Age-related thymic activity in adults following chemotherapy-induced lymphopenia

Primary and secondary defects of the thymus

The thymus is the primary site of T-cell development, enabling generation, and selection of a diverse repertoire of T cells that recognize non-self, whilst remaining tolerant to self- antigens. Severe congenital disorders of thymic development (athymia) can be fatal if left untreated due to infections, and thymic tissue implantation is the only cure. While newborn screening for severe combined immune deficiency has allowed improved detection at birth of congenital athymia, thymic disorders acquired later in life are still underrecognized and assessing the quality of thymic function in such conditions remains a challenge. The thymus is sensitive to injury elicited from a variety of endogenous and exogenous factors, and its self-renewal capacity decreases with age. Secondary and age-related forms of thymic dysfunction may lead to an increased risk of infections, malignancy, and autoimmunity. Promising results have been obtained in preclinical models and clinical trials upon administration of soluble factors promoting thymic regeneration, but to date no therapy is approved for clinical use. In this review we provide a background on thymus development, function, and age-related involution. We discuss disease mechanisms, diagnostic, and therapeutic approaches for primary and secondary thymic defects.

Multiparametric Evaluation of Radiomics Features and Dual-Energy CT Iodine Maps for Discrimination and Outcome Prediction of Thymic Masses

RATIONALE AND OBJECTIVES

To investigate the diagnostic value of radiomics features and dual-source dual-energy CT (DECT) based material decomposition in differentiating low-risk thymomas, high-risk thymomas, and thymic carcinomas.

MATERIALS AND METHODS

This retrospective study included 32 patients (16 males, mean age 66 ± 14 years) with pathologically confirmed thymic masses who underwent contrast-enhanced DECT between 10/2014 and 01/2023. Two experienced readers evaluated all patients regarding conventional radiomics features, as well as DECT-based features, including attenuation (HU), iodine density (mg/mL), and fat fraction (%). Data comparisons were performed using analysis of variance and chi-square statistic tests. Receiver operating characteristic curve analysis and Cox-regression tests were used to discriminate between low-risk/high-risk thymomas and thymic carcinomas.

RESULTS

Of the 32 thymic tumors, 12 (38%) were low-risk thymomas, 11 (34%) were high-risk thymomas, and 9 (28%) were thymic carcinomas. Values differed significantly between low-risk thymoma, high-risk thymoma, and thymic carcinoma regarding DECT-based features (p ≤ 0.023) and 30 radiomics features (p ≤ 0.037). The area under the curve to differentiate between low-risk/high-risk thymomas and thymic cancer was 0.998 (95% CI, 0.915-1.000; p < 0.001) for the combination of DECT imaging parameters and radiomics features, yielding a sensitivity of 100% and specificity of 96%. During a follow-up of 60 months (IQR, 35-60 months), the multiparametric approach including radiomics features, DECT parameters, and clinical parameters showed an excellent prognostic power to predict all-cause mortality (c-index = 0.978 [95% CI, 0.958-0.998], p = 0.003).

CONCLUSION

A multiparametric approach including conventional radiomics features and DECT-based features facilitates accurate, non-invasive discrimination between low-risk/high-risk thymomas and thymic carcinomas.

Impact of lymphopenia on efficacy of nivolumab in head and neck cancer patients

INTRODUCTION

Lymphopenia has been correlated with poorer survival in patients with metastatic cancers treated with anti-PD-1 immunotherapy. Treatments such as chemotherapy, surgery or radiotherapy can induce lymphopenia. Radiation-induced lymphopenia is common and prolonged in head and neck cancer (HNSCC) patients. We evaluated the impact of lymphopenia, on efficacy of anti PD-1 nivolumab immunotherapy in HNSCC patients.

METHODS

a multicenter retrospective study included consecutive patients treated with nivolumab for recurrent/metastatic (R/M) HNSCC between January 2017 and June 2019. Lymphopenia was defined as lymphocyte counts below 1000 cells/mm³ upon initiation of nivolumab. Logistical regression was performed on factors associated with lymphopenia and ROC analyses assessed association between lymphopenia and survival.

RESULTS

median age was 65. Of the 100 included patients, 60% had been treated by surgery, 67% had had first-line chemotherapy, and 89% loco-regional radiotherapy, 65% had concurrent chemotherapy with radiotherapy. Lymphopenia occurred in 56 (56%) patients upon initiation of nivolumab, with 29 (29%) patients having radiation-related lymphopenia. Prior locoregional radiotherapy was the only factor associated with lymphopenia upon initiation of nivolumab by logistical regression (OR 0.144 [0.029-0.706], p - 0.017). Lymphopenia upon initiation of nivolumab did not affect progression-free survival (PFS) (p - 0.815), overall survival (OS) (p - 0.783) or disease control rate (DCR) (p - 0.125). Locoregional symptomatology (HR - 2.37 [1.24-4.54], p - 0.009), metastatic symptomatology (HR - 4.74 [2.21-10.15], and persistent lymphopenia under nivolumab (HR 3.96 [1.19-13.17] p - 0.034) were associated with poorer OS in multivariate analysis.

CONCLUSIONS

Lymphopenia upon initiation of nivolumab was not associated with poorer survival in R/M HNSCC patients, but persistence of lymphopenia during immunotherapy might be a prognostic marker of patient survival.

The CXCR4-CXCL12 axis promotes T cell reconstitution via efficient hematopoietic immigration

T cells play a critical role in immunity to protect against pathogens and malignant cells. T cell immunodeficiency is detrimental, especially when T cell perturbation occurs during severe infection, irradiation, chemotherapy, and age-related thymic atrophy. Therefore, strategies that enhance T cell reconstitution provide considerable benefit and warrant intensive investigation. Here, we report the construction of a T cell ablation model in Tg(coro1a:DenNTR) zebrafish via metronidazole administration. The nascent T cells are mainly derived from the hematopoietic cells migrated from the kidney, the functional homolog of bone marrow and the complete recovery time is 6.5 days post-treatment. The cxcr4b gene is upregulated in the responsive hematopoietic cells. Functional interference of CXCR4 via both genetic and chemical manipulations does not greatly affect T lymphopoiesis, but delays T cell regeneration by disrupting hematopoietic migration. In contrast, cxcr4b accelerates the replenishment of hematopoietic cells in the thymus. Consistently, Cxcl12b, a ligand of Cxcr4, is increased in the thymic epithelial cells of the injured animals. Decreased or increased expression of Cxcl12b results in compromised or accelerated T cell recovery, respectively, similar to those observed with Cxcr4b. Taken together, our study reveals a role of CXCR4-CXCL12 signaling in promoting T cell recovery and provides a promising target for the treatment of immunodeficiency due to T cell injury.

Thymic rebound hyperplasia post-chemotherapy mistaken as disease progression in a patient with lymphoma involving mediastinum: a case report and reflection

Background

Chemotherapy can cause thymic atrophy and reduce T-cell output in cancer patients. However, the thymus in young adult patients has regenerative potential after chemotherapy, manifesting as thymic hyperplasia which can be easily mistaken as residual disease or recurrence in patients suffering lymphoma.

