T-cell Receptor Rearrangement Excision Circles Research Articles

A Blood-Based Molecular Clock for Biological Age Estimation.

In the last decade, extensive efforts have been made to identify biomarkers of biological age. DNA methylation levels of ELOVL fatty acid elongase 2 (ELOVL2) and the signal joint T-cell receptor rearrangement excision circles (sjTRECs) represent the most promising candidates. Although these two non-redundant biomarkers echo important biological aspects of the ageing process in humans, a well-validated molecular clock exploiting these powerful candidates has not yet been formulated. The present study aimed to develop a more accurate molecular clock in a sample of 194 Italian individuals by re-analyzing the previously obtained EVOLV2 methylation data together with the amount of sjTRECs in the same blood samples. The proposed model showed a high prediction accuracy both in younger individuals with an error of about 2.5 years and in older subjects where a relatively low error was observed if compared with those reported in previously published studies. In conclusion, an easy, cost-effective and reliable model to measure the individual rate and the quality of aging in human population has been proposed. Further studies are required to validate the model and to extend its use in an applicative context.

Bone Marrow-Derived Mesenchymal Stromal Cells Promote Thymopoiesis and Function Recovery in Acute Graft-Versus-Host Disease Murine Models

Background: The thymus is the primary lymphoid organ of T-cells development and plays a crucial role for immune tolerance following allogeneic hematopoietic stem cell transplantation (allo-HSCT). The toxicity of chemoradiotherapy conditioning regimen and acute graft-versus-host disease (aGVHD) damage the thymic structure and function, which result in the production of autoreactive T-cells and the reduction of natural regulatory T cells (nTregs) to aggravate the development of aGVHD. Nowadays, mesenchymal stromal cells (MSCs) as multipotent stem cells, have been widely recognized as a promising therapeutic strategy for aGVHD. However, the well-known mechanisms of MSCs ameliorating aGVHD mainly focus on their immunoregulatory effect on peripheral immune compartments. The contribution of MSCs to thymus, the central immunological organs, is rarely reported.Methods: In this study, we carried out studies in a murine aGVHD models of fully MHC-mismatched myeloablative bone marrow transplantation (C57BL/6 to BALB/c). We randomly divided aGVHD mice into two groups, including MSCs group and control group without MSCs treatment. In MSCs group, aGVHD mice were intravenously administrated GFP-labelled bone marrow (BM) derived MSCs at a dose of 5×105 cells/mice at 7 day after allo-HSCT. The mice were killed at 1d, 2d, 4d and 20d after MSCs injection in MSCs group and the corresponding time in control group, respectively. Thymic tissues were collected and manufactured into frozen sections or thymic single-cell suspension. And then we analyzed the distribution of GFP-MSCs in thymus and thymic size, the expression of thymic T cells subsets (CD4+CD8-, CD4-CD8+, CD4+CD8+ T, CD4+CD25+Foxp3+Tregs), thymic epithelial cells (TECs) substes (CD45-CD326+Ly51+ cortical TECs and CD45-CD326+UEA-1+ medullary TECs) and the level of T cell receptor rearrangement excision circles (TRECs) in thymus between the two groups to evaluate the repair effect of MSCs for thymus.Results: We found that MSCs treated mice have longer survival and alleviate the clinical signs of aGVHD compared to the control group (P<0.05). Next, we observed that GFP-MSCs can home to thymic tissue and mainly locate in the corticomedullary boundary at 2d, 4da after MSCs infusion. MSCs treated thymus exhibited a more organized corticomedullary architecture, compared with the conrol group. Significant increases in thymus size and weight, as well as the number of total thymocytes were seen in MSCs group. To further investigate whether MSCs promote thymopoiesis and ameliorate thymic functions after allo-HSCT, we found that in MSCs group the proportion of thymic T cells subets composition (CD4+CD8-, CD4-CD8+, CD4+CD8+), especially Foxp3+ Tregs, and the expression of TECs, especially cTECs, were significantly higher than control group at 20d after the MSCs infusion (P<0.001). Furthermore, MSCs administration resulted in a remarkable increase in the levels of TRECs in the thymocyte at 20d after the MSCs infusion compared with the control group (P=0.007).Conclusions: Collectively, our data proposed a new mechanism for MSCs ameliorating aGVHD by central immune organ, including promoting thymopoiesis and enhancing thymic output. DisclosuresNo relevant conflicts of interest to declare.

