Inflammation-relevant microbiome signature of the stroke brain, gut, spleen, and thymus and the impact of exercise.

Stroke remains a significant unmet need in the clinic with few therapeutic options. We, and others, have implicated the role of inflammatory microbiota in stroke secondary cell death. Elucidating this inflammation microbiome as a biomarker may improve stroke diagnosis and treatment. Here, adult Sprague-Dawley rats performed 30 minutes of exercise on a motorized treadmill for 3 consecutive days prior to transient middle cerebral artery occlusion (MCAO). Stroke animals that underwent exercise showed 1) robust behavioral improvements, 2) significantly smaller infarct sizes and increased peri-infarct cell survival and 3) decreasing trends of inflammatory microbiota BAC303, EREC482, and LAB158 coupled with significantly reduced levels of inflammatory markers ionized calcium binding adaptor molecule 1, tumor necrosis factor alpha, and mouse monoclonal MHC Class II RT1B in the brain, gut, spleen, and thymus compared to non-exercised stroke rats. These results suggest that a specific set of inflammatory microbiota exists in central and peripheral organs and can serve as a disease biomarker and a therapeutic target for stroke.

Effect of probiotics on thymus size and markers of infection in late infancy: a randomized controlled trial.

BACKGROUND: Probiotics are known to stimulate the immune system but the effect on thymus size in late infancy is unknown. We examined the effect of probiotics on thymus size and C-reactive protein (CRP) in healthy Danish infants starting daycare. We further examined associations between thymus size, CRP and recent infections. METHODS: The study included 186 children randomized to a combination of Lactobacillus rhamnosus, LGG® and Bifidobacterium animalis spp. lactis, BB-12® or placebo for 6 months. Thymus size, assessed as thymus index (TI) and thymus weight index (TWI), was measured by ultrasound at baseline and at endpoint. Blood samples were drawn to measure CRP. Infections were parent-reported. RESULTS: There was no significant difference in thymus size between the probiotic group and placebo (p ≥ 0.248) but TWI tended to be higher in the probiotic group corresponding to 5% higher than placebo (p = 0.068) in an adjusted model. There was no effect of probiotics on CRP (p = 0.331). At the endpoint, thymus size was inversely associated with CRP (p ≤ 0.040), diarrhea (p ≤ 0.050), and TI was also associated with the absence from daycare due to respiratory or gastrointestinal infections (p = 0.010). CONCLUSION: The probiotic intervention had no effect on thymus size or CRP in Danish children at the age of starting daycare. IMPACT: Overall there was no effect on thymus size of a combination of Lactobacillus rhamnosus, LGG® and Bifidobacterium animalis spp. lactis, BB-12® administered to Danish children starting daycare. This study examines the effect of probiotics on thymus size in healthy children when they start daycare thus exposed for infections while their immune system is still developing. This has to our knowledge not been described before. We found no significant difference in thymus size between the probiotic and placebo groups, but for thymus weight index, there was a trend. This should be investigated further in studies designed for this as primary outcome.

The effects of feed naturally contaminated with Fusarium mycotoxins on the thymus in suckling piglets.

In this study, feed naturally containing Fusarium mycotoxins was fed to gilts during the perinatal period, and the effects on the thymus were investigated in one-week-old piglets. Twenty gilts were divided into equal control (0.26 mg deoxynivalenol, DON) and experimental (5.08 mg DON, 0.09 mg zearalenone and 21.61 mg fusaric acid per kg of feed) groups. One suckling piglet from each litter (n = 20) was sacrificed at one week of age to obtain thymus samples for further analysis. The cortex to medulla ratio of the thymus was morphometrically analysed using NIS Elements BR (Nikon) software. Paraffin-embedded thymus sections were stained to quantify apoptosis (with terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling - TUNEL method), cellular proliferation (Ki-67) and macrophages (MAC 387). The results showed that the thymus cortex (P = 0.023) to medulla (P = 0.023) ratio was significantly lower in the experimental group. The number of apoptotic cells (cortex, P = 0.010, medulla, P = 0.001) and the number of proliferating cells in the thymus cortex (P = 0.001) and medulla (P < 0.001) were significantly higher in the experimental group. Our results indicate that feeding Fusarium mycotoxins to a parent animal during the perinatal period induces significant alterations in the thymus of one-week-old piglets, which indicates an immunosuppressive effect in piglets.

