The thymus is a common target in malnutrition and infection

The thymus road to a T cell: migration, selection, and atrophy

The thymus plays a pivotal role in generating a highly-diverse repertoire of T lymphocytes while preventing autoimmunity. Thymus seeding progenitors (TSPs) are a heterogeneous group of multipotent progenitors that migrate to the thymus via CCR7 and CCR9 receptors. While NOTCH guides thymus progenitors toward T cell fate, the absence or disruption of NOTCH signaling renders the thymus microenvironment permissive to other cell fates. Following T cell commitment, developing T cells undergo multiple selection checkpoints by engaging with the extracellular matrix, and interacting with thymic epithelial cells (TECs) and other immune subsets across the different compartments of the thymus. The different selection checkpoints assess the T cell receptor (TCR) performance, with failure resulting in either repurposing (agonist selection), or cell death. Additionally, environmental cues such as inflammation and endocrine signaling induce acute thymus atrophy, contributing to the demise of most developing T cells during thymic selection. We discuss the occurrence of acute thymus atrophy in response to systemic inflammation. The thymus demonstrates high plasticity, shaping inflammation by abrogating T cell development and undergoing profound structural changes, and facilitating regeneration and restoration of T cell development once inflammation is resolved. Despite the challenges, thymic selection ensures a highly diverse T cell repertoire capable of discerning between self and non-self antigens, ultimately egressing to secondary lymphoid organs where they complete their maturation and exert their functions.

High risk of malnutrition among hospitalised coronavirus disease 2019 (COVID-19) patients is associated with mortality and other clinical outcomes

INTRODUCTION

Increasing evidence indicates an association between nutritional status and Coronavirus disease 2019 (COVID-19) disease severity. The aim of the study was to describe the risk of malnutrition, body mass index (BMI) and vitamin D status of hospitalised COVID-19 patients and assess whether they are associated with duration of hospital stay, intensive care unit (ICU) admission, mechanical ventilation, and mortality.

METHODS

The study is a descriptive retrospective study of 273 patients with COVID-19 admitted to Hospital from February 2020 to March 2021. Patients were screened for risk of malnutrition using a validated screening tool. BMI was calculated from height and weight. Insufficient Vitamin D status was defined as 25(OH)vitD <50 nmol/L. Logistic regression analysis was used to assess the association between indicators of nutritional status of patients with COVID-19, and outcomes such as duration of stay >7 days, ICU admission, mechanical ventilation, and mortality. Interaction between risk of malnutrition and BMI of ≥30 kg/m2 was assessed using the likelihood ratio test with hospital stay, ICU admission, mechanical ventilation, and mortality as outcomes.

RESULTS

Screening for risk of malnutrition identified 201 (74%) patients at a medium to high risk of malnutrition. Patients defined as being at a medium or high risk of malnutrition were more likely to be hospitalised for >7 days compared to those defined as low risk (OR: 10.72; 95% CI: 3.9-29.46; p < 0.001 and OR: 61.57; 95% CI: 19.48-194.62; p < 0.001, respectively). All patients who were admitted to ICU (n = 41) and required mechanical ventilation (n = 27) were defined as having medium or high risk of malnutrition. High risk of malnutrition was also associated with increased odds of mortality (OR: 8.87; 955 CI 1.08-72,96; p = 0.042). BMI of ≥30 kg/m2 (43%) and 25(OH)vitD <50 nmol/L (20%) were not associated with duration of stay >7 days or mortality, although BMI ≥30 kg/m2 was associated with increased risk of ICU admission (OR: 7.12; 95% CI: 1.59-31.94; p = 0.010) and mechanical ventilation (OR: 8.86; 95% CI: 1.12-69.87; p = 0.038). Interactions between risk of malnutrition and BMI ≥30 kg/m2 were not significant to explain the outcomes of hospital stay >7 days, ICU admission, mechanical ventilation, or mortality.

CONCLUSION

High risk of malnutrition among hospitalised COVID-19 patients was associated with longer duration of hospital stay, ICU admission, mechanical ventilation and mortality, and BMI ≥30 kg/m2 was associated with ICU admission and mechanical ventilation. Insufficient Vitamin D status was not associated with duration of hospital stay, ICU admission, mechanical ventilation, or mortality.

Molecular Linkage between Immune System Disorders and Atherosclerosis

A strong relationship exists between immune dysfunction and cardiovascular disease. Immune dysregulation can promote the development of cardiovascular diseases as well as exacerbate their course. The disorders may occur due to the presence of primary immune defects (currently known as inborn errors of immunity) and the more common secondary immune deficiencies. Secondary immune deficiencies can be caused by certain chronic conditions (such as diabetes, chronic kidney disease, obesity, autoimmune diseases, or cancer), nutritional deficiencies (including both lack of nutrients and bioactive non-nutrient compounds), and medical treatments and addictive substances. This article unravels the molecular linkage between the aforementioned immune system disorders and atherosclerosis.

Small fetal thymus and adverse perinatal outcome in maternal vasculitis: A prospective case-control study

BACKGROUND

Ultrasonographic evaluation of fetal thymus size may be used to predict the adverse perinatal outcome in pregnant women with vasculitis.

AIM

To compare fetal thymus size in pregnant women with vasculitis and healthy pregnant women and to evaluate whether fetal thymus size predicts the adverse perinatal outcome.

METHODS

Twenty-two pregnant women with previously diagnosed vasculitis, 18 of them with Behçet's disease, three with Takayasu arteritis, and one with Wegener's granulomatosis, were included in the case group. The control group comprised 66 healthy pregnant women whose gestational ages matched the case group. Thymic thoracic ratio (TTR) was measured to assess fetal thymus size in the view of three vessels and trachea.

RESULTS

In the case group, fetal TTR was significantly lower (0.32 ± 0.03 vs. 0.36 ± 0.02, p = < 0.001). Fetal TTR was significantly lower in those using prednisone than those not (p = .001) in the case group. There was no significant difference in fetal TTR between colchicine used and not used (p = .078) in the case group. Also, for the TTR, a sensitivity of 100% and a specificity of 92% were achieved with a cut-off value of 0.33 for predicting adverse perinatal outcomes.

CONCLUSION

The fetuses of pregnant women with maternal vasculitis had a smaller TTR. The small fetal thymus may alert clinicians to possible adverse perinatal outcomes and, with other supporting risk factors, may help predict adverse perinatal outcomes in pregnant women with vasculitis.

Characterization of fetal microchimeric immune cells in mouse maternal hearts during physiologic and pathologic pregnancies

Introduction: During pregnancy, fetal cells can be incorporated into maternal tissues (fetal microchimerism), where they can persist postpartum. Whether these fetal cells are beneficial or detrimental to maternal health is unknown. This study aimed to characterize fetal microchimeric immune cells in the maternal heart during pregnancy and postpartum, and to identify differences in these fetal microchimeric subpopulations between normal and pregnancies complicated by spontaneous preterm induced by ascending infection. Methods: A Cre reporter mouse model, which when mated with wild-type C57BL/6J females resulted in cells and tissues of progeny expressing red fluorescent protein tandem dimer Tomato (mT+), was used to detect fetal microchimeric cells. On embryonic day (E)15, 104 colony-forming units (CFU) E. coli was administered intravaginally to mimic ascending infection, with delivery on or before E18.5 considered as preterm delivery. A subset of pregnant mice was sacrificed at E16 and postpartum day 28 to harvest maternal hearts. Heart tissues were processed for immunofluorescence microscopy and high-dimensional mass cytometry by time-of-flight (CyTOF) using an antibody panel of immune cell markers. Changes in cardiac physiologic parameters were measured up to 60 days postpartum via two-dimensional echocardiography. Results: Intravaginal E. coli administration resulted in preterm delivery of live pups in 70% of the cases. mT + expressing cells were detected in maternal uterus and heart, implying that fetal cells can migrate to different maternal compartments. During ascending infection, more fetal antigen-presenting cells (APCs) and less fetal hematopoietic stem cells (HSCs) and fetal double-positive (DP) thymocytes were observed in maternal hearts at E16 compared to normal pregnancy. These HSCs were cleared while DP thymocytes persisted 28 days postpartum following an ascending infection. No significant changes in cardiac physiologic parameters were observed postpartum except a trend in lowering the ejection fraction rate in preterm delivered mothers. Conclusion: Both normal pregnancy and ascending infection revealed distinct compositions of fetal microchimeric immune cells within the maternal heart, which could potentially influence the maternal cardiac microenvironment via (1) modulation of cardiac reverse modeling processes by fetal stem cells, and (2) differential responses to recognition of fetal APCs by maternal T cells.

