The CD27- subset of peripheral blood memory CD4+ lymphocytes contains functionally differentiated T lymphocytes that develop by persistent antigenic stimulation in vivo

Placental circulating T cells: a novel, allogeneic CAR-T cell platform with preserved T-cell stemness, more favorable cytokine profile, and durable efficacy compared to adult PBMC-derived CAR-T

BACKGROUND

Chimeric antigen receptor (CAR)-T cell quality and stemness are associated with responsiveness, durability, and memory formation, which benefit clinical responses. Autologous T cell starting material across patients with cancer is variable and CAR-T expansion or potency can fail during manufacture. Thus, strategies to develop allogeneic CAR-T platforms including the identification and expansion of T cell subpopulations that correspond with CAR-T potency are an active area of investigation. Here, we compared CAR-T cells generated from healthy adult peripheral blood T cells versus placental circulating T (P-T) cells.

METHODS

CAR-T cells from healthy adult peripheral blood mononuclear cells (PBMCs) and P-T cells were generated using the same protocol. CAR-T cells were characterized in detail by a combination of multiparameter flow cytometry, functional assays, and RNA sequencing. In vivo antitumor efficacy and persistence of CAR-T cells were evaluated in a Daudi lymphoma xenograft model.

RESULTS

P-T cells possess stemness advantages compared with T cells from adult PBMCs. P-T cells are uniformly naïve prior to culture initiation, maintain longer telomeres, resist immune checkpoint upregulation, and resist further differentiation compared with PBMC T cells during CD19 CAR-T manufacture. P-T CD19 CAR-T cells are equally cytotoxic as PBMC-CD19 CAR-T cells but produce less interferon gamma in response to lymphoma. Transcriptome analysis shows P-T CD19 CAR-T cells retain a stem-like gene signature, strongly associate with naïve T cells, an early memory phenotype, and a unique CD4 T cell signature compared with PBMC-CD19 CAR-T cells, which enrich for exhaustion and stimulated memory T cell signatures. Consistent with functional data, P-T CD19 CAR-T cells exhibit attenuated inflammatory cytokine and chemokine gene signatures. In a murine in vivo model, P-T CD19 CAR-T cells eliminate lymphoma beyond 90 days. PBMC-CD19 CAR-T cells provide a non-durable benefit, which only delays disease onset.

CONCLUSION

We identified characteristics of T cell stemness enriched in P-T CD19 CAR-T which are deficient in PBMC-derived products and translate into response durability in vivo. Our findings demonstrate that placental circulating T cells are a valuable cell source for allogeneic CAR-T products. Stemness advantages inherent to P-T cells translate to in vivo persistence advantages and long-term durable activity.

Are CD45RO+ and CD45RA- genuine markers for bovine memory T cells?

Effective vaccination induces memory T cells, which protect the host against pathogen re-infections. Therefore, detection of memory T cells is essential for evaluating vaccine efficacy, which was originally dependent on cytokine induction assays. Currently, two isoforms of CD45 tyrosine phosphatase, CD45RO expression and CD45RA exclusion (CD45RO+/ CD45RA-) are used extensively for detecting memory T cells in cattle. The CD45RO+/CD45RA- markers were first established in humans around three decades ago, and were adopted in cattle soon after. However, in the last two decades, some published data in humans have challenged the initial paradigm, and required multiple markers for identifying memory T cells. On the contrary, memory T cell detection in cattle still mostly relies on CD45RO+/CD45RA- despite some controversial evidence. In this review, we summarized the current literature to examine if CD45RO+/CD45RA- are valid markers for detecting memory T cells in cattle. It seems CD45RA and CD45RO (CD45RA/RO) as markers for identifying bovine memory T cells are questionable.

Characterization of Antigen-Induced CD4+ T-Cell Senescence in Multiple Sclerosis

Antigen-induced T-cell exhaustion and T-cell senescence are peripheral regulatory mechanisms that control effector T-cell responses. Markers of exhaustion and senescence on T Cells indicate the previous activation by repetitive stimulation with specific antigens. Malignant tumors are accompanied by enhanced T-cell exhaustion and T-cell senescence resulting in immune evasion, while these control mechanisms might be diminished in autoimmune diseases including multiple sclerosis (MS). To better understand the involvement of antigen-induced T-cell senescence in controlling CD4+ T-cell-mediated autoimmune responses in MS, we have analyzed the re-expression of CD45RA and the downregulation of CD28 and CD27 molecules as markers of antigen-induced T-cell senescence in fresh cerebrospinal fluid (CSF)-infiltrating and paired circulating T cells from patients with MS. Patients with different levels of CD4+ T-cell senescence were identified and characterized regarding demographical and clinical features as well as intrathecal markers of neurodegeneration. CD4+ T-cell senescence was also analyzed in control patients to explore a putative deficit of this regulatory mechanism in MS. This study shows heterogeneity of markers of CD4+ T-cell senescence in patients with MS. Patients with high levels of CD4+ T-cell senescence in peripheral blood showed increased frequencies of CSF-infiltrating CD28+ CD27-EM CD4+ T cells with a proinflammatory Th1 functional phenotype. The correlation of these cells with the intrathecal levels of neurofilament light chain, a marker of neurodegeneration, suggests their relevance in disease pathogenesis and the involvement of T-cell senescence in their regulation. Markers of antigen-induced T-senescence, therefore, show promise as a tool to identify pathogenic CD4+ T cells in patients with MS.

High-dimensional analysis defines multicytokine T-cell subsets and supports a role for IL-21 in atopic dermatitis

BACKGROUND

Flow cytometry is a well-accepted approach for immune profiling; however, its value is restricted by the limited number of markers that can be analyzed simultaneously. Mass cytometry/CyTOF offers broad-scale immune characterization integrating large number of parameters. While partial blood phenotyping was reported in atopic dermatitis (AD), patients' comprehensive profiling, critical for leveraging new targeted treatments, is not available. IL-21 may be involved in inflammatory skin diseases but its role in AD is not well established.

METHODS

We studied T-cell polarization in the blood of 20 moderate-to-severe AD and 15 controls. Using CyTOF and an unsupervised analysis, we measured the frequencies and mean metal intensities of activated polar CD4⁺ /CD8⁺ T-cell subsets. Immunohistochemistry, immunofluorescence, and qRT-PCR were used to analyze skin samples.

RESULTS

Examining 24 surface, intracellular markers, and transcription factors, we identified six CD4⁺ and five CD8⁺ T-cell metaclusters. A CD4⁺ skin-homing IL-13⁺ monocytokine and a novel IL-13⁺ IL-21⁺ multicytokine metaclusters were increased in AD vs. controls (p < .01). While IL-13 signature characterized both clusters, levels were significantly higher in the IL-21⁺ group. Both clusters correlated with AD severity (r = 0.49, p = .029). Manual gating corroborated these results and identified additional multicytokine subsets in AD. Immunohistochemistry and immunofluorescence, validated by mRNA expression, displayed significantly increasedIL-21 counts and colocalization with IL-13/IL-4R in AD skin.

CONCLUSION

A multicytokine signature characterizes moderate-to-severe AD, possibly explaining partial therapeutic responses to one cytokine targeting, particularly in severe patients. Prominent IL-21 signature in blood and skin hints for a potential pathogenic role of IL-21 in AD.

Loss of T cells expressing CD27 at the site of active tuberculosis - A prospective diagnostic study

The lack of a rapid and reliable diagnostic test for active tuberculosis is still a burden to the control of the infection. The accumulation of Mycobacterium tuberculosis (MTB)-specific CD4⁺ T cells at the site of infection and the increase of MTB-specific CD27^- cells seem to be characteristic for active tuberculosis. We evaluated CD27 expression of non-stimulated T cells at the site of infection compared to peripheral blood of seventy-two patients (n = 72) presenting with symptoms of active MTB-infection. Twenty patients (n = 20, 27.8%) were actually confirmed to have active tuberculosis. Overall, a significant increase of terminally differentiated CD27^- CD4⁺ T cells at the site of disease was noted when compared to peripheral blood (<0.001). However, the loss of CD27 at the site of disease was not restricted to active tuberculosis (p = 0.253). The CD27 expression profile of tuberculosis patients was only discriminative to patients with malignancy.