Case presentation

This study reports a case of lymphoma in a young female adult who was initially diagnosed with an anterior mediastinal mass, and was found to have soft tissue occupying the anterior mediastinum repeatedly after chemotherapy, suggesting a lymphoma residue or disease progression. From discussions by a multi-disciplinary team (MDT), the anterior mediastinal mass of the patient was considered unknown and might be thymus tissue or tumor tissue, and it was eventually identified as thymus tissue via histopathology.

Conclusions

The anterior mediastinal mass appearing after chemotherapy in patients with lymphoma can be considered as enlarged thymus, and such phenomenon is frequent in young adult patients who undergo chemotherapy or autologous hematopoietic stem cell transplantation. Additionally, detection of thymic output cells in peripheral blood might be a feasible approach to differentiate thymic hyperplasia from lymphoma.

T cell regeneration after immunological injury

Following periods of haematopoietic cell stress, such as after chemotherapy, radiotherapy, infection and transplantation, patient outcomes are linked to the degree of immune reconstitution, specifically of T cells. Delayed or defective recovery of the T cell pool has significant clinical consequences, including prolonged immunosuppression, poor vaccine responses and increased risks of infections and malignancies. Thus, strategies that restore thymic function and enhance T cell reconstitution can provide considerable benefit to individuals whose immune system has been decimated in various settings. In this Review, we focus on the causes and consequences of impaired adaptive immunity and discuss therapeutic strategies that can recover immune function, with a particular emphasis on approaches that can promote a diverse repertoire of T cells through de novo T cell formation.

Effect of Rebound Thymic Hyperplasia on Survival in Chemotherapy-Treated Lung Cancer

OBJECTIVES

Thymus is a lymphoepithelial system in which cells responsible for the immune system are produced and directed. The aim of this study is to determine the overall survival effect of rebound thymic hyperplasia (RTH) in patients with non-small cell lung cancer (NSCLC) treated with systemic chemotherapy (CT).

MATERIALS AND METHODS

The study was designed as retrospective case series. One hundred and thirty patients who met the inclusion criteria were evaluated. Demographic data, type of tumor, and treatments administered were recorded. The frequency of RTH development and the relationship between RTH development and survival was investigated.

RESULTS

The median age of the patients was 59, and nine of 13 patients (69.4%) with RTH were iden-tified as stable disease, two patients had a partial response (15.3%), and two were evaluated as progres-sive disease (15.3%). Of the remaining 117 patients, 78 (66.6%) had stable disease, 11 (9.4%) had com-plete response, 21 (17.9%) had partial response, and seven patients were evaluated as having progressive disease (5.9%). The patients were categorized into two groups: Group 1 - without RTH and group 2 - with RTH. Thirteen (10%) of 130 patients developed RTH (group 2), while the remaining 117 (90%) patients did not have RTH (group 1). There was no difference between the two groups (59.1 years) in terms of age (p = 0.933). The RTH developed after a median time of 4.5 months (2-7 months) after CT had been administered. Overall survival was longer in patients with RTH than in patients without RTH (20.04 months) (95% CI, 4.79-35.29) vs. 10.05 months (95% CI, 8.74-11.36; p=0.049).

CONCLUSION

The developing of RTH during systemic CT may be a prognostic marker in stage 4 non-small cell lung cancer.

Why the Outcome of Anti-Tumor Immune Responses is Heterogeneous: A Novel Idea in the Context of Immunological Heterogeneity in Cancers

The question as to why some hosts can eradicate their tumors while others succumb to tumor-progression remains unanswered. Here, a provocative concept is proposed that intrinsic differences in the T cell receptor (TCR) repertoire of individuals may influence the outcome of anti-tumor immunity by affecting the frequency and/or variety of tumor-reactive CD8 and/or CD4 tumor-infiltrating lymphocytes. This idea implicates that the TCR repertoire in a given patient might not provide sufficiently different TCR clones that can recognize tumor antigens, namely, "a hole in the TCR repertoire" might exist. This idea may provide a novel perspective to further dissect the mechanisms underlying heterogeneous anti-tumor immune responses in different hosts. Besides tumor-intrinsic heterogeneity and host microbiome, the various factors that may constantly shape the dynamic TCR repertoire are also discussed. Elucidating mechanistic differences in different individuals' immune systems will allow to better harness immune system to design new personalized cancer immunotherapy.

Fludarabine exposure in the conditioning prior to allogeneic hematopoietic cell transplantation predicts outcomes

Fludarabine is the most frequently used agent in conditioning regimens for allogeneic hematopoietic cell transplantation (HCT). Body surface area-based dosing leads to highly variable fludarabine exposure. We studied the relation between fludarabine exposure and clinical outcomes. A retrospective, pharmacokinetic-pharmacodynamic analysis was conducted with data from patients undergoing HCT with fludarabine (160 mg/m²) as part of a myeloablative conditioning (busulfan targeted to an area under the plasma-concentration-time curve [AUC] of 90 mg*h/L) and rabbit antithymocyte globulin (6-10 mg/kg; from day -9/-12) between 2010 and 2016. Fludarabine exposure as AUC was calculated for each patient using a previously published population pharmacokinetic model and related to 2-year event-free survival (EFS) by means of (parametric) time-to-event models. Relapse, nonrelapse mortality (NRM), and graft failure were considered events. One hundred ninety-two patients were included (68 benign and 124 malignant disorders). The optimal fludarabine exposure was determined as an AUC of 20 mg*h/L. In the overexposed group, EFS was lower (hazard ratio [HR], 2.0; 95% confidence interval [CI], 1.1-3.5; P = .02), due to higher NRM (HR, 3.4; 95% CI, 1.6-6.9; P <001) associated with impaired immune reconstitution (HR, 0.43; 95% CI, 0.26-0.70; P <001). The risks of NRM and graft failure were increased in the underexposed group (HR, 3.3; 95% CI, 1.2-9.4; P = .02; HR, 4.8; 95% CI, 1.2-19; P = .02, respectively). No relationship with relapse was found. Fludarabine exposure is a strong predictor of survival after HCT, stressing the importance of optimum fludarabine dosing. Individualized dosing, based on weight and "renal function" or "therapeutic drug monitoring," to achieve optimal fludarabine exposure might improve survival.

[Mechanisms of radiation-induced lymphopenia and therapeutic impact]

Radiation induced lymphopenia is frequent and can be severe and durable. Although lymphocytes have long been known as highly radiosensitive cells, it is poorly characterized. Radiation-induced lymphopenia seems to affect lymphocyte subpopulations differently and seems to be influenced by radiation modalities. The depth and duration of lymphopenia depend on the location of the irradiation and the volumes of treatment. Importantly, radiation-induced lymphopenia has been associated with poorer prognosis in several tumor types. The knowledge about radiation-induced lymphopenia might lead to a rethinking of the modalities of radiotherapy and new approaches to restore lymphocytes counts.