Intrathymic somatotropic circuitry: consequences upon thymus involution

Growth hormone (GH) is a classic pituitary-derived hormone crucial to body growth and metabolism. In the pituitary gland, GH production is stimulated by GH-releasing hormone and inhibited by somatostatin. GH secretion can also be induced by other peptides, such as ghrelin, which interacts with receptors present in somatotropic cells. It is well established that GH acts directly on target cells or indirectly by stimulating the production of insulin-like growth factors (IGFs), particularly IGF-1. Notably, such somatotropic circuitry is also involved in the development and function of immune cells and organs, including the thymus. Interestingly, GH, IGF-1, ghrelin, and somatostatin are expressed in the thymus in the lymphoid and microenvironmental compartments, where they stimulate the secretion of soluble factors and extracellular matrix molecules involved in the general process of intrathymic T-cell development. Clinical trials in which GH was used to treat immunocompromised patients successfully recovered thymic function. Additionally, there is evidence that the reduction in the function of the somatotropic axis is associated with age-related thymus atrophy. Treatment with GH, IGF-1 or ghrelin can restore thymopoiesis of old animals, thus in keeping with a clinical study showing that treatment with GH, associated with metformin and dehydroepiandrosterone, could induce thymus regeneration in healthy aged individuals. In conclusion, the molecules of the somatotrophic axis can be envisioned as potential therapeutic targets for thymus regeneration in age-related or pathological thymus involution.

The Association between Nutritional Status and Parasite Density in Children with Vivax Malaria in Kualuh Leidong, Indonesia

Background: Nutritional status is believed to affect the immune system and parasite density in children diagnosed with malaria from Plasmodium vivax infection. It is known that nutritional status could facilitate the growth of protective immune response towards malaria antigen, but some studies have shown that poor nutrition could cause clinical complications and lead to severe malaria. There have also been different reports on the relationship between nutritional status and parasite density. Objectives: This study aimed to examine the association between nutritional status and parasite density in children with vivax malaria in Kualuh Leidong area. Methods: This cross-sectional study was conducted from October 2019 to January 2020 in Kualuh Leidong to investigate 48 children aged between 2 - 18 and diagnosed with vivax malaria. The nutritional status of children with fever and positive Plasmodium vivax confirmed by microscopic examination were evaluated. Parasite density was determined in order to assess the severity of the infection. A non-parametric test was performed to examine the association between these two conditions. Results: There was a significant association (P = 0.032) between sexual parasite density and nutritional status. A post hoc test showed that overweight or mild malnutrition significantly correlated (P = 0.029) with high sexual parasite density. However, no significant association was found between nutritional status and asexual parasite density (P = 0.222).

Linkages between malaria and malnutrition in co-endemic regions of India

INTRODUCTION

Malaria and malnutrition are key public health challenges in India. However, the relationship between them is poorly understood. Here, we aimed to elucidate the potential interactions between the two health conditions by identifying the areas of their spatial overlap.

METHODS

We have analysed the district-wise undernutrition and malaria data of 638 districts of India across 28 states and 8 union territories. Data on malnutrition parameters viz. stunting, wasting, underweight and anaemia, sourced from the fourth National Family Health Survey (2015-2016), and malaria Annual Parasite Index (API) data of the same year (i.e, 2015), sourced from National Center of Vector Borne Diseases Control were analysed using local Moran's I Index and logistic regression.

RESULTS

Among all the malnutrition parameters, we found underweight in children and anaemia in men to co-occur with malaria in the districts of Chhattisgarh, Jharkhand, Madhya Pradesh and Odisha. Further, districts with more than 36% underweight children (OR (95% CI): 2.31 (1.53 to 3.48)) and/or more than 23.6% male population with anaemia (OR (95% CI): 2.06 (1.37 to 3.11)) had higher odds of being malaria endemic districts (ie, Annual Parasite Index >1).

CONCLUSION

Malaria and malnutrition co-occur in the malaria-endemic parts of India. The high prevalence of undernutrition in children and anaemia among men may contribute to malaria endemicity in a particular region. Therefore, future research should be prioritised to generate data on the individual level. Further, malaria control interventions could be tailored to integrate nutrition programmes to disrupt indigenous malaria transmission in endemic districts.

Preparing Patients for Cosmetic Surgery and Aesthetic Procedures: Ensuring an Optimal Nutritional Status for Successful Results

Aesthetic and cosmetic medical practices have attracted considerable consumer attention globally. However, possible complications vary and range from mild, self-resolving ecchymoses or edema to more persistent complications. The aim of this review is to identify the nutritional deficits or excesses associated with the major complications of reconstructive surgery, aesthetic surgery, and mini-invasive aesthetic procedures. An additional goal is to provide a bundle of actions for professionals working in the industry in order to reduce the risks of aesthetic procedures and improve the clinical outcomes. Granulomas, hypertrophic scars and keloids, seromas, infections and xerosis, hyperpigmentation, petechiae, livedo reticularis, slower wound healing, and other poor outcomes are frequently associated with nutritional deficiencies. Nutritional status can markedly affect wound healing and tissue repair following surgical interventions, as well as the outcomes of aesthetic and cosmetic medical practices. Professionals working in this industry, therefore, need to consider the nutritional aspects of their patients to obtain the best results.

Risk of Malnutrition in Hospitalized COVID-19 Patients: A Systematic Review and Meta-Analysis

(1) Background: Studies have reported that COVID-19 may increase the risk of malnutrition among patients. However, the prevalence of such risk in hospitalized COVID-19 patients is uncertain due to the inconsistent use of assessment methods. (2) Methods: PubMed, Web of Science, and EMBASE were searched to identify studies on the nutritional status of hospitalized COVID-19 patients. A pooled prevalence of malnutrition risk evaluated by Nutrition Risk Score (NRS-2002) was obtained using a random effects model. Differences by study-level characteristics were examined by hospitalization setting, time of assessment, age, and country. Risk of bias was assessed using the Newcastle−Ottawa Scale. (3) Results: 53 studies from 17 countries were identified and summarized. A total of 17 studies using NRS-2002, including 3614 COVID-19 patients were included in the primary meta-analysis. The pooled prevalence of risk of malnutrition was significantly higher among ICU patients (92.2%, 95% CI: 85.9% to 96.8%) than among general ward patients (70.7%, 95% CI: 56.4% to 83.2%) (p = 0.002). No significant differences were found between age groups (≥65 vs. <65 years, p = 0.306) and countries (p = 0.893). (4) Conclusions: High risk of malnutrition is common and concerning in hospitalized patients with COVID-19, suggesting that malnutrition screening and nutritional support during hospitalization are needed.

Thymus, undernutrition, and infection: Approaching cellular and molecular interactions

Undernutrition remains a major issue in global health. Low protein-energy consumption, results in stunting, wasting and/or underweight, three deleterious forms of malnutrition that affect roughly 200 million children under the age of five years. Undernutrition compromises the immune system with the generation of various degrees of immunodeficiency, which in turn, renders undernourished individuals more sensitive to acute infections. The severity of various infectious diseases including visceral leishmaniasis (VL), influenza, and tuberculosis is associated with undernutrition. Immunosuppression resulting from protein-energy undernutrition severely impacts primary and secondary lymphoid organs involved in the response to related pathogens. The thymus-a primary lymphoid organ responsible for the generation of T lymphocytes-is particularly compromised by both undernutrition and infectious diseases. In this respect, we will discuss herein various intrathymic cellular and molecular interactions seen in undernutrition alone or in combination with acute infections. Many examples illustrated in studies on humans and experimental animals clearly revealed that protein-related undernutrition causes thymic atrophy, with cortical thymocyte depletion. Moreover, the non-lymphoid microenvironmental compartment of the organ undergoes important changes in thymic epithelial cells, including their secretory products such as hormones and extracellular matrix proteins. Of note, deficiencies in vitamins and trace elements also induce thymic atrophy. Interestingly, among the molecular interactions involved in the control of undernutrition-induced thymic atrophy is a hormonal imbalance with a rise in glucocorticoids and a decrease in leptin serum levels. Undernutrition also yields a negative impact of acute infections upon the thymus, frequently with the intrathymic detection of pathogens or their antigens. For instance, undernourished mice infected with Leishmania infantum (that causes VL) undergo drastic thymic atrophy, with significant reduction in thymocyte numbers, and decreased levels of intrathymic chemokines and cytokines, indicating that both lymphoid and microenvironmental compartments of the organ are affected. Lastly, recent data revealed that some probiotic bacteria or probiotic fermented milks improve the thymus status in a model of malnutrition, thus raising a new field for investigation, namely the thymus-gut connection, indicating that probiotics can be envisioned as a further adjuvant therapy in the control of thymic changes in undernutrition accompanied or not by infection.

