Immune dysregulation after cardiothoracic surgery and incidental thymectomy: maintenance of regulatory T cells despite impaired thymopoiesis

Pneumonia, wheezing and asthma were more common in children after thymectomy due to open-heart surgery

AIM

This nationwide study evaluated the clinical impact that an early thymectomy, during congenital heart defect (CHD) surgery, had on the health of children and adolescents.

METHODS

The subjects were patients aged 1-15 years who had undergone CHD surgery at the University Children's Hospital, Helsinki, where all CHD surgery in Finland is carried out, from 2006 to 2018. The parents or the cases and population-based controls, matched for sex, age and hospital district, completed electronic questionnaires. We excluded those with low birth weights or a known immunodeficiency. Adjusted odds ratios (aOR) and 95% confidence intervals (CI) were calculated for prespecified outcomes.

RESULTS

We received responses relating to 260/450 (58%) cases and 1403/4500 (31%) controls and excluded 73 cases with persistent cardiac or respiratory complaints after surgery. The CHD group reported more recurrent hospitalisations due to infections (aOR 6.3, 95% CI 3.0-13) than the controls and more pneumonia episodes (aOR 3.5, 95% CI 2.1-5.6), asthma (aOR 2.5, 95% CI 1.5-4.1) and wheezing (aOR 2.1, 95% CI 1.5-2.9).

CONCLUSION

Hospitalisation due to infections, pneumonia, wheezing and asthma was more common in children after a thymectomy due to open-heart surgery than population-based controls, underlining the importance of immunological follow-ups.

Effects of antibiotics, hospitalisation and surgical complications on self-reported immunological vulnerability following paediatric open-heart surgery and thymectomy: a single-centre retrospective cohort study

BACKGROUND

Partial or complete thymectomy is routinely performed in paediatric open-heart surgeries when treating congenital heart defects. Whether or not thymectomised children require systematic immunological monitoring later in life is unknown. The objective of this study was to investigate the effects of preoperatively and postoperatively used antibiotics, hospitalisation and surgical complications on self-reported immunological vulnerability in paediatric patients with early thymectomy to better recognise the patients who could benefit from immunological follow-up in the future.

METHODS

We conducted a retrospective cohort study, including 98 children and adolescents aged 1-15 years, who had undergone an open-heart surgery and thymectomy in infancy and who had previously answered a survey regarding different immune-mediated symptoms and diagnoses. We performed a comprehensive chart review of preoperative and postoperative factors from 1 year preceding and 1 year following the open-heart surgery and compared the participants who had self-reported symptoms of immunological vulnerability to those who had not.

RESULTS

The median age at primary open-heart surgery and thymectomy was 19.5 days in the overall study population (60% men, n=56) and thymectomies mainly partial (80%, n=78). Broad-spectrum antibiotics were more frequently used preoperatively in participants with self-reported immunological vulnerability (OR=3.05; 95% CI 1.01 to 9.23). This group also had greater overall use of antibiotics postoperatively (OR=3.21; 95% CI 1.33 to 7.76). These findings were more pronounced in the subgroup of neonatally operated children. There was no statistically significant difference in the duration of intensive care unit stay, hospitalisation time, prevalence of severe infections, surgical complications or glucocorticoid use between the main study groups.

CONCLUSION

Antimicrobial agents were more frequently used both preoperatively and postoperatively in thymectomised children with self-reported immunological vulnerability after thymectomy. Substantial use of antimicrobial agents early in life should be considered a potential risk factor for increased immunological vulnerability when evaluating the significance of immune-mediated symptom occurrence in thymectomised paediatric patients.

Alterations in the immune phenotype of thymectomized children and the development of atopic disorders after heart transplantation

BACKGROUND

Atopic disorders are more common in children after heart transplant (HTx). We hypothesized that HTx at an early age and thymus excision (TE) affect development of T and B cells, especially regulatory T cells (Tregs), which help maintain tolerance.

METHODS

In this single-center study including 24 patients transplanted between 2013 and 2018, we investigated lymphocyte patterns in relation to these factors using flow cytometry. Clinical data were collected from standardized questionnaires and medical charts. Patients were stratified into TE and non-TE groups as well as patients with and without post-transplant atopy development/worsening.

RESULTS

64% of TE patients experienced new or worsening asthma/eczema post-transplant compared to 20% of non-TE patients. TE patients had higher total Treg proportions (CD4+CD25+CD127lo) than non-TE patients (p = .043), but borderline significantly lower naïve Tregs (CD45RA+CD27-) (p = .057). Memory CD4+ T cells were higher in TE patients in trend (p = .084). Total Tregs did not differ between atopic/nonatopic groups, although naïve Tregs were significantly lower in atopic patients (p = .028). Memory CD4+ T cells were higher in atopic patients in trend (p = .082). IgM+IgD+ B cells were higher in nonatopic patients in trend (p = .064).