Mixed-effects association of single cells identifies an expanded effector CD4+ T cell subset in rheumatoid arthritis

High-dimensional single-cell analyses have improved the ability to resolve complex mixtures of cells from human disease samples; however, identifying disease-associated cell types or cell states in patient samples remains challenging because of technical and interindividual variation. Here, we present mixed-effects modeling of associations of single cells (MASC), a reverse single-cell association strategy for testing whether case-control status influences the membership of single cells in any of multiple cellular subsets while accounting for technical confounders and biological variation. Applying MASC to mass cytometry analyses of CD4⁺ T cells from the blood of rheumatoid arthritis (RA) patients and controls revealed a significantly expanded population of CD4⁺ T cells, identified as CD27^- HLA-DR⁺ effector memory cells, in RA patients (odds ratio, 1.7; P = 1.1 × 10^-3). The frequency of CD27^- HLA-DR⁺ cells was similarly elevated in blood samples from a second RA patient cohort, and CD27^- HLA-DR⁺ cell frequency decreased in RA patients who responded to immunosuppressive therapy. Mass cytometry and flow cytometry analyses indicated that CD27^- HLA-DR⁺ cells were associated with RA (meta-analysis P = 2.3 × 10^-4). Compared to peripheral blood, synovial fluid and synovial tissue samples from RA patients contained about fivefold higher frequencies of CD27^- HLA-DR⁺ cells, which comprised ~10% of synovial CD4⁺ T cells. CD27^- HLA-DR⁺ cells expressed a distinctive effector memory transcriptomic program with T helper 1 (T_H1)- and cytotoxicity-associated features and produced abundant interferon-γ (IFN-γ) and granzyme A protein upon stimulation. We propose that MASC is a broadly applicable method to identify disease-associated cell populations in high-dimensional single-cell data.

Rapid diagnosis of pulmonary tuberculosis by combined molecular and immunological methods

Diagnosing pulmonary tuberculosis (TB) may be delayed until culture results become available.We ascertained the accuracy of a stepwise diagnostic algorithm for the rapid diagnosis of pulmonary TB by GeneXpert from sputum and/or bronchoalveolar lavage (BAL) followed by a Mycobacterium tuberculosis-specific BAL ELISPOT assay in patients with a suspected diagnosis of pulmonary TB at a clinical referral centre in Germany.Among 166 patients with a presumptive diagnosis of pulmonary TB, 81 cases were confirmed by M. tuberculosis culture from sputum and/or BAL. In 66 out of 81 (81.5%) cases, patients initially had M. tuberculosis detected by GeneXpert from sputum; in addition, six out of 81 (7.4%) cases were diagnosed by GeneXpert on BAL fluid (together 72 out of 81 (88.9%) patients). Out of the remaining nine patients with negative GeneXpert results from sputum and BAL, BAL ELISPOT identified eight patients with culture-confirmed TB correctly (median time to culture positivity 26 days). At a cut-off of >4000 early secretory antigenic target-6- or culture filtrate protein-10-specific interferon-γ-producing lymphocytes per 1 000 0000 lymphocytes, the specificity of the BAL ELISPOT for active TB was 97%.In low TB incidence countries, nearly all patients with active pulmonary TB can be identified within the first few days of clinical presentation using a stepwise strategy with GeneXpert and BAL ELISPOT.

Distinct predictive biomarker candidates for response to anti-CTLA-4 and anti-PD-1 immunotherapy in melanoma patients

BACKGROUND

While immune checkpoint blockade has greatly improved clinical outcomes in diseases such as melanoma, there remains a need for predictive biomarkers to determine who will likely benefit most from which therapy. To date, most biomarkers of response have been identified in the tumors themselves. Biomarkers that could be assessed from peripheral blood would be even more desirable, because of ease of access and reproducibility of sampling.

METHODS

We used mass cytometry (CyTOF) to comprehensively profile peripheral blood of melanoma patients, in order to find predictive biomarkers of response to anti-CTLA-4 or anti-PD-1 therapy. Using a panel of ~ 40 surface and intracellular markers, we performed in-depth phenotypic and functional immune profiling to identify potential predictive biomarker candidates.

RESULTS

Immune profiling of baseline peripheral blood samples using CyTOF revealed that anti-CTLA-4 and anti-PD-1 therapies have distinct sets of candidate biomarkers. The distribution of CD4⁺ and CD8⁺ memory/non-memory cells and other memory subsets was different between responders and non-responders to anti-CTLA-4 therapy. In anti-PD-1 (but not anti-CTLA-4) treated patients, we discovered differences in CD69 and MIP-1β expressing NK cells between responders and non-responders. Finally, multivariate analysis was used to develop a model for the prediction of response.

CONCLUSIONS

Our results indicate that anti-CTLA-4 and anti-PD-1 have distinct predictive biomarker candidates. CD4⁺ and CD8⁺ memory T cell subsets play an important role in response to anti-CTLA-4, and are potential biomarker candidates. For anti-PD-1 therapy, NK cell subsets (but not memory T cell subsets) correlated with clinical response to therapy. These functionally active NK cell subsets likely play a critical role in the anti-tumor response triggered by anti-PD-1.

CNS Aquaporin-4-specific B cells connect with multiple B-cell compartments in neuromyelitis optica spectrum disorder

Objectives

Neuromyelitis optica spectrum disorder (NMOSD) is a severe inflammatory disorder of the central nervous system (CNS) targeted against aquaporin‐4 (AQP4). The origin and trafficking of AQP4‐specific B cells in NMOSD remains unknown.

Methods

Peripheral (n = 7) and splenic B cells (n = 1) recovered from seven NMOSD patients were sorted into plasmablasts, naïve, memory, and CD27‐IgD‐ double negative (DN) B cells, and variable heavy chain (VH) transcriptome sequences were generated by deep sequencing. Peripheral blood (PB) VH repertoires were compared to the same patient's single‐cell cerebrospinal fluid (CSF) plasmablast (PB) VH transcriptome, CSF immunoglobulin (Ig) proteome, and serum Ig proteome. Recombinant antibodies were generated from paired CSF heavy‐ and light chains and tested for AQP4 reactivity.

Results

Approximately 9% of the CSF VH sequences aligned with PB memory B cells, DN B cells, and plasmablast VH sequences. AQP4‐specific VH sequences were observed in each peripheral B‐cell compartment. Lineage analysis of clonally related VH sequences indicates that CSF AQP4‐specific B cells are closely related to an expanded population of DN B cells that may undergo antigen‐specific B‐cell maturation within the CNS. CSF and serum Ig proteomes overlapped with the VH sequences from each B‐cell compartment; the majority of matches occurring between the PB VH sequences and serum Ig proteome.

Interpretation

During an acute NMOSD relapse, a dynamic exchange of B cells occurs between the periphery and CNS with AQP4‐specific CSF B cells emerging from postgerminal center memory B cells and plasmablasts. Expansion of the PB DN B‐cell compartment may be a potential biomarker of NMOSD activity.

HCV monoinfection and HIV/HCV coinfection enhance T-cell immune senescence in injecting drug users early during infection

Background

Injecting drug users (IDU) are at premature risk of developing multimorbidity and mortality from causes commonly observed in the elderly. Ageing of the immune system (immune-senescence) can lead to premature morbidity and mortality and can be accelerated by chronic viral infections. Here we investigated the impact of HCV monoinfection and HIV/HCV coinfection on immune parameters in (ex-) IDU. We analyzed telomere length and expression of activation, differentiation and exhaustion markers on T cells at baseline (t = 1) and at follow-up (t = 2) (median interval 16.9 years) in IDU who were: HCV mono-infected (n = 21); HIV/HCV coinfected (n = 23) or multiple exposed but uninfected (MEU) (n = 8).

Results

The median time interval between t = 1 and t = 2 was 16.9 years. Telomere length within CD4⁺ and CD8⁺ T cells decreased significantly over time in all IDU groups (p ≤ 0.012). CD4⁺ T-cell telomere length in HCV mono-infected IDU was significantly reduced compared to healthy donors at t = 1 (p < 0.008). HIV/HCV coinfected IDU had reduced CD4⁺ and CD8⁺ T-cell telomere lengths (p ≤ 0.002) to healthy donors i at t = 1. This was related to persistent levels of immune activation but not due to increased differentiation of T cells over time. Telomere length decrease was observed within all T-cell subsets, but mainly found in immature T cells (CD27⁺CD57⁺) (p ≤ 0.015).

Conclusions

HCV mono-infection and HIV/HCV coinfection enhance T-cell immune-senescence. Our data suggest that this occurred early during infection, which warrants early treatment for both HCV and HIV to reduce immune senescence in later life.

Electronic supplementary material

The online version of this article (doi:10.1186/s12979-016-0065-0) contains supplementary material, which is available to authorized users.

Clonal expansion of CD4(+) cytotoxic T lymphocytes in patients with IgG4-related disease

BACKGROUND

IgG4-related disease (IgG4-RD) is a systemic condition of unknown cause characterized by highly fibrotic lesions with dense lymphoplasmacytic infiltrates. CD4(+) T cells constitute the major inflammatory cell population in IgG4-RD lesions.