Thymectomy in Juvenile Myasthenia Gravis Is Safe Regarding Long Term Immunological Effects

Thymectomy is an established treatment in adult MG and also recommended for the treatment of post-pubertal onset juvenile MG. Whether the youngest children should be thymectomized is still debated. Signs of premature aging of the immune system have been shown in studies on early perioperative thymectomy in children with congenital heart defect. In this retrospective cohort study the objective was to investigate the long-term effects of treatment related thymectomy on T cell subsets and T cell receptor rearrangement excision circles (TRECs) in peripheral blood of juvenile myasthenia gravis (MG) patients, as well as clinical occurrence of autoimmune disorders, malignancies and infectious diseases. Forty-seven patients with onset of myasthenia gravis before the age of 19 years were included; 32 (68.1%) had been thymectomized and 15 (31.8%) had not. They were studied at varying times after thymectomy (7–26 years). We found a significant lower number of naïve helper T cells (CD4+CD45RA+) with an increased proportion of memory helper T cells (CD4+CD45RO+), and a significant lower number of naïve cytotoxic T cells (CD8+CD27+CD28+) in the thymectomized patients. In addition they showed a significant reduction in the number of TRECs and proportion of recent thymic emigrants (RTE) compared to non-thymectomized patients. In none of them an increased frequency of malignancies or infections was found. Our findings indicate a premature aging of the immune system after thymectomy in juvenile MG, but associated clinical consequences could not be verified.

Telomere length and signal joint T-cell receptor rearrangement excision circles as biomarkers for chronological age estimation

Background Chronological age estimation is a challenging marker in the field of forensic medicine. The current study aimed to investigate the accuracy of signal joint T-cell receptor rearrangement excision circles (sjTRECs) quantification and telomere length measurement as methods for estimating chronological age. Methods Telomere length was estimated in the DNA derived from the buccal cells through estimating the telomeric restriction fragment (TRF) length using TeloTTAGGG Telomere Length Assay while the sjTRECs quantification was carried out on DNA isolated from the blood samples using qPCR. Results The TRF length was shortened with increased age (r = −0.722, p < 0.001). The sjTRECs were also decreased with increased age (r = −0.831, p < 0.001). Stronger coefficient and lower standard error of the estimate was obtained when multiple regression analysis for age prediction based on the values of both methods was applied (r = −0.876, p < 0.001).

Decrease in naïve T cell production due to HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) development

Human T-lymphocytic virus 1 (HTLV-1) is mainly associated with adult T-cell leukemia/lymphoma (ATLL) and HTLV-1–associated myelopathy/tropical spastic paraparesis (HAM/TSP). Patients with HAM/TSP exhibit significant changes in their immune response, and HTLV-1 infection can interfere in cytokine production and perhaps in T cell production. The aims of this study were to evaluate thymic function in HAM/TSP patients and HTLV-1 healthy carriers (HCs) and correlate it to age and interleukin 7 (IL-7) gene expression. Thymic function in 21 HAM/TSP patients and 12 HCs was evaluated by quantifying T cell receptor rearrangement excision circle (TREC) particles and IL-7 gene expression, both measured by quantitative polymerase chain reaction. HAM/TSP patients presented lower TREC particle counts (p = 0.0112) and lower IL-7 expression (p = 0.0102) than HCs. Both TREC particles and IL-7 gene expression were separately analyzed in two age groups: ≤ 59 years and ≥60 years, The ≤59-year-old HAM/TSP patients had a lower TREC count compared with the ≤59-year-old HCs (p = 0.0476). In conclusion, HAM/TSP development could interfere with thymic function because the results showed TREC particle reduction in HAM/TSP patients in relation to HCs, and it could be associated with a concomitant reduction in IL-7 expression.