Nutritional Aspects of People Living with HIV (PLHIV) Amidst COVID-19 Pandemic: an Insight

Purpose of Review

This review elaborates the role of malnutrition in PLHIV (people living with HIV) in the context of COVID-19 and emphasis the need of supplementation, dietary intervention, and nutritional counselling in the post-COVID era. One of the most critical challenges among HIV/AIDS patients is malnutrition since it weakens the immune system and increases risk to opportunistic infections. In HIV (human immunodeficiency virus) infection, weight loss is prevalent due to reduced nutritional consumption, malabsorption, abnormal metabolism, and antiretroviral therapy. Sufficient nutrition is required for optimal immune function, as a result, food therapy is now considered an important adjuvant in the treatment of HIV patients.

Recent Findings

Nutritional intervention, such as the use of dietary supplements, can help to prevent nutrient deficiency, lowering the death risk among malnourished HIV population. Immunocompromised individuals are at very high risk for COVID-19 and malnutrition increases the risk of infection by multiple folds. Interventions, such as nutrition education and counselling are important, to improve the condition of HIV Patients by optimising their nutritional status.

Summary

A balanced diet should be one of the most important priorities in preventing PLHIV against the potentially deadly consequences of COVID-19. It is to be ensured that HIV-positive persons continue to get enough and appropriate assistance, such as nutrition and psychological counselling, in the context of COVID-19 infection. The use of telemedicine to maintain nutritional intervention can be beneficial. To meet their nutritional needs and minimise future difficulties, PLHIV infected with COVID-19 should get specialised nutritional education and counselling.

Graphical abstract

A single-cell analysis of thymopoiesis and thymic iNKT cell development in pigs

Many aspects of the porcine immune system remain poorly characterized, which poses a barrier to improving swine health and utilizing pigs as preclinical models. Here, we employ single-cell RNA sequencing (scRNA-seq) to create a cell atlas of the early-adolescent pig thymus. Our data show conserved features as well as species-specific differences in cell states and cell types compared with human thymocytes. We also describe several unconventional T cell types with gene expression profiles associated with innate effector functions. This includes a cell census of more than 11,000 differentiating invariant natural killer T (iNKT) cells, which reveals that the functional diversity of pig iNKT cells differs substantially from the iNKT0/1/2/17 subset differentiation paradigm established in mice. Our data characterize key differentiation events in porcine thymopoiesis and iNKT cell maturation and provide important insights into pig T cell development.

Thymic Dysfunction and Atrophy in COVID-19 Disease Complicated by Inflammation, Malnutrition and Cachexia

Background: The current COVID-19 pandemic has put millions of people, especially children at risk of protein-energy malnutrition (PEM) by pushing them into poverty and disrupting the global food supply chain. The thymus is severely affected by nutritional deficiencies and is known as a barometer of malnutrition. Aim: The present commentary provides a novel perspective on the role of malnutrition-induced thymic dysfunction, involution and atrophy on the risk and severity of disease in children during the COVID-19 pandemic. Methods: A review of pertinent indexed literature including studies examining the effects of malnutrition on the thymus and immune dysfunction in COVID-19. Results: Protein-energy malnutrition and micronutrient deficiencies of zinc, iron and vitamin A are known to promote thymic dysfunction and thymocyte loss in children. Malnutrition- and infection-induced thymic atrophy and immune dysfunction may increase the risk of first, progression of COVID-19 disease to more severe forms including development of multisystem inflammatory syndrome in children (MIS-C); second, slow the recovery from COVID-19 disease; and third, increase the risk of other infections. Furthermore, malnourished children may be at increased risk of contracting SARS-CoV-2 infection due to socioeconomic conditions that promote viral transmission amongst contacts and create barriers to vaccination. Conclusion: National governments and international organizations including WHO, World Food Program, and UNICEF should institute measures to ensure provision of food and micronutrients for children at risk in order to limit the health impact of the ongoing COVID-19 pandemic.

Decreased fetal thymus size at 24 weeks gestation by ultrasound measurement in gestational diabetes mellitus fetal thymus examination for diabetes

AIM

This study aimed to evaluate the difference in fetal thymus diameter, which we measured ultrasonographically, between the healthy pregnant group and the pregnant group with gestational diabetes.

METHOD

Fetal thymus and thymus/thorax ratio parameters were assessed in this case-control study. Patients were examined in two groups. They included 49 diabetics (study group) women and 71 nondiabetic (control group). We performed a binary logistic regression analysis to determine the predictive value of ultrasonographic measurements. We completed the receiver curve characteristic analysis to evaluate the cut-off thymus diameter.

RESULTS

The median age of pregnant women was 27. Thymus diameter and thymus-thorax ratio were smaller in fetuses of diabetic mothers than in the nondiabetic group (p <0.05). Thymus diameter was found to be more predictive of gestational diabetes prediction (p: 0.019). There was no correlation between fasting blood glucose and thymus diameter.

CONCLUSION

Decreased fetal thymus anterior-posterior diameter seems to be associated with diabetic pregnancy.

Structural and immunoendocrine remodeling in gut, pancreas and thymus in weaning rats fed powdered milk diets rich in Maillard reactants

Western diet is extending worldwide and suspected to be associated with various metabolic diseases. Many food products have skim milk powder added to it and, during processing, lactose reacts with milk proteins and Maillard reaction products (MRPs) are formed. Dietary MRPs are suggested risk factors for metabolic dysregulation, but the mechanisms behind are still enigmatic. Here we describe that weaning rats fed diets rich in MRPs are affected in both their immune and endocrine systems. Marked structural changes in pancreas, intestine and thymus are noted already after 1 week of exposure. The pancreatic islets become sparser, the intestinal mucosa is thinner, and thymus displays increased apoptosis and atrophy. Glucagon- like peptide-1 (GLP-1) seems to play a key role in that the number of GLP-1 expressing cells is up-regulated in endocrine pancreas but down-regulated in the intestinal mucosa. Further, intestinal GLP-1-immunoreactive cells are juxta positioned not only to nerve fibres and tuft cells, as previously described, but also to intraepithelial CD3 positive T cells, rendering them a strategic location in metabolic regulation. Our results suggest dietary MRPs to cause metabolic disorders, dysregulation of intestinal GLP-1- immunoreactive cells, arrest in pancreas development and thymus atrophy.

Identification of four novel mutations in BTK from six Chinese families with X-linked agammaglobulinemia

BACKGROUND

The defect of Bruton's tyrosine kinase (BTK) gene resulted in X-linked agammaglobulinemia (XLA), which is characterized by recurrent bacterial infections, immunodeficiency with low B-cell numbers and immunoglobulin. Diagnosis of XLA depends on clinical phenotype and genetic testing.

METHODS

Six unrelated Chinese families with high suspicion of XLA were enrolled in this study. Potential pathogenic variants were detected and validated by Whole Exome Sequencing (WES) and Sanger Sequencing. Western blot, Quantitative PCR (qPCR) analysis and immunofluorescence analysis were used to evaluate the preliminary function of candidate BTK variants.

RESULTS

A total of six variants were identified, four of which were not reported before. The novel missense mutation(c.1900T>G) and deletion(c.897delG) were found that the mutant protein and mRNA expression levels have fallen by Western Blot and qPCR identification. We also constructed minigene expression vector to determine the deletion (c.1751-6_1755delttctagGGGTT) resulting a 35bp skipping in exon 18. Meanwhile, the break point of gross deletion (Exon2-5) discovered based on WES was confirmed to be located at site ChX:101367539_101376531 through qPCR and Gap-PCR.