CONCLUSIONS

New/worsening atopy is more common in thymectomized HTx children and is associated with alterations in T-cell profiles. Avoiding TE may prevent these alterations and reduce incidence of atopy post-HTx.

Immunity and inflammation: the neglected key players in congenital heart disease?

Although more than 90% of children born with congenital heart disease (CHD) survive into adulthood, patients face significantly higher and premature morbidity and mortality. Heart failure as well as non-cardiac comorbidities represent a striking and life-limiting problem with need for new treatment options. Systemic chronic inflammation and immune activation have been identified as crucial drivers of disease causes and progression in various cardiovascular disorders and are promising therapeutic targets. Accumulating evidence indicates an inflammatory state and immune alterations in children and adults with CHD. In this review, we highlight the implications of chronic inflammation, immunity, and immune senescence in CHD. In this context, we summarize the impact of infant open-heart surgery with subsequent thymectomy on the immune system later in life and discuss the potential role of comorbidities and underlying genetic alterations. How an altered immunity and chronic inflammation in CHD influence patient outcomes facing SARS-CoV-2 infection is unclear, but requires special attention, as CHD could represent a population particularly at risk during the COVID-19 pandemic. Concluding remarks address possible clinical implications of immune changes in CHD and consider future immunomodulatory therapies.

Tonsillectomy as a risk factor of periodontitis: a population-based cohort study

AIM

To determine whether patients who had undergone tonsillectomy would have higher risks of postoperative periodontitis.

METHODS

Data were collected from the Taiwan Longitudinal Health Insurance Dataset from 1999 to 2013, a population-based cohort study consisting of cases of newly-onset sleep apnoea, chronic diseases of tonsils and adenoids, peritonsillar abscess, and periodontal diseases. 1,482 tonsillectomy cases and 14,796 non-tonsillectomy controls were selected. Propensity score matching between the tonsillectomy group and the non-tonsillectomy group was conducted to exclude the confounding effect resulting from indications of tonsillectomy. Cox proportional hazard model and subgroup analyses were conducted to identify subpopulations at risk of tonsillectomy-associated periodontitis, and a sub-outcome analysis was applied to identify the subtype of tonsillectomy-associated periodontitis.

RESULTS

A total of 648 patients who had undergone tonsillectomy and 648 out of 6,509 propensity score-matched controls were retrieved, among which 230 cases in the tonsillectomy group were associated with post-surgical periodontitis (adjusted HR = 1.31, 95% CI = 1.08-1.59). The association persisted in a subpopulation of patients with periodontitis who received mechanical and surgical treatments for periodontitis (adjusted HR = 1.33, 95% CI = 1.09-1.63). The incidence of periodontitis was significantly high in the individuals who underwent tonsillectomy and was particularly high in those that were below 12 years of age (HR = 1.58, 95% CI = 1.10-2.27). The risk of periodontitis increased 4 years after tonsillectomy (HR = 1.82; 95% CI = 1.29-2.59). The majority of post-tonsillectomy periodontitis was aggressive and acute periodontitis (HR = 1.37; 95% CI = 1.10 - 1.71).

CONCLUSIONS

Tonsillectomy performed in paediatric patients of less than 12 years old, increased the risk of developing periodontitis. Aggressive and acute periodontitis as a long-term, postoperative adverse event took place at 4 years or longer after tonsillectomy. This article is protected by copyright. All rights reserved.

T cell phenotype in paediatric heart transplant recipients

Paediatric heart transplantation recipients suffer an increased incidence of infectious, autoimmune and allergic problems. The relative roles of thymus excision and immunosuppressive treatments in contributing to these sequelae are not clear. We compared the immunological phenotypes of 25 heart transplant recipients (Tx), 10 children who underwent thymus excision during non-transplantation cardiac surgery (TE) and 25 age range-matched controls, in two age bands: 1-9 and 10-16 years. Significant differences from controls were seen mainly in the younger age band with Tx showing lower CD3 and CD4 cell counts whilst TE showed lower CD8 cell counts. Naïve T cell and recent thymic emigrant proportions and counts were significantly lower than controls in both groups in the lower age band. T cell recombination excision circle (TREC) levels were lower than controls in both groups in both age bands. There were no differences in regulatory T cells, but in those undergoing thymus excision in infancy, their proportions were higher in TE than Tx, a possible direct effect of immunosuppression. T cell receptor V beta spectratyping showed fewer peaks in both groups than in controls (predominantly in the older age band). Thymus excision in infancy was associated with lower CD8 cell counts and higher proportions of Tregs in TE compared to Tx. These data are consistent with thymus excision, particularly in infancy, being the most important influence on immunological phenotype after heart transplantation.

