Thymic hypoplasia induced by copy number variations contributed to explaining sudden infant death based on forensic autopsies.

Thymic hypoplasia is a primary cellular immunodeficiency that causes susceptibility to serious infections leading to sudden death in infants. Some genetic disorders in humans could result in the evident permanent hypoplasia or occasional aplasia of the thymus at birth. However, determining the genetic etiology of thymic hypoplasia is challenging for the sudden infant death due to primary cellular immunodeficiency. In this study, in order to find the fundamental reasons for sudden death of infants with thymic hypoplasia, 5 infants with suspected thymic hypoplasia and 10 control infants were assessed, and the immunohistochemistry and DNA analysis were used to investigate whether the infants with thymic hypoplasia had DiGeorge syndrome (DGS) with copy number variations (CNVs) in 22q11.2 and other chromosomes. The results showed that the weight of the thymus was significantly lower than the normal except the case 4, and that all the infants had hypocalcemia and a significant decrease or even absence of the markers CD1a, CD2, CD3, CD4 and CD8, which are related to T-cell maturation. In addition, multiplex ligation-dependent probe amplification (MLPA) analysis showed that these infants carried CNVs in 22q11.2 and other associated chromosomes with deletion and duplication of 25 genes. The results of thymus weight, histopathology, molecular pathology and MLPA analysis suggested that DGS predominantly with thymic hypoplasia induced by CNVs caused the sudden death of these infants under various infections or other unexplained reasons, which may provide new insights into the diagnosis of sudden infant death and could help the parents of deceased infants to attach more importance of genetic screening and thymus ultrasound to reduce the postnatal mortality of the infant, and demonstrates the value of genetic diagnosis in the forensic pathology.

Initial validation of the diagnostic performance of Thymic-Thoracic Ratio as a marker of conotruncal abnormalities and for prediction of surgical prognosis in fetuses without 22q11.2 deletion.

AIM: The present study aimed to perform an initial validation of the Thymic-Thoracic Ratio as a sonographic marker of conotruncal defects in non-syndromic fetuses and to assess the possible correlation between the grade of thymic hypoplasia and the severity of conotruncal defects. METHODS: The study was conducted between January and June 2018 on singleton pregnant women who underwent fetal echocardiography at our institution. Fetuses with a diagnosis of conotruncal defects without 22q11.2 deletion composed the study group, while healthy appropriate for gestational age fetuses composed the control group. The Thymic-Thoracic Ratio was measured in all included fetuses and compared between the study and control group. A ROC curve analysis to evaluate the diagnostic performance of Thymic-Thoracic Ratio toward the diagnosis of conotruncal defects was performed, with determination of sensitivity, specificity, PPV, NPV, positive likelihood ratio, and negative likelihood ratio. The severity of conotruncal defects was defined with the Aristotle score in each newborn who underwent a surgical operation. The correlation between Thymic-Thoracic Ratio and Aristotle score was assessed. RESULTS: During the study period, 23 fetuses with conotruncal defects without 22q11.2 deletion constituted the study group, and 67 healthy appropriate for gestational age fetuses were included in the control group. The T-T ratio of the study group was significantly lower than the control group (0.32 ± 0.08 vs. 0.41 ± 0.08, p < .001). The ROC curve analysis showed an AUC of 0.80 (95% CI, 0.71-0.89, p < .001) and a T-T ratio cutoff value of 0.35 for the identification of a CTD, with a sensibility of 73.9% (95% CI: 51.6-89.8%), a specificity of 79.1% (95% CI: 67.4-88.1%) a PPV of 54.8% (95% CI: 41.8-67.3%), a NPV of 89.8% (95% CI: 81.5-94.7), a positive likelihood ratio of 3.54 (95% CI 2.09-5.98), and a negative likelihood ratio of 0.33 (95% CI 0.16-0.66). A negative correlation between Aristotle score and T-T ratio was found, with a Kendall-Tau coefficient of -0.41, p = .04. CONCLUSION: T-T ratio measurement could be useful to identify fetuses at higher risk of conotruncal heart diseases, even without chromosomic deletion, with a cutoff of 0.35. Since a lower T-T ratio seems to be related to a worse surgical neonatal prognosis, it could be possible to provide effective counseling and refer patients to high-specialized centers for fetal echocardiography and cardiac surgery.

Thymic Engraftment by in vitro-Derived Progenitor T Cells in Young and Aged Mice.