CONCLUSION

This study makes definitive diagnosis for 6 families with suspected XLA and further expands the spectrum of BTK mutations, providing new information for the diagnosis of the disease.

Malnutrition and Dietary Habits Alter the Immune System Which May Consequently Influence SARS-CoV-2 Virulence: A Review

COVID-19, resulting from the SARS-CoV-2 virus, is a major pandemic that the world is fighting. SARS-CoV-2 primarily causes lung infection by attaching to the ACE2 receptor on the alveolar epithelial cells. However, the ACE2 receptor is also present in intestinal epithelial cells, suggesting a link between nutrition, virulence and clinical outcomes of COVID-19. Respiratory viral infections perturb the gut microbiota. The gut microbiota is shaped by our diet; therefore, a healthy gut is important for optimal metabolism, immunology and protection of the host. Malnutrition causes diverse changes in the immune system by repressing immune responses and enhancing viral vulnerability. Thus, improving gut health with a high-quality, nutrient-filled diet will improve immunity against infections and diseases. This review emphasizes the significance of dietary choices and its subsequent effects on the immune system, which may potentially impact SARS-CoV-2 vulnerability.

Effectiveness of interleukin-4 administration or zinc supplementation in improving zinc deficiency-associated thymic atrophy and fatty degeneration and in normalizing T cell maturation process

Nutritional zinc deficiency induces thymic atrophy, but the underlying mechanisms remain unknown. In this study, we investigated the mechanism of thymic atrophy and fatty degeneration associated with zinc deficiency, and its effect on T cell maturation. Building on previous research demonstrating the beneficial effect of IL-4 administration or zinc supplementation on the spleen in zinc deficiency rats, we further examined whether these supplements also improve thymic atrophy. Five-week-old male Sprague-Dawley rats were fed a standard diet, zinc-deficient diet (n = 16 each) with either saline or IL-4, or a zinc-deficient diet for 6 weeks followed by a standard diet for 4 weeks. Relative thymus weights, serum thymulin concentrations, and the number of cytokeratin-8-positive cells, AIRE-positive cells, IL-7-positive cells, CD8⁺ T cells, CD4⁺ T cells, pre T cells, and CD25⁺ CD44⁺ (DN3) cells in the thymus of zinc deficiency rats significantly decreased compared with those in all other groups. Conversely, PPAR-γ-positive cells, oil red O-positive areas, pro T cells, CD25^- CD44⁺ cells, TUNEL positive cells, Viobility 405/452 Fixable Dye-positive cells, CD68-, CD163- or CD169- macrophages, and IL-1β concentrations were significantly increased in the thymus of zinc deficiency rats as compared to those in the other groups. After IL-4 administration or zinc supplementation for zinc deficiency, all the measurement indices were recovered to levels in standard rats. It was demonstrated that zinc deficiency caused thymic atrophy, accompanied by fatty degeneration in the cortical regions and affected T cell maturation. IL-4 administration or zinc supplementation for zinc deficiency ameliorated thymic fatty degeneration.

Probiotic Consumption Boosts Thymus in Obesity and Senescence Mouse Models

The ability of the immune system to respond to different pathogens throughout life requires the constant production and selection of T cells in the thymus. This immune organ is very sensitive to age, infectious processes and nutrition disorders (obesity and malnutrition). Several studies have shown that the incorporation of some probiotic bacteria or probiotic fermented milk in the diet has beneficial effects, not only at the intestinal level but also on distant mucosal tissues, improving the architecture of the thymus in a malnutrition model. The aim of the present study was to determine whether supplementation with the probiotic strain Lactobacillus casei CRL 431 and/or its cell wall could improve body weight, intestinal microbiota and thymus structure and function in both obese and aging mice. We evaluated probiotic administration to BALB/c mice in 2 experimental mouse models: obesity and senescence, including mice of different ages (21, 28, 45, 90 and 180 days). Changes in thymus size and histology were recorded. T-lymphocyte population and cytokine production were also determined. The consumption of probiotics improved the cortical/medullary ratio, the production and regulation of cytokines and the recovery of mature T-lymphocyte populations of the thymus in obese and old mice. Probiotic incorporation into the diet could not only modulate the immune system but also lead to thymus function recovery, thus improving quality of life.

Effects of intrauterine growth restriction during late pregnancy on the cell growth, proliferation, and differentiation in ovine fetal thymuses

Objective

This study investigated the effects of intrauterine growth restriction (IUGR) during late pregnancy on the cell growth, proliferation, and differentiation in ovine fetal thymuses.

Methods

Eighteen time-mated Mongolian ewes with singleton fetuses were allocated to three groups at d 90 of pregnancy: restricted group 1 (RG1, 0.18 MJ ME/body weight [BW]^0.75/d, n = 6), restricted group 2 (RG2, 0.33 MJ ME/BW^0.75/d, n = 6) and control group (CG, ad libitum, 0.67 MJ ME/BW^0.75/d, n = 6). Fetuses were recovered at slaughter on d 140.

Results

The G0/G1 phase cell number in fetal thymus of the RG1 group was increased but the proliferation index and the expression of proliferating cell nuclear antigen (PCNA) were reduced compared with the CG group (p<0.05). Fetuses in the RG1 group exhibited decreased growth hormone receptor (GHR), insulin-like growth factor 2 receptor (IGF-2R), and their mRNA expressions (p<0.05). For the RG2 fetuses, there were no differences in the proliferation index and PCNA expression (p>0.05), but growth hormone (GH) and the mRNA expression of GHR were lower than those of the CG group (p<0.05). The thymic mRNA expressions of cyclin-dependent protein kinases (CDKs including CDK1, CDK2, and CDK4), CCNE, E2-factors (E2F1, E2F2, and E2F5) were reduced in the RG1 and RG2 groups (p<0.05), and decreased mRNA expressions of E2F4, CCNA, CCNB, and CCND were occurred in the RG1 fetuses (p<0.05). The decreased E-cadherin (E-cad) as a marker for epithelial-mesenchymal transition (EMT) was found in the RG1 and RG2 groups (p< 0.05), but the OB-cadherin which is a marker for activated fibroblasts was increased in fetal thymus of the RG1 group (p<0.05).

Conclusion

These results indicate that weakened GH/IGF signaling system repressed the cell cycle progression in G0/G1 phase in IUGR fetal thymus, but the switch from reduced E-cad to increased OB-cadherin suggests that transdifferentiation process of EMT associated with fibrogenesis was strengthened. The impaired cell growth, retarded proliferation and modified differentiation were responsible for impaired maturation of IUGR fetal thymus.

One-carbon metabolism in children with marasmus and kwashiorkor

BACKGROUND

Kwashiorkor is a childhood syndrome of edematous malnutrition. Its precise nutritional precipitants remain uncertain despite nine decades of study. Remarkably, kwashiorkor's disturbances resemble the effects of experimental diets that are deficient in one-carbon nutrients. This similarity suggests that kwashiorkor may represent a nutritionally mediated syndrome of acute one-carbon metabolism dysfunction. Here we report findings from a cross-sectional exploration of serum one-carbon metabolites in Malawian children.

METHODS

Blood was collected from children aged 12-60 months before nutritional rehabilitation: kwashiorkor (N = 94), marasmic-kwashiorkor (N = 43) marasmus (N = 118), moderate acute malnutrition (N = 56) and controls (N = 46). Serum concentrations of 16 one-carbon metabolites were quantified using LC/MS techniques, and then compared across participant groups.

FINDINGS

Twelve of 16 measured one-carbon metabolites differed significantly between participant groups. Measured outputs of one-carbon metabolism, asymmetric dimethylarginine (ADMA) and cysteine, were lower in marasmic-kwashiorkor (median µmol/L (± SD): 0·549 (± 0·217) P = 0·00045 & 90 (± 40) P < 0·0001, respectively) and kwashiorkor (0·557 (± 0·195) P < 0·0001 & 115 (± 50) P < 0·0001), relative to marasmus (0·698 (± 0·212) & 153 (± 42)). ADMA and cysteine were well correlated with methionine in both kwashiorkor and marasmic-kwashiorkor.

INTERPRETATION

Kwashiorkor and marasmic-kwashiorkor were distinguished by evidence of one-carbon metabolism dysfunction. Correlative observations suggest that methionine deficiency drives this dysfunction, which is implicated in the syndrome's pathogenesis. The hypothesis that kwashiorkor can be prevented by fortifying low quality diets with methionine, along with nutrients that support efficient methionine use, such as choline, requires further investigation.