Inborn Errors of Adaptive Immunity in Down Syndrome

Down syndrome fits an immunophenotype of combined immunodeficiency with immunodysregulation, manifesting with increased susceptibility to infections, autoimmunity, autoinflammatory diseases, and hematologic malignancies. Qualitative and quantitative alterations in innate and adaptive immunity are found in most individuals with Down syndrome. However, there is substantial heterogeneity and no correlation between immunophenotype and clinical presentation. Previously, it was thought that the immunological changes in Down syndrome were caused by precocious aging. We emphasize in this review that the immune system in Down syndrome is intrinsically different from the very beginning. The overexpression of specific genes located on chromosome 21 contributes to immunodeficiency and immunodysregulation, but gene expression differs between genes located on chromosome 21 and depends on tissue and cell type. In addition, trisomy 21 results in gene dysregulation of the whole genome, reflecting the complex nature of this syndrome in comparison to well-known inborn errors of immunity that result from monogenic germline mutations. In this review, we provide an updated overview focusing on inborn errors of adaptive immunity in Down syndrome.

Risk of incident autoimmune diseases in patients with thymectomy

OBJECTIVES

The data concerning the association between Tx and ADs remain unclear and are scarce. This study was undertaken to investigate whether people with Tx are more likely to develop ADs, compared to those without Tx.

METHODS

Individuals who received Tx between 2002 and 2015 were identified and matched on age and sex with individuals without Tx. We performed multivariate and stratified analysis using the Kaplan-Meier method and Cox proportional hazards models in order to estimate the association between Tx and the risk of developing ADs.

RESULTS

A total of 2550 thymectomized (Txd) patients and 24,664.941 non-Txd comparison subjects were selected from NHIRD. Tx-MG (myasthenia gravis) as compared with general population (nonTx-nonMG), adjusted hazard ratio (aHR) were higher for incident Addison disease (aHR = 10.40, 95% CI 1.01-107), autoimmune hemolytic anemia (aHR = 21.54, 95% CI 2.06-14.8), Hashmoto thyroiditis (aHR = 5.52, 95% CI 1.34-34.7), ankylosing spondylitis (aHR = 2.73, 95% CI 1.09-6.84), rheumatoid arthritis (aHR = 5.25, 95% CI 1.79-15.47), primary Sjogren syndrome (pSS) (aHR = 3.77, 95% CI 1.30-11.0), and systemic lupus erythemtoasus (aHR = 10.40). Tx-nonMG as compared with general population, aHR were higher for incident autoimmune hemolytic anemia (aHR = 25.50), Hashmoto thyroiditis (aHR = 6.75) and systemic lupus erythematosus (SLE) (aHR = 13.38). NonTx-MG as compared with general population, aHR were higher for incident Hashmoto thyroiditis (aHR = 6.57), pSS (aHR = 4.50), SLE (aHR = 17.29), and systemic vasculitis (aHR = 25.86).

INTERPRETATION

In conclusion, based on a retrospective cohort study throughout Taiwan, patients with Tx have a higher risk of new onset ADs than patients without Tx.

Impaired histomorphology might provoke cell cycle regulators alteration in thymus of children with various congenital heart defects

Thymus, as a primary site of appropriate adaptive immunity formation, is an essential organ in face of a self-tolerance as well as a potential menace from impairment of body integrity. Due to vital selection processes during differentiation and maturation of T lymphocytes, control over cell survival and programmed cell death must be orchestrated in detail. Indeed, thymus is highly sensitive to wide spectrum of stressors that initiate acute structural changes. Hypoxia, one of the most common complications in congenital heart defects (CHDs) patients, provokes stress-induced thymus involution. Disrupted embryolonic development of thymus in association with congenital heart defects, may negatively affect physiological immune mechanisms. We propose that detailed analysis of thymic morphology could critically contribute to unveil the pathophysiology of diseases associated with disrupted adaptive immunity in children with heterogeneous congenital heart diseases.

T-Cell Receptor Excision Circles in Newborns with Congenital Heart Disease

OBJECTIVES

To determine if children with congenital heart disease (CHD) have lower newborn T-cell receptor excision circles (TREC) levels than the general population and to evaluate if low TREC levels in newborns with CHD are associated with clinical complications such as hospitalization for infection.

STUDY DESIGN

The Connecticut Newborn Screening Program reported TREC levels for newborns with CHD delivered between October 2011 and September 2016 at 2 major Connecticut children's hospitals. TREC levels for children with CHD were compared with the general population. TREC levels and outcome measures, including hospitalization for infection, were compared.