OBJECTIVE

We used an unbiased approach to characterize CD4(+) T-cell subsets in patients with IgG4-RD based on their clonal expansion and ability to infiltrate affected tissue sites.

METHODS

We used flow cytometry to identify CD4(+) effector/memory T cells in a cohort of 101 patients with IgG4-RD. These expanded cells were characterized by means of gene expression analysis and flow cytometry. Next-generation sequencing of the T-cell receptor β chain gene was performed on CD4(+)SLAMF7(+) cytotoxic T lymphocytes (CTLs) and CD4(+)GATA3(+) TH2 cells in a subset of patients to identify their clonality. Tissue infiltration by specific T cells was examined by using quantitative multicolor imaging.

RESULTS

CD4(+) effector/memory T cells with a cytolytic phenotype were expanded in patients with IgG4-RD. Next-generation sequencing revealed prominent clonal expansions of these CD4(+) CTLs but not CD4(+)GATA3(+) memory TH2 cells in patients with IgG4-RD. The dominant T cells infiltrating a range of inflamed IgG4-RD tissue sites were clonally expanded CD4(+) CTLs that expressed SLAMF7, granzyme A, IL-1β, and TGF-β1. Clinical remission induced by rituximab-mediated B-cell depletion was associated with a reduction in numbers of disease-associated CD4(+) CTLs.

CONCLUSIONS

IgG4-RD is prominently linked to clonally expanded IL-1β- and TGF-β1-secreting CD4(+) CTLs in both peripheral blood and inflammatory tissue lesions. These active, terminally differentiated, cytokine-secreting effector CD4(+) T cells are now linked to a human disease characterized by chronic inflammation and fibrosis.

A Numerically Subdominant CD8 T Cell Response to Matrix Protein of Respiratory Syncytial Virus Controls Infection with Limited Immunopathology

CD8 T cells are involved in pathogen clearance and infection-induced pathology in respiratory syncytial virus (RSV) infection. Studying bulk responses masks the contribution of individual CD8 T cell subsets to protective immunity and immunopathology. In particular, the roles of subdominant responses that are potentially beneficial to the host are rarely appreciated when the focus is on magnitude instead of quality of response. Here, by evaluating CD8 T cell responses in CB6F1 hybrid mice, in which multiple epitopes are recognized, we found that a numerically subdominant CD8 T cell response against D^bM₁₈₇ epitope of the virus matrix protein expressed high avidity TCR and enhanced signaling pathways associated with CD8 T cell effector functions. Each D^bM₁₈₇ T effector cell lysed more infected targets on a per cell basis than the numerically dominant K^dM2₈₂ T cells, and controlled virus replication more efficiently with less pulmonary inflammation and illness than the previously well-characterized K^dM2₈₂ T cell response. Our data suggest that the clinical outcome of viral infections is determined by the integrated functional properties of a variety of responding CD8 T cells, and that the highest magnitude response may not necessarily be the best in terms of benefit to the host. Understanding how to induce highly efficient and functional T cells would inform strategies for designing vaccines intended to provide T cell-mediated immunity.

CD8 T cells play a key role in RSV clearance, immunopathology and disease. Therefore, CD8 T cells can help or harm the host depending on their timing, magnitude, and function. The CD8 T cell response represents a heterogeneous population of cells with phenotypically and functionally diverse subsets, and needs to at least be studied at the level of epitope specificity to understand how to diminish the risk of immunopathology. Studying the bulk response masks distinct contributions of individual CD8 T subsets to immunity and immunopathology. Focusing on CD8 T cell response with the highest magnitude overlooks role of subdominant responses. Here, we studied response to different epitopes and revealed that a numerically subdominant CD8 T cell response against D^bM₁₈₇ epitope of the virus matrix protein controlled virus replication efficiently with limited pulmonary inflammation and illness compared to the previously well-characterized and numerically dominant K^dM2₈₂ T cell response. Our data show that selectively boosting of epitope-specific CD8 T cell responses may be more beneficial than indiscriminant boosting of all available epitopes to achieve rapid viral clearance while limiting immunopathology. This work has implications for antigen design of vaccines intended to induce T-cell-mediated immunity.

CD27-IgD- memory B cells are modulated by in vivo interleukin-6 receptor (IL-6R) blockade in rheumatoid arthritis

Introduction

Enhanced B cell activity, particularly memory B cells have gained interest in evaluating response during therapies with biologics. CD27-IgD- double-negative (DN) B cells lacking the conventional memory marker CD27 are reported to be part of the memory compartment, however, only scarce data is available for rheumatoid arthritis (RA). We therefore focused on DN B cells in RA, studied their isotypes and modulation during interleukin-6 receptor (IL-6R) inhibition by tocilizumab (TCZ).

Methods

DN B cells were phenotypically analyzed from 40 RA patients during TCZ at baseline week 12, week 24 and 1 year. A single B cell polymerase chain reaction (PCR) approach was used to study Ig receptors, V_H gene rearrangements and specific isotypes.

Results

Phenotypic analysis showed a significantly expanded population of DN B cells in RA which contain a heterogeneous mixture of IgG-, IgA- and IgM-expressing cells with a clear dominance of IgG+ cells. DN B cells carry rearranged heavy chain gene sequences with a diversified mutational pattern consistent with memory B cells. In contrast to tumor necrosis factor alpha (TNF-α) inhibition, a significant reduction in mutational frequency of BCR gene rearrangements at week 12, 24 and 1 year (P <0.0001) was observed by in vivo IL-6R inhibition. These changes were observed for all BCR isotypes IgG, IgA and IgM at week 12, 24 and 1 year (P <0.0001). IgA-RF, IgA serum level and IgA+ DN B cells decreased significantly (P <0.05) at week 12 and week 24 during TCZ. Patients with a good European League Against Rheumatism (EULAR) response to TCZ had less DN B cells at baseline as compared to moderate responders (P = 0.006). Univariate logistic regression analysis revealed that the frequency of DN B cells at baseline is inversely correlated to a subsequent good EULAR response (P = 0.024) with an odds ratio of 1.48 (95% confidence interval as 1.05 to 2.06).

Conclusions

In RA, the heterogeneous DN B cell compartment is expanded and dominated by IgG isotype. TCZ can modulate the mutational status of DN Ig isotype receptors over 1 year. Interestingly, the frequency of DN B cells in RA may serve as a baseline predictor of subsequent EULAR response to TCZ.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-015-0580-y) contains supplementary material, which is available to authorized users.

Increased frequency of a unique spleen tyrosine kinase bright memory B cell population in systemic lupus erythematosus

OBJECTIVE

Systemic lupus erythematosus (SLE) is characterized by B cell hyperactivity and autoantibody production. As spleen tyrosine kinase (Syk) is pivotal in B cell activation, these experiments aimed to examine the extent to which Syk was abnormally expressed in SLE B cells and the nature of the B cell subset that differently expressed Syk.

METHODS

B cells from healthy donors and SLE patients were analyzed by flow cytometry to assess basal expression of Syk and phosphorylated Syk. B cell subsets expressing higher levels of Syk were found, and their detailed phenotype, in vitro differentiation into plasmablasts/plasma cells, and Syk induction by cytokines were determined.

RESULTS

Syk expression was higher in CD27+ memory B cells than in naive B cells from SLE patients. However, a significantly increased frequency of CD27- B cells with bright expression of Syk (Syk++) was found in SLE patients. CD27-Syk++ B cells showed enhanced basal expression of p-Syk and stronger Syk phosphorylation upon B cell receptor (BCR) engagement as compared to CD27-Syk+ B cells. CD27-Syk++ B cells were CD38- as well as CD19++, CD20++, and mainly CD21-, with decreased ABCB1 transporter activity. In contrast to CD27-Syk+ B cells, CD27-Syk++ B cells exhibited enhanced differentiation into CD27++ IgG-secreting cells and expressed somatically mutated BCR gene rearrangements. Syk++ B cells were inducible in vitro by stimulation with interferon-γ, lipopolysaccharide, or tumor necrosis factor α.

CONCLUSION

SLE patients exhibit an increased frequency of hitherto unknown CD27-Syk++ memory-like B cells, indicating that intracellular Syk density could distinguish CD27- memory B cells from truly naive B cell subsets. Furthermore, the CD27-Syk++ subset is a candidate for a source of increased plasma cells in SLE.