FUNDING

The Hickey Family Foundation, the American College of Gastroenterology, the NICHD, and the USDA/ARS.

IFNγ and iNOS-Mediated Alterations in the Bone Marrow and Thymus and Its Impact on Mycobacterium avium-Induced Thymic Atrophy

Disseminated infection with the high virulence strain of Mycobacterium avium 25291 leads to progressive thymic atrophy. We previously showed that M. avium-induced thymic atrophy results from increased glucocorticoid levels that synergize with nitric oxide (NO) produced by interferon gamma (IFNγ) activated macrophages. Where and how these mediators act is not understood. We hypothesized that IFNγ and NO promote thymic atrophy through their effects on bone marrow (BM) T cell precursors and T cell differentiation in the thymus. We show that M. avium infection cause a reduction in the percentage and number of common lymphoid progenitors (CLP). Additionally, BM precursors from infected mice show an overall impaired ability to reconstitute thymi of RAGKO mice, in part due to IFNγ. Thymi from infected mice present an IFNγ and NO-driven inflammation. When transplanted under the kidney capsule of uninfected mice, thymi from infected mice are unable to sustain T cell differentiation. Finally, we observed increased thymocyte death via apoptosis after infection, independent of both IFNγ and iNOS; and a decrease on active caspase-3 positive thymocytes, which is not observed in the absence of iNOS expression. Together our data suggests that M. avium-induced thymic atrophy results from a combination of defects mediated by IFNγ and NO, including alterations in the BM T cell precursors, the thymic structure and the thymocyte differentiation.

A Locally-Produced Plant-Based Supplement Swathi Savi (SAVI) Enrichment Improves Body Growth, Bone Development, and Immune Functions in Protein Malnourished Mice: Implications for Strategies to Combat Child Malnutrition

Child malnutrition is a critical global challenge. India alone is home to nearly 46 million stunted children, a third of the world's total. Supplementing locally-produced foods has been acknowledged as a sustainable strategy for combating child malnutrition. We used an established protein malnutrition (PM) model in young mice to evaluate the safety and efficacy of the SAVI-enriched diet as a food supplement to combat child malnutrition in India. Results indicate that feeding the SAVI-enriched diet improves body weight, lean muscle mass, bone, and immune health in PM young mice. Based on the results of our study in mice, we suggest future human trials to examine the supplement's potential benefits for humans.

Coronavirus Disease 2019 (COVID-19) and Nutritional Status: The Missing Link?

Coronavirus disease 2019 (COVID-19) is an emerging disease that has reached pandemic status by rapidly spreading worldwide. Elderly individuals and patients with comorbidities such as obesity, diabetes, and hypertension show a higher risk of hospitalization, severe disease, and mortality by acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. These patients frequently show exacerbated secretion of proinflammatory cytokines associated with an overreaction of the immune system, the so-called cytokine storm. Host nutritional status plays a pivotal role in the outcome of a variety of different infectious diseases. It is known that the immune system is highly affected by malnutrition, leading to decreased immune responses with consequent augmented risk of infection and disease severity. Body composition, especially low lean mass and high adiposity, has consistently been linked to worsened prognosis in many different diseases. In this review, evidence concerning the impact of nutritional status on viral infection outcomes is discussed.

Nutritional status, diet and viral respiratory infections: perspectives for severe acute respiratory syndrome coronavirus 2

COVID-19, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), was recognised by the WHO as a pandemic in 2020. Host preparation to combat the virus is an important strategy to avoid COVID-19 severity. Thus, the relationship between eating habits, nutritional status and their effects on the immune response and further implications in viral respiratory infections is an important topic discussed in this review. Malnutrition causes the most diverse alterations in the immune system, suppressing of the immune response and increasing the susceptibility to infections such as SARS-CoV-2. On the other hand, obesity induces low-grade chronic inflammation caused by excess adiposity, which increases angiotensin-converting enzyme 2. It decreases the immune response favouring SARS-CoV-2 virulence and promoting respiratory distress syndrome. The present review highlights the importance of food choices considering their inflammatory effects, consequently increasing the viral susceptibility observed in malnutrition and obesity. Healthy eating habits, micronutrients, bioactive compounds and probiotics are strategies for COVID-19 prevention. Therefore, a diversified and balanced diet can contribute to the improvement of the immune response to viral infections such as COVID-19.

In Utero and Early Life Exposure to the Great Chinese Famine and Risk of Rheumatoid Arthritis in Adulthood

OBJECTIVE

To investigate whether early life exposure to the Great Chinese Famine of 1959-1961 is associated with the risk of RA development in adulthood.

METHODS

This study included 101,510 participants who were enrolled in the Kailuan Study in 2006. RA cases were confirmed by medical record review. Logistic regression was used to calculate the odds ratio (OR) and 95% confidence interval (95% CI) for RA according to famine exposure status (exposed in utero or between ages 0 and 3 years, between ages 3 and 6 years, or at age 6 years or older), in comparison to participants born after 1961 who were not exposed to famine.

RESULTS

During 12 years of follow-up (2006-2018), we identified 187 RA cases. Individuals exposed to famine in utero or between ages 0 and 3 years had a higher prevalence of RA relative to other groups (0.2-0.35% versus 0.08-0.20%). After adjustment for potential confounders, the OR for RA was 2.95 (95% CI 1.55-5.59) for individuals exposed in utero, 4.53 (95% CI 2.72-7.54) for those exposed between ages 0 and 3 years, 2.55 (95% CI 1.43-4.57) for those exposed between ages 3 and 6 years, and 2.72 (95% CI 1.70-4.36) for those exposed at age 6 years or older versus individuals born after 1961. Similar associations with the risk of RA were observed for men and women when subjects were stratified by sex (P for interaction = 0.89).

CONCLUSION

Individuals exposed to famine in utero or in early childhood (between ages 0 and 3 years) were more likely to develop RA in adulthood, highlighting the importance of early life as a vulnerable developmental period.

Is nuclear sirtuin SIRT6 a master regulator of immune function?

The ability to ward off pathogens with minimal damage to the host determines the immune system's robustness. Multiple factors, including pathogen processing, identification, secretion of mediator and effector molecules, and immune cell proliferation and differentiation into various subsets, constitute the success of mounting an effective immune response. Cellular metabolism controls all of these intricate processes. Cells utilize diverse fuel sources and switch back and forth between different metabolic pathways depending on their energy needs. The three most critical metabolic pathways on which immune cells depend to meet their energy needs are oxidative metabolism, glycolysis, and glutaminolysis. Dynamic switching between these metabolic pathways is needed for optimal function of the immune cells. Moreover, switching between these metabolic pathways needs to be tightly regulated to achieve the best results. Immune cells depend on the Warburg effect for their growth, proliferation, secretory, and effector functions. Here, we hypothesize that the sirtuin, SIRT6, could be a negative regulator of the Warburg effect. We also postulate that SIRT6 could act as a master regulator of immune cell metabolism and function by regulating critical signaling pathways.

Dietary Regulation of the Crosstalk between Gut Microbiome and Immune Response in Inflammatory Bowel Disease

Inflammatory bowel disease (IBD), a chronic, recurring inflammatory response, is a growing global public health issue. It results from the aberrant crosstalk among environmental factors, gut microbiota, the immune system, and host genetics, with microbiota serving as the core of communication for differently-sourced signals. In the susceptible host, dysbiosis, characterized by the bloom of facultative anaerobic bacteria and the decline of community diversity and balance, can trigger an aberrant immune response that leads to reduced tolerance against commensal microbiota. In IBD, such dysbiosis has been profoundly proven in animal models, as well as clinic data analysis; however, it has not yet been conclusively ascertained whether dysbiosis actually promotes the disease or is simply a consequence of the inflammatory disorder. Better insight into the complex network of interactions between food, the intestinal microbiome, and host immune response will, therefore, contribute significantly to the diagnosis, treatment, and management of IBD. In this article, we review the ways in which the mutualistic circle of dietary nutrients, gut microbiota, and the immune system becomes anomalous during the IBD process, and discuss the roles of bacterial factors in shaping the intestinal inflammatory barrier and adjusting immune capacity.