T cells play a critical role in mediating antigen-specific and long-term immunity against viral and bacterial pathogens, and their development relies on the highly specialized thymic microenvironment. T cell immunodeficiency can be acquired in the form of inborn errors, or can result from perturbations to the thymus due to aging or irradiation/chemotherapy required for cancer treatment. Hematopoietic stem cell transplant (HSCT) from compatible donors is a cornerstone for the treatment of hematological malignancies and immunodeficiency. Although it can restore a functional immune system, profound impairments exist in recovery of the T cell compartment. T cells remain absent or low in number for many months after HSCT, depending on a variety of factors including the age of the recipient. While younger patients have a shorter refractory period, the prolonged T cell recovery observed in older patients can lead to a higher risk of opportunistic infections and increased predisposition to relapse. Thus, strategies for enhancing T cell recovery in aged individuals are needed to counter thymic damage induced by radiation and chemotherapy toxicities, in addition to naturally occurring age-related thymic involution. Preclinical results have shown that robust and rapid long-term thymic reconstitution can be achieved when progenitor T cells, generated in vitro from HSCs, are co-administered during HSCT. Progenitor T cells appear to rely on lymphostromal crosstalk via receptor activator of NF-κB (RANK) and RANK-ligand (RANKL) interactions, creating chemokine-rich niches within the cortex and medulla that likely favor the recruitment of bone marrow-derived thymus seeding progenitors. Here, we employed preclinical mouse models to demonstrate that in vitro-generated progenitor T cells can effectively engraft involuted aged thymuses, which could potentially improve T cell recovery. The utility of progenitor T cells for aged recipients positions them as a promising cellular therapy for immune recovery and intrathymic repair following irradiation and chemotherapy, even in a post-involution thymus.

Molecular Insights Into the Causes of Human Thymic Hypoplasia With Animal Models.

22q11.2 deletion syndrome (DiGeorge), CHARGE syndrome, Nude/SCID and otofaciocervical syndrome type 2 (OTFCS2) are distinct clinical conditions in humans that can result in hypoplasia and occasionally, aplasia of the thymus. Thymic hypoplasia/aplasia is first suggested by absence or significantly reduced numbers of recent thymic emigrants, revealed in standard-of-care newborn screens for T cell receptor excision circles (TRECs). Subsequent clinical assessments will often indicate whether genetic mutations are causal to the low T cell output from the thymus. However, the molecular mechanisms leading to the thymic hypoplasia/aplasia in diverse human syndromes are not fully understood, partly because the problems of the thymus originate during embryogenesis. Rodent and Zebrafish models of these clinical syndromes have been used to better define the underlying basis of the clinical presentations. Results from these animal models are uncovering contributions of different cell types in the specification, differentiation, and expansion of the thymus. Cell populations such as epithelial cells, mesenchymal cells, endothelial cells, and thymocytes are variably affected depending on the human syndrome responsible for the thymic hypoplasia. In the current review, findings from the diverse animal models will be described in relation to the clinical phenotypes. Importantly, these results are suggesting new strategies for regenerating thymic tissue in patients with distinct congenital disorders.

Enfermedades del timo por exceso y por defecto / Thymus diseases by excess and default

El timo es un órgano cervicotorácico, impar y mediano, situado en la base del cuello y parte superior del mediastino. Junto a la médula ósea es uno de los dos órganos primarios del sistema inmune y ejerce su función en los neonatos y en los niños, fundamentalmente. Entra en regresión a partir de la pubertad, aunque algunos autores plantean que la involución puede comenzar un poco antes, cuando los principales tejidos linfoides están plenamente desarrollados. Interviene sinérgicamente con otras glándulas de secreción interna: tiroides, suprarrenal, hipófisis, para elaborar substancias necesarias para el desarrollo general del organismo. Es un órgano muy sensible a todo influjo. Como todos los órganos de la economía el timo presenta enfermedades producidas tanto por crecimiento exagerado, como por hipoplasias o atrofias. Dentro de las primeras las más comunes son la hiperplasia tímica y el timoma y, entre las últimas el síndrome de DiGeorge ha sido bien caracterizado en la literatura internacional desde la segunda mitad del siglo pasado. Sin embrago, en los últimos tiempos los inmunólogos hablan de la hipoplasia tímica como entidad que puede asociarse o no a estados de inmunodeficiencia. Se describen brevemente estas afecciones(AU)

The thymus is a cervicothoracic organ, odd and medium, located at the base of the neck and upper part of the mediastinum. Next to the bone marrow is one of the two primary organs of the immune system and exerts its function in neonates and children, fundamentally. It regresses after puberty, although some authors suggest that the involution can begin a little earlier, when the main lymphoid tissues are fully developed. It intervenes synergistically with other glands of internal secretion: thyroid, adrenal, pituitary gland, to develop substances necessary for the general development of the organism. It is a very sensitive organ to all influence. Like all the organs of the economy, the thymus presents diseases caused both by exaggerated growth, as by hypoplasias or atrophies. Among the former, the most common are thymic hyperplasia and thymoma and, among the latter, DiGeorge syndrome has been well characterized in international literature since the second half of the last century. However, in recent times immunologists speak of thymic hypoplasia as an entity that may or may not be associated with immunodeficiency states. These conditions are briefly described(AU)

Prenatal nicotine exposure induces thymic hypoplasia in mice offspring from neonatal to adulthood.