RESULTS

We enrolled 575 participants with CHD in the study. The median TREC level for newborns with CHD was lower than the general population (180.1 copies/μL vs 312.5 copies/μL; P < .01). patients with CHD requiring hospitalization for infection had lower median TREC levels than their counterparts (143.0 copies/μL vs 186.7 copies/μL; P < .01). The combination of prematurity and low TREC level had a strong relationship to hospitalization for infection (area under the receiver operative characteristic curve of 0.89). There was no association between TREC level and CHD severity.

CONCLUSIONS

Newborns with CHD demonstrated lower TREC levels than the general population. Low TREC levels were associated with hospitalization for infection in preterm children with CHD. Study limitations include that this was a retrospective chart review. These findings may help to identify newborns with CHD at highest risk for infection, allowing for potential opportunities for intervention.

Recurrent oral ulcerations following heart transplant in a pediatric patient: A diagnostic dilemma

Oral ulceration is a non-specific clinical finding with many potential causes. The persistence of oral ulcers in the context of a patient post-SOT is concerning for PTLD. There is growing evidence that SOT recipients may also be at higher risk of autoimmune diseases. This case report describes a pediatric patient with persistent oral ulcers after heart transplant, who underwent an extensive workup for PTLD, including repeat investigations, with a subsequent diagnosis of Behçet's disease.

Allergies and autoimmune disorders in children after heart transplantation

Pediatric heart transplantation requires lifelong immune suppression and may require thymectomy, both of which alter T-cell repertoires. We hypothesized that atopic and autoimmune diseases are more common in pediatric heart transplant patients than the general population, and that transplantation in early childhood increases the risk of development or worsening of atopic or autoimmune disease. A cross-sectional single-center study including 21 heart transplant patients aged ≤18 years was conducted. Data collected included age at transplant, induction, thymectomy, and development and severity of atopic or autoimmune disease. A majority (67%) reported having any atopic disease post-transplant, all of whom reported onset or worsening post-transplantation. Thymectomized patients were significantly more likely to have asthma (P = 0.018) and report asthma worsening post-transplant (P = 0.045). Patients with worsening of asthma post-transplant were transplanted at a significantly younger age (P = 0.040). ABO incompatible and ABO compatible recipients presented similarly. Anemia was common (38%) but not always clearly of autoimmune origin. Atopic diseases are common in children following heart transplantation: Compared to the general population, there is a higher prevalence of eczema (43% vs 11%) and asthma (33% vs 9%). Both thymectomy and younger age at transplant are associated with atopic disorders, possibly due to altered T-cell repertoires.

Systemic lupus erythematosus-myasthenia gravis overlap syndrome: Presentation and treatment depend on prior thymectomy

In this study, we investigated four patients who met the diagnostic criteria for overlapping systemic lupus erythematosus (SLE) and myasthenia gravis (MG) but responded differently to treatment. All patients were acetylcholine receptor (AChR) and antinuclear antibody positive at the time of SLE diagnosis. Two patients presented with SLE who have been effectively treated with cholinesterase inhibitors for MG. These patients developed SLE with photosensitivity, rash, and arthritis post thymectomy, which had been performed 29 years and 40 years earlier, respectively. Two other patients were found to have AChR antibodies and MG in the context on new-onset SLE. These subjects were responsive to hydroxychloroquine and immunosuppression but failed cholinesterase inhibitors. The evolution of these cases is relevant for the role of thymus in lupus pathogenesis during aging and for treatment selection in SLE-MG overlap patients.

Human naïve regulatory T-cells feature high steady-state turnover and are maintained by IL-7

Naïve FoxP3-expressing regulatory T-cells (Tregs) are essential to control immune responses via continuous replenishment of the activated-Treg pool with thymus-committed suppressor cells. The mechanisms underlying naïve-Treg maintenance throughout life in face of the age-associated thymic involution remain unclear. We found that in adults thymectomized early in infancy the naïve-Treg pool is remarkably well preserved, in contrast to conventional naïve CD4 T-cells. Naïve-Tregs featured high levels of cycling and pro-survival markers, even in healthy individuals, and contrasted with other circulating naïve/memory CD4 T-cell subsets in terms of their strong γc-cytokine-dependent signaling, particularly in response to IL-7. Accordingly, ex-vivo stimulation of naïve-Tregs with IL-7 induced robust cytokine-dependent signaling, Bcl-2 expression, and phosphatidylinositol 3-kinase (PI3K)-dependent proliferation, whilst preserving naïve phenotype and suppressive capacity. Altogether, our data strongly implicate IL-7 in the thymus-independent long-term survival of functional naïve-Tregs, and highlight the potential of targeting the IL-7 pathway to modulate Tregs in different clinical settings.

