thymic epithelial cells be infected by human T-lymphotropic virus type 1?

The human T-lymphotropic virus type-1 (HTLV-1) is the cause of adult T cell leukaemias/lymphoma. Because thymic epithelial cells (TEC) express recently defined receptors for the virus, it seemed conceivable that these cells might be a target for HTLV-1 infection. We developed an in vitro co-culture system comprising HTLV-1+-infected T cells and human TECs. Infected T cells did adhere to TECs and, after 24 h, the viral proteins gp46 and p19 were observed in TECs. After incubating TECs with culture supernatants from HTLV-1+-infected T cells, we detected gp46 on TEC membranes and the HTLV-1 tax gene integrated in the TEC genome. In conclusion, the human thymic epithelium can be infected in vitro by HTLV-1, not only via cell-cell contact, but also via exposure to virus-containing medium.

Efeitos da infecção pelo Trypanosoma cruzi sobre os componentes linfóide e microambiental do timo: relação com interação timócito-epitélio tímico e morte celular / Effects of Trypanosoma cruzi on lymphoid and microenvironmental components of the thymus: relationship with thymic epithelium-thymocyte interaction and cell death

A infecção pelo Trypanosoma cruzi promove alterações em órgãos linfóides. O timo apresenta-se atrofiado com depleção de células CD4+CD8+ (DP) na fase aguda. Em órgãos linfóides periféricos, os linfonodos subcutâneos (LSC) e o baço apresentam-se hipertrofiados com aumento de células T e B, enquanto os linfonodos mesentéricos (LM) apresentam-se atrofiados devido à morte dessas células. Nesse trabalho estudamos os efeitos da infecção pelo T. cruzi sobre células epiteliais tímicas (TEC) e timócitos, bem como o papel do timo no comportamento de órgãos linfóides periféricos. Em experimentos de infecção in vitro, avaliamos TEC, abordando a expressão de ligantes e receptores da matriz extracelular (ECM), e ainda, as possíveis conseqüências desse aumento de ECM sobre a interação de TEC/timócitos ou TEC/parasita. Nossos resultados demonstram que a infecção promove diminuição do número de TEC, alterações morfológicas e aumento de ECM em culturas infectadas. Observamos também que componentes da ECM são requeridos na interação entre TEC/parasita. [...] No que se refere à interação TEC/timócitos, observamos que a adesão foi maior nas culturas infectadas, especialmente sobre TEC parasitadas. Esse aumento de adesão entre TEC/timócitos corrobora a hipótese descrita anteriormente pelo nosso grupo que a infecção favorece a migração de timócitos para periferia. Estendendo nossa análise ao compartimento linfóide do timo, investigamos a apoptose de timócitos na infecção. Observamos que a celularidade do timo diminui viii durante a infecção, juntamente com aumento de apoptose de timócitos CD4-CD8- (DN), DP, CD4 e CD8.

Procurando entender a via envolvida na apoptose desses timócitos, demonstramos que a atividade de caspases total, caspase 8, caspase 9 e caspase 3 estão aumentadas na infecção. Observamos que ambas caspases iniciadoras caspase 8 (via extrínseca, Fas, TNF, TRAIL) e caspase 9 (via intrínseca, privação de fatores) parecem estar envolvidas na depleção desses timócitos. [...] Além disso, animais infectados e tratados com zVAD apresentaram a celularidade do timo parcialmente recuperada, mais especificamente em timócitos DN e DP. Finalmente, procurando entender o papel do timo na resposta imune regional de órgãos linfóides periféricos na infecção, camundongos foram timectomizados antes da infecção para avaliação da celularidade dos LSC, LM e baço. Nossos dados demonstram que, mesmo com a ausência do timo, a hipertrofia dos LSC e a atrofia dos LM permaneciam inalterados, entretanto, encontramos significativo acúmulo de linfócitos T e B no baço de animais infectados. Em conjunto, nossos resultados demonstram que as alterações observadas no componente epitelial do microambiente tímico, assim como em timócitos de animais infectados favorecem a migração e morte destes timócitos e a atrofia desse tecido. Além disso, demonstramos que células do timo possuem papel imunoregulatório no baço durante a infecção.