Thymus Imaging Detection and Size Is Inversely Associated With Metabolic Syndrome and Frailty in People With HIV

BACKGROUND

People with HIV (PWH) may experience accentuating aging in relation to immuno-activation. Little is known regarding thymus (THY) involution in this process. We sought to investigate the relationship between THY imaging detection/size and clinically relevant aging outcomes such as metabolic syndrome (MetS), multimorbidity (MM), and frailty in PWH.

METHODS

This was a cross-sectional observational study including 665 HIV patients (81% males; median age, 53 years) attending Modena HIV Metabolic Clinic from 2014 to 2017. They underwent thoracic computed tomography scan as part of the medical assessment for cardiovascular disease, in which THY detection and size were reported using a semiquantitative score. Outcome measures were MetS, MM, and frailty.

RESULTS

THY was detected in 27.0% of subjects; 71.1% showed THY size of grade 1-2, and 28.9% exhibited grade ≥3. Covariates that inversely correlated with THY detection were age, male gender, body mass index (BMI), and HIV duration. Covariates that inversely correlated with MetS were age, HIV duration, BMI, and THY grade 1-2. Covariates that inversely correlated with MM were age, HIV duration, and CD4 nadir. Covariates that inversely correlated with frailty were age, HIV duration, CD4 nadir, BMI, and THY detection.

CONCLUSIONS

THY is inversely associated with MetS and frailty in PWH.

Lymphopenia in Cancer Patients and its Effects on Response to Immunotherapy: an opportunity for combination with Cytokines?

Quantitative lymphocyte alterations are frequent in patients with cancer, and strongly impact prognosis and survival. The development of cancers in immunosuppressed patients has demonstrated the contribution of different T cell populations, including CD4⁺ cells, in the control of cancer occurrence.Whereas absolute numbers of neutrophils, platelets and red blood cells are routinely monitored in clinic following treatments, because of possible short-term complications, absolute lymphocyte counts (ALC), their subpopulations or diversity (phenotype, TCR) are rarely analyzed and never used to choose therapy or as prognostic criteria. The recent identification of immune checkpoint inhibitors (ICPi) as powerful therapeutic agents has revitalized immunotherapy of cancer in a broader group of diseases than anticipated. The status of the immune system is now recognized as an important biomarker for response to these novel treatments. Blood ALC values, along with tumor infiltration by CD8⁺T cells, and ICPi and ICPi-ligand expression, are likely to be a potential marker of sensitivity to anti-ICPi therapy.In this article, we review the current knowledge on the incidence and significance of lymphopenia in cancer patients, and discuss therapeutic strategies to restore lymphocyte numbers.

Rebound thymic hyperplasia after bone marrow transplantation in children with haemato-oncological diseases

Aim of the study

To evaluate prevalence of rebound thymic hyperplasia (RTH) after bone marrow transplantation (BMT) in paediatric patients with haemato-oncological diseases.

Material and methods

Between February 2013 and December 2017, BMT was performed in 189 paediatric patients with haemato-oncological diseases in our institution. Fifty-six patients who underwent at least two chest computed tomography (CT) exams performed before and after BMT were included in the study. Maximum transverse and anterior-posterior (AP) diameters and CT attenuation of the thymus were measured on axial images. Thymic enlargement was considered when both transverse and AP diameters increased. RTH was defined as the presence of thymic enlargement on CT after BMT relative to the CT taken before.

Results

Twenty of 56 patients (36%) demonstrated RTH (12 boys, 8 girls; age range = 4-18 years; median age = 9.8 years). In 20 patients with RTH, seven patients (35%) were diagnosed with ALL, five patients (25%) with thalassemia, two patients (10%) with AML, and one patient (5%) with various diseases. Mean follow-up period between pre-BMT CT and BMT was 46 days, which was 239 days between BMT and post-BMT CT. Mean thymic transverse and AP diameters were 9 mm and 16 mm, respectively, before BMT, which were 17 mm and 33 mm after BMT. Mean HU was 57 on contrast enhanced and 35 on unenhanced images before BMT, which were 59 and 36, respectively, after BMT.

Conclusions

RTH is common finding after BMT in children with various haemato-oncological diseases and should be taken under consideration in paediatric patients after BMT.

Investigating Factors Associated with Thymic Regeneration after Chemotherapy in Patients with Lymphoma

The factors involved in thymus regeneration after chemotherapy has not been sufficiently explored. This study was aimed to identify the clinical characteristics and single-nucleotide polymorphisms in the gene (IL7R) encoding IL-7Rα associated with thymus renewal after chemotherapy in Chinese Han individuals with lymphoma. The dynamics of thymic activity in 134 adults with Hodgkin lymphoma (HL) and B cell lymphoma from baseline to 12 months post-chemotherapy were analyzed by assessing thymic structural changes using serial computed tomography scans and correlating these with measurements of thymic output by concurrent analysis of single-joint T-cell receptor excision circles (sjTREC) and CD31⁺ recent thymic emigrants (RTE) in peripheral blood. The association of clinical variables and IL7R polymorphisms with the occurrence of rebound thymic hyperplasia (TH) and the recovery of thymic output following chemotherapy were evaluated. Thymic regeneration was observed, with the evidence that TH occurred in 38/134 (28.4%) cases, and thymic output, assessed by CD31⁺ RTE numbers and sjTREC content, recovered to baseline levels within 1 year after the end of therapy. The frequencies of the T allele and TT + GT genotype of rs7718919 located in the promoter of IL7R were significantly higher in patients with TH compared with those without TH (P = 0.031 and 0.027, respectively). In contrast, no significant difference was found between two groups with respect to the distribution of allele and genotype frequencies of rs6897932. By general linear models repeated-measure analysis, rs7718919 and rs6897932 were determined to exert no significant effects on the recovery of thymic output after therapy. Univariate analysis revealed host age under 30, the diagnosis of HL, baseline thymic index and CD31⁺ RTE counts, and rs7718919 genotype as potential predictors for TH after chemotherapy (P < 0.05); after multivariate adjustment, only host age was independently associated with the occurrence of TH (odds ratios = 4.710, 95% confidence intervals: 1.727–12.845, P = 0.002). These findings indicate that patient age is an independent predictor for thymic regrowth after chemotherapy, which should promote awareness among physicians to make a timely diagnosis of TH in young adults and help physicians to prioritize intervention strategies for thymus rejuvenation in this population.