Human neonatal thymectomy induces altered B-cell responses and autoreactivity

An association between T‐cell lymphopenia and autoimmunity has long been proposed, but it remains to be elucidated whether T‐cell lymphopenia affects B‐cell responses to autoantigens. Human neonatal thymectomy (Tx) results in a decrease in T‐cell numbers and we used this model to study the development of autoreactivity. Two cohorts of neonatally thymectomized individuals were examined, a cohort of young (1–5 years post‐Tx, n = 10–27) and older children (>10 years, n = 26), and compared to healthy age‐matched controls. T‐cell and B‐cell subsets were assessed and autoantibody profiling performed. Early post‐Tx, a decrease in T‐cell numbers (2.75 × 10⁹/L vs. 0.71 × 10⁹/L) and an increased proportion of memory T cells (19.72 vs. 57.43%) were observed. The presence of autoantibodies was correlated with an increased proportion of memory T cells in thymectomized children. No differences were seen in percentages of different B‐cell subsets between the groups. The autoantigen microarray showed a skewed autoantibody response after Tx. In the cohort of older individuals, autoantibodies were present in 62% of the thymectomized children, while they were found in only 33% of the healthy controls. Overall, our data suggest that neonatal Tx skews the autoantibody profile. Preferential expansion and preservation of Treg (regulatory T) cell stability and function, may contribute to preventing autoimmune disease development after Tx.

Autoimmunity and allergy control in adults submitted to complete thymectomy early in infancy

The contribution of the decline in thymic activity for the emergence of autoimmunity is still debatable. Immune-competent adults submitted to complete thymectomy early in life provide a unique model to address this question. We applied here strict criteria to identify adults lacking thymic activity based on sjTREC levels, to exclude thymic rebound and/or ectopic thymuses. In agreement, they featured severe naïve CD4 T-cell depletion and contraction of T-cell receptor diversity. Notwithstanding this, there was neither increased incidence of autoimmune disease in comparison with age-matched controls nor significant changes in their IgG/IgA/IgM/IgE autoreactivity profiles, as assessed through extensive arrays. We reasoned that the observed relative preservation of the regulatory T-cell compartment, including maintenance of naïve regulatory CD4 T-cells, may contribute to limit the emergence of autoimmunity upon thymectomy. Our findings have implications in other clinical settings with impaired thymic activity, and are particularly relevant to studies of autoimmunity in ageing.

Effect of cryopreservation on viability and growth efficiency of stromal-epithelial cells derived from neonatal human thymus

The thymus is the major site of T lymphocyte generation and so is critical for a functional adaptive immune system. Since, thymectomy is a component of neonatal surgery for congenital heart diseases, it provides great potential for collection and storage of thymic tissue for autologous transplantation. However, specific investigation into the optimum parameters for thymic tissue cryopreservation have not been conducted. In this research, we evaluated the effect of different cryoprotective media compositions, which included penetrating (Me₂SO, glycerol) and non-penetrating (dextran-40, sucrose, hydroxyethyl starch) components, on the viability and functionality of frozen-thawed human thymic samples to select an optimal cryoprotective medium suitable for long-term storage of thymic tissue and a stromal-epithelial enriched population. Our primary focus was on receiving, low-temperature storage, culturing and evaluation of thymic tissue samples from newborns and infants with congenital heart diseases, who had undergone thymectomy as a part of standard surgical procedure. Thus, this work builds the platform for autologous clinical intervention into the thymus-deficient patients with congenital heart diseases. From our data, we conclude that although there were no significant differences in efficiency of tested cryoprotective media compositions, the combination of Me₂SO and dextran-40 compounds was the most suitable for long-term storage both thymic cell suspensions and thymic fragments based on the viability of CD326⁺ epithelial cells and stromal-epithelial cell monolayer formation.

Aberrant Intrathyroid Tissue: a Report of Intrathyroid Lymph Node Metastasis and a Review of Literature

Aberrant histological elements have been infrequently reported to exist within the intact thyroid gland. In addition to distant metastases to the thyroid, a number of ectopic tissue rests and unusual cysts have been described within the thyroid gland. In this article, we report the presence of a true intrathyroid lymph node and describe the first reported case of intrathyroid lymph node metastasis of papillary thyroid cancer. Other reported aberrant intrathyroid tissues, possible pathophysiology, diagnostic features and surgical implications are also discussed.