Impaired Thymic Output Can Be Related to the Low Immune Reconstitution and T Cell Repertoire Disturbances in Relapsing Visceral Leishmaniasis Associated HIV/AIDS Patients

Background: Visceral leishmaniasis/HIV-co-infected patients (VL/HIV) accounts for around 8% of VL reported cases in Brazil. Relapses of Leishmania infection after anti-leishmanial treatment constitute a great challenge in the clinical practice because of the disease severity and drug resistance. We have shown that non-relapsing-VL/HIV (NR-) evolved with increase of CD4+ T-cell counts and reduction of activated CD4+ and CD8+ T cells after anti-leishmanial treatment. This immune profile was not observed in relapsing-VL/HIV patients (R-), indicating a more severe immunological compromising degree. Elevated activation status may be related to a deficient immune reconstitution and could help to explain the frequent relapses in VL/HIV co-infection. Our aim was to evaluate if this gain of T cells was related to changes in the peripheral TCRVβ repertoire and inflammatory status, as well as the possible thymus involvement in the replenishment of these newly formed T lymphocytes.Methods: VL/HIV patients, grouped into non-relapsing (NR- = 6) and relapsing (R- = 12) were evaluated from the active phase up to 12 months post-treatment (mpt). HIV-infected patients (non-VL) and healthy subjects (HS) were included. The TCRVβ repertoire was evaluated ex vivo by flow cytometry, whereas the plasmatic cytokine levels were assessed by Luminex assay. To evaluate the thymic output, DNA was extracted from PBMCs for TCR rearrangement excision circles (TREC) quantification by qPCR.Results: VL/HIV cases presented an altered mobilization profile (expansions or retractions) of the TCRVβ families when compared to HS independent of the follow-up phase (p < 0.05). TCRVβ repertoire on CD4+ T-cells was more homogeneous in the NR-VL/HIV cases, but heterogeneous on CD8+ T-cells, since different Vβ-families were mobilized. NR-VL/HIV had the inflammatory pattern reduced after 6 mpt. Importantly, VL/HIV patients showed number of TREC copies lower than controls during all follow-up. An increase of recent thymic emigrants was observed in NR-VL/HIV individuals at 10 mpt compared to R- patients (p < 0.01), who maintained lower TREC contents than the HIV controls.Conclusions: VL/HIV patients that maintain the thymic function, thus generating new T-cells, seem able to replenish the T lymphocyte compartment with effector cells, then enabling parasite control.

Mesenchymal Stem Cells Improve the Structure and Function of the Graft-Versus-Host Disease Receptor Thymus: CCR9 Plays an Important Role in Its Homing Thymus

Background: Insufficient thymic function of allogeneic hematopoietic stem cell transplantation (allo-HSCT) receptors results in continuous production of alloreactive T cells, which leads to the development of graft-versus-host disease (GVHD), especially chronic GVHD (cGVHD). We have previously found that patients with acute GVHD (aGVHD) treated with mesenchymal stem cells (MSCs) have increased thymic output and decreased incidence of cGVHD, thus hypothesized that MSCs may reduce the incidence of cGVHD by remodeling the thymus. Chemokine receptor 9 (CCR9), the receptor that specifically guides migration of T-lineage precursors into thymus, is also expressed on MSCs, and thus may be a key factor mediating MSCs homing to the thymus. This in turn allows MSCs to reduce GVHD by repairing thymus tissue structure and saving thymus function. Methods: We carried out studies in a murine GVHD model of fully MHC-mismatched myeloablative bone marrow transplantation (C57BL/6 to BALB/c), a model that can observe the prolongation of aGVHD to cGVHD. We randomly divided GVHD mice into four groups, including three MSCs treated groups and one untreated group. CCR9 over-expressed (MSC/CCR9+), knocked-down (MSC/CCR9-) and empty-load MSCs (MSC/Control) were generated and administrated intravenously at dose of 5 × 105 cells/infusion at 7th and 21th day post HCT to the treated groups respectively to compare their thymic homing ability, and therapeutic effects of GVHD with the untreated group. Clinical scores were recorded once every five days to evaluate GVHD symptoms. Mice of MSCs treated groups and the untreated group were sacrificed at 30d, 45d and 60d after HCT. Thymuses of each group were collected and assessed for size and weight before being manufactured into frozen sections or thymic single-cell suspension. We then analyzed the number and distribution of MSCs in the thymus of the treated groups to assess the role of CCR9 in thymic homing, and analyzed the expression of thymic T cells subsets (CD4+CD8-, CD4-CD8+, CD4+CD8+ T, CD4+CD25+Foxp3+Tregs), thymic epithelial cells (TECs) substes (CD45-CD326+Ly51+ cortical TECs and CD45-CD326+UEA-1+ medullary TECs) and the level of T cell receptor rearrangement excision circles (TRECs) in thymus among the four groups to evaluate the repair effect of MSCs for thymus. Radiation-pretreated murine TECs were cultured alone or co-cultured with murine MSCs in vitro to assess the effect of MSCs on damaged TECs. Results: The infusion of MSC/CCR9+ potently alleviated the clinical signs of GVHD and prolonged the survival of GVHD mice (P&lt;0.05 versus MSC/CCR9- and untreated group). Significant increases in thymus size and weight were observed in the MSC/CCR9+ group, as well as the number of total thymocytes and the more organized cortical medullary structure compared to the other groups. MSCs enter the thymus from the microvascular region at the cortex-medium junction. MSC/CCR9+ were found to appear in the cortex-medium junction of thymus in a greater amount 24 hours after the first infusion, then distribute throughout the whole thymus and relocate in proximity with TECs 48 hours thereafter. MSC/Control could be observed in the cortical and cortex-medium junction, whereas MSC/CCR9- was observed only in the cortex-medium junction with a small amount of distribution. Immunofluorescence of thymus frozen sections showed that, compared with other groups, TECs had decreased apoptosis and significantly increased proliferation and maturation levels in MSC/CCR9+ group, indicating MSCs potently repaired injured TECs and promoted their proliferation and maturation. The number of TECs and its proportion of thymus stroma were significantly improved, including cortical TEC and medullary TECs. As for thymocyte, MSC/CCR9+ infusion significantly increased the number and proportion of CD4+CD8+T cells and Tregs, which were reported deficiency in GVHD thymus. Furthermore, MSC/CCR9+ administration resulted in a remarkable increase in the levels of TRECs in the thymocyte at 45d and 60d after HCT (P&lt;0.05 versus MSC/CCR9- and untreated group). In vitro study showed co-cultured TECs had a decreased apoptosis and increased proliferation compared to TECs cultured alone. Conclusion: This study demonstrates that CCR9 plays an important role in guiding migration of MSCs to thymus and thus highly intensify their issue repair and immunomodulatory effect to rescue thymus function in GVHD model. Disclosures No relevant conflicts of interest to declare.