Trypanosoma cruzi infection promotes lymphoid organ alterations. The thymusis atrophied with CD4+CD8+(DP) thymocyte depletion in the acute phase of infection.In peripheral lymphoid organs, subcutaneous lymph nodes (LSC) and spleen presenthypertrophy, with increase of T and B cells, whereas mesenteric lymph nodes (LM)are atrophied due to the death of these cells. In this work, we studied the effects of T.cruzi infection in thymic epithelial cells (TEC) and thymocytes, as well as the role ofthymus in the behavior of peripheral lymphoid organs. In experiments of in vitro infection, we evaluated TEC, concerning the expression of extracellular matrix (ECM)ligands and receptors, and also the possible consequences of ECM increase inTEC/thymocyte or TEC/parasite interactions. Our data demonstrate that T. cruziinfection promotes a decrease of TEC number, morphological alterations and ECMincrease in infected cultures. We observed that ECM components are required in theinteraction between TEC and parasites. [...] ConcerningTEC/thymocyte interactions, we observed that adhesion was greater in infectedcultures, especially on parasitized TEC. This increase in TEC/thymocyte adhesioncorroborates the hypothesis previously described by our group that the infectionfavors migration of thymocytes to the periphery. Extending our analysis to thymiclymphoid compartment, we investigated thymocyte apoptosis following infection. We observed that thymus cellularity decreases during infection, together with theincrease of apoptosis in CD4-CD8-(DN), DP, CD4 and CD8 thymocytes.

Searching to understand what death pathway is involved in thymocyte apoptosis, wedemonstrated that the activity of total caspases, caspase-8, caspase-9 and caspase-x3 (effector caspase) are increased in infection. We observed that both initiatorcaspase-8 (extrinsic pathway, Fas, TNF, TRAIL) and caspase-9 (intrinsic pathway,factor deprivation) seem to be involved in thymocyte depletion. [...] Moreover, infected animalstreated with zVAD showed a partial recovery of thymus cellularity, more specifically inDN and DP thymocytes. Finally, searching to understand the role of the thymus in theregional immune response of peripheral lymphoid organs in infection, mice werethymectomized prior to infection to evaluation of LSC, LM and spleen cellularity. Ourdata demonstrated that, even in the absence of the thymus, LSC hypertrophy and LMatrophy were not altered; however, we found a significant accumulation of T and Blymphocytes in the spleen of infected animals. Conjointly, our results show that thealterations observed in the epithelial component of the thymus microenvironment, aswell as in thymocytes of infected animals favor the migration and death ofthymocytes and the atrophy of this tissue. Besides that, we demonstrated that thymiccells have an immunoregulatory role in the spleen during infection.

Glucocorticoids, master modulators of the thymic catecholaminergic system?

There is evidence that the major mediators of stress, i.e., catecholamines and glucocorticoids, play an important role in modulating thymopoiesis and consequently immune responses. Furthermore, there are data suggesting that glucocorticoids influence catecholamine action. Therefore, to assess the putative relevance of glucocorticoid-catecholamine interplay in the modulation of thymopoiesis we analyzed thymocyte differentiation/maturation in non-adrenalectomized and andrenalectomized rats subjected to treatment with propranolol (0.4 mg·100 g body weight-1·day-1) for 4 days. The effects of β-adrenoceptor blockade on thymopoiesis in non-adrenalectomized rats differed not only quantitatively but also qualitatively from those in adrenalectomized rats. In adrenalectomized rats, besides a more efficient thymopoiesis [judged by a more pronounced increase in the relative proportion of the most mature single-positive TCRαβhigh thymocytes as revealed by two-way ANOVA; for CD4+CD8- F (1,20) = 10.92, P < 0.01; for CD4-CD8+ F (1,20) = 7.47, P < 0.05], a skewed thymocyte maturation towards the CD4-CD8+ phenotype, and consequently a diminished CD4+CD8-/CD4-CD8+ mature TCRαβhigh thymocyte ratio (3.41 ± 0.21 in non-adrenalectomized rats vs 2.90 ± 0.31 in adrenalectomized rats, P < 0.05) were found. Therefore, we assumed that catecholaminergic modulation of thymopoiesis exhibits a substantial degree of glucocorticoid-dependent plasticity. Given that glucocorticoids, apart from catecholamine synthesis, influence adrenoceptor expression, we also hypothesized that the lack of adrenal glucocorticoids affected not only β-adrenoceptor- but also α-adrenoceptor-mediated modulation of thymopoiesis.