Clinical study showed that smoking during pregnancy deceased the thymus size in newborns. However, the long-term effect remains unclear. This study was aimed to observe the effects of prenatal nicotine exposure (PNE) on the development of thymus and the T-lymphocyte subpopulation in mice offspring from the neonatal to adulthood. Both the thymus weight and cytometry data indicated that PNE caused persistent thymic hypoplasia in male offspring from neonatal to adult period and transient changes in female offspring from neonatal to prepuberal period. Flow cytometry analysis disclosed a permanent decreased proportion and number of mature CD4 single-positive (SP) T cells in thymus of both sex. In addition, the PNE male offspring showed a more serious thymus atrophy in the ovalbumin (OVA)-sensitized model. Moreover, increased autophagic vacuole and elevated mRNA expression of Beclin 1 were noted in PNE fetal thymus. In conclusion, PNE offspring showed thymus atrophy and CD 4 SP T cell reduction at different life stages. Mechanically, PNE induced excessive autophagy in fetal thymocytes might be involved in these changes. All the results provided evidence for elucidating the PNE-induced programmed immune diseases.

Abordaje inmunológico del síndrome por deleción 22q11 / Immunological approaches to 22q11 deletion syndrome

El síndrome por deleción 22q11 (SD22q11) es el síndrome por deleción cromosómica más frecuente en humanos y se caracteriza por la tríada clínica que incluye cardiopatía congénita, hipocalcemia e inmunodeficiencia primaria. El 85-90% de los pacientes tienen microdeleciones en el cromosoma 22q11.2. Tomando como punto cardinal la cardiopatía congénita, se diseñó una estrategia para tamización y diagnóstico de SD22q11 con énfasis en la evaluación inmune. Es imprescindible realizar una historia clínica detallada y, posteriormente, un análisis cuantitativo y funcional de las subpoblaciones de linfocitos en sangre periférica para clasificarlo en SD22q11 completo (<1%) o parcial (95-99%) e instaurar las pautas de tratamiento en aspectos como: aislamiento del paciente, vacunación, profilaxis contra microorganismos oportunistas, uso de productos sanguíneos irradiados y reconstitución inmunológica. Sin embargo, el abordaje del paciente debe ser multidisciplinario para detectar y prevenir complicaciones a largo plazo que pueden ser graves, especialmente en los pacientes con SD22q11 completo.

In humans, 22q11 deletion syndrome (22q11DS) is considered the most common chromosome deletion syndrome. It is characterised by a clinical triad that includes congenital heart disease, hypocalcaemia and primary immunodeficiency. Approximately 85-90% of patients with this syndrome exhibit microdeletions in chromosome 22q11.2. Using congenital heart disease as a starting point, we designed a strategy for the screening and diagnosis of 22q11DS with an emphasis on immunological evaluation. A detailed clinical history and the subsequent quantitative and functional analyses of the lymphocyte subpopulations in the peripheral blood is crucial to classify as complete (<1%) or partial (95-99%) the disease and to guide clinicians in terms of patient isolation, vaccination, prophylaxis for opportunistic infections, use of irradiated blood products and immunological reconstitution. However, multidisciplinary care is necessary to detect and prevent long-term complications that could be severe, particularly in cases of complete 22q11DS.

Estado inmunonutricional en niños con diarrea crónica inespecífica / Immunenutritional state of children with chronic nonspecific diarrhea