QPCR Applications for the Determination of the Biological Age.

Individual age is a phenotypic trait that provides useful information not only in forensic investigations but also in the aging research which is becoming an urgent call due to the dramatic growth of the aging population worldwide.TaqMan quantification PCR (qPCR) can be successfully applied to biological age estimation, using method defined in Zubakov et al. (Curr Biol 20:R970-R971, 2010). Since levels of signal joint T-cell receptor rearrangement excision circle (sjTREC) in human lymphocytes are known to decrease with age increasing, the qPCR of sjTREC represents a simple and relatively reproducible technique which offers highly accurate age estimation results.

T cell receptor rearrangement excision circles (TRECs) and CD31+ regulatory T cells for assessing recent thymic output in patients with chronic hepatitis B

Objective To evaluate the clinical value of combined detection of T cell receptor rearrangement excision circles (TRECs) and CD31+ regulatory T (Treg) cells for accessing the recent thymic output in patients with chronic hepatitis B. Methods Four groups involving 135 subjects were set up in this study as follows: mild chronic hepatitis B (Mild CHB, n=35), moderate chronic hepatitis B (Moderate CHB, n=35), severe chronic hepatitis B (Severe CHB, n=35) and healthy control (HCs, n=30) groups. CD4+ CD25+ Treg cells in these subjects were sorted out using magnetic cell separation. The ratio of peripheral CD31+ Treg cells to Treg cells in each group was analyzed by flow cytometry. Real-time PCR was performed to detect TRECs in CD4+ CD25+ Treg cells. The percentages of CD3+ , CD4+ and CD8+ T cell subsets were also measured. Results The ratios of CD31+ Treg/Treg cells and the numbers of TRECs in peripheral blood of the Moderate CHB and Severe CHB groups were significantly lower than those of the Mild CHB and HCs groups (P 0.05). No significant difference in the percentages of CD3+ , CD4+ or CD8+ T cell subsets was observed between the four groups (P>0.05). CD31+ Treg/Treg cell ratio had a positive correlation with the number of TRECs (r=0.551, P=0.014). Conclusions Both CD31+ Treg/Treg cell ratio and the number of TRECs were reduced in the peripheral blood of patients with moderate or severe CHB. CD31+ Treg/Treg cell ratio and the number of TRECs were positively correlated and could be used as new indices to evaluate recent thymus output. Key words: Chronic hepatitis B; CD4+ CD25+ regulatory T cell; CD31+ regulatory T cell; T cell receptor rearrangement excision circles

Immune senescence and immune activation in elderly colorectal cancer patients.