Functionally Diverse NK-Like T Cells Are Effectors and Predictors of Successful Aging

The fundamental challenge of aging and long-term survivorship is maintenance of functional independence and compression of morbidity despite a life history of disease. Inasmuch as immunity is a determinant of individual health and fitness, unraveling novel mechanisms of immune homeostasis in late life is of paramount interest. Comparative studies of young and old persons have documented age-related atrophy of the thymus, the contraction of diversity of the T cell receptor (TCR) repertoire, and the intrinsic inefficiency of classical TCR signaling in aged T cells. However, the elderly have highly heterogeneous health phenotypes. Studies of defined populations of persons aged 75 and older have led to the recognition of successful aging, a distinct physiologic construct characterized by high physical and cognitive functioning without measurable disability. Significantly, successful agers have a unique T cell repertoire; namely, the dominance of highly oligoclonal αβT cells expressing a diverse array of receptors normally expressed by NK cells. Despite their properties of cell senescence, these unusual NK-like T cells are functionally active effectors that do not require engagement of their clonotypic TCR. Thus, NK-like T cells represent a beneficial remodeling of the immune repertoire with advancing age, consistent with the concept of immune plasticity. Significantly, certain subsets are predictors of physical/cognitive performance among older adults. Further understanding of the roles of these NK-like T cells to host defense, and how they integrate with other physiologic domains of function are new frontiers for investigation in Aging Biology. Such pursuits will require a research paradigm shift from the usual young-versus-old comparison to the analysis of defined elderly populations. These endeavors may also pave way to age-appropriate, group-targeted immune interventions for the growing elderly population.

Sex steroid ablation: an immunoregenerative strategy for immunocompromised patients

Age-related decline in thymic function is a well-described process that results in reduced T-cell development and thymic output of new naïve T cells. Thymic involution leads to reduced response to vaccines and new pathogens in otherwise healthy individuals; however, reduced thymic function is particularly detrimental in clinical scenarios where the immune system is profoundly depleted such as after chemotherapy, radiotherapy, infection and shock. Poor thymic function and restoration of immune competence has been correlated with an increased risk of opportunistic infections, tumor relapse and autoimmunity. Apart from their primary role in sex dimorphism, sex steroid levels profoundly affect the immune system in general and, in fact, age-related thymic involution has been at least partially attributed to the increase in sex steroids at puberty. Subsequently it has been demonstrated that the removal of sex steroids, or sex steroid ablation (SSA), triggers physiologic changes that ultimately lead to thymic re-growth and improved T-cell reconstitution in settings of hematopoietic stem cell transplant (HSCT). Although the cellular and molecular process underlying these regenerative effects are still poorly understood, SSA clearly represents an attractive therapeutic approach to enhance thymic function and restore immune competence in immunodeficient individuals.

Thymic hyperplasia after chemotherapy in adults with mature B cell lymphoma and its influence on thymic output and CD4(+) T cells repopulation

To investigate the thymic regenerative potential in adults accepting chemotherapy for lymphoma. The dynamics of thymic activity in 54 adults from baseline to 12 mo post-chemotherapy was analyzed by assessing thymic structural changes with serial computed tomography (CT) scans, and correlating these with measurements of thymic output by concurrent analysis of single-joint (sj) T-cell receptor excision circles (sjTREC) and CD31⁺ recent thymic emigrants (RTE) in peripheral blood. Furthermore, the consequence of thymic renewal on peripheral CD4⁺ T cell recovery after chemotherapy was evaluated. Time-dependent changes of thymic size and thymic output assessed by both sjTREC levels and CD31⁺ RTE counts in peripheral blood were observed during and after chemotherapy. Enlargement of thymus over baseline following chemotherapy regarded as rebound thymic hyperplasia (TH) was identified in 20 patients aged 18−53 y (median 33 y). By general linear models repeated measure analysis, it was found that, patients with TH (n = 20) had a faster recovery of sjTREC levels and CD31⁺ RTE counts after chemotherapy than patients with comparable age, gender, diagnosis, disease stage, thymic volume and output function at baseline but without TH (n = 18) (p = 0.035, 0.047); besides, patients with TH had a faster repopulation of both naïve CD4⁺ T cell and natural regulatory CD4⁺ T cell subsets than those without TH (p = 0.042, 0.038). These data suggested that adult thymus retains the capacity of regeneration after chemotherapy, especially in young adults. The presence of TH could contribute to the renewal of thymopoiesis and the replenishment of peripheral CD4⁺ T cell pool following chemotherapy in adults.

Homeostatic cytokines in immune reconstitution and graft-versus-host disease

For numerous patients, allogeneic stem cell transplantation (SCT) is the only therapeutic option that could potentially cure their disease. Despite significant progress made in clinical management of allogeneic SCT, acute graft-versus-host disease (aGVHD) remains the second cause of death after disease recurrence. aGVHD is highly immunosuppressive and the adverse effect of allogeneic SCT on T cell regeneration is typically more important than the levels of immunosuppression normally seen after autologous SCT. In these patients, immune reconstitution often takes several years to occur and restoring immunocompetence after allogeneic SCT represents an important challenge, principally because clinical options are limited and current methods used to accelerate immune reconstitution are associated with increased GVHD. Interleukin-7 and IL-15 are both under clinical investigation and demonstrate the greatest potential on peripheral T cells regeneration in mice and humans. However, awareness has been raised about the use of IL-7 and IL-15 after allogeneic SCT with regards to potential adverse effects on aGVHD. In this review, we will discuss about recent progress made in lymphocyte regeneration, the critical role played by IL-7 and IL-15 in T cell homeostasis and how these cytokines could be used to improve immune reconstitution after allogeneic SCT.

Thymic emigration patterns in patients with type 2 diabetes treated with metformin

Recent data suggest that thymic output, which provides the naive T cells necessary for the normal functioning of T-cell-dependent immunosurveillance cellular immunity including anti-cancer protection, can be disturbed in the course of type 2 diabetes. Metformin, an anti-diabetic drug commonly confirmed as an agent with many potential anti-cancer activities, might be helpful in this immune correction. The profile of thymic output was evaluated in the current study on the basis of the signal-joint T-cell receptor excision circle (sjTREC) concentration in peripheral blood polymorphonuclear cells and thymic emigrant content in peripheral blood evaluated from CD127 and/or CD132 antigen expression. It was revealed that recent thymic emigrants and more differentiated CD127(+) CD132(+) cell populations were decreased among naive T cells and CD8(+) T cells, whereas RTE count was increased in CD4(+) T cells, and the CD127(+) CD132(+) cell population was less numerous than in non-diabetic participants. Terminally differentiated thymic emigrants, i.e. CD127(-) CD132(+) cells, were increased in naive T cells and in CD8(+) T cells. Metformin affects mainly the early phases of thymic export, increasing CD127(+) CD132(-) and CD127(+) CD132(+) cell populations in naive T cells and the CD127(+) CD132(-) population in CD4(+) T lymphocytes. It could be concluded that type 2 diabetes deteriorates thymic immunostasis. The decreased thymic output could be compensated by metformin, especially with regard to CD4(+) naive T cells. It is the first time that therapy with metformin has been documented by us as particularly useful in the control and normalization of thymus function, regarding correction of early populations of thymic emigrants.