Introducción : la ruptura del equilibrio inmunonutricional en los pacientes con diarrea crónica inespecífica (DCI) entorpece la evolución clínica y favorece la aparición de complicaciones.Objetivo: caracterizar el estado inmunonutricional de niños con Diarrea Crónica Inespecífica. Materiales y Método: se realizó un estudio descriptivo transversal a 44 niños menores de 6 años con diagnóstico de diarrea crónica inespecífica, atendidos en el Instituto de Gastroenterología en el período comprendido de marzo del 2012 a mayo 2014. A todos se les aplicó cuestionario, previo consentimiento informado y se les realizó mensuraciones antropométricas, exámenes parasitológicos y bacteriológicos en heces, hemograma completo, determinación de hierro sérico, dosificación de inmunoglobulinas totales y ultrasonido de timo. Para el análisis estadístico se emplearon distribuciones de frecuencia y para la comparación entre los grupos se utilizó la prueba del X2. Se consideró significativo una p < 0,05. Resultados: la población objeto de estudio no superó los 4 años de edad, con un predominio del sexo masculino sin asociación entre edad y sexo. El 43.2 por ciento de los pacientes presentó algún grado de malnutrición con un comportamiento similar entre los malnutridos por defecto y por exceso. Poco menos de la mitad de los pacientes tuvo anemia. La hipoplasia tímica y los niveles séricos bajos de IgA fueron condiciones frecuentes en la población estudiada. Conclusiones: el compromiso del estado inmunonutricional de los niños con diarrea crónica inespecífica no es infrecuente. Se manifiesta en elevada frecuencia de malnutrición, anemia, hipoplasia tímica y niveles séricos bajos de IgA(AU)

Introduction: breaking down the immune nutritional balance in patients with chronic nonspecific diarrhea (ICD) hinders the clinical course and promotes complications.Objective: to characterize the immune nutritional state of children with ICD. Material and Methods: a cross-sectional study in 44 children younger than 6 years prior consent was performed with a diagnosis of chronic nonspecific diarrhea treated at the Institute of Gastroenterology from March 2012 to May 2014. Aconsent informed questionnaire was applied previously to all patients, who underwent anthropometric assessment, bacteriological and parasitological stool examinations, complete blood count, determination of serum iron, determination of total immunoglobulin and ultrasound thymus. Statistical analysis included, frequency distributions, to comparison among the test groups, Chi-square test was done (considering significant; p<0.05). Results: the population did not exceed 4 years old, with a male predominance and no association between age and sex. 43.2 percent of patients had some grade of malnutrition without differences between calorie and protein malnutrition and overweight. Just under half of the patients had anemia. Thymic hypoplasia and low serum IgA levels were more common conditions. Conclusions: the commitment of immune nutritional status of children with chronic nonspecific diarrhea is not uncommon. It manifests itself in high frequency of malnutrition, anemia, thymic hypoplasia, and low serum IgA(AU)

Hipoplasia tímica en un niño con fibrosis quística / Thymic hypoplasia in an infant with cystic fibrosis

La fibrosis quística es la enfermedad autosómica recesiva más frecuente en poblaciones caucásicas; en Cuba, uno de cada 5 000 recién nacidos están afectados. En 1989 fue clonado el gen regulador de la conductancia transmembranal de la fibrosis quística e identificada su mutación principal, F508del. Desde entonces han sido descritas más de 1 300 mutaciones diferentes en este gen. El timo es el principal órgano de maduración de los linfocitos T, es relativamente grande y muy activo al nacer. El síndrome de Di George, descrito en 1965, incluye varias malformaciones congénitas y déficit inmunológico, principalmente de células T por hipoplasia del timo. Actualmente existen criterios definitivos, probables y posibles que diagnostican la entidad y se reportan síndromes completos y parciales en dependencia de los síntomas y signos presentes en el enfermo; sin embargo, puede observarse hipoplasia severa del timo en pacientes sin diagnóstico de Di George. Se presenta el caso de un paciente pediátrico en el que se define el diagnóstico de fibrosis quística por estudios moleculares y se identifica como homocigótico para la mutación F508del con hipoplasia severa del timo

Cystic fibrosis is the most common autosomal recessive disease in Caucasian populations; in Cuba, one in 5 000 newborns are affected. In 1989, the conductance regulator gene for cystic fibrosis transmembrane was cloned and its main mutation F508del was identified. Since then, over 1 300 different mutations in the gene have been described. The thymus is the primary organ of T cell maturation, is relatively large and very active at birth. DiGeorge syndrome, described in 1965, includes several birth defects and immune deficits, mainly of T cells by thymic hypoplasia. Currently, definitive, probable and possible criteria to diagnose the entity exist as well as reports of full and partial syndromes depending of symptoms present in the patient; nevertheless, severe thymic hypoplasia can be observed in patients without diagnosis of Di George. We report the case of a pediatric patient with diagnosis of cystic fibrosis by molecular studies identified as homozygous for the mutation F508del with severe thymic hypoplasia

Estado inmunológico en niños con diarrea crónica inespecífica / Immune status in children with chronic nonspecific diarrhea