Baicalin mitigated Mycoplasma gallisepticum-induced structural damage and attenuated oxidative stress and apoptosis in chicken thymus through the Nrf2/HO-1 defence pathway.

The thymus is a primary lymphoid organ and plays a critical role in the immune response against infectious agents. Baicalin is a naturally derived flavonoid famous for its pharmacological properties, but the preventive effects of baicalin against immune impairment remain unclear. We examined this effect in the context of Mycoplasma gallisepticum (MG) infection-induced structural damage in the chicken thymus. Histopathological examination showed that the compact arrangement of cells in the thymus was lost in the MG-infected group. Inflammatory cell infiltration and nuclear debris accumulated, and the boundary between the cortex and medulla was not clearly visible. The mRNA and protein expression of apoptosis-related genes were significantly increased in the MG-infected group compared to the control group and the baicalin group. The number of positively stained nuclei in the terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling (TUNEL) assay were increased in the MG-infected group. In addition, electron microscopic examination showed chromatin condensation, mitochondrial swelling and apoptotic vesicles in the MG-infected group. However, baicalin treatment significantly alleviated the oxidative stress and apoptosis induced by MG infection. Importantly, the abnormal morphology was partially ameliorated by baicalin treatment. Compared to the MG-infected group, the baicalin-treated group showed significantly reduced expression of apoptosis-related genes at both the mRNA and protein levels. Meanwhile, the nuclear factor erythroid 2-related factor 2 (Nrf2) signalling pathway and downstream genes were significantly upregulated by baicalin to counteract MG-induced oxidative stress and apoptosis in the thymocytes of chickens. In summary, these findings suggest that baicalin treatment efficiently attenuated oxidative stress and apoptosis by activating the Nrf2 signalling pathway and could protect the thymus from MG infection-mediated structural and functional damage.

Thymic Tuberculosis Shown on FDG PET/CT Despite Coexisting Pulmonary Tuberculosis With No Increased FDG Activity.

Extrapulmonary tuberculosis could involve multiple organs. However, thymic tuberculosis is relatively rare. We report a 21-year-old man who was referred for an F-FDG PET/CT imaging to assess his newly detected pulmonary nodule. The images showed the pulmonary nodule had minimal activity uptake. Unexpectedly, the thymus with elevated FDG accumulation was noted. The pulmonary nodule and thymic lesion were confirmed as tuberculosis by pathology.

MAIT cells: programmed in the thymus to mediate immunity within tissues.

MAIT cells are an evolutionarily conserved T cell subset recognizing ubiquitous microbial metabolites. Herein, we review recent literature showing that MAIT cells can be divided into type 1 and type 17 subsets, which acquire a tissue resident differentiation program in the thymus and localize in specific tissues. We also discuss the nature and in vivo availability of the different agonist and antagonist MAIT ligands with potential consequences for MAIT cell biology.

The development of cellular immune defence in marine medaka Oryzias melastigma.

Environmentally induced alterations of the immune system during sensitive developmental stages may manifest as abnormalities in immune organ configuration and/or immune cell differentiation. These not only render the early life stages more vulnerable to pathogens, but may also affect the adult immune competence. Knowledge of these sensitive periods in fish would provide an important prognostic/diagnostic tool for aquatic risk assessment of immunotoxicants. The marine medaka Oryzias melastigma is an emerging seawater fish model for immunotoxicology. Here, the presence and onset of four potentially sensitive periods during the development of innate and adaptive cellular immune defence were revealed in O. melastigma: 1.) initiation of phagocyte differentiation, 2.) migration and expansion of lymphoid progenitor cells, 3.) colonization of immune organs through lymphocyte progenitors and 4.) establishment of immune competence in the thymus. By using an established bacterial resistance assay for O. melastigma, larval immune competence (from newly hatched 1dph to 14dph) was found concomitantly increased with advanced thymus development and the presence of mature T-lymphocytes. A comparison between the marine O. melastigma and the freshwater counterpart Oryzias latipes disclosed a disparity in the T-lymphocyte maturation pattern, resulting in differences in the length of T-lymphocyte maturation. The results shed light on a potential difference between seawater and freshwater medaka in their sensitivity to environmental immunotoxicants. Further, medaka immune system development was compared and contrasted to economically important fish. The present study has provided a strong scientific basis for advanced investigation of critical windows for immune system development in fish.