In our previous study, we found that low thymic output and short telomere length were associated with a higher risk of tumor in elderly cancer patients. Here, we aimed to examine in depth the impact of immunological and biological senescence and immune activation on disease outcome in elderly patients with colorectal cancer (CRC).Peripheral blood samples from 81 CRC patients were studied for immune activation, immune senescence and recent thymic emigrant(RTE) CD4 and CD8 cells by flow cytometry. T-cell receptor rearrangement excision circle (TREC) levels and telomere lengths were measured by real-time PCR. Plasma levels of microbial translocation markers, LPS and sCD14, were quantified by ELISA. While TREC levels and telomere length were not prognostic of disease outcome, high percentages of immune senescent and immune activated CD8 cells were associated with a higher risk of a negative event (relapse, progression, or death) in all studied patients and disease relapse in I-III staged patients. Levels of sCD14 and LPS were higher in patients who will experience a negative event than in patients who will not. In conclusion, in elderly CRC patients higher immunological senescence and immune activation negatively impact the disease outcome; how these characteristics influence the antineoplastic treatments remains to be investigated.

Biological Age versus Chronological Age in the Prevention of Age Associated Diseases

Aging is associated with an increasing incidence of major diseases among which cancer, cardiovascular, neurodegenerative, metabolic and autoimmune diseases. Primary prevention and early diagnosis of these diseases have a dramatic impact on incidence, outcome and quality of life and are commonly applied as age-dependent indications based on evidence of efficacy for specific groups of the aging population. They likely contribute to the observed increase in life expectancy through the reduction of incidence and the retardation of onset of age-associated diseases. In the present article, we develop the hypothesis that age-dependent preventative measures and diagnostic screenings might perform better if the biological age would be used instead of the chronological age for the definition of the population to be included. This is based on the observation that there are individual differences in the age-associated decline in performance that are reflected by measurable biological indicators, such as telomere length, signal joint T-cell receptor rearrangement excision circle, and specific DNA-methylation and gene expression events.

SjTREC quantification using SYBR quantitative PCR for age estimation of bloodstains in a Japanese population.

Individual age is a phenotypic trait that provides useful information in forensic investigations. Levels of signal joint T-cell receptor rearrangement excision circle (sjTREC) in human peripheral blood are known to decline with increasing age. The advantages of sjTREC quantification are the simple procedures and highly accurate age estimation results. Whereas TaqMan quantification PCR (qPCR) is widely used for sjTREC quantification, SYBR qPCR assay is not routinely used for evaluating ethnic data. Therefore, we focused on the advantages of the SYBR qPCR assay, which is cheaper and simpler to set up than the TaqMan probe assay. In this study, we developed a SYBR qPCR assay for sjTREC quantification from bloodstains from a Japanese population and evaluated the strength of correlation between sjTREC levels and actual age. The results were obtained from 194 individuals ranging from 18 to 81 years old, and showed a negative correlation between sjTREC level and individual age (r = -0.786). The equation for age estimation was Age = -6.27 dCt (CtTBP - CtsjTREC) - 25.841 with standard error ±8.0 years. Furthermore, this formula for the SYBR assay can be applied to not only fresh bloodstains, but also whole blood and bloodstains up to 1 month old. These results indicate that SYBR qPCR is an effective method for age estimation from bloodstains, and its practicality and affordability make it an attractive sjTREC quantification technique.

HIV-DNA content in different CD4+ T-cell subsets correlates with CD4+ cell : CD8+ cell ratio or length of efficient treatment.

HIV establishes a latent infection at different degrees within naïve (TN) or central (TCM) and effector memory (TEM) CD4 T cell. Studying patients in whom HIV production was suppressed by combined antiretroviral therapy, our main aim was to find which factors are related or can influence intracellular viral reservoir in different CD4 T-cell subsets. We enrolled 32 HIV patients successfully treated for more than 2 years, with a CD4 T-cell count more than 500 cells/μl and plasma viremia undetectable from at least 1 year. Proviral HIV-DNA, the amount of cells expressing signal-joint T-cell receptor rearrangement excision circles and telomere length were quantified by droplet digital PCR in highly purified, sorted CD4 T-cell subsets; plasma IL-7 and IL-15 were measured by ELISA. HIV-DNA was significantly lower in TN cells compared with TCM or to TEM. Conversely, TN cells contained more signal-joint T-cell receptor rearrangement excision circles compared with TCM or to TEM; no appreciable changes were observed in telomere length. HIV-DNA content was significantly higher in TN and TCM cells, but not in TEM, from patients with shorter time of treatment, or in those with lower CD4 : CD8 ratio. Length of treatment or recovery of CD4 : CD8 ratio significantly influences viral reservoir in both TN and TCM. Measuring HIV-DNA in purified lymphocyte populations allows a better monitoring of HIV reservoir and could be useful for designing future eradication strategies.