Assessment of the novel T-cell activation marker-tuberculosis assay for diagnosis of active tuberculosis in children: a prospective proof-of-concept study

BACKGROUND

The diagnosis of paediatric tuberculosis is complicated by non-specific symptoms, difficult specimen collection, and the paucibacillary nature of the disease. We assessed the accuracy of a novel immunodiagnostic T-cell activation marker-tuberculosis (TAM-TB) assay in a proof-of-concept study to identify children with active tuberculosis.

METHODS

Children with symptoms that suggested tuberculosis were prospectively recruited at the NIMR-Mbeya Medical Research Center in Mbeya, and the Ifakara Health Institute in Bagamoyo, Tanzania, between May 10, 2011, and Sept 4, 2012. Sputum and peripheral blood mononuclear cells were obtained for Mycobacterium tuberculosis culture and performance assessment of the TAM-TB assay. The children were assigned to standardised clinical case classifications based on microbiological and clinical findings.

FINDINGS

Among 290 children screened, we selected a subgroup of 130 to ensure testing of at least 20 with culture-confirmed tuberculosis. 17 of 130 children were excluded because of inconclusive TAM-TB assay results. The TAM-TB assay enabled detection of 15 of 18 culture-confirmed cases (sensitivity 83·3%, 95% CI 58·6-96·4). Specificity was 96·8% (95% CI 89·0-99·6) in the cases that were classified as not tuberculosis (n=63), with little effect from latent tuberculosis infection. The TAM-TB assay identified five additional patients with highly probable or probable tuberculosis, in whom M tuberculosis was not isolated. The median time to diagnosis was 19·5 days (IQR 14-45) for culture.

INTERPRETATION

The sputum-independent TAM-TB assay is a rapid and accurate blood test that has the potential to improve the diagnosis of active tuberculosis in children.

FUNDING

European and Developing Countries Clinical Trials Partnership, German Federal Ministry of Education and Research, and Swiss National Science Foundation.

Memory T cells maintain protracted protection against malaria

Immunologic memory is one of the cardinal features of antigen-specific immune responses, and the persistence of memory cells contributes to prophylactic immunizations against infectious agents. Adequately maintained memory T and B cell pools assure a fast, effective and specific response against re-infections. However, many aspects of immunologic memory are still poorly understood, particularly immunologic memory inducible by parasites, for example, Plasmodium spp., the causative agents of malaria. For example, memory responses to Plasmodium antigens amongst residents of malaria endemic areas appear to be either inadequately developed or maintained, because persons who survive episodes of childhood malaria remain vulnerable to intermittent malaria infections. By contrast, multiple exposures of humans and laboratory rodents to radiation-attenuated Plasmodium sporozoites (γ-spz) induce sterile and long-lasting protection against experimental sporozoite challenge. Multifactorial immune mechanisms maintain this protracted and sterile protection. While the presence of memory CD4 T cell subsets has been associated with lasting protection in humans exposed to multiple bites from Anopheles mosquitoes infected with attenuated Plasmodium falciparum, memory CD8 T cells maintain protection induced with Plasmodium yoelii and Plasmodium berghei γ-spz in murine models. In this review, we discuss our observations that show memory CD8 T cells specific for antigens expressed by P. berghei liver stage parasites as an indispensable component for the maintenance of protracted protective immunity against experimental malaria infection; moreover, the provision of an Ag-depot assures a quick recall of memory T cells as IFN-γ-producing effector CD8 T cells and IL-4- producing CD4 T cells that collaborate with B cells for an effective antibody response.

Chronic exposure to Plasmodium falciparum is associated with phenotypic evidence of B and T cell exhaustion

Naturally acquired immunity to malaria develops slowly, requiring several years of repeated exposure to be effective. The cellular and molecular factors underlying this observation are only partially understood. Recent studies suggest that chronic Plasmodium falciparum exposure may induce functional exhaustion of lymphocytes, potentially impeding optimal control of infection. However, it remains unclear whether the "atypical" memory B cells (MBCs) and "exhausted" CD4 T cells described in humans exposed to endemic malaria are driven by P. falciparum per se or by other factors commonly associated with malaria, such as coinfections and malnutrition. To address this critical question we took advantage of a "natural" experiment near Kilifi, Kenya, and compared profiles of B and T cells of children living in a rural community where P. falciparum transmission is ongoing to the profiles of age-matched children living under similar conditions in a nearby community where P. falciparum transmission ceased 5 y prior to this study. We found that continuous exposure to P. falciparum drives the expansion of atypical MBCs. Persistent P. falciparum exposure was associated with an increased frequency of CD4 T cells expressing phenotypic markers of exhaustion, both programmed cell death-1 (PD-1) alone and PD-1 in combination with lymphocyte-activation gene-3 (LAG-3). This expansion of PD-1-expressing and PD-1/LAG-3-coexpressing CD4 T cells was largely confined to CD45RA(+) CD4 T cells. The percentage of CD45RA(+)CD27(+) CD4 T cells coexpressing PD-1 and LAG-3 was inversely correlated with frequencies of activated and classical MBCs. Taken together, these results suggest that P. falciparum infection per se drives the expansion of atypical MBCs and phenotypically exhausted CD4 T cells, which has been reported in other endemic areas.

CD4+ regulatory and effector/memory T cell subsets profile motor dysfunction in Parkinson's disease

Animal models and clinical studies have linked the innate and adaptive immune system to the pathology of Parkinson’s disease (PD). Despite such progress, the specific immune responses that influence disease progression have eluded investigators. Herein, we assessed relationships between T cell phenotype and function with PD progression. Peripheral blood lymphocytes from two separate cohorts, a discovery cohort and a validation cohort, totaling 113 PD patients and 96 age- and environment-matched caregivers were examined by flow cytometric analysis and T cell proliferation assays. Increased effector/memory T cells (Tem), defined as CD45RO+ and FAS+ CD4+ T cells and decreased CD31+ and α4β7+ CD4+ T cells were associated with progressive Unified Parkinson’s Disease Rating Scale III scores. However, no associations were seen between immune biomarkers and increased age or disease duration. Impaired abilities of regulatory T cells (Treg) from PD patients to suppress effector T cell function was observed. These data support the concept that chronic immune stimulation, notably Tem activation and Treg dysfunction is linked to PD pathobiology and disease severity, but not disease duration. The association of T cell phenotypes with motor symptoms provides fresh avenues for novel biomarkers and therapeutic designs.

Reduced frequency of memory T cells and increased Th17 responses in patients with active tuberculosis

Phenotypic and functional alterations in Mycobacterium tuberculosis T cell subsets have been reported in patients with active tuberculosis. A better understanding of these alterations will increase the knowledge about immunopathogenesis and also may contribute to the development of new diagnostics and prophylactic strategies. Here, the ex vivo phenotype of CD4(+) and CD8(+) T cells and the frequency and phenotype of gamma interferon (IFN-γ)- and interleukin 17 (IL-17)-producing cells elicited in short-term and long-term cultures following CFP-10 and purified protein derivative (PPD) stimulation were determined in noninfected persons (non-TBi), latently infected persons (LTBi), and patients with active tuberculosis (ATB). Phenotypic characterization of T cells was done based on the expression of CD45RO and CD27. Results show that ATB had a reduced frequency of circulating CD4(+) CD45RO(+) CD27(+) T cells and an increased frequency of CD4(+) CD45RO(-) CD27(+) T cells. ATB also had a higher frequency of circulating IL-17-producing CD4(+) T cells than did LTBi after PPD stimulation, whereas LTBi had more IFN-γ-producing CD4(+) T cells than did non-TBi. The phenotype of IFN-γ-producing cells at 24 h differs from the phenotype of IL-17-producing cells with no differences between LTBi and ATB. At 144 h, IFN-γ- and IL-17-producing cells were mainly CD45RO(+) CD27(+) T cells and they were more frequent in ATB. These results suggest that M. tuberculosis infection induces alterations in T cells which interfere with an adequate specific immune response.

Systemic BCG immunization induces persistent lung mucosal multifunctional CD4 T(EM) cells which expand following virulent mycobacterial challenge

To more closely understand the mechanisms of how BCG vaccination confers immunity would help to rationally design improved tuberculosis vaccines that are urgently required. Given the established central role of CD4 T cells in BCG induced immunity, we sought to characterise the generation of memory CD4 T cell responses to BCG vaccination and M. bovis infection in a murine challenge model. We demonstrate that a single systemic BCG vaccination induces distinct systemic and mucosal populations of T effector memory (T_EM) cells in vaccinated mice. These CD4⁺CD44^hiCD62L^loCD27⁻ T cells concomitantly produce IFN-γ and TNF-α, or IFN-γ, IL-2 and TNF-α and have a higher cytokine median fluorescence intensity MFI or ‘quality of response’ than single cytokine producing cells. These cells are maintained for long periods (>16 months) in BCG protected mice, maintaining a vaccine–specific functionality. Following virulent mycobacterial challenge, these cells underwent significant expansion in the lungs and are, therefore, strongly associated with protection against M. bovis challenge. Our data demonstrate that a persistent mucosal population of T_EM cells can be induced by parenteral immunization, a feature only previously associated with mucosal immunization routes; and that these multifunctional T_EM cells are strongly associated with protection. We propose that these cells mediate protective immunity, and that vaccines designed to increase the number of relevant antigen-specific T_EM in the lung may represent a new generation of TB vaccines.