Effect of IL-7 Therapy on Naive and Memory T Cell Homeostasis in Aged Rhesus Macaques

Aging is associated with gradual deterioration of adaptive immune function, a hallmark of which is the profound loss of naive T cells (TN) associated with decline in thymic output and export of new cells into the peripheral T cell pool. Because the lymphotropic cytokine IL-7 plays crucial roles in both development of TN in the thymus and TN homeostasis in the periphery, we sought to determine the extent to which therapeutic administration of IL-7 could reverse TN deficiency in aging rhesus macaques (RM), either by enhancement of the demonstrably reduced thymopoiesis or by peripheral TN expansion. Our results indicate that treatment of both adult (8-15 y) and old (>20 y) RM with recombinant simian IL-7 (rsIL-7) results in only transient increases in peripheral CD4(+) and CD8(+) TN numbers with no long-term benefit, even with repeated therapy. This transient effect was due to peripheral TN expansion and not enhanced thymic function, and appeared to be limited by induction of IL-7 nonresponsiveness. However, rsIL-7 therapy had a more promising effect on the central memory T cell (TCM) population (both CD4(+) and CD8(+)) in adult and old RM, doubling the numbers of these cells in circulation and maintaining this larger population long term. IL-7 therapy did not reduce TCR diversity of the memory T cell compartment, suggesting that rsIL-7-induced expansion was symmetrical. Thus, although rsIL-7 failed to counter age-associated TN loss, the ability of this therapy to expand clonotypically diverse CD4(+) and CD8(+) TCM populations might potentially improve adaptive immune responsiveness in the elderly.

Optimal management of cervical cancer in HIV-positive patients: a systematic review

The clinical management of cervical cancer in HIV-positive patients has challenges mainly due to the concerns on immune status. At present, their mode of management is similar to HIV-seronegative patients involving the use of chemotherapy and radiotherapy concurrently as indicated. HIV infection, cancer, radiotherapy, and chemotherapy lower immunity through reduction in CD4 cell counts. At present there are no treatment guidelines for HIV-positive patients. This study was done to systematically review the literature on cervical cancer management in HIV-positive patients and treatment outcomes. A systematic literature search was done in the major databases to identify studies on the management of HIV-positive patients with cervical cancer. Identified studies were assessed for eligibility and inclusion in the review following the guidelines of The Cochrane Handbook for Systematic Reviews and CRD's (Centre for Reviews and Dissemination) guidance for undertaking reviews in health care. Eight eligible studies were identified from the literature. Three of them were prospective while five were retrospective studies. Notably, the average age at diagnosis of cervical cancer in HIV-positive patients was a decade lower than in seronegative patients. There was no difference in distribution of stages of disease at presentation between HIV-positive and negative patients. Mild acute toxicity (Grades 1 and 2) was higher in HIV-positive patients than in HIV-negative patients in hematopoietic system. In the grades 3 and 4 reactions, anemia was reported in 4% versus 2% while gastrointestinal reactions were reported in 5% versus 2% respectively. In general, patients who were started early on HAART had higher rates of treatment completion. The study supports the suggestion that HAART should be commenced early at cervical cancer diagnosis in HIV-positive patients diagnosed with cervical cancer to ensure less toxicity and better treatment compliance.

Prolonged severe immunodeficiency following thymectomy and radiation: a case report

Introduction

Immunodeficiency can occur both in patients undergoing radiation therapy, as well as in patients who have had thymectomies. However, few studies have examined the immune recovery of a patient following both procedures. We aim to emphasize the need for assessment and consistent monitoring of patients with thymoma prior to and after combined treatment of thymectomy and radiation, both of which are likely to result in an increased risk for immunodeficiency.

Case presentation

We describe the longitudinal progress of a 59-year-old Asian male who underwent thymectomy followed by radiation therapy and subsequently presented with generalized urticaria. Revelation of a low absolute lymphocyte count (615 cells/mcL) on initial evaluation prompted further analysis of his immunoglobulin levels and antigen response to a polysaccharide pneumococcal vaccine (PneumoVax-23). Although his immunoglobulin levels were unremarkable, he failed to respond to 11 of 12 serotypes of the pneumococcal vaccine. As a result, he was placed on Bactrim^® (trimethoprim-sulfamethoxazole) prophylaxis to prevent opportunistic infections, and his CD4+ and CD8+ counts were monitored over the course of 8 years. His lymphocyte counts 87 months after thymectomy and 85 months after radiation therapy were as follows: absolute lymphocyte count 956 cells/mcL, absolute CD3+/CD4+ 164/mm³ (16%) and absolute CD3+/CD8+ 257/mm³ (25%). The patient was able to discontinue Bactrim^® (trimethoprim-sulfamethoxazole) prophylaxis after 9 years of treatment.

Conclusions

The lymphocytopenia, low CD4+ count, and failed response to pneumococcal vaccination that presented in our patient are consistent with immunodeficiency. After radiation alone, a recovery of T-lymphocytes is usually observed after approximately 3 weeks. Over the course of 8 years, he has still not made a full recovery according to laboratory markers, which seem to have stabilized at chronically low levels. To prevent serious complications, we suggest that patients who have undergone both thymectomy and radiation therapy be monitored for immunodeficiency. This case report informs the practices of allergists, oncologists, and neurologists in the continuing care of patients with thymoma.

Chemical castration of melanoma patients does not increase the frequency of tumor-specific CD4 and CD8 T cells after peptide vaccination

Peptide vaccination against tumor-associated antigens remains one of the most common methods of immunization in cancer vaccine clinical trials. Although peptide vaccination has been reported to increase circulating antigen-specific T-cells, they have had limited clinical efficacy and there is a necessity to increase their capacity to generate strong antitumor responses. We sought to improve the clinical efficacy of peptide-based vaccines in cancer immunotherapy of metastatic melanoma using a LHRH agonist (leuprolide) as adjuvant. Seventy HLA-A*0201 stage IIb-IV melanoma patients were vaccinated with class I HLA-A*0201-restricted gp100209-2M peptide and stratified for HLA-DP4 restriction. HLA-DP4 patients were also vaccinated with class II HLA-DP4-restricted MAGE-3243-258 peptide. Patients from both groups were randomized to receive 2 doses of leuprolide or not. Here we report the increase in PBMC TREC levels at week 24 after peptide vaccination, which was independent of the leuprolide treatment. This change was mirrored by a small increase in the TREC-enriched CD8CD45RAROCD27CD103, but not the TREC-enriched CD4CD45RAROCD31 T-cell population. Serum concentration of 2 important factors for thymopoiesis was measured: insulin growth factor 1 (IGF-1) levels were not changed, whereas a moderate increase in IL-7 levels was noted in the sera of all patients 6 weeks after vaccination. Increased expression of CD127 (IL-7 receptor-α) at week 24, compared with baseline, was only seen in the CD8CD45RAROCD27CD103 T-cell population. Our results suggest that leuprolide has no effect on thymic output when used as peptide vaccine adjuvant, but IFA-based peptide vaccination may unexpectedly affect the thymus by increasing thymic output of new T cells.