Introducción: la diarrea crónica inespecífica (DCI) en la infancia constituye motivo frecuente de consulta, no se ha podido determinar aún el origen de este padecimiento, se invocan varias teorías que tratan de explicar su fisiopatología sobre la base de trastornos inmunológicos asociados.Objetivo: caracterizar el estado inmunológico de niños con DCI.Materiales y Método: se realizó un estudio descriptivo transversal a 36 niños menores de 6 años con diagnóstico de diarrea crónica inespecífica, atendidos en el Instituto de Gastroenterología en el período comprendido de marzo a diciembre del 2012. A todos se les realizó determinación de hemoglobina, hierro sérico, dosificación de inmunoglobulinas totales y ultrasonido de timo. Para el análisis estadístico se emplearon pruebas paramétricas y las diferencias se consideraron significativas con p < 0,05. Resultados: el abandono de la lactancia materna exclusiva antes de los 6 meses y los niveles séricos bajos de Inmunoglobulina A (IgA) tuvieron una elevada frecuencia. No se demostró asociación entre duración de la lactancia materna exclusiva recibida, área tímica y niveles séricos de IgA. Conclusiones: la mayoría de los niños con diarrea crónica inespecífica tienen compromiso de su estado inmunológico. Los principales trastornos inmunológicos presentes son la hipoplasia tímica y los niveles séricos bajos de IgA(AU)

Introduction: chronic nonspecific diarrhea (CID) in childhood is frequent complaint, has not yet been able to determine the origin of this disease, and is invoked several theories that attempt to explain its pathophysiology based on associated immunological disorders. Objective: to characterize the immune status of children with DCI. Materials and Methods: we carried out a cross-sectional study of 36 children less than 6 years diagnosed with chronic nonspecific diarrhea treated at the Institute of Gastroenterology in the period March to December 2012. An All patients underwent complete blood count, determination of serum iron, total immunoglobulin dose and thymus´s ultrasound. For statistical analysis, parametric tests were used and differences were considered significant at p <0.05. Results: the abandonment of exclusive breastfeeding before 6month and low serum immunoglobulin A (IgA) levels had a high frequency in our study. No association was found between cessation of breastfeeding before 6 months, thymic hypoplasia and low serum IgA levels. Conclusions: most children with chronic nonspecific diarrhea have compromised their immune status. The main immune disorders are the thymic hypoplasia and low serum IgA levels(AU)

Estado inmunológico en niños con diarrea crónica inespecífica / Immune status in children with chronic nonspecific diarrhea

Introducción: la diarrea crónica inespecífica (DCI) en la infancia constituye motivo frecuente de consulta, no se ha podido determinar aún el origen de este padecimiento, se invocan varias teorías que tratan de explicar su fisiopatología sobre la base de trastornos inmunológicos asociados. Objetivo: caracterizar el estado inmunológico de niños con DCI. Materiales y Método: se realizó un estudio descriptivo transversal a 36 niños menores de 6 años con diagnóstico de diarrea crónica inespecífica, atendidos en el Instituto de Gastroenterología en el período comprendido de marzo a diciembre del 2012. A todos se les realizó determinación de hemoglobina, hierro sérico, dosificación de inmunoglobulinas totales y ultrasonido de timo. Para el análisis estadístico se emplearon pruebas paramétricas y las diferencias se consideraron significativas con p < 0,05. Resultados: el abandono de la lactancia materna exclusiva antes de los 6 meses y los niveles séricos bajos de Inmunoglobulina A (IgA) tuvieron una elevada frecuencia. No se demostró asociación entre duración de la lactancia materna exclusiva recibida, área tímica y niveles séricos de IgA. Conclusiones: la mayoría de los niños con diarrea crónica inespecífica tienen compromiso de su estado inmunológico. Los principales trastornos inmunológicos presentes son la hipoplasia tímica y los niveles séricos bajos de IgA.

Introduction: chronic nonspecific diarrhea (CID) in childhood is frequent complaint, has not yet been able to determine the origin of this disease, and is invoked several theories that attempt to explain its pathophysiology based on associated immunological disorders. Objective: to characterize the immune status of children with DCI. Materials and Methods: we carried out a cross-sectional study of 36 children less than 6 years diagnosed with chronic nonspecific diarrhea treated at the Institute of Gastroenterology in the period March to December 2012. An All patients underwent complete blood count, determination of serum iron, total immunoglobulin dose and thymus´s ultrasound. For statistical analysis, parametric tests were used and differences were considered significant at p <0.05. Results: the abandonment of exclusive breastfeeding before 6month and low serum immunoglobulin A (IgA) levels had a high frequency in our study. No association was found between cessation of breastfeeding before 6 months, thymic hypoplasia and low serum IgA levels. Conclusions: most children with chronic nonspecific diarrhea have compromised their immune status. The main immune disorders are the thymic hypoplasia and low serum IgA levels.