IL-7-Induced Proliferation of Human Naive CD4 T-Cells Relies on Continued Thymic Activity

Naive CD4 T-cell maintenance is critical for immune competence. We investigated here the fine-tuning of homeostatic mechanisms of the naive compartment to counteract the loss of de novo CD4 T-cell generation. Adults thymectomized in early childhood during corrective cardiac surgery were grouped based on presence or absence of thymopoiesis and compared with age-matched controls. We found that the preservation of the CD31^- subset was independent of the thymus and that its size is tightly controlled by peripheral mechanisms, including prolonged cell survival as attested by Bcl-2 levels. Conversely, a significant contraction of the CD31⁺ naive subset was observed in the absence of thymic activity. This was associated with impaired responses of purified naive CD4 T-cells to IL-7, namely, in vitro proliferation and upregulation of CD31 expression, which likely potentiated the decline in recent thymic emigrants. Additionally, we found no apparent constraint in the differentiation of naive cells into the memory compartment in individuals completely lacking thymic activity despite upregulation of DUSP6, a phosphatase associated with increased TCR threshold. Of note, thymectomized individuals featuring some degree of thymopoiesis were able to preserve the size and diversity of the naive CD4 compartment, further arguing against complete thymectomy in infancy. Overall, our data suggest that robust peripheral mechanisms ensure the homeostasis of CD31^- naive CD4 pool and point to the requirement of continuous thymic activity to the maintenance of IL-7-driven homeostatic proliferation of CD31⁺ naive CD4 T-cells, which is essential to secure T-cell diversity throughout life.

Pediatric Chest Radiographs: Common and Less Common Errors

OBJECTIVE

Radiographic imaging of the pediatric chest presents several unique challenges and nuances, stemming from congenital variants and pathologic processes specific to this population. Errors in interpretation may lead to inappropriate further imaging, incurring additional radiation exposure and cost, as well as psychologic effects on the patients and their families.

CONCLUSION

Here, we aim to highlight some common and less common pitfalls in pediatric chest radiography, as well as some tools for avoiding potential mistakes.

Neonatal thymectomy reveals differentiation and plasticity within human naive T cells

The generation of naive T cells is dependent on thymic output, but in adults, the naive T cell pool is primarily maintained by peripheral proliferation. Naive T cells have long been regarded as relatively quiescent cells; however, it was recently shown that IL-8 production is a signatory effector function of naive T cells, at least in newborns. How this functional signature relates to naive T cell dynamics and aging is unknown. Using a cohort of children and adolescents who underwent neonatal thymectomy, we demonstrate that the naive CD4+ T cell compartment in healthy humans is functionally heterogeneous and that this functional diversity is lost after neonatal thymectomy. Thymic tissue regeneration later in life resulted in functional restoration of the naive T cell compartment, implicating the thymus as having functional regenerative capacity. Together, these data shed further light on functional differentiation within the naive T cell compartment and the importance of the thymus in human naive T cell homeostasis and premature aging. In addition, these results affect and alter our current understanding on the identification of truly naive T cells and recent thymic emigrants.

Human umbilical vein endothelial cells promote the inhibitory activation of CD4(+)CD25(+)Foxp3(+) regulatory T cells via PD-L1

BACKGROUND

Atherosclerosis (AS) is a chronic inflammation characterized by massive infiltration of inflammatory cells in arterial wall plaques. Programmed death ligand-1 (PD-L1), a co-stimulatory molecule, plays a vital role in regulating immune responses. We investigated the role and mechanisms of PD-L1 expressed on oxidized low-density lipoprotein (ox-LDL)-impaired human umbilical vein endothelial cells (HUVECs) in promoting activation and cytokine production of CD4(+)CD25(+) forkhead box P3 (FoxP3) regulatory T cells (Tregs).

METHODS AND RESULTS

Tregs were incubated alone, with HUVECs or HUVECs pre-stimulated with ox-LDL in the presence of anti-CD3 monoclonal antibodies (mAbs) for 48 h. HUVECs were shown to upregulate the immune phenotypic markers of Tregs, such as glucocorticoid-induced TNF receptor (GITR), cytotoxic T lymphocyte antigen-4 (CTLA-4) and programmed cell death-1 protein (PD-1). Moreover, HUVECs modulated cytokine production of Tregs (e.g., interleukin-10 (IL-10) and transforming growth factor-β1 (TGF-β1)). HUVECs treated with anti-PD-L1 mAbs were unable to regulate the surface expression and cytokine production of Tregs. The Transwell culture system suggested that interaction between HUVECs and Tregs via PD-L1 requires cell-to-cell contact.

CONCLUSION

Expression of the negative co-stimulatory molecule PD-L1 on HUVECs may upregulate the inhibitory activation and cytokine production of CD4(+)CD25(+)Foxp3(+) regulatory T cells in AS.

Immunologic Aging in Adults with Congenital Heart Disease: Does Infant Sternotomy Matter?