Characteristics and PD-1 expression of peripheral CD4+CD127loCD25hiFoxP3+ Treg cells in chronic HCV infected-patients

Background

Both regulatory T cells (Tregs) and PD-1/PD-L1 pathway were critically involved in HCV viral persistence. However, the association between them was not well investigated. Herein, we aimed to investigate the distributional profiles of Tregs subsets and association between PD-1 expression on these subsets and development of HCV long-term persistence.

Methods

CD45RA and CD27 were employed to separate peripheral Tregs as naïve/central memory/effector memory/effector subsets. The phenotypic characteristics and PD-1 expression of Tregs were studied by flow cytometry.

Results

In the present study, the majority of Tregs was identified as central memory phenotype in chronic hepatitis C patients compared with nearly equal contribution of naïve and central memory subsets in healthy individuals. PD-1 expression was elevated in all CD4+ T cell subset in chronic HCV infected patients, including Tregs. Of note, higher level of PD-1 expression was found on TEM- and effector-Treg than naïve- and TCM-Tregs subsets. The ratio of TEM-Tregs/naive-Tregs and TEM-Tregs/TCM-Tregs regarding to PD-1 MFI were significantly lower in CHC patients compared to controls.

Conclusions

Our study indicated that distinctive characteristics of PD-1 expression on Tregs in HCV infection suggests associated with impaired adaptive immunity as well as viral long-term persistence. The cross talk between Treg cells and PD-1 induced inhibition in chronic HCV infection deserved further exploration for HCV infection associated immune pathogenesis.

Generation of human regulatory gammadelta T cells by TCRgammadelta stimulation in the presence of TGF-beta and their involvement in the pathogenesis of systemic lupus erythematosus

As a component of the innate immune cell population, γδ T cells are involved in tumor immunosurveillance and host defense against viral invasion. In this study, we demonstrated a novel function of human γδ T cells as regulatory cells by detecting their suppressive effect on the proliferation of autologous naive CD4(+) T cells. These regulatory γδ T cells (γδ Tregs) could be generated in vitro by stimulating with anti-TCRγδ in the presence of TGF-β and IL-2. Similar to CD4(+)Foxp3(+) Tregs, γδ Tregs also expressed Foxp3. Additionally, they primarily belonged to the Vδ1 subset with a CD27(+)CD25(high) phenotype. Furthermore, these γδ Tregs showed an immunoregulatory activity mainly through cell-to-cell contact. Importantly, this γδ regulatory population decreased in the peripheral blood of systemic lupus erythematosus patients, suggesting a potential mechanism in understanding the pathogenesis of systemic lupus erythematosus.

Lung T-cell subset composition at the time of surgical resection is a prognostic indicator in non-small cell lung cancer

NSCLC arises in the complex environment of chronic inflammation. Depending on lung immune polarization, infiltrating immune cells may either promote or suppress tumor growth. Despite the importance of the immune microenvironment, current staging techniques for NSCLC do not take into consideration the immune milieu in which the neoplasms arise. T-cell subset content was compared between paired tumor-bearing and contralateral lungs, patient and control peripheral blood. The relationship between T-cell subset distribution and survival were evaluated. CD4 and CD8+ T cells were subsetted by CD45RA/CD27 and analyzed for expression of activation, adhesion, and homing markers. Strikingly, T-cell content was indistinguishable between lungs. Compared with peripheral blood, naïve CD4 and CD8 T cells were rare in BAL. CD4+ BAL T cells showed increased CD95 (higher apoptotic potential) and CD103 expression (epithelial adhesion), but decreased CD38 (activation) and CCR7 expression (lymph node homing). CD8+ BAL T cells showed increased CD103 expression and decreased CD28 expression (co-stimulation). Differences in CD28, CD95, and CCR7 expression were more pronounced within memory cells, while differences in CD4+ CD103 expression were more prominent in effector/memory cells. Of these populations, the absence of lung CD4 T cells with an effector-like phenotype (CD45RA+/CD27-) emerged as a predictor of favorable outcome. Patients with a low proportion (≤0.44%) had 90% 5-year survival (n = 10, median survival 2,343 days), compared with 0% (n = 9, median survival 516 days) of patients with a higher proportion. Further study is required to confirm this association prospectively and define the function of this subpopulation.

Identification, frequency, activation and function of CD4+ CD25(high)FoxP3+ regulatory T cells in children with juvenile idiopathic arthritis

The aim of the study was to test the frequency of CD4+ CD25^highFoxP3 regulatory T cells in JIA patients and to assess their activation status and functional activity. The study involved 12 children with JIA and 35 healthy control subjects. PBMC were stained with monoclonal antibodies (anti-CD25, anti-CD4, anti-CD127, anti-CD69, anti-CD71, and anti-FoxP3). The samples were evaluated using flow cytometer. CD4+ CD25− and CD4+ CD25+ cells were isolated by negative and positive selection with magnetic microbeads. CD4+ CD25+ and CD4+ CD25− cells were cultured separately and co-cultured (1:1) with or without PHA. The percentage of Tregs in JIA patients was significantly decreased in comparison with controls (median, 3.2 vs. 4.6; P = 0.042). Relative fluorescence intensities of FoxP3 were higher in JIA patients than in controls (median, 9.1 vs. 6.8). The percentage of activated Tregs (CD71+) was significantly higher in JIA patients in comparison with controls (median, 6.5 vs. 2.8; P = 0.00043). CD4+ CD25+ cells derived from JIA patients and controls were anergic upon PHA stimulation, while CD4+ CD25− cells showed intensive proliferative response. The proliferation rate of CD4+ CD25− cells stimulated by PHA was decreased in co-cultures. In JIA patients, the inhibition of proliferation of CD4+ CD25− cells by CD4+ CD25+ cells was 37.9%, whereas in controls it was significantly lower (55.7%, P = 0.046). JIA patients had statistically lower percentage of Tregs in peripheral blood compared to controls. CD4+ CD25+ cells sorted from peripheral blood of JIA patients had statistically lower ability to suppress CD4+ CD25− cell proliferation in comparison with cells obtained from controls.

CD27 expression on lymphocyte and sCD27 levels in children with asthma

BACKGROUND

CD27, a lymphocyte specific member of the Tumour Necrosis Factor- Receptor (TNF-R) family is expressed on the majority of peripheral blood T cells. Activation of T cells via TCR/CD3 induces high CD27 surface expression and release of a soluble form (sCD27) of the molecule. sCD27 level increases in patients suffering from a variety of chronic inflammatory diseases. In the present study we aimed to measure both the serum sCD27 levels and CD27 expression on T cells in asthmatic patients, to evaluate the state of this molecule in allergic inflammation.

METHODS

Forty-three patients with asthma were included in to the study. CD27 molecule expression and soluble form of this molecule were analysed in atopic asthmatic (n:17) and non-atopic asthmatic (n:13) patients receiving inhaled corticosteroid treatment, in asthmatic patients whose treatment ceased at least for 6 months (n:13) and healthy control subjects (n:14).

RESULTS

There were no differences in the expression of CD27 molecule on peripheral blood lymphocyte nor in its soluble form sCD27 levels in sera between the atopic asthmatic and non-atopic asthmatic patients receiving ICS treatment, treatment free asthmatic patients and healthy control subjects.

CONCLUSIONS

Neither the soluble form of CD27 nor its expression on T cells seem to be a reliable marker of atopic or non-atopic asthmatic inflammation.

Persistence of effector memory Th1 cells is regulated by Hopx

Th1 cells are prominent in inflamed tissue, survive conventional immunosuppression, and are believed to play a pivotal role in driving chronic inflammation. Here, we identify homeobox only protein (Hopx) as a critical and selective regulator of the survival of Th1 effector/memory cells, both in vitro and in vivo. Expression of Hopx is induced by T-bet and increases upon repeated antigenic restimulation of Th1 cells. Accordingly, the expression of Hopx is low in peripheral, naïve Th cells, but highly up-regulated in terminally differentiated effector/memory Th1 cells of healthy human donors. In murine Th1 cells, Hopx regulates the expression of genes involved in regulation of apoptosis and survival and makes them refractory to Fas-induced apoptosis. In vivo, adoptively transferred Hopx-deficient murine Th1 cells do not persist. Consequently, they cannot induce chronic inflammation in murine models of transfer-induced colitis and arthritis, demonstrating a key role of Hopx for Th1-mediated immunopathology.