Paracoccidioides brasiliensis infection promotes thymic disarrangement and premature egress of mature lymphocytes expressing prohibitive TCRs.

BACKGROUND: Paracoccidioidomycosis, a chronic granulomatous fungal disease caused by Paracoccidioides brasiliensis yeast cells affects mainly rural workers, albeit recently cases in immunosuppressed individuals has been reported. Protective immune response against P. brasiliensis is dependent on the activity of helper T cells especially IFN-γ-producing Th1 cells. It has been proposed that Paracoccidioides brasiliensis is able to modulate the immune response towards a permissive state and that the thymus plays a major role in it. METHODS: In this paper, we show that acute infection of BALB/c mice with P. brasiliensis virulent isolate (Pb18) might cause alterations in the thymic environment as well as the prohibitive TCR-expressing T cells in the spleens. RESULTS: After seven days of infection, we found yeast cells on the thymic stroma, the thymic epithelial cells (TEC) were altered regarding their spatial-orientation and inflammatory mediators gene expression was increased. Likewise, thymocytes (differentiating T cells) presented higher migratory ability in ex vivo experiments. Notwithstanding, P. brasiliensis-infected mice showed an increased frequency of prohibitive TCR-expressing T cells in the spleens, suggesting that the selection processes that occur in the thymus may be compromised during the acute infection. CONCLUSION: In this paper, for the first time, we show that acute infection with Paracoccidioides brasiliensis yeast cells promotes thymic alterations leading to a defective repertoire of peripheral T cells. The data presented here may represent new mechanisms by which P. brasiliensis subverts the immune response towards the chronic infection observed in humans.

Beneficial bacteria inhibit cachexia.

Muscle wasting, known as cachexia, is a debilitating condition associated with chronic inflammation such as during cancer. Beneficial microbes have been shown to optimize systemic inflammatory tone during good health; however, interactions between microbes and host immunity in the context of cachexia are incompletely understood. Here we use mouse models to test roles for bacteria in muscle wasting syndromes. We find that feeding of a human commensal microbe, Lactobacillus reuteri, to mice is sufficient to lower systemic indices of inflammation and inhibit cachexia. Further, the microbial muscle-building phenomenon extends to normal aging as wild type animals exhibited increased growth hormone levels and up-regulation of transcription factor Forkhead Box N1 [FoxN1] associated with thymus gland retention and longevity. Interestingly, mice with a defective FoxN1 gene (athymic nude) fail to inhibit sarcopenia after L. reuteri therapy, indicating a FoxN1-mediated mechanism. In conclusion, symbiotic bacteria may serve to stimulate FoxN1 and thymic functions that regulate inflammation, offering possible alternatives for cachexia prevention and novel insights into roles for microbiota in mammalian ontogeny and phylogeny.

Dietary zinc deficiency impairs humoral and cellular immune responses to BCG and ESAT-6/CFP-10 vaccination in offspring and adult rats.

BACKGROUND: Besides being the world's most widely used vaccine, BCG is the most controversial vaccine in current use. Estimates of protection impaired by BCG against pulmonary TB vary from nil to 80%. Dietary zinc deficiency has been confirmed to impair the immune function of animals. However, knowledge about effects of mild dietary zinc deficiency and the time of vaccination on BCG vaccine responsiveness in offspring and adult rats is limited. This work investigated the consequences of feeding zinc deficient and normal zinc diets to rats during gestation, infancy or adulthood on the immune responses to BCG vaccination. METHODS: On gestation day 0, sixteen maternal rats were divided into two groups and fed with diets bellow: a control diet ad libitum (30 µg zinc/g diet, NC), a zinc deficient diet ad libitum (8 µg zinc/g diet, ZnD). Pup rats were served as experimental subjects. From day 1 of pregnancy upon delivery, maternal rats were given a standard diet (30 mg/kg/day zinc) or zinc deficient diet (8 mg/kg/day zinc) respectively. Adult male 10-week Wistar rats were divided into two dietary groups for 17 weeks of feeding: a control diet ad libitum (30 µg zinc/g diet, NC), a zinc deficient diet ad libitum (8 µg zinc/g diet, ZnD). The birth time of newborn pups was recorded as the zero week. For adult male rats, the time of receiving different assigned diet was recorded as the zeroth week. Newborn pups of these maternal rats were immunized with BCG vaccine or MTB antigen ESAT-6/CFP-10 at postnatal 0 and 2 week. The adult male rats were immunized on the 12th and 14th week. Then, blood samples, thymus and spleen from the rats were harvested for detection of humoral and cell-mediated immune responses using ELISA, MTT and QRT-PCR analysis. Decreased INF-γ and TNF-α production in plasma, changes of expression level of ZIP2, ZIP8, NF-κB and IL-6 mRNA in immune organs, together with reduced T cell proliferation was observed in pups and adult BCG rats suffered from dietary zinc deficiency. Small differences were observed between rats received BCG vaccine and MTB antigen ESAT-6/CFP-10. RESULTS: Our data clearly indicate that dietary zinc deficiency can weaken the plasma cytokine levels and cell-mediated responses to BCG and ESAT-6/CFP-10 vaccine via decreasing T cell proliferation, down-regulating INF-γ and TNF-α production and affecting the expression of ZIP2, ZIP8, NF-κB and IL-6 mRNA. In addition, the vaccine immunogenicity of BCG and ESAT-6/CFP-10 was not significantly affected by the time of vaccination.