Immunomodulatory effects of betulinic acid from the bark of white birch on mice

The objective of this study was to explore the immunomodulatory effects of betulinic acid (BA) extracted from the bark of white birch on mice. Female mice were orally administered BA for 14 days in doses of 0, 0.25, 0.5, and 1 mg/kg body weight. We found that BA significantly enhanced the thymus and spleen indices, and stimulated lymphocyte proliferation induced by Concanavalin A and lipopolysaccharide as shown by MTT assay. Flow cytometry revealed that BA increased the percentage of CD4+ cells in thymus as well as the percentage of CD19+ and the ratios of CD4+/CD8+ in spleen. BA increased the number of plaque-forming cell and macrophage phagocytic activity as indicated by a neutral red dye uptake assay, and the peritoneal macrophages levels of TNF-alpha were also increased. In contrast, serum levels of IgG and IgM and serum concentrations of IL-2 and IL-6 were significantly decreased in BA-treated mice compared to the control as assayed by haemagglutination tests and ELISA, respectively. Taken together, these results suggest that BA enhances mouse cellular immunity, humoral immunity, and activity of macrophages. Thus, BA is a potential immune stimulator and may strengthen the immune response of its host.

Histological comparison of human thymus glands between groups of different ages

To compare the thickness of the capsule and interlobular connective tissue, and number and diameter of Hassal's corpuscles in human thymus between two groups of young and old patients. Comparative study. The study was carried out in the Anatomy Department at Army Medical College Rawalpindi from Sep 2007 to Oct 2007. Forty specimens of human thymus were separated into two groups. Group A included 20 specimens from patients between 1-25 years while Group B had same number of specimens of more than 40 years of age. These specimens were fixed in 10% formalin solution and then processed for paraffin embedding. Five micron thick sections were made. Haematoxylin and eosin stain, and PAS stain were used. The thickness of thymic capsule and interlobular connective tissue, number and diameter of Hassal's corpuscles in both groups were noted. Statistically significant differences were found in the thickness of capsule and interlobular connective tissue, number and size of Hassal's corpuscles in specimens of different age groups. In old age, there is definite increase in the thicknesses of capsule and interlobular connective tissue with Hassal's corpuscles decreasing in number but increasing in diameter

Expression of 4-1BB and 4-1BBL in thymocytes during thymus regeneration

4-1BB, a member of the tumor necrosis factor receptor (TNFR) superfamily, is a major costimulatory receptor that is rapidly expressed on the surface of CD4+ and CD8+ T cells after antigen- or mitogen-induced activation. The interaction of 4-1BB with 4-1BBL regulates immunity and promotes the survival and expansion of activated T cells. In this study, the expression of 4-1BB and 4-1BBL was examined during regeneration of the murine thymus following acute cyclophosphamide-induced involution. Four-color flow cytometry showed that 4-1BB and 4-1BBL were present in the normal thymus and were preferentially expressed in the regenerating thymus, mainly in CD4+CD8+ double-positive (DP) thymocytes. Furthermore, the CD4loCD8lo, CD4+CD8lo and CD4loCD8+ thymocyte subsets, representing stages of thymocyte differentiation intermediate between DP and single-positive (SP) thymocytes, also expressed 4-1BB and 4-1BBL during thymus regeneration but to a lesser degree. Interestingly, the 4-1BB and 4-1BBL positive cells among the CD4+CD8+ DP thymocytes present during thymus regeneration were TCR(hi) and CD69+ unlike the corresponding controls. Moreover, the 4-1BB and 4-1BBL positive cells among the intermediate subsets present during thymus regeneration also exhibited TCRhi/int and CD69+/int phenotypes, indicating that 4-1BB and 4-1BBL are predominantly expressed by the positively selected population of the CD4+CD8+ DP and the intermediate thymocytes during thymus regeneration. RT-PCR and Western blot analyses confirmed the presence and elevated levels of 4-1BB and 4-1BBL mRNA and protein in thymocytes during thymus regeneration. We also found that the interaction of 4-1BB with 4-1BBL promoted thymocyte adhesion to thymic epithelial cells. Our results suggest that 4-1BB and 4-1BBL participate in T lymphopoiesis associated with positive selection during recovery from acute thymic involution.