Greater than the sum of their parts: combination strategies for immune regeneration following allogeneic hematopoietic stem cell transplantation

Cytoreductive conditioning regimes designed to allow for successful allogeneic hematopoietic stem cell transplantation (allo-HSCT) paradoxically are also detrimental to recovery of the immune system in general but lymphopoiesis in particular. Post-transplant immune depletion is particularly striking within the T cell compartment which is exquisitely sensitive to negative regulation, evidenced by the profound decline in thymic function with age. As a consequence, regeneration of the immune system remains a significant unmet clinical need. Over the past decade studies have revealed several promising therapeutic strategies to address ineffective lymphopoiesis and post-transplant immune deficiency. These include the use of cytokines such as IL-7, IL-12 and IL-15; growth factors and hormones like keratinocyte growth factor (KGF), insulin-like growth factor (IGF)-1 and growth hormone (GH); adoptive transfer of ex vivo-generated precursor T cells (pre-T) and sex steroid ablation (SSA). Moreover, recently several novel approaches have been proposed to generate whole thymii ex vivo using stem cell technologies and bioscaffolds. Increasingly, however, when transferred to the clinic, these strategies alone are not sufficient to restore thymopoiesis in all patients leading to the potential of combination strategies as a way to reign in non-responders. Synergistic enhancement in combination may be due to differential targets may therefore be effective in improving clinical outcomes in the transplant settings as well as in other lymphopenic states induced by high dose chemotherapy/radiation therapy or HIV, and may also be useful in improving responses to vaccination and augmenting anti-tumor immunotherapy.

Clinical predictors of immune reconstitution following combination antiretroviral therapy in patients from the Australian HIV Observational Database

Background

A small but significant number of patients do not achieve CD4 T-cell counts >500cells/µl despite years of suppressive cART. These patients remain at risk of AIDS and non-AIDS defining illnesses. The aim of this study was to identify clinical factors associated with CD4 T-cell recovery following long-term cART.

Methods

Patients with the following inclusion criteria were selected from the Australian HIV Observational Database (AHOD): cART as their first regimen initiated at CD4 T-cell count <500cells/µl, HIV RNA<500copies/ml after 6 months of cART and sustained for at least 12 months. The Cox proportional hazards model was used to identify determinants associated with time to achieve CD4 T-cell counts >500cells/µl and >200cells/µl.

Results

501 patients were eligible for inclusion from AHOD (n = 2853). The median (IQR) age and baseline CD4 T-cell counts were 39 (32–47) years and 236 (130–350) cells/µl, respectively. A major strength of this study is the long follow-up duration, median (IQR) = 6.5(3–10) years. Most patients (80%) achieved CD4 T-cell counts >500cells/µl, but in 8%, this took >5 years. Among the patients who failed to reach a CD4 T-cell count >500cells/µl, 16% received cART for >10 years. In a multivariate analysis, faster time to achieve a CD4 T-cell count >500cells/µl was associated with higher baseline CD4 T-cell counts (p<0.001), younger age (p = 0.019) and treatment initiation with a protease inhibitor (PI)-based regimen (vs. non-nucleoside reverse transcriptase inhibitor, NNRTI; p = 0.043). Factors associated with achieving CD4 T-cell counts >200cells/µl included higher baseline CD4 T-cell count (p<0.001), not having a prior AIDS-defining illness (p = 0.018) and higher baseline HIV RNA (p<0.001).

Conclusion

The time taken to achieve a CD4 T-cell count >500cells/µl despite long-term cART is prolonged in a subset of patients in AHOD. Starting cART early with a PI-based regimen (vs. NNRTI-based regimen) is associated with more rapid recovery of a CD4 T-cell count >500cells/µl.

DNA damage-mediated induction of a chemoresistant niche

While numerous cell-intrinsic processes are known to play decisive roles in chemotherapeutic response, relatively little is known about the impact of the tumor microenvironment on therapeutic outcome. Here, we use a well-established mouse model of Burkitt's lymphoma to show that paracrine factors in the tumor microenvironment modulate lymphoma cell survival following the administration of genotoxic chemotherapy. Specifically, IL-6 and Timp-1 are released in the thymus in response to DNA damage, creating a "chemo-resistant niche" that promotes the survival of a minimal residual tumor burden and serves as a reservoir for eventual tumor relapse. Notably, IL-6 is released acutely from thymic endothelial cells in a p38-dependent manner following genotoxic stress, and this acute secretory response precedes the gradual induction of senescence in tumor-associated stromal cells. Thus, conventional chemotherapies can induce tumor regression while simultaneously eliciting stress responses that protect subsets of tumor cells in select anatomical locations from drug action.

Transplantation of mouse HSCs genetically modified to express a CD4-restricted TCR results in long-term immunity that destroys tumors and initiates spontaneous autoimmunity

The development of effective cancer immunotherapies has been consistently hampered by several factors, including an inability to instigate long-term effective functional antitumor immunity. This is particularly true for immunotherapies that focus on the adoptive transfer of activated or genetically modified mature CD8+ T cells. In this study, we sought to alter and enhance long-term host immunity by genetically modifying, then transplanting, mouse HSCs. We first cloned a previously identified tumor-reactive HLA-DR4-restricted CD4+ TCR specific for the melanocyte differentiation antigen tyrosinase-related protein 1 (Tyrp1), then constructed both a high-expression lentivirus vector and a TCR-transgenic mouse expressing the genes encoding this TCR. Using these tools, we demonstrated that both mouse and human HSCs established durable, high-efficiency TCR gene transfer following long-term transplantation into lethally irradiated mice transgenic for HLA-DR4. Recipients of genetically modified mouse HSCs developed spontaneous autoimmune vitiligo that was associated with the presence of a Th1-polarized memory effector CD4+ T cell population that expressed the Tyrp1-specific TCR. Most importantly, large numbers of CD4+ T cells expressing the Tyrp1-specific TCR were detected in secondary HLA-DR4-transgenic transplant recipients, and these mice were able to destroy subcutaneously administered melanoma cells without the aid of vaccination, immune modulation, or cytokine administration. These results demonstrate the creation of what we believe to be a novel translational model of durable lentiviral gene transfer that results in long-term effective immunity.

Regulation of cancer germline antigen gene expression: implications for cancer immunotherapy

Cancer germline (CG; also known as cancer-testis) antigen genes are normally expressed in germ cells and trophoblast tissues and are aberrantly expressed in a variety of human malignancies. CG antigen genes have high clinical relevance as they encode a class of immunogenic and highly selective tumor antigens. CG antigen-directed immunotherapy is undergoing clinical evaluation for the treatment of a number of solid tumor malignancies and has been demonstrated to be safe, provoke immune responses and be of therapeutic benefit. Achieving an improved understanding of the mechanisms of CG antigen gene regulation will facilitate the continued development of targeted therapeutic approaches against tumors expressing these antigens. Substantial evidence suggests epigenetic mechanisms, particularly DNA methylation, as a primary regulator of CG antigen gene expression in normal and cancer cells as well as in stem cells. The roles of sequence-specific transcription factors and signal transduction pathways in controlling CG antigen gene expression are less clear but are emerging. A combinatorial therapeutic approach involving epigenetic modulatory drugs and CG antigen immunotherapy is suggested based on these data and is being actively pursued. In this article, we review the mechanisms of CG antigen gene regulation and discuss the implications of these mechanisms for the development of cancer immunotherapy approaches targeting CG antigens.