Presence of toll like receptor-2 in spleen, lymph node and thymus of Swiss albino mice and its modulation by Staphylococcus aureus and bacterial lipopolysaccharide. .

Toll-like receptors (TLR) are a family of pattern recognition receptors identifying pathogen associated molecular patterns (PAMPs). They play a critical role in the innate immune response during the initial interaction between the infecting microorganism and phagocytic cells. Here, we verified the presence of TLR-2 in spleen, lymph node and thymus of Swiss albino mice and their modulation after infection with Staphylococcus aureus and Lipopolysaccharide (LPS) challenge. It was seen that TLR-2 gene transcribed to its respective mRNA on S. aureus infection, in thymus, spleen and lymph node of mice but their levels and mode of expression varied. When challenged with LPS no prominent changes in the expression of TLR-2 receptor was observed but its expression increased gradually with time in the thymus, spleen and lymph node of S. aureus infected mice. TLR-2 expression was also found enhanced in infected splenic macrophages. By studying the serum cytokine profile the functionality of the receptor was measured. The results indicate the presence of TLR-2 in thymus, spleen and lymph node of Swiss albino strain of mice and that they are modulated by S. aureus.

Suspension of thymic emigration promotes the maintenance of antigen-specific memory T cells and the recall responses.

Thymic involution is evolutionarily conserved and occurs early in life. However, the physiological significance remains elusive of this seemingly detrimental process. The present study investigated the potential impact of altered thymic output on T cell memory using ovalbumin (OVA) expressed by Listeria monocytogenes as a model antigen. Suspension of thymic emigration by thymectomy was shown to lead to a marked increase in the frequency and total number of OVA-specific memory T cells. In contrast, oversupply of thymic emigrants through thymic grafting caused a significant decrease of such cells. When rechallenged with L. monocytogenes expressing OVA, the thymectomized mice mounted a more potent recall response as evidenced by the enlarged population of OVA-specific tetramer⁺ cells and the accelerated clearance of the bacteria. Notably, the memory-enhancing effect of thymectomy was abrogated following weekly adoptive transfer of naive T cells. Together, data from the present study indicate that reduced thymic output favors the maintenance of the memory T cell pool.

Primary immunodeficiency diagnosed at autopsy: a case report.

BACKGROUND: DiGeorge syndrome may manifest as severe immunodeficiency diagnosed at infancy. The diagnosis of primary immunodeficiency is based on characteristic clinical features, immunophenotyping by flow cytometry, molecular diagnostics and functional lymphocyte evaluation. At autopsy, gross evaluation, conventional histology and immunohistochemistry may be useful for the diagnosis of primary immunodeficiency. This case report illustrates the application of autopsy and immunohistochemistry in the diagnosis of DiGeorge syndrome. CASE PRESENTATION: A four-month-old African female infant died while undergoing treatment at Kenyatta National Hospital, a Referral and Teaching Hospital in Nairobi, Kenya. She presented with a month's history of recurrent respiratory infections, a subsequent decline in the level of consciousness and succumbed to her illness within four days. Her two older siblings died following similar circumstances at ages 3 and 5 months respectively. Autopsy revealed thymic aplasia, bronchopneumonia and invasive brain infection by Aspergillus species. Microbial cultures of cerebrospinal fluid, jejunal contents, spleen and lung tissue revealed multi drug resistant Klebsiella spp, Pseudomonas spp, Serratia spp and Escherichia coli. Immunohistochemistry of splenic tissue obtained from autopsy confirmed reduction of T lymphocytes. CONCLUSION: Use of immunohistochemistry on histological sections of tissues derived from autopsy is a useful adjunct for post mortem diagnosis of DiGeorge syndrome.