Roles of Embryonic and Adult Lymphoid Tissue Inducer Cells in Primary and Secondary Lymphoid Tissues

The nomenclature "embryonic lymphoid tissue inducer (LTi) cell" reflects the fundamental role of the cell in secondary lymphoid tissue organization. In addition, it is equally important in primary lymphoid tissue development as it regulates central tolerance to self-antigens in the thymus. An adult LTi cell constitutively expresses two sets of tumor necrosis factor (TNF) family members, whereas its embryonic counterpart expresses only one. The first set is lymphotoxin (LT)alpha, LTbeta, and TNFalpha, which are essential for the secondary lymphoid organogenesis during embryogenesis and for maintaining an organized secondary lymphoid structure during adulthood. The second set is OX40- and CD30-ligands, which are critical for memory T cell generation. Adult LTi cells regulate adaptive immune responses by providing LTbetaR signals to stromal cells to maintain secondary lymphoid tissue structure, and determine adaptive immune responses by providing OX40 and CD30 survival signals to activated T cells in memory T cell generation. Along with the consideration of the roles of embryonic LTi cells in primary and secondary lymphoid tissues, this review highlights the roles of adult LTi cells in secondary lymphoid tissue function.

RANKL stimulates proliferation, adhesion and IL-7 expression of thymic epithelial cells

Abstract In many clinical situations which cause thymic involution and thereby result in immune deficiency, T cells are the most often affected, leading to a prolonged deficiency of T cells. Since only the thymic-dependent T cell production pathway secures stable regeneration of fully mature T cells, seeking strategies to enhance thymic regeneration should be a key step in developing therapeutic methods for the treatment of these significant clinical problems. This study clearly shows that receptor activator of NF-kappaB ligand (RANKL) stimulates mouse thymic epithelial cell activities including cell proliferation, thymocyte adhesion to thymic epithelial cells, and the expression of cell death regulatory genes favoring cell survival, cell adhesion molecules such as ICAM-1 and VCAM-1, and thymopoietic factors including IL-7. Importantly, RANKL exhibited a significant capability to facilitate thymic regeneration in mice. In addition, this study demonstrates that RANKL acts directly on the thymus to activate thymus regeneration regardless of its potential influences on thymic regeneration through an indirect or systemic effect. In light of this, the present study provides a greater insight into the development of novel therapeutic strategies for effective thymus repopulation using RANKL in the design of therapies for many clinical conditions in which immune reconstitution is required.

Antioxidant activity of extract of Rhus oxyacantha root cortex.

In the present study, the root extract of Rhus oxyacantha contained 25.33 mg of catechin equivalent per mg of fresh wt and was found rich in proanthocyanidins compared to vine shoot, grape pips and leaves. The chromatographic analysis of the extract suggested the presence of (+) catechin, (-) epicatechin -3-O-gallate as well as proanthocyanidinic oligomers and polymers. Root cortex inhibited the ascorbic acid oxidation by dioxygen. It also prevented DDT-induced thymocytes death in a dose-dependent manner. The results suggested antioxidant property of root extract of Rhus oxyacantha which could be ascribed to its free radical scavenging nature.

Glycolytic inhibitor, 2-deoxy-D-glucose, does not enhance radiation-induced apoptosis in mouse thymocytes and splenocytes in vitro.

Earlier studies have shown that 2-deoxy-D-glucose (2-DG), a glucose analogue and inhibitor of glycolytic ATP production selectively enhances radiation-induced damage in cancer cells by inhibiting the energy (ATP) dependent postirradiation DNA and cellular repair processes. A reduction in radiation induced cytogenetic damage has been reported in normal cells viz., peripheral blood lymphocytes and bone marrow cells. Since induction of apoptosis plays a major role in determining the radiosensitivity of some most sensitive normal cells including splenocytes and thymocytes, we investigated the effects of 2-DG on radiation induced apo tosis in these cells in vitro. Thymocytes and splenocytes isolated from normal Swiss albino mouse were irradiated with Co60 gamma-rays and analyzed for apoptosis at various post-irradiation times. 2-DG added at the time of irradiation was present till the termination of cultures. A time dependent, spontaneous apoptosis was evident in both the cell systems, with nearly 40% of the cells undergoing apoptosis at 12 hr of incubation. The dose response of radiation-induced apoptosis was essentially similar in both the cell systems and was dependent on the incubation time. More than 70% of the splenocytes and 60% of the thymocytes were apoptotic by 12 hr following an absorbed dose of 2 Gy. Presence of 2-DG marginally reduced the fraction of splenocytes undergoing apoptosis at all absorbed doses, while no change was observed in thymocytes. Presence of 2-DG did not significantly alter either the level or the rate of induction of spontaneous apoptosis in both these cell systems. These results are consistent with the earlier findings on radiation-induced cytogenetic damage in human PBL in vitro and mouse bone marrow cells and lend further support to the proposition that 2-DG does not enhance radiation damage in normal cells, while radiosensitizing the tumors and hence is an ideal adjuvant in the radiotherapy of tumors.