Dissemination of mycobacteria to the thymus renders newly generated T cells tolerant to the invading pathogen

The ability of the thymus to generate a population of T cells that is, for the most part, self-restricted and self-tolerant depends to a great extent on the Ags encountered during differentiation. We recently showed that mycobacteria disseminate to the thymus, which raised the questions of how mycobacteria within the thymus influence T cell differentiation and whether such an effect impacts host-pathogen interactions. Athymic nude mice were reconstituted with thymic grafts from Mycobacterium avium-infected or control noninfected donors. T cells generated from thymi of infected donors seemed generally normal, because they retained the ability to reconstitute the periphery and to respond to unspecific stimuli in vitro as well as to antigenic stimulation with third-party Ags, such as OVA, upon in vivo immunization. However, these cells were unable to mount a protective immune response against a challenge with M. avium. The observation that thymic infection interferes with T cell differentiation, generating T cells that are tolerant to pathogen-specific Ags, is of relevance to understand the immune response during chronic persistent infections. In addition, it has potential implications for the repertoire of T cells generated in patients with a mycobacterial infection recovering from severe lymphopenia, such as patients coinfected with HIV and receiving antiretroviral therapy.

Sex steroid ablation enhances hematopoietic recovery following cytotoxic antineoplastic therapy in aged mice

Cytotoxic antineoplastic therapy is widely used in the clinic as a treatment for malignant diseases. The treatment itself, however, leads to long-term depletion of the adaptive immune system, which is more pronounced in older patients, predominantly due to thymic atrophy. We and others have previously shown that withdrawal of sex steroids is able to regenerate the aged thymus and enhance recovery from autologous and allogeneic hematopoietic stem cell transplant. In this study we have examined the effects of sex steroid ablation (SSA) on the recovery of lymphopoiesis in the bone marrow (BM) and thymus following treatment with the chemotherapeutic agent cyclophosphamide (Cy) in middle-aged and old mice. Furthermore, we have also examined the impact of this regeneration on peripheral immunity. SSA enhanced the recovery of BM resident hematopoietic stem cells and lymphoid progenitors and promoted lymphopoiesis. Interestingly, Cy alone caused a profound increase in the recently described common lymphoid progenitor 2 (CLP-2) population in the BM. In the thymus, SSA caused a profound increase in cellularity as well as all intrathymic T-lineage progenitors including early T-lineage progenitors (ETPs) and non-canonical T cell progenitors such as the CLP-2. We also found that these transferred into numerical increases in the periphery with enhanced B and T cell numbers. Furthermore, these lymphocytes were found to have an enhanced functional capacity with no perturbation of the TCR repertoire. Taken together, these results provide the basis for the use of SSA in the clinic to enhance treatment outcomes from cytotoxic antineoplastic therapy.

Limited impact of the thymus on immunological recovery during and after chemotherapy in patients with diffuse large B-cell lymphoma

To investigate the impact of thymus on immunological recovery after dose-dense chemotherapy a prospective study of 17 patients diagnosed with diffuse large B-cell lymphoma (DLBCL) was conducted. Patients were monitored before, during and until 3 months after chemotherapy. The thymus was visualized using computer tomographic scans. Patients were divided into two groups according to thymic size, one group comprising of patients without detectable thymus and one group of patients with detectable thymus. Naïve CD4 and CD8 counts were measured by flow cytometry, and to measure thymic output determination of CD4+ cells containing T-cell receptor excision circles (TREC) was done. During chemotherapy, the naïve CD4 count decreased significantly as did the CD4-TREC%. Significant difference in recovery of naïve CD4 counts between patients with detectable and undetectable thymic tissue during treatment with chemotherapy was not found. CD4-TREC% was associated with lower age. It was not possible to demonstrate an association between thymic size and recovery of the naïve CD4+ cells. The study terminated 3 months after the last cycle of chemotherapy, and at that time point the naïve CD4 counts and the CD4-TREC% had not returned to pretreatment levels. However, patients with detectable thymic tissue had higher naïve CD4 counts after the first cycles of chemotherapy, suggesting that these patients may be less susceptible to infectious complications related to chemotherapy.

Strategies for reconstituting and boosting T cell-based immunity following haematopoietic stem cell transplantation: pre-clinical and clinical approaches

Poor immune recovery is characteristic of bone marrow transplantation and leads to high levels of morbidity and mortality. The primary underlying cause is a compromised thymic function, resulting from age-induced atrophy and further compounded by the damaging effects of cytoablative conditioning regimes on thymic epithelial cells (TEC). Several strategies have been proposed to enhance T cell reconstitution. Some, such as the use of single biological agents, are currently being tested in clinical trials. However, a more rational approach to immune restoration will be to leverage the evolving repertoire of new technologies. Specifically, the combined targeting of TEC, thymocytes and peripheral T cells, together with the bone marrow niches, promises a more strategic clinical therapeutic platform.

Longitudinal assessment of immunological status and rate of immune recovery following treatment in children with ALL

BACKGROUND

We prospectively evaluated the immunological status, immune recovery and risk of infection in pediatric ALL patients treated on the BFM 95 protocol.

PROCEDURE

Humoral and cellular immunity were evaluated in 72 children with ALL at the end of intensive therapy and values were compared to those at the completion of therapy and 6-monthly. Parameters investigated included lymphocyte subpopulation by flow cytometry, immunoglobulin levels by nephelometry, antibody titers to previous immunizations and delayed hypersensitivity with skin testing. Immune responses were correlated to duration of therapy, CNS radiotherapy, age and sex.

RESULTS

Humoral immunity was severely depressed by the end of intensive therapy with low immunoglobulin levels and CD19, improved after therapy cessation. Cellular immune responses were normal at the end of intensive treatment but declined significantly by the end of therapy and both CD4 and CD8 remained low at later evaluation points whereas CD4/CD8 ratio was increasing. Duration of therapy and CNS radiotherapy did not affect the rate of immune recovery whereas female had higher CD19, CD45RO, and IgM and children >7 years had higher CD19 and lower CD16 and CD3DR. Among immunized children, 86.7% maintained protective antibodies to MMR and 63% to polio. Despite impairment of immunity, infections outside the neutropenic periods were common viral illnesses.

CONCLUSION

Humoral immunity was depressed in children with ALL at the end of intensive therapy but began to recover after cessation of therapy. In contrast, cellular immunity declined significantly by the end of therapy and remained abnormal for at least 1 year post-therapy.

Common adjuvant breast cancer therapies do not inhibit cancer vaccine induced T cell immunity

Cancer vaccines may have the most potential for clinical impact when used in the adjuvant setting when tumor burden is at its lowest. Application of cancer vaccines in the adjuvant setting, however, requires integration of immunization with more standard cytotoxic or cytostatic therapies. Common adjuvant therapies for breast cancer patients, i.e. trastuzumab, bisphosphonates and hormonal agents are often administered over several years requiring concurrent administration of these drugs with active immunization. We questioned whether these common adjuvant therapies would impact a patient's ability to develop tumor specific immunity with vaccination. Immune parameters from 36 subjects were evaluated. We determined these adjuvant therapies have no impact on the ability to develop an immune response specific for HER-2/neu peptides (P>0.1) nor do they have an impact on the magnitude of T cell immunity developed with concurrent vaccination (P>0.1). This is the first report to show that the use of trastuzumab, bisphosphonates and hormonal therapy concurrent with cancer vaccine administration have no impact on either the generation or the magnitude of vaccine induced immunity.