Tuberculosis of the thymus in a 6-month-old infant with literature review.

Tuberculosis of the thymus is very uncommon. Most previously reported cases have involved adolescents or adults. Herein, we report a case of tuberculosis of the thymus diagnosed in a 6-month-old infant, presenting with progressive dyspnea and a mediastinal mass. Both clinical and radiologic findings were nonspecific, while pathologic findings confirmed thymic tissue with massive caseous granulomas consistent with tuberculosis.

Mature peripheral T cells are important to preserve thymus function and selection of thymocytes during Mycobacterium tuberculosis infection.

Evaluation of: Nobrega C, Nunes-Alves C, Cerqueira-Rodrigues B et al. T cells home to the thymus and control infection. J. Immunol. 190, 1646-1658 (2013). It is well documented that the thymus is a target organ for a large variety of pathogens (virus, bacteria, fungi and protozoa). Moreover, the presence of pathogen-derived antigens in the thymus of infected mice seems to interfere with the capacity of mature T cells to respond to the invading organism. In this way, Nobrega and colleagues demonstrated in 2010 that Mycobacterium avium infection in the thymus leads to the appearance of differentiated T cells tolerogenic for bacterial antigens. In the present and elegant study, the same group demonstrates that T-cell recirculation from the periphery to the thymus is a mechanism that allows the immune system to respond to thymic infection. A Mycobacterium-infected thymus increases the production of Th1-effector chemokines, such as CXCL9 and CXCL10, which in turn recruit CXCR3(+) peripheral T cells involved in intrathymic bacterial control. Taken together, these findings may represent an important issue of the host response, in terms of different pathogens able to infect the thymus.

Dynamics of the systemic components of the chicken (Gallus gallus domesticus) immune system following activation by Escherichia coli; implications for the costs of immunity.

The immune response is thought to be costly and deters from growth and reproduction, but the magnitude and sources of these costs are unknown. Thus, we quantified the changes in mass of leukocytes (CD4(+) and CD8(+) T cells, Bu1(+) IgM(+) and Bu1(+) IgG(+) B cells, monocytes/macrophages, heterophils and thrombocytes) and protective plasma proteins in systemic (non-mucosal) components of adult chickens injected intravenously with dead Escherichia coli. During the first day after E. coli injection most types of blood leukocytes decreased and α-1-acid glycoprotein increased. Specific IgM, specific IgY, total IgM, Bu1(+) lymphocytes in the spleen and bone marrow and thymic CD8(+) lymphocytes increased at 5d post-injection. Quantitatively, the increases in the weight of cells and antibodies due to E. coli were dwarfed by the increase in the weight of the liver and acute phase proteins. Thus the acute phase response was markedly more costly than the subsequent adaptive response. The weight of the cells and proteins of the systemic immune system prior to challenge was 0.14% of body weight. Following E. coli injection, the additional weight of the immune components and the hypertrophy of the liver resulted in a 3.6-fold increase in weight which is equivalent to 18.5% of a large egg.

T cells home to the thymus and control infection.

The thymus is a target of multiple pathogens. How the immune system responds to thymic infection is largely unknown. Despite being considered an immune-privileged organ, we detect a mycobacteria-specific T cell response in the thymus following dissemination of Mycobacterium avium or Mycobacterium tuberculosis. This response includes proinflammatory cytokine production by mycobacteria-specific CD4(+) and CD8(+) T cells, which stimulates infected cells and controls bacterial growth in the thymus. Importantly, the responding T cells are mature peripheral T cells that recirculate back to the thymus. The recruitment of these cells is associated with an increased expression of Th1 chemokines and an enrichment of CXCR3(+) mycobacteria-specific T cells in the thymus. Finally, we demonstrate it is the mature T cells that home to the thymus that most efficiently control mycobacterial infection. Although the presence of mature T cells in the thymus has been recognized for some time, to our knowledge, these data are the first to show that T cell recirculation from the periphery to the thymus is a mechanism that allows the immune system to respond to thymic infection. Maintaining a functional thymic environment is essential to maintain T cell differentiation and prevent the emergence of central tolerance to the invading pathogens.