Influences of DTC and zinc supplementation on the cellular response restoration in restrained mice

The studies were conducted on Balb/c mice exposed to restraint stress twice for 12 h at 24 h intervals. Prior to restraint stress the mice were treated with sodium diethyldithiocarbamate (DTC) i.p. at a dose of 20 mg/kg five times at 48 h intervals. DTC was used per se or with zinc ions interaction, by adding zinc sulfate to drinking water at a dose of 72 microgram/mouse daily. The results obtained in the study show that restraint stress causes involution of lymphatic organs, decreased the percentage of immature (CD4+CD8+) and, mature (CD4+) thymocytes and CD4+, CD8+and CD19 + splenocytes and proliferative response of thymocytes stimulated in vitro with concanavalin A (Con A) and phytohemagglutinin (PHA). The restraint stress decreased also interleukin-1 (IL-1) production by murine intraperitoneal macrophages stimulated in vitro with lipopolysaccharide (LPS) from E. coli. Pretreatment with DTC counteracted restraint stress-induced immunosuppression, which is expressed as partial normalisation of the total number of thymocytes, splenocytes and IL-1 production, accelerated regeneration of thymus and spleen, shorter suppressive action of restraint stress on the percentage of CD4+CD8+thymocytes and in total normalisation of the CD4+thymocytes and splenocytes. DTC administered prior to restraint stress augmented the proliferative response of thymocytes to two mitogens. The immunocorrecting action of DTC is enhanced by zinc supplementation, expressed in the increased percentage of CD4+thymocytes and splenocytes, CD19 + splenocytes, proliferative activity of thymocytes stimulated with PHA and IL-1 production. The obtained results show that DTC administration can be supplemented with zinc in order to restore the immune system impaired by stress.

Dieldrin initiates apoptosis in rat thymocytes.

In vitro incubation for 6 hr to pesticide dieldrin resulted in a dose-dependent decrease of cell viability comparable to that of dexamethasone. In vivo experiments also demonstrated that dieldrin administration induced a dose-dependent thymic atrophy which appeared to be mediated by endogenous corticosteroids. Agarose gel electrophorosis analysis, revealed the generation of typical apoptotic oligosomal DNA fragmentation in presence of dieldrin. However, in response to high concentrations of pesticide, cells seemed to undergo necrosis pathway. Thus, it may be concluded that dieldrin induced apoptosis in rat thymocytes.

Characterization and biological activities of Chenopodium leaf hemagglutinin (CLH).

A hemagglutinin (CLH) having native molecular mass of 58 kDa and subunit molecular mass of 33 kDa had been purified from the leaves of Chenopodium amaranticolor. The protein agglutinated rabbit erythrocytes and no agglutination was observed with any of the groups A, B or O of human blood. The amino acid composition revealed that CLH was rich in aspartic acid, glutamic acid, glycine and phenylalanine and also significant amount of methionine. The N-terminal amino acid sequence analysis showed that CLH had no homology with any of the plant hemagglutinins studied so far. It was inactive towards human peripheral blood cells but mitogenic for mouse spleen B-lymphocytes. CLH inhibited protein synthesis in rat thymocytes at high concentration. CLH did not inhibit TMV infection of leaves indicating absence of antiviral properties.

Gap junction modulation by extracellular signaling molecules: the thymus model

Gap junctions are intercellular channels which connect adjacent cells and allow direct exchange of molecules of low molecular weight between them. Such a communication has been described as fundamental in many systems due to its importance in coordination, proliferation and differentiation. Recently, it has been shown that gap junctional intercellular communication (GJIC) can be modulated by several extracellular soluble factors such as classical hormones, neurotransmitters, interleukins, growth factors and some paracrine substances. Herein, we discuss some aspects of the general modulation of GJIC by extracellular messenger molecules and more particularly the regulation of such communication in the thymus gland. Additionally, we discuss recent data concerning the study of different neuropeptides and hormones in the modulation of GJIC in thymic epithelial cells. We also suggest that the thymus may be viewed as a model to study the modulation of gap junction communication by different extracellular messengers involved in non-classical circuits, since this organ is under bidirectional neuroimmunoendocrine control