T cell immune reconstitution following lymphodepletion

T cell reconstitution following lymphopenia from chemotherapy or stem cell transplant is often slow and incompetent, contributing to the development of infectious diseases, relapse, and graft-versus-host disease. This is due to the fact that de novo T cell production is impaired following cytoreductive regimens. T cells can be generated from two pathways: (1) thymus derived through active thymopoiesis and (2) peripherally expanded clones through homeostatic proliferation. During recovery from lymphopenia, the thymic pathway is commonly compromised in adults and T cells rely upon peripheral expansion to restore T cell numbers. This homeostatic proliferation exploits the high cytokine levels following lymphopenia to rapidly generate T cells in the periphery. Moreover, this early peripheral expansion of T cells can also be driven by exogenous antigen. This results in loss of T cell repertoire diversity and may predispose to auto- or allo-immunity. Alternatively, the high homeostatic proliferation following lymphopenia may facilitate expansion of anti-tumor immunity. Murine and human studies have provided insight into the cytokine and cellular regulators of these two pathways of T cell generation and the disparate portraits of T cell immunity created through robust thymopoiesis or peripheral expansion following lymphopenia. This insight has permitted the manipulation of the immune system to maximize anti-tumor immunity through lymphopenia and led to an appreciation of mechanisms that underlie graft versus host disease.

Immunosenescence: deficits in adaptive immunity in the elderly

Aging is associated clinically with increases in the frequency and severity of infectious diseases and an increased incidence of cancer, chronic inflammatory disorders and autoimmunity. These age-associated immune dysfunctions are the consequence of declines in both the generation of new naïve T and B lymphocytes and the functional competence of memory populations. These alterations collectively are termed immunosenescence.

Recent thymic emigrants in lymphoma patients with and without human immunodeficiency virus infection candidates for autologous peripheral stem cell transplantation

Signal joint T cell receptor excision circles (sjTRECs) have been reported as a clinical marker to measure the potential for recovery of the immune system after immunosuppressive treatments. The aim of this study was to investigate the thymic regenerative potential in 55 human immunodeficiency virus (HIV)-1 infected (HIV(+)) and non-infected (HIV(-)) lymphoma patients, candidates for autologous stem cell transplantation (ASCT). Moreover, the possible associations between sjTRECs and other immunological and clinical parameters were examined. SjTRECs levels in peripheral blood mononuclear cells (PBMCs) were quantified by real-time polymerase chain reaction and T lymphocyte subsets were analysed by flow cytometry. Our data showed that sjTRECs were reduced in lymphoma patients compared to healthy controls, although a weak significant association between low sjTRECs levels and increasing age was maintained [odds ratio (OR) = 4.00; 95% confidence interval (CI) 1.09-17.17]. We found that different chemotherapeutic treatments seem to induce similar effects on the thymic reservoir, independently from their intensity (type and number of cycles of previous chemotherapy). Results from multivariate models including adjustment for patients' sex, type of lymphoma and type of chemotherapy showed that thymic output was independent from HIV infection (OR, 0.95; 95% CI 0.20-4.48). SjTRECs levels correlated with naive T cell subsets in overall lymphoma patients and after stratification by HIV infection (r > 0.37). HIV replication should be maximally suppressed to properly evaluate thymic output by sjTREC markers. Our results suggested that de novo T cell generation is maintained partially in pretreated recurrent lymphoma patients, candidates for ASCT, and could contribute to restore the immune function after transplantation.

Increased expression of the FoxP3 functional marker of regulatory T cells following B cell depletion with rituximab in patients with lupus nephritis

B cell depletion may affect T cell activation and costimulation status in rituximab-treated patients with SLE. We examined whether rituximab administration in patients with active lupus nephritis is related to changes in mRNA expression of genes that define regulatory T cells (Tregs) in peripheral blood lymphocytes, measured by real-time PCR. At the early phase of B cell depletion mRNA levels of CD25, CTLA-4, GITR and the bona fide Treg functional marker FOXP3 increased significantly in all 7 patients examined. In contrast, mRNA levels of the costimulatory/activation T cell molecule CD40L were profoundly reduced, while mRNA levels of TGF-beta, a cytokine contributing to Treg induction, increased significantly in all. During follow-up, increased FOXP3 mRNA persisted in those patients in clinical remission, while in those patients with active disease subsequent decreases were noted. Further studies should examine whether modulation of Tregs by therapeutic B cell depletion contributes and/or predicts lupus disease remission.

Osteoclastic differentiation and function regulated by old and new pathways

The osteoclast is a specialized multinucleated variant of the macrophage family. It degrades mineralized tissue, and is required for modeling and remodeling of bone. The osteoclast has long been known to require vitamin D for its differentiation and to be regulated by parathyroid hormone via circulating Ca(2+) levels. Two local signals important in osteoclast survival and differentiation, CSF-1 and RANKL, were characterized by the mid-1990 s. A basic framework of specialized cell attachment and resorption molecules was also clear by that time, including the alpha(v)beta(3) integrin, the key adhesion molecule of the mature osteoclast, the highly expressed vacuolar-type H(+)-ATPase that drives acid secretion to dissolve mineral, and cathepsin K, the predominant acid proteinase for collagenolysis. Recently, additional detail has been added to this framework, showing that the osteoclast has more complex regulation than was previously believed. These include the findings that one component of the V-H(+)-ATPase is unique to the osteoclast, that chloride transport and probably Cl(-)/H(+) exchange are also required for mineral degradation, and that additional receptors besides RANK and Fms regulate osteoclast formation and survival. Additional receptors include estrogen receptor-alpha, TNF-family receptors other than RANK, and, at least in some cases, glycoprotein hormone receptors including the TSH-R and the FSH-R. Challenges in understanding osteoclast biology include how the signalling mechanisms function cooperatively. Recent findings suggest that there is a network of cytoplasmic adapters, including Gab-2 and BCAR1, which are modified by multiple signalling mechanisms and which serve to integrate the signalling pathways.

Combining cancer vaccines with chemotherapy

Clinical experience is now demonstrating the efficacy of combining chemotherapy and targeted therapies. Although the combination of chemotherapy and immunotherapy would at first seem to be counterproductive, supportive preclinical and clinical data have revealed that cyclophosphamide, gemcitabine and doxorubicin enhance the efficacy of vaccines when used as a form of 'pretreatment'. Possible mechanisms of action include inhibition of regulatory T cells, enhancement of antigen presentation by tumours, or some yet unknown method. As such, more preclinical and clinical trials are needed to explore the synergistic effects of chemotherapy combined with immunotherapy, particularly the proper dose and timing of chemotherapy.