Thymectomy is performed routinely in infants undergoing cardiothoracic surgery. Children post-sternotomy have decreased numbers of T lymphocytes, although the mechanisms involved and long-term consequences of this have not been defined. We hypothesized that lymphopenia in patients with adult congenital heart disease (ACHD) would be reflective of premature T cell maturation and exhaustion. Adults with ACHD who had sternotomy to repair congenital heart disease as infants (<1 year) and age-matched ACHD patients without prior sternotomy were studied using polychromatic flow cytometry interrogating markers of lymphocyte maturation, exhaustion and senescence. Group differences were analyzed using Mann-Whitney U and Fisher's exact tests. Eighteen ACHD patients aged 21-40 years participated: 10 cases and 8 controls. Median age at sternotomy for cases was 52 days. Cases and controls were matched for age (28.9 vs. 29.1 years; p = 0.83), gender (p = 0.15) and race (p = 0.62) and had similar case complexity. Cases had a lower mean percentage of cytotoxic CD8 lymphocytes compared to controls (26.8 vs. 33.9 %; p = 0.016), with fewer naive, undifferentiated CD8 T cells (31.0 vs. 53.6 %; p = 0.027). CD8 cells expressing PD1, a marker of immune exhaustion, trended higher in cases versus controls (25.6 vs. 19.0 %; p = 0.083). Mean percentage of CD4 cells was higher in cases versus controls (65.6 vs. 59.6 %; p = 0.027), without differences in CD4 T cell maturation subtype. In summary, ACHD patients who undergo sternotomy as infants exhibit differences in T lymphocyte composition compared to ACHD controls, suggesting accelerated immunologic exhaustion. Investigation is warranted to assess the progressive nature and clinical impact of this immune phenotypic change.

Relationship of thymic changes and complications after congenital heart surgery

BACKGROUND

The true role of thymic function in children with congenital heart defects is largely unknown.

AIM

To study the possible role of thymic CD3 (T-lymphocyte marker) and CD20 (B-lymphocyte marker) expression and thymic histopathological changes in complications after surgery for congenital heart defects.

METHODS

Between January and July 2014, thymic tissue samples were obtained from 13 (69% male, 31% female, mean age 10.9 ± 2 years) of 25 Iraqi patients who underwent open heart surgery with partial thymectomy for correction of congenital heart defects. The samples were evaluated for thymic expression of CD markers (CD3 and CD20) and histopathological changes. For up to 6 months after surgery, data on complications were collected from each patient, including wound infection, cardiac arrhythmias, heart failure, rehospitalization, chest infection, and death.

RESULTS

The prevalence of thymic hypoplasia was 15% and it occurred more frequently in patients with absent thymic CD3 expression (p = 0.005). Only wound infection (n = 2) and atrial fibrillation (n = 1) comprised the postoperative complications in our patients. Absence of thymic CD20 expression correlated significantly with postoperative complications and obstructive cardiac defects (p = 0.04), whereas no significant correlations were found between thymic hypoplasia with CD3 expression and postoperative complications (p > 0.05).

CONCLUSION

Patients with absent thymic CD20 expression had significantly more postoperative complications and cardiac obstructive defects than those with positive CD20 expression.

CD4+ T cells in aged or thymectomized recipients of allogeneic stem cell transplantations

Background

CD4+CD25highFOXP3+ regulatory T (Treg) cells, which include thymus-derived and peripherally induced cells, play a central role in immune regulation, and are therefore crucial to prevent graft-versus-host disease (GVHD). The increasing use of allogeneic hematopoietic stem cell transplantation (allo-HSCT) for elderly patients with thymus regression, and our case of allo-HSCT shortly after total thymectomy, raised questions about the activity of thymus-derived Treg cells and peripherally induced Treg cells, which are otherwise indistinguishable.

Results

We found that despite pre-transplant thymectomy or older age, both naïve and effector Treg cells, as well as naïve and effector conventional T cells, proliferated in allo-HSCT recipients. Higher proportions of total Treg cells 1 month post allo-HSCT, and naïve Treg cells 1 year post allo-HSCT, appeared in patients achieving complete chimera without developing significant chronic GVHD, including our thymectomized patient, compared with patients who developed chronic GVHD.

Conclusions

Treg cells that modulate human allogeneic immunity may arise peripherally as well as in the thymus of allo-HSCT recipients.

Thymic and bone marrow output in individuals with 22q11.2 deletion syndrome

BACKGROUND

The 22q11.2 deletion syndrome (22q11.2DS) is a congenital multisystem anomaly characterized by typical facial features, palatal anomalies, congenital heart defects, hypocalcemia, immunodeficiency, and cognitive and neuropsychiatric symptoms. The aim of our study was to investigate T- and B-lymphocyte characteristics associated with 22q11.2DS.

METHODS

Seventy-five individuals with 22q11.2DS were tested for T and B lymphocytes by examination of T-cell receptor rearrangement excision circles (TRECs) and B-cell κ-deleting recombination excision circles (KRECs), respectively.