Body Weight Loss Before Allogeneic Hematopoietic Stem Cell Transplantation Predicts Survival Outcomes in Acute Leukemia Patients

Most acute leukemia patients receive consecutive intensive chemotherapy, which usually takes several months before allogeneic hematopoietic stem cell transplantation (allo-HCT). Intensive chemotherapy often induces gastrointestinal adverse events. These adverse events leave patients in a state of malnutrition, leading to a reduction in body weight. In this study, we analyzed the impact of body weight loss before allo-HCT on survival outcomes of acute leukemia patients (acute myeloid leukemia, acute lymphoid leukemia and mixed phenotype acute leukemia). A loss of body weight (LBW), which was a reduction of body weight from diagnosis or relapse to transplantation, was calculated in 182 acute leukemia patients who received first allo-HCT at our center between June 2006 and September 2019. A receiver operating characteristics curve for nonrelapse mortality (NRM) was plotted for defining the cut-off value of LBW. The cutoff value of LBW was defined as 13.2%. A higher LBW was significantly associated with inferior NRM and overall survival (OS) (2-year [2y] NRM 36.1% versus 11.5%, P = .0025; 2y-OS 39.9% versus 65.8%, P = .020). The adverse impact of LBW was also confirmed in multivariate analyses for NRM and OS (HR of NRM 2.74 [1.25-6.03], P = .0012; HR of OS 2.06 [1.00-3.07], P = .0049). The main cause of death included disease progression (n = 34) and infection (n = 35). Death cause by infection was more frequently observed in the high-LBW group (15 cases [35.7%] versus 20 cases [14.3%]; P = .0035). In addition, subgroup analyses based on a combination of the body mass index at diagnosis and LBW were performed. When the non-overweight-low LBW group (body mass index [BMI] ≤25 and LBW ≤13.2%) was used as a reference in multivariate analysis, the overweight-high LBW group (BMI >25 and LBW >13.2%) showed an increased risk of poor survival outcomes (HR of NRM 4.27 [95% confidence interval {CI}, 1.82-10.0], P < .001; HR of OS 1.93 [95%, CI 1.00-3.71], P = .050). High LBW was significantly associated with inferior survival outcomes, and the adverse effect of malnutrition might be greater than the favorable effect of the reduction in overweight.

Thymus size and its correlates among children admitted with severe acute malnutrition: a cross-sectional study in Uganda

Background

Malnutrition continues to be a major cause of mortality and morbidity among children in resource limited settings. Children with severe acute malnutrition (SAM) experience severe thymus atrophy, possibly reflecting poor immune function. This immune dysfunction is responsible for the severe infections they experience which lead to mortality. Since their immune dysfunction is not fully understood and there has been a lapse in research in this field, more research is needed. Knowing the correlates of thymus size may help clinicians identify those with more severe atrophy who might have more severe immune impairment. We aimed to describe thymus size and its correlates at admission among children hospitalized with SAM.

Methods

This cross-sectional study involved children 6-59 months admitted with complicated SAM in Mulago National Referral Hospital. Well-nourished children from same communities were used as a community reference group for thymus size. At admission, thymus size was measured by ultrasound scan. Demographic, clinical and laboratory variables were identified at admission. A linear regression model was used to determine correlates of thymus size among children with SAM.

Results

Among 388 children with SAM, the mean age was 17±8.5 months and 58% were boys. The mean thymus size was 3.14 (95% CI 2.9; 3.4) cm² lower than that of the 27 healthy community reference children (1.06 vs 4.2 cm², p<0.001) when controlled for age. Thymus size positively correlated with current breastfeeding (0.14, 95% CI 0.01, 0.26), anthropometric measurements at admission (weight, length, mid-upper-arm circumference, weight-for-height Z scores and length-for-age Z scores) and suspected tuberculosis (0.12, 95% CI 0.01; 0.22). Thymus size negatively correlated with > 2 weeks duration of sickness (-0.10; 95% CI -0.19; -0.01).

Conclusion

The thymus is indeed a barometer for nutrition since all anthropometric measurements and breastfeeding were associated with bigger thymus. The immune benefits of breastfeeding among children with SAM is underscored. Children with longer duration of illness had a smaller thymus gland indicating that infections have a role in the cause or consequence of thymus atrophy.

Induced Prostanoid Synthesis Regulates the Balance between Th1- and Th2-Producing Inflammatory Cytokines in the Thymus of Diet-Restricted Mice

Multiple external and internal factors have been reported to induce thymic involution. Involution involves dramatic reduction in size and function of the thymus, leading to various immunodeficiency-related disorders. Therefore, clarifying and manipulating molecular mechanisms governing thymic involution are clinically important, although only a few studies have dealt with this issue. In the present study, we investigated the molecular mechanisms underlying thymic involution using a murine acute diet-restriction model. Gene expression analyses indicated that the expression of T helper 1 (Th1)-producing cytokines, namely interferon-γ and interleukin (IL)-2, was down-regulated, while that of Th2-producing IL-5, IL-6, IL-10 and IL-13 was up-regulated, suggesting that acute diet-restriction regulates the polarization of naïve T cells to a Th2-like phenotype during thymic involution. mRNAs for prostanoid biosynthetic enzymes were up-regulated by acute diet-restriction. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) analyses detected the increased production of prostanoids, particularly prostaglandin D₂ and thromboxane B₂, a metabolite of thromboxane A₂, in the diet-restricted thymus. Administration of non-steroidal anti-inflammatory drugs, namely aspirin and etodolac, to inhibit prostanoid synthesis suppressed the biased expression of Th1- and Th2-cytokines as well as molecular markers of Th1 and Th2 cells in the diet-restricted thymus, without affecting the reduction of thymus size. In vitro stimulation of thymocytes with phorbol myristate acetate (PMA)/ionomycin confirmed the polarization of thymocytes from diet-restricted mice toward Th2 cells. These results indicated that the induced production of prostanoids during diet-restriction-induced thymic involution is involved in the polarization of naïve T cells in the thymus.

Vitamin B1 Supports the Differentiation of T Cells through TGF-β Superfamily Production in Thymic Stromal Cells

Homeostatic generation of T cells, which occurs in the thymus, is controlled at least in part by endogenous cytokines and ligands. In addition, nutritional factors are other key regulators for the homeostasis of host immunity, but whether and how nutrition affects the homeostatic generation of thymocytes remains to be established. Here, we showed that vitamin B1 deficiency resulted in a bias toward the maturation of γδ thymocytes accompanied by decreased differentiation into double-positive thymocytes during thymic involution. These events were mediated through the increased production of TGF-β superfamily members due to the accumulation of branched-chain α-keto acids in thymic stromal cells. These findings revealed essential roles of vitamin B1 in the appropriate differentiation of T cells through the metabolism of thymic stromal cells.

The Thymus in Chagas Disease: Molecular Interactions Involved in Abnormal T-Cell Migration and Differentiation

Chagas disease, caused by the protozoan parasite T. cruzi, is a prevalent parasitic disease in Latin America. Presently, it is spreading around the world by human migration, thus representing a new global health issue. Chronically infected individuals reveal a dissimilar disease progression: while nearly 60% remain without apparent disease for life, 30% develop life-threatening pathologies, such as chronic chagasic cardiomyopathy (CCC) or megaviscerae. Inflammation driven by parasite persistence seems to be involved in the pathophysiology of the disease. However, there is also evidence of the occurrence of autoimmune events, mainly caused by molecular mimicry and bystander activation. In experimental models of disease, is well-established that T. cruzi infects the thymus and causes locally profound structural and functional alterations. The hallmark is a massive loss of CD4⁺CD8⁺ double positive (DP) thymocytes, mainly triggered by increased levels of glucocorticoids, although other mechanisms seem to act simultaneously. Thymic epithelial cells (TEC) exhibited an increase in extracellular matrix deposition, which are related to thymocyte migratory alterations. Moreover, medullary TEC showed a decreased expression of AIRE and altered expression of microRNAs, which might be linked to a disrupted negative selection of the T-cell repertoire. Also, almost all stages of thymocyte development are altered, including an abnormal output of CD4⁻CD8⁻ double negative (DN) and DP immature and mature cells, many of them carrying prohibited TCR-Vβ segments. Evidence has shown that DN and DP cells with an activated phenotype can be tracked in the blood of humans with chronic Chagas disease and also in the secondary lymphoid organs and heart of infected mice, raising new questions about the relevance of these populations in the pathogenesis of Chagas disease and their possible link with thymic alterations and an immunoendocrine imbalance. Here, we discuss diverse molecular mechanisms underlying thymic abnormalities occurring during T. cruzi infection and their link with CCC, which may contribute to the design of innovative strategies to control Chagas disease pathology.