Pre-transplantation thymic function is associated with the risk of acute graft versus host disease and cytomegalovirus viremia after allogeneic hematopoietic stem cell transplantation

ABSTRACTObjectives: To analyze the kinetics of T-cell subsets and thymic function reconstitution after allogeneic hematopoietic stem cell transplantation (AHSCT); to determine whether sjTREC (signal joint TCR rearrangement excision circle) and CD31-positive recent thymic emigrant (CD31 + RTE) are correlated with acute graft versus host disease (aGVHD) or CMV (cytomegalovirus) viremia after AHSCT.Methods: Forty-nine patients who underwent AHSCT in our institution were prospectively enrolled. Periphery blood samples were collected before conditioning and at 1, 2, 3 months after AHSCT. T-cell subsets were analyzed with flow cytometry. Genomic DNA was purified from peripheral blood mononuclear cells (PBMCs), and sjTREC was quantified by real-time PCR. Impact of sjTREC and CD31 + RTE on aGVHD and CMV viremia was evaluated by univariate and multivariate Cox regression analyses.Results: The analyzed T-cell subsets and sjTREC of patients before AHSCT were all significantly lower than those of healthy donors (p < 0.05). sjTREC and CD31 + RTE were remarkably decreased in 3 months after AHSCT (p < 0.05). Patients with lower pre-transplantation sjTREC and CD31 + RTE level had higher incidence of CMV viremia after AHSCT (p < 0.05). sjTREC/106 PBMCs was negatively correlated with aGVHD (p = 0.024).Conclusion: Thymic function was impaired before transplantation, and was consistently decreased in 3 months after AHSCT. Patients who had lower pre-transplantation sjTREC level were at high risk of aGVHD and CMV viremia after AHSCT, low pre-transplantation CD31 + RTE was correlated with CMV viremia after AHSCT.

Premature aging and immune senescence in HIV-infected children.

Several pieces of evidence indicate that HIV-infected adults undergo premature aging. The effect of HIV and antiretroviral therapy (ART) exposure on the aging process of HIV-infected children may be more deleterious since their immune system coevolves from birth with HIV. Seventy-one HIV-infected (HIV+), 65 HIV-exposed-uninfected (HEU), and 56 HIV-unexposed-uninfected (HUU) children, all aged 0-5 years, were studied for biological aging and immune senescence. Telomere length and T-cell receptor rearrangement excision circle levels were quantified in peripheral blood cells by real-time PCR. CD4 and CD8 cells were analysed for differentiation, senescence, and activation/exhaustion markers by flow cytometry. Telomere lengths were significantly shorter in HIV+ than in HEU and HUU children (overall, P < 0.001 adjusted for age); HIV+ ART-naive (42%) children had shorter telomere length compared with children on ART (P = 0.003 adjusted for age). T-cell receptor rearrangement excision circle levels and CD8 recent thymic emigrant cells (CD45RACD31) were significantly lower in the HIV+ than in control groups (overall, P = 0.025 and P = 0.005, respectively). Percentages of senescent (CD28CD57), activated (CD38HLA-DR), and exhausted (PD1) CD8 cells were significantly higher in HIV+ than in HEU and HUU children (P = 0.004, P < 0.001, and P < 0.001, respectively). Within the CD4 cell subset, the percentage of senescent cells did not differ between HIV+ and controls, but programmed cell death receptor-1 expression was upregulated in the former. HIV-infected children exhibit premature biological aging with accelerated immune senescence, which particularly affects the CD8 cell subset. HIV infection per se seems to influence the aging process, rather than exposure to ART for prophylaxis or treatment.

Thymic Function Is Most Severely Impaired in Chronic HIV-1 Infection, but Individuals With Faster Disease Progression During Early HIV-1 Infection Expressed Lower Levels of RTEs.