RESULTS

The 22q11.2DS individuals displayed low levels of TRECs, while exhibiting normal levels of KRECs. There was a significant positive correlation between TREC and KREC in the 22q11.2DS group, but not in controls. Both TREC and KREC levels showed a significant decrease with age and only TREC was low in 22q11.2DS individuals with recurrent infections. No difference in TREC levels was found between 22q11.2DS individuals who underwent heart surgery (with or without thymectomy) and those who did not.

CONCLUSION

T-cell immunodeficiency in 22q11.2DS includes low TREC levels, which may contribute to recurrent infections in individuals with this syndrome. A correlation between T- and B-cell abnormalities in 22q11.2DS was identified. The B-cell abnormalities could account for part of the immunological deficiency seen in 22q11.2DS.

Routine thymectomy in congenital cardiac surgery changes adaptive immunity without clinical relevance

The actual importance of the thymus in both children and adults is largely unclear. In congenital cardiac surgery, a partial or total thymectomy is frequently performed to improve access to the heart and great vessels. We performed a literature search to evaluate the effect on the adaptive immune system of the removal of thymus tissue in patients with congenital heart disease. A PubMed search according to Dunning's standard provided 149 articles, of which 13 addressed our search question. Each study has been tabulated with author, cases, controls, follow-up, methods, results and limitations. A first group of articles repeatedly showed the effect on the T-cell compartment, including the impact on subgroups of this compartment. More recent studies, usually with a longer follow-up, confirm that the earlier changes in T-cell population appear to be permanent. Only one author found a normalization of T-cell population five years after thymectomy. In contrast to these clear changes in T-cell population, there is currently no clear clinical relevance. A literature search on thymectomy in congenital cardiac surgery revealed clear changes in T-cell-related immunity; however, there is a lack of clinical relevance. Further investigation of the adaptive immune system is required to explain this discrepancy.

Elevated preoperative neutrophil/lymphocyte ratio as a predictor of increased long-term survival in minimal invasive coronary artery bypass surgery compared to sternotomy

Background

Neutrophil lymphocyte ratio (NLR) is a predictor of major adverse cardiovascular outcomes. Our study explores the value of NLR in predicting long-term mortality after minimally invasive coronary artery bypass surgery (MICS) via lateral left-thoracotomy versus conventional sternotomy coronary artery bypass grafting (CABG) surgery.

Methods

A total of 1126 consecutive patients (729 sternotomy CABG and 397 MICS) from a single tertiary center between 2005 and 2008 were followed until 2011. We stratified the patients into equal tertiles according to preoperative NLR. The primary outcome, all-cause mortality, was compared among the NLR tertiles.

Results

Out of the 1126 patients included in the study, 1030 (91%) patients underwent off-pump CABG . The first (NLR <2.3) tertile had a significantly lower 5-year mortality (30/371 =8%) in comparison to the second (NLR =2.3-3.4) and third (NLR ≥3.5) tertiles (49/375 =13% and 75/380 =20%), respectively with p < 0.0001. After multivariate adjustment, NLR was a significant independent predictor of mortality (hazard ratio [HR] per each unit increase of NLR was 1.05, 95% confidence interval [CI] 1.01-1.10, p = 0.008). MICS and sternotomy CABG groups with NLR <3 had similar mortality (21/221 =9.5% and 40/403 =9.9%), p = 1. However among patients with NLR ≥3, MICS had a significantly lower mortality (23/176 = 13.1%) compared to the sternotomy CABG (70/326 =21.5%), p = 0.02. According to the multivariate analysis of patients with NLR ≥3, MICS had a significantly lower mortality compared to sternotomy CABG (HR = 0.44, 95% CI 0.24-0.78, p = 0.005).

Conclusion

Elevated preoperative NLR is an independent predictor of long-term mortality after CABG. Among the patients with NLR ≥ 3, MICS was associated with a significantly improved survival compared with sternotomy CABG.

Isolated adrenocorticotropin deficiency associated with painless thyroiditis: a case report and review of the literature

A 53-year-old Japanese man was admitted with a 3-month history of transient headache followed by general fatigue and weight loss. He had a history of ocular myasthenia gravis which had been in remission following thymectomy 30 years ago. He had a small diffuse goiter without tenderness, and was diagnosed as having painless thyroiditis with mild thyrotoxicosis on admission. Endocrinological studies showed he had isolated adrenocorticotropin deficiency. Magnetic resonance imaging of the pituitary gland revealed no abnormalities. His symptoms improved soon after replacement of glucocorticoid. After an episode of hypothyroidism, he spontaneously became euthyroid. It is likely that thyrotoxicosis uncovered adrenal insufficiency that had developed insidiously, and hypoadrenocorticism-induced immunological changes may have triggered the development of painless thyroiditis. Moreover, thymectomy might have facilitated the development of pituitary and thyroid autoimmunity.