The Teleost Thymus in Health and Disease: New Insights from Transcriptomic and Histopathological Analyses of Turbot, Scophthalmus maximus

The thymus is a primary lymphoid organ that plays a pivotal role in the adaptive immune system. The immunobiology of the thymus in fish is considered to be similar to that of mammals, but it is actually poorly characterized in several cultured teleost species. In particular, while investigations in human and veterinary medicine have highlighted that the thymus can be affected by different pathological conditions, little is known about its response during disease in fish. To better understand the role of the thymus under physiological and pathological conditions, we conducted a study in turbot (Scophthalmus maximus), a commercially valuable flatfish species, combining transcriptomic and histopathological analyses. The myxozoan parasite Enteromyxum scophthalmi, which represents a major challenge to turbot production, was used as a model of infection. The thymus tissues of healthy fish showed overrepresented functions related to its immunological role in T-cell development and maturation. Large differences were observed between the transcriptomes of control and severely infected fish. Evidence of inflammatory response, apoptosis modulation, and declined thymic function associated with loss of cellularity was revealed by both genomic and morphopathological analyses. This study presents the first description of the turbot thymus transcriptome and provides novel insights into the role of this organ in teleosts’ immune responses.

Supplementation of Ocean-Based Advance Protein Powder (APP) for Restoration of Body Growth, Bone Development and Immune Functions in Protein Malnourished Mice: Implications for Preventing Child Malnutrition

Child malnutrition is a global public health challenge. A protein malnutrition (PM) model in young mice was established in this study. The efficacy of an ocean-based protein (APP) extracted from by-catch fish as compared to casein and soy on restoring body weight, bone growth, and immunity of PM mice was evaluated. Results show that supplementation of APP increases body weight, lean muscle mass, bone area, mineral content and density. APP supplementation increases spleen, thymus weight, and interlukin-6 production. In conclusion, APP is an alternative source of protein to effectively restore body weight, bone growth and immune function of PM mice.

Thymopentin ameliorates dextran sulfate sodium-induced colitis by triggering the production of IL-22 in both innate and adaptive lymphocytes

Background: Ulcerative colitis (UC) is a chronic inflammatory gastrointestinal disease, notoriously challenging to treat. Previous studies have found a positive correlation between thymic atrophy and colitis severity. It was, therefore, worthwhile to investigate the effect of thymopentin (TP5), a synthetic pentapeptide corresponding to the active domain of the thymopoietin, on colitis. Methods: Dextran sulfate sodium (DSS)-induced colitis mice were treated with TP5 by subcutaneous injection. Body weight, colon length, colon weight, immune organ index, disease activity index (DAI) score, and the peripheral blood profile were examined. The immune cells of the spleen and colon were analyzed by flow cytometry. Histology was performed on isolated colon tissues for cytokine analysis. Bacterial DNA was extracted from mouse colonic feces to assess the intestinal microbiota. Intestinal lamina propria mononuclear cells (LPMCs), HCT116, CT26, and splenocytes were cultured and treated with TP5. Results: TP5 treatment increased the body weight and colon length, decreased the DAI score, and restored colon architecture of colitic mice. TP5 also decreased the infiltration of immune cells and expression levels of pro-inflammatory cytokines such as IL-6. Importantly, the damaged thymus and compromised lymphocytes in peripheral blood were significantly restored by TP5. Also, the production of IL-22, both in innate and adaptive lymphoid cells, was triggered by TP5. Given the critical role of IL-22 in mucosal host defense, we tested the effect of TP5 on mucus barrier and gut microbiota and found that the number of goblet cells and the level of Mucin-2 expression were restored, and the composition of the gut microbiome was normalized after TP5 treatment. The critical role of IL-22 in the protective effect of TP5 on colitis was further confirmed by administering the anti-IL-22 antibody (αIL-22), which completely abolished the effect of TP5. Furthermore, TP5 significantly increased the expression level of retinoic acid receptor-related orphan receptor γ (RORγt), a transcription factor for IL-22. Consistent with this, RORγt inhibitor abrogated the upregulation of IL-22 induced by TP5. Conclusion: TP5 exerts a protective effect on DSS-induced colitis by triggering the production of IL-22 in both innate and adaptive lymphocytes. This study delineates TP5 as an immunomodulator that may be a potential drug for the treatment of UC.

Dynamics of T cell receptor distributions following acute thymic atrophy and resumption

Naive human T cells are produced and developed in the thymus, which atrophies abruptly and severely in response to physical or psychological stress. To understand how an instance of stress affects the size and "diversity" of the peripheral naive T cell pool, we derive a mean-field autonomous ODE model of T cell replenishment that allows us to track the clone abundance distribution (the mean number of different TCRs each represented by a specific number of cells). We identify equilibrium solutions that arise at different rates of T cell production, and derive analytic approximations to the dominant eigenvalues and eigenvectors of the mathematical model linearized about these equilibria. From the forms of the eigenvalues and eigenvectors, we estimate rates at which counts of clones of different sizes converge to and depart from equilibrium values-that is, how the number of clones of different sizes "adjusts" to the changing rate of T cell production. Under most physiological realizations of our model, the dominant eigenvalue (representing the slowest dynamics of the clone abundance distribution) scales as a power law in the thymic output for low output levels, but saturates at higher T cell production rates. Our analysis provides a framework for quantitatively understanding how the clone abundance distribution evolves under small changes in the overall T cell production rate.

Prenatal and childhood exposures are associated with thymulin concentrations in young adolescent children in rural Nepal

The thymus undergoes a critical period of growth and development early in gestation and, by mid-gestation, immature thymocytes are subject to positive and negative selection. Exposure to undernutrition during these periods may permanently affect phenotype. We measured thymulin concentrations, as a proxy for thymic size and function, in children (n = 290; aged 9-13 years) born to participants in a cluster-randomized trial of maternal vitamin A or β-carotene supplementation in rural Nepal (1994-1997). The geometric mean (95% confidence interval) thymulin concentration was 1.37 ng/ml (1.27, 1.47). A multivariate model of early-life exposures revealed a positive association with gestational age at delivery (β = 0.02; P = 0.05) and higher concentrations among children born to β-carotene-supplemented mothers (β = 0.19; P < 0.05). At ∼9-12 years of age, thymulin was positively associated with all anthropometric measures, with height retained in our multivariate model (β = 0.02; P < 0.001). There was significant seasonal variation: concentrations tended to be lower pre-monsoon (β = -0.13; P = 0.15), during the monsoon (β = -0.22; P = 0.04), and pre-harvest (β = -0.34; P = 0.01), relative to the post-harvest season. All early-life associations, except supplementation, were mediated in part by nutritional status at follow-up. Our findings underscore the known sensitivity of the thymus to nutrition, including potentially lasting effects of early nutritional exposures. The relevance of these findings to later disease risk remains to be explored, particularly given the role of thymulin in the neuroendocrine regulation of inflammation.

Thymic Microenvironment Is Modified by Malnutrition and Leishmania infantum Infection

Detrimental effects of malnutrition on immune responses to pathogens have long been recognized and it is considered a main risk factor for various infectious diseases, including visceral leishmaniasis (VL). Thymus is a target of both malnutrition and infection, but its role in the immune response to Leishmania infantum in malnourished individuals is barely studied. Because we previously observed thymic atrophy and significant reduction in cellularity and chemokine levels in malnourished mice infected with L. infantum, we postulated that the thymic microenvironment is severely compromised in those animals. To test this, we analyzed the microarchitecture of the organ and measured the protein abundance in its interstitial space in malnourished BALB/c mice infected or not with L. infantum. Malnourished-infected animals exhibited a significant reduction of the thymic cortex:medulla ratio and altered abundance of proteins secreted in the thymic interstitial fluid. Eighty-one percent of identified proteins are secreted by exosomes and malnourished-infected mice showed significant decrease in exosomal proteins, suggesting that exosomal carrier system, and therefore intrathymic communication, is dysregulated in those animals. Malnourished-infected mice also exhibited a significant increase in the abundance of proteins involved in lipid metabolism and tricarboxylic acid cycle, suggestive of a non-proliferative microenvironment. Accordingly, flow cytometry analysis revealed decreased proliferation of single positive and double positive T cells in those animals. Together, the reduced cortical area, decreased proliferation, and altered protein abundance suggest a dysfunctional thymic microenvironment where T cell migration, proliferation, and maturation are compromised, contributing for the thymic atrophy observed in malnourished animals. All these alterations could affect the control of the local and systemic infection, resulting in an impaired response to L. infantum infection.