Role of CD4+ cytotoxic T lymphocytes in the control of viral diseases and cancer

Our knowledge on the physiological role of CD4(+) T lymphocytes has improved in the last decade: available data convincingly demonstrate that, besides the 'helper' activity, CD4(+) T cells may be also endowed with lytic properties. The cytotoxic function of these effector cells has a relevant role in the control of pathogenic infections and in mediating antitumor immune responses. On these bases, several immunotherapeutic approaches exploiting the cytotoxic properties of CD4(+) T cells are under investigation. This review summarizes available data supporting the functional and therapeutic relevance of cytotoxic CD4(+) T cells, with a particular focus on Epstein-Barr virus (EBV)-related disorders.

Analyses of T cell phenotype and function reveal an altered T cell homeostasis in systemic sclerosis. Correlations with disease severity and phenotypes

We investigated in systemic sclerosis (SSc) patients the T cell homeostasis and its relationship with the clinical course of the disease. Distribution of peripheral T cell subsets, thymic output, lymphocyte proliferation and apoptosis were analyzed by flow cytometry or ELISA. Age inappropriate levels of naive CD4(+) T cells and thymic output were observed. Proliferation of CD4(+) T cells, lymphocyte apoptosis and CD4(+) regulatory T (Treg) cell frequency were significantly higher than those observed in controls and significantly correlated with clinical phenotypes and clinical progression parameters i.e., diffusing capacity of the lung for carbon monoxide (DLCO) and disease activity. These data indicate that the evaluation of the T cell homeostasis can represent a valuable prognostic tool for SSc patients and it is useful to distinguish between limited and diffuse phenotypes. A therapeutic intervention targeted at reversing T cell homeostasis abnormalities would therefore potentially be helpful in counteracting disease progression.

Perforin level in CD4+ T cells from patients with systemic lupus erythematosus

CD4(+) T cells from patients with systemic lupus erythematosus (SLE) exhibit increased expression of various proteins contributing to defective function of CD4(+) T cells. We evaluated the transcript and protein levels of perforin (PRF1) in CD4(+) T cells from SLE patients (n = 41) and healthy individuals (n = 34). The CD4(+) T cells were obtained by a positive biomagnetic separation system. The amounts of mRNA were determined by reverse transcription and real-time quantitative PCR. The protein levels in the CD4(+) T cells were evaluated by Western blotting analysis. We observed significantly higher levels of PRF1 protein (p = 0.013) in SLE CD4(+) T cells than in controls. There was no significant increase in PRF1 transcript levels (p = 0.908) in CD4(+) T cells from SLE patients as compared to healthy individuals. Moreover, we did not observe a correlation between PRF1 transcript and protein levels in SLE CD4(+) T cells and disease activity expressed by the SLEDAI scale. We confirmed previous observations that demonstrated higher levels of PRF1 protein in CD4(+) T cells from SLE patients. However, we did not find a correlation between PRF1 transcripts and proteins in CD4(+) T cells and SLE disease activity.

Autoregulation of Th1-mediated inflammation by twist1

The basic helix-loop-helix transcriptional repressor twist1, as an antagonist of nuclear factor κB (NF-κB)–dependent cytokine expression, is involved in the regulation of inflammation-induced immunopathology. We show that twist1 is expressed by activated T helper (Th) 1 effector memory (EM) cells. Induction of twist1 in Th cells depended on NF-κB, nuclear factor of activated T cells (NFAT), and interleukin (IL)-12 signaling via signal transducer and activator of transcription (STAT) 4. Expression of twist1 was transient after T cell receptor engagement, and increased upon repeated stimulation of Th1 cells. Imprinting for enhanced twist1 expression was characteristic of repeatedly restimulated EM Th cells, and thus of the pathogenic memory Th cells characteristic of chronic inflammation. Th lymphocytes from the inflamed joint or gut tissue of patients with rheumatic diseases, Crohn's disease or ulcerative colitis expressed high levels of twist1. Expression of twist1 in Th1 lymphocytes limited the expression of the cytokines interferon-γ, IL-2, and tumor necrosis factor-α, and ameliorated Th1-mediated immunopathology in delayed-type hypersensitivity and antigen-induced arthritis.

Differential regulation of human IL-7 receptor alpha expression by IL-7 and TCR signaling

IL-7Ralpha is essential for the development and homeostatic maintenance of mature T cells. Studies in humans and mice have shown that IL-7Ralpha expression is reduced by its cognate cytokine, IL-7, and Ag, suggesting that active regulation of IL-7 responsiveness is necessary to balance T cell numbers. We show that IL-7- or TCR/CD28-mediated signaling induced a rapid down-regulation of IL-7Ralpha expression on naive T cells on the mRNA and protein level, with a mild (10-fold) or strong (50-fold) gene suppression, respectively. In both situations, the down-regulation of IL-7Ralpha was blocked by cyclohexamide and actinomycin D, indicating the involvement of an active mechanism dependent on new transcription and protein synthesis. Upon IL-7 withdrawal, IL-7Ralpha mRNA and surface protein reappeared in a transcription-dependent manner within 7 h. Yet, IL-7Ralpha was hardly re-expressed during the same period after TCR/CD28-activation. Likewise, T cells that were activated through CMV in vivo did not re-express IL-7Ralpha after in vitro culture. Functionally, IL-7-induced down-regulation of IL-7Ralpha did not hinder the responsiveness of naive T cells to IL-7. Conversely, down-regulation of IL-7Ralpha on TCR/CD28-activated cells limited IL-7 responsiveness. Strikingly, ectopic expression of IL-7Ralpha cells on TCR/CD28-activated cells conferred a selective advantage in the response to IL-7. In conclusion, our data show that IL-7- and TCR/CD28-mediated signaling differentially regulate IL-7Ralpha expression on human T cells with a transient and chronic effect, respectively. The stringent and active regulation of IL-7Ralpha may constitute a homeostatic mechanism to curtail unwarranted T cell expansion.

Cytotoxic human CD4(+) T cells

The induction of adaptive immune responses critically depends on helper signals provided by CD4(+) T cells. These signals not only license antigen presenting cells (APC) to activate naïve CD8(+) T cells leading to the formation of vast numbers of cytotoxic T lymphocytes but also support the differentiation of B cells into immunoglobulin-secreting plasma cells. Next to these helper functions, a subpopulation of CD4(+) T cells can also directly function as effector cells by executing cytotoxicity in a peptide-specific and MHC class II-restricted manner. Cytotoxic CD4(+) T cells may function in combating pathogens but additionally their presence has been associated with autoimmune disease and vascular damage. On the contrary, the induction of cytotoxic CD4(+) T cells may be a future target for vaccine strategies.

Altered homeostasis of CD4(+) memory T cells in allogeneic hematopoietic stem cell transplant recipients: chronic graft-versus-host disease enhances T cell differentiation and exhausts central memory T cell pool

An increased risk of late infection is a serious complication after allogeneic hematopoietic stem cell transplantation (AHSCT), especially for recipients with defective CD4(+) T cell recovery. Although chronic graft-versus-host disease (cGVHD) negatively influences CD4(+) T cell reconstitution, the mechanisms leading to this defect are not well understood. We found that the proportion of CD27(-) CD4(+) T cells was remarkably increased in ASHCT recipients with cGVHD or with repetitive infectious episodes. Isolated CD27(-) CD4(+) T cells from ASHCT recipients had significantly shortened telomere length, displayed enhanced vulnerability to activation-induced cell death, and showed extremely reduced clonal diversity, when compared with CD27(-) CD4(+) T cells from healthy donors. Also, CD27(+) CD4(+) T cells from AHSCT recipients easily lost their expression of CD27 in response to antigen stimulation regardless of cGVHD status. Taken together, these data indicate that homeostasis of memory CD4(+) T cells from AHSCT recipients is altered, and that they easily transit into CD27(-) effector memory T cells. Increased in vivo T cell stimulation observed in recipients with cGVHD further promotes the transition to effector memory cells, a change that decreases the central memory CD4(+) T cell pool and consequently weakens the recipient's defense against persistently infecting pathogens.