In HIV disease course, the decline of peripheral CD4 T-cell count correlates with rapid disease progression. The supply of peripheral naive T cells by the thymus requires precursor T-cell proliferation within the thymus. In the setting of HIV-1 infection, when both naive and memory T cells are progressively depleted, the contribution of thymic dysfunction in CD4 depletion needs to be studied. Previous research has shown that thymic function may also be impaired in HIV-1 infection. However, it is inconclusive regarding whether this impairment occurred at the early time or during the chronic phase. In addition, the relationship between thymic dysfunction and disease progression remains unknown. In this study, we examined the thymic function in 65 HIV-infected individuals. Among them, 17 were in acute phase, 15 were in early chronic phase, 15 were in chronic phase with no ART (antiretroviral therapy), and 18 were on ART. We also included 11 uninfected individuals as controls. We measured the peripheral blood levels of T-cell receptor rearrangement excision circles and PTK7 and CD31 expressions for the frequency of circulating recent thymic emigrants. We observed that the 2 indicators of thymic function, sj/β-TREC and PTK7, seemed to be lower in the chronic infection group than those in the acute and early chronic groups. Both indicators returned to the normal level after ART. However, after 1-year follow-up of patients with early HIV-1 infection, rapid progressors (n = 4) had lower PTK7 and CD31 expressions than chronic progressors (n = 6).

IL-7 and SCF Levels Inversely Correlate with T Cell Reconstitution and Clinical Outcomes after Cord Blood Transplantation in Adults.

Recovery of thymopoiesis is critical for immune reconstitution after HSCT. IL-7 and SCF are two major thymotropic cytokines. We investigated whether the kinetics of circulating levels of these cytokines might provide insight into the prolonged immunodeficiency after double umbilical cord blood transplantation (dUCBT) in adults. We examined plasma levels of IL-7 and SCF, T-cell receptor rearrangement excision circle (TREC) levels and T cell subsets in 60 adult patients undergoing dUCBT. Median levels of IL-7 increased by more than 3-fold at 4 weeks and remained elevated through 100 days after dUCBT. SCF showed a less than 2-fold increase and more protracted elevation than IL-7. IL-7 levels inversely correlated with the reconstitution of various T cell subsets but not with TRECs. SCF levels inversely correlated with reconstitution of CD4+T cells, especially the naïve CD4+CD45RA+ subset, and with TRECs suggesting that SCF but not IL-7 had an effect on thymic regeneration. In Cox models, elevated levels of IL-7 and SCF were associated with higher non-relapse mortality (p = 0.03 and p = 0.01) and worse overall survival (p = 0.002 and p = 0.001). Elevated IL-7 but not SCF was also associated with development of GvHD (p = 0.03). Thus, IL-7 and SCF are elevated for a prolonged period after dUCBT and persistently high levels of these cytokines may correlate with worse clinical outcomes.

Gene analysis of signal-joint T cell receptor excision circles and their relationship to age in dogs

The quantification of DNA excision circles produced during T cell receptor (TCR) rearrangement, termed signal joint TCR rearrangement excision circles (sjTRECs), has been employed as a measure of age and thymic function in humans and animals. δRec-ψJα sjTRECs are ring-shaped DNAs that are generated during TCRδ locus deletion that occurs at a late stage of T cell development. In this study, the nucleotide sequences of δRec-ψJα signal joints of canine δRec-ψJα sjTRECs were analyzed. The gene structure of canine δRec-ψJα signal joints was found to be similar to that of humans and mice. However, diversity of signal joints was detected and found to derive from N nucleotide insertions, recombination signal sequence combinational diversity and single-base substitutions at the recombination signal sequence. In addition, an adenine insertion or deletion was found approximately 280 bases from the ψJα signal end. Blood samples were collected from 46 dogs, ranging in age from 3 to 192 months, with a mean age of 96.4 and a SD of 51.5 months. Although δRec-ψJα sjTRECs were detectable in most of the dogs evaluated, the level did not significantly correlate with age. These results indicated that δRec-ψJα sjTREC levels were ineffective as a measure of age in dogs.

Premature senescence of T-cell subsets in axial spondyloarthritis

ObjectiveTo investigate the possible occurrence of early thymic failure and premature senescence of naïve and memory T-cells in patients with axial spondyloarthritis (aSpA).MethodsProspective, cross-sectional study of consecutive patients with aSpA...

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

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. 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. 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. 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.