Bifidobacterium Abundance in Early Infancy and Vaccine Response at 2 Years of Age

BACKGROUND

The intestinal microbiome in early infancy affects immunologic development and thus may affect vaccine memory, though few prospective studies have examined such associations. We examined the association of Bifidobacterium levels in early infancy with memory responses to early vaccination measured at 2 years of age.

METHODS

In this prospective observational study, we examined the association of Bifidobacterium abundance in the stool of healthy infants at 6 to 15 weeks of age, near the time of vaccination, with T-cell and antibody responses measured at 6 weeks, 15 weeks, and 2 years of age. Infants were vaccinated with Bacillus Calmette-Guérin (BCG) (at birth), oral polio virus (at birth and at 6, 10, and 14 weeks), tetanus toxoid (TT) (at 6, 10, and 14 weeks), and hepatitis B virus (at 6, 10, and 14 weeks). Fecal Bifidobacterium was measured at 6, 11, and 15 weeks. Bifidobacterium species and subspecies were measured at 6 weeks.

RESULTS

Mean Bifidobacterium abundance in early infancy was positively associated with the CD4 T-cell responses to BCG, TT, and hepatitis B virus at 15 weeks, with CD4 responses to BCG and TT at 2 years, and with plasma TT-specific immunoglobulin G and stool polio-specific immunoglobulin A at 2 years. Similar associations were seen for the predominant subspecies, Bifidobacterium longum subspecies infantis.

CONCLUSIONS

Bifidobacterium abundance in early infancy may increase protective efficacy of vaccines by enhancing immunologic memory. This hypothesis could be tested in clinical trials of interventions to optimize Bifidobacterium abundance in appropriate populations.

Disassembling and Reaggregating the Thymus: The Pros and Cons of Current Assays

This review briefly describes the last decades of experimental work on the thymus. Given the histological complexity of this organ, the multiple embryological origins of its cellular components and its role in carefully regulating T lymphocyte maturation and function, methods to dissect and understand this complexity have been developed through the years. The possibility to study ex vivo the thymus organ function has been achieved by developing Fetal Thymus Organ Cultures (FTOC). Subsequently, the combination of organ disaggregation and reaggregation in vitro represented by Reaggregate Thymus Organ cultures (RTOC) allowed mixing cellular components from different genetic backgrounds. Moreover, RTOC allowed dissecting the different stromal and hematological components to study the interactions between Major Histocompatibility Complex (MHC) molecules and the T-cell receptors during thymocytes selection. In more recent years, prospective isolation of stromal cells and thymocytes at different stages of development made it possible to explore and elucidate the molecular and cellular players in both the developing and adult thymus. Finally, the appearance of novel cell sources such as embryonic stem (ES) cells and more recently induced pluripotent stem (iPS) cells has opened new scenarios in modelling thymus development and regeneration strategies. Most of the work described was carried out in rodents and the current challenge is to develop equivalent or even more informative assays and tools in entirely human model systems.

t-BHQ Protects Against Oxidative Damage and Maintains the Antioxidant Response in Malnourished Rats

Objective:

Tert-butylhydroquinone (t-BHQ) protective effect against oxidative damage in thymus from malnourished pops-rats was evaluated.

Methods:

Malnutrition in pops-rats was induced during the lactation period and first-, second-, and third-degree malnourished rats were studied (MN1, MN2, and MN3). To determine t-BHQ protective effect, lipid peroxidation (LPx) was assessed, as well as the carbonyl content. The reduced glutathione and glutathione disulfide content were determined and antioxidant enzyme activities were measured.

Results:

Oxidative protein damage, LPx, and Nuclear Factor-κB (NF-κB) content, increased in the MN2 and MN3 compared to well-nourished rats, associated with lower protein content and antioxidant activity of superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase. Tert-butylhydroquinone treatment induced a protective effect against lipids and proteins oxidative damage, as well as decrease in NF-κB in MN rats and restored the antioxidant mechanisms, mostly GPx and SOD. No differences were found between male and female animals.

Conclusions:

Results show that higher body weight deficit leads to increased oxidative damage and probably inflammation, attributable to alterations in antioxidant mechanisms. These effects were reversed by the t-BHQ-treatment, which restores the antioxidant response. Our findings suggest that t-BHQ could be an interesting pharmacological intervention, but it needs to be studied further.

Changes in Nutritional Status Impact Immune Cell Metabolism and Function

Immune cell function and metabolism are closely linked. Many studies have now clearly demonstrated that alterations in cellular metabolism influence immune cell function and that, conversely, immune cell function determines the cellular metabolic state. Less well understood, however, are the effects of systemic metabolism or whole organism nutritional status on immune cell function and metabolism. Several studies have demonstrated that undernutrition is associated with immunosuppression, which leads to both increased susceptibility to infection and protection against several types of autoimmune disease, whereas overnutrition is associated with low-grade, chronic inflammation that increases the risk of metabolic and cardiovascular disease, promotes autoreactivity, and disrupts protective immunity. Here, we review the effects of nutritional status on immunity and highlight the effects of nutrition on circulating cytokines and immune cell populations in both human studies and mouse models. As T cells are critical members of the immune system, which direct overall immune response, we will focus this review on the influence of systemic nutritional status on T cell metabolism and function. Several cytokines and hormones have been identified which mediate the effects of nutrition on T cell metabolism and function through the expression and action of key regulatory signaling proteins. Understanding how T cells are sensitive to both inadequate and overabundant nutrients may enhance our ability to target immune cell metabolism and alter immunity in both malnutrition and obesity.

Impact of Childhood Malnutrition on Host Defense and Infection

The global impact of childhood malnutrition is staggering. The synergism between malnutrition and infection contributes substantially to childhood morbidity and mortality. Anthropometric indicators of malnutrition are associated with the increased risk and severity of infections caused by many pathogens, including viruses, bacteria, protozoa, and helminths. Since childhood malnutrition commonly involves the inadequate intake of protein and calories, with superimposed micronutrient deficiencies, the causal factors involved in impaired host defense are usually not defined. This review focuses on literature related to impaired host defense and the risk of infection in primary childhood malnutrition. Particular attention is given to longitudinal and prospective cohort human studies and studies of experimental animal models that address causal, mechanistic relationships between malnutrition and host defense. Protein and micronutrient deficiencies impact the hematopoietic and lymphoid organs and compromise both innate and adaptive immune functions. Malnutrition-related changes in intestinal microbiota contribute to growth faltering and dysregulated inflammation and immune function. Although substantial progress has been made in understanding the malnutrition-infection synergism, critical gaps in our understanding remain. We highlight the need for mechanistic studies that can lead to targeted interventions to improve host defense and reduce the morbidity and mortality of infectious diseases in this vulnerable population.

Altered bone marrow lymphopoiesis and interleukin-6-dependent inhibition of thymocyte differentiation contribute to thymic atrophy during Trypanosoma cruzi infection

Thymic atrophy occurs during infection being associated with apoptosis of double positive (DP) and premature exit of DP and double negative (DN) thymocytes. We observed for the first time that a significant bone marrow aplasia and a decrease in common lymphoid progenitors (CLPs) preceded thymic alterations in mice infected with Trypanosoma cruzi. In addition, depletion of the DN2 stage was previous to the DN1, indicating an alteration in the differentiation from DN1 to DN2 thymocytes. Interestingly, infected mice deficient in IL-6 expression showed higher numbers of DP and CD4⁺ thymocytes than wild type infected mice, while presenting similar percentages of DN1 thymocytes. Moreover, the drop in late differentiation stages of DN thymocytes was partially abrogated in comparison with wild type littermates. Thus, our results suggest that thymic atrophy involves a drop in CLPs production in bone marrow and IL-6-dependent and independent mechanisms that inhibits the differentiation of DN thymocytes.