Shift of CMV-specific CD4+ T-cells to the highly differentiated CD45RO-CD27- phenotype parallels loss of proliferative capacity and precedes progression to HIV-related CMV end-organ disease

To identify factors related to progression to CMV end-organ disease, cytokine production, proliferative capacity and phenotype of CMV-specific CD4(+) T-cells were analysed longitudinally. Numbers of IFNgamma(+)CD4(+) and IFNgamma(+)IL-2(+)CD4(+) T-cells tended to decrease in individuals progressing to AIDS with CMV end-organ disease (AIDS-CMV), whereas they remained detectable in long-term asymptomatics (LTAs) and progressors to AIDS with opportunistic infections (AIDS-OI). In parallel, CMV-specific proliferative capacity was lost in AIDS-CMV. Initially, the majority of the CMV-specific IFNgamma(+)CD4(+) T-cells were of the CD45RO(+)CD27(-) subset, but during progression to AIDS-CMV a shift in phenotype to the CD45RO(-)CD27(-) subset was observed. Our data indicate that a decrease in CMV-specific cytokine production and proliferative capacity precedes progression to AIDS-CMV. Accumulation of CD4(+) T-cells with a CD45RO(-)CD27(-) phenotype suggests that persistent antigen exposure drives differentiation of CMV-specific CD4(+) T-cells towards a poorly proliferating, and highly differentiated "effector" subset, which eventually fails to produce IFNgamma in patients developing AIDS-CMV.

Propensity to excessive proinflammatory response in chronic Lyme borreliosis

The clinical course of Lyme borreliosis is extremely variable. However, all the clinical manifestations, acute or chronic, are characterized by strong inflammation. Borrelia burgdorferi can induce the production of several proinflammatory and anti-inflammatory cytokines. The aim of our study was to find out whether the balance between inflammatory and regulatory mechanisms is important in determining the course of Lyme borreliosis. 13 patients with early Lyme borreliosis, 8 patients with chronic Lyme disease with neurological or joint manifestations, and 15 age- and sex-matched healthy controls were studied. Chronic forms of Lyme borreliosis were characterized by stronger TNF-alpha response by monocytes to lipopolysaccharide as well as to borrelia antigen compared to early Lyme borreliosis and the healthy state. The percentage of IL-10-secreting monocytes in response to borrelia lysate was lower in the Lyme borreliosis patients than in healthy controls. The percentage of CD4(+) CTLA-4(+) regulatory T cells showed the highest values in early Lyme borreliosis. We conclude that chronic forms of Lyme borreliosis can evolve due to an aberrant innate proinflammatory response.

CD27low CD4 T lymphocytes that accumulate in the mouse lungs during mycobacterial infection differentiate from CD27high precursors in situ, produce IFN-gamma, and protect the host against tuberculosis infection

The generation of effector, IFN-gamma producing T lymphocytes and their accumulation at sites of infection are critical for host protection against various infectious diseases. The activation and differentiation of naive T lymphocytes into effector memory cells starts in lymphoid tissues, but it is not clear whether the Ag-experienced cells that leave lymph nodes (LN) are mature or if they undergo further changes in the periphery. We have previously shown that CD44(high)CD62L(low) effector CD4 T lymphocytes generated during the course of mycobacterial infection can be segregated into two subsets on the basis of CD27 receptor expression. Only the CD27(low) subset exhibited a high capacity for IFN-gamma secretion, indicating that low CD27 expression is characteristic of fully differentiated effector CD4 T lymphocytes. We demonstrate now that CD27(low) IFN-gamma-producing CD4 T lymphocytes accumulate in the lungs but are rare in LNs. Several factors contribute to their preferential accumulation. First, CD27(low) CD4 T lymphocytes present in the LN are highly susceptible to apoptosis. Second, circulating CD27(low) CD4 T cells do not enter the LN but efficiently migrate to the lungs. Third, CD27(high) effector CD4 T cells that enter the lungs down-regulate CD27 expression in situ. In genetically heterogeneous mice that exhibit varying susceptibility to tuberculosis, the accumulation of mature CD27(low) CD4 T cells in the lungs correlates with the degree of protection against infection. Thus, we propose that terminal maturation of effector CD4 T lymphocytes in the periphery provides the host with efficient local defense and avoids potentially harmful actions of inflammatory cytokines in lymphoid organs.

Tetramer visualization of gut-homing gluten-specific T cells in the peripheral blood of celiac disease patients

Tetramers of MHC-peptide complexes are used for detection and characterization of antigen-specific T cell responses, but they require knowledge about both antigenic peptide and the MHC restriction element. The successful application of these reagents in human diseases involving CD4+ T cells is limited. Celiac disease, an intestinal inflammation driven by mucosal CD4+ T cells recognizing wheat gluten peptides in the context of disease-associated HLA-DQ molecules, is an ideal model to test the potential clinical use of these reagents. We investigated whether gluten-specific T cells can be detected in the peripheral blood of celiac disease patients using DQ2 tetramers. Nine DQ2+ patients and six control individuals on a gluten-free diet were recruited to the study. Participants consumed 160 g of gluten-containing bread daily for 3 days. After bread-challenge, gluten-specific T cells were detectable in the peripheral blood of celiac patients but not controls both directly by tetramer staining and indirectly by enzyme-linked immunospot. These T cells expressed the beta(7) integrin indicative of gut-homing properties. Most of the cells had a memory phenotype, but many other phenotypic markers showed a heterogeneous pattern. Tetramer staining of gluten-specific T cells has the potential to be used for diagnosis of celiac disease.

'Normal counterparts' of nodal peripheral T-cell lymphoma

Peripheral T-cell lymphomas (PTCL) have been difficult to classify. A homogeneous principle of classification is still lacking, partly because lymph node compartments containing functionally distinct T-cell subsets have not been identified. A correlation to differentiated T-cell subsets, as CD4(+) or CD8(+) cells as well as cytotoxic populations has not revealed clinically meaningful entities. Upon antigen encounter, mature T-cells pass through distinct stages characterized by their surface molecule expression. Naïve T-cells are CD45RA(+)/CD45R0(-)/CD27(+)/CCR7(+), however, after antigen contact CD45RA expression is replaced by CD45R0. They differentiate to central memory cells, which retain CD27 and CCR7, or to effector-memory cells, which loose expression of both molecules depending on the strength of the antigen interaction. Immunohistological analysis of PTCL showed an effector or effector-memory cell phenotype (CD45RA(-)/CD45R0(+)/CD27(-)) for both angioimmunoblastic T-cell lymphoma (AILT) and anaplastic large cell lymphoma (ALCL), but different cytotoxic and activation markers expressed by these tumours. A subset of CD4(+) PTCL-not otherwise specified (PTCL-NOS) may correspond to a central memory cell phenotype (CD45RA(-)/CD45R0(+)/CD27(+)). Thus, a correlation of PTCL to stages of differentiation, rather than to the direction of differentiation, may reveal homogeneous categories. A comparison between the lymphomas and their normal counterparts may contribute to the understanding of the underlying transformation mechanisms.

CCR8 expression identifies CD4 memory T cells enriched for FOXP3+ regulatory and Th2 effector lymphocytes

CD4+ Th2 cells are important regulators of allergic inflammation. CCR8 is thought to play a role in Th2-mediated responses, however, expression of CCR8 in peripheral blood has not been fully characterized. Using a fluorescent form of the ligand selective for CCR8 (F-CCL1), we identified the leukocytes expressing CCR8 in human, monkey, and mouse peripheral blood. CCR8 expression is primarily restricted to a subset of human CD4 memory T lymphocytes (15%). Approximately 40% of CCR8+CD4+ T cells express Th2 cytokines IL-4 or IL-13 while 13% express the Th1 cytokine IFN-gamma. In fact, 50% of all Th2, but only 5% of Th1, cells express CCR8. Upon anti-CD3/anti-CD28 mAb-mediated activation, CCR8+CD4+ T cells secrete 3- to 7-fold higher levels of IL-4, IL-5, IL-9, and IL-13 and 10- to 20-fold lower levels of IFN-gamma or IL-17, compared with CCR8-CD4+ memory T cells. Two-thirds of CCR8+CD4 T cells express cutaneous lymphocyte-associated Ag while the majority lack gut-homing receptors. CCR8+CD4+ cells express CCR7 and CD62L and are present in spleen and lymph nodes of mice. Approximately 25% of CCR8+CD4 T cells express CD25high while 20% of CCR8+CD4+ express the T regulatory cell transcription factor FOXP3 accounting for 60% of all FOXP3-expressing CD4+ T cells. In conclusion, CCR8 marks a diverse subset of CD4 memory T cells enriched for T regulatory and Th2 cells which have the potential for recruitment into sites of allergic inflammation where they could participate in the induction and regulation of the allergic response.

Nodal peripheral T-cell lymphomas correspond to distinct mature T-cell populations

Peripheral T-cell lymphomas (PTCL) have not been successfully correlated with specific developmental stages of reactive T-cells. Mature T-cells pass through distinct stages upon antigen encounter. Naïve T-cells are CD45RA(+)/CD45R0(-)/CD27(+)/CCR7(+). After antigen contact they replace CD45RA expression with CD45R0. The mature T-cells differentiate to central memory cells, which retain CD27 and CCR7, or to effector memory cells, which lose expression of both molecules depending on the strength of the antigen interaction. In this study, we evaluated lymph node biopsies from eight PTCL-not otherwise specified (PTCL-NOS), seven angioimmunoblastic T-cell lymphomas (AILT), and 15 anaplastic large cell lymphomas (ALCL). Detection of tumour cells with antibodies that recognize specific rearranged T-cell receptor Vbeta segments allowed us to investigate the expression of various differentiation-associated molecules. Results were analysed by hierarchical cluster analysis. All AILT and ALCL showed a homogeneous effector cell phenotype (CD45RA(-)/CD45R0(+)/CD27(-)), but differed in the cytotoxic and activation markers expressed. Several (5/8) PTCL-NOS clustered together; these cases all exhibited a CD4(+) central memory cell phenotype (CD45RA(-)/CD45R0(+)/CD27(+)) and four expressed the lymph node homing receptor CCR7. In conclusion, AILT and ALCL tumour cells correspond to different subsets of effector cells, while a subset of PTCL-NOS correlates with a non-effector T-cell population.

Selective accumulation of differentiated CD8+ T cells specific for respiratory viruses in the human lung

The lungs are frequently challenged by viruses, and resident CD8⁺ T cells likely contribute to the surveillance of these pathogens. To obtain insight into local T cell immunity to respiratory viruses in humans, we determined the specificity, phenotype, and function of lung-residing CD8⁺ T cells and peripheral blood CD8⁺ T cells in a paired analysis. The lung contained markedly higher frequencies of influenza (FLU)-specific and respiratory syncytial virus (RSV)-specific CD8⁺ T cells when compared with the circulation. This contrasted with an equal distribution of cytomegalovirus- and Epstein-Bar virus–specific CD8⁺ T cells. Noticeably, a substantial fraction of the lung-residing FLU- and RSV-specific CD8⁺ T cells had progressed to a relatively late differentiation phenotype, reflected by low expression of CD28 and CD27. Lung-derived FLU-specific CD8⁺ T cells had low activation requirements, as expansion of these cells could be initiated by cognate peptide in the absence of helper cell–derived signals. Thus, the human lung contains high numbers of differentiated FLU- and RSV-specific memory CD8⁺ T cells that can readily expand upon reexposure to virus. Resident lung T cells may provide immediate immunological protection against pulmonary virus infections.

Abnormal differentiation of memory T cells in systemic lupus erythematosus

OBJECTIVE

The chemokine receptor CCR7 and the tumor necrosis factor receptor family member CD27 define 3 distinct, progressively more differentiated maturational stages of CD4 memory subpopulations in healthy individuals: the CCR7+, CD27+, the CCR7-, CD27+, and the CCR7-, CD27- populations. The goal of this study was to examine maturational disturbances in CD4 T cell differentiation in systemic lupus erythematosus (SLE), using these phenotypic markers.

METHODS

Phenotypic analysis by flow cytometry, in vitro stimulation experiments, telomere length measurement, and determination of inducible telomerase were carried out. RESULTS. In SLE patients, significant increases of CCR7-, CD27- and CCR7-, CD27+ and a reduction of CCR7+, CD27+ CD4 memory T cells were found. In vitro stimulation of SLE T cells showed a stepwise differentiation from naive to CCR7+, CD27+ to CCR7-, CD27+ to CCR7-, CD27-; telomere length and inducible telomerase decreased in these subsets in the same progressive sequence. The in vitro proliferative response of these populations progressively declined as their susceptibility to apoptosis increased. Interestingly, a significant reduction in inducible telomerase was noted in SLE naive and CCR7+, CD27+ CD4+ memory T cells. Additionally, SLE CCR7-, CD27+ and CCR7-, CD27- CD4 memory T cells proliferated poorly in response to in vitro stimulation and underwent significantly more apoptosis than their normal counterparts. Finally, expression of CXCR4 was significantly reduced in all SLE subsets compared with normal.

CONCLUSION

Together these data indicate an increased degree of in vivo T cell stimulation in SLE, resulting in the accumulation of terminally differentiated memory T cells with a decreased proliferative capacity and an increased tendency to undergo apoptosis upon stimulation.

IL-2 administration increases CD4+ CD25(hi) Foxp3+ regulatory T cells in cancer patients

Interleukin-2 (IL-2) is historically known as a T-cell growth factor. Accumulating evidence from knockout mice suggests that IL-2 is crucial for the homeostasis and function of CD4+ CD25+ regulatory T cells in vivo. However, the impact of administered IL-2 in an immune intact host has not been studied in rodents or humans. Here, we studied the impact of IL-2 administration on the frequency and function of human CD4+ CD25(hi) T cells in immune intact patients with melanoma or renal cancer. We found that the frequency of CD4+ CD25(hi) T cells was significantly increased after IL-2 treatment, and these cells expressed phenotypic markers associated with regulatory T cells. In addition, both transcript and protein levels of Foxp3, a transcription factor exclusively expressed on regulatory T cells, were consistently increased in CD4 T cells following IL-2 treatment. Functional analysis of the increased number of CD4+ CD25(hi) T cells revealed that this population exhibited potent suppressive activity in vitro. Collectively, our results demonstrate that administration of high-dose IL-2 increased the frequency of circulating CD4+ CD25(hi) Foxp3+ regulatory T cells. Our findings suggest that selective inhibition of IL-2-mediated enhancement of regulatory T cells may improve the therapeutic effectiveness of IL-2 administration.

Stepwise Differentiation of CD4 Memory T Cells Defined by Expression of CCR7 and CD27

To study the steps in the differentiation of human memory CD4 T cells, we characterized the functional and lineage relationships of three distinct memory CD4 subpopulations distinguished by their expression of the cysteine chemokine receptor CCR7 and the TNFR family member CD27. Using the combination of these phenotypic markers, three populations were defined: the CCR7+CD27+, the CCR7-CD27+, and the CCR7-CD27- population. In vitro stimulation led to a stepwise differentiation from naive to CCR7+CD27+ to CCR7-CD27+ to CCR7-CD27-. Telomere length in these subsets differed significantly (CCR7+CD27+ > CCR7-CD27+ > CCR7-CD27-), suggesting that these subsets constituted a differentiative pathway with progressive telomere shortening reflecting antecedent in vivo proliferation. The in vitro proliferative response of these populations declined, and their susceptibility to apoptosis increased progressively along this differentiation pathway. Cytokine secretion showed a differential functional capacity of these subsets. High production of IL-10 was only observed in CCR7+CD27+, whereas IFN-gamma was produced by CCR7-CD27+ and to a slightly lesser extent by CCR7-CD27- T cells. IL-4 secretion was predominantly conducted by CCR7-CD27- memory CD4 T cells. Thus, by using both CCR7 and CD27, distinct maturational stages of CD4 memory T cells with different functional activities were defined.

Properties of murine CD8+CD27- T cells

In humans, loss of CD27 expression is associated with the stable acquisition of effector functions by CD8+ T cells. We found that murine (CD8+)CD27- T cells were confined to the primed CD62L(dull/-)CD44(bright)CCR7- T cell population. (CD8+)CD27- T cells were absent from lymph nodes but could be found in blood, spleen and in non-lymphoid organs such as lung and liver. Late after primary influenza virus infection, low percentages of antigen-specific CD27- cells emerged in the lung and spleen. After recovery from secondary influenza virus infection, high percentages of influenza-specific CD27- T cells were found in the lung and the loss of CD27 on lung CD8+ T cells coincided with high granzyme B expression. After murine cytomegalovirus infection, loss of CD27 expression on virus-specific CD8+ T cell populations was sustained and especially marked in liver and lung. We suggest that in mice, CD27 is lost from CD8+ T cells only after repetitive antigenic stimulation. Moreover, the high expression of both granzyme B and perforin in the CD27- T cells suggests that the lack of CD27 on murine CD8+ T cells can be used to identify memory T cells with expression of cytotoxic effector molecules.

Coexpression of CD25 and CD27 identifies FoxP3+ regulatory T cells in inflamed synovia

A better understanding of the role of CD4⁺CD25⁺ regulatory T cells in disease pathogenesis should follow from the discovery of reliable markers capable of discriminating regulatory from activated T cells. We report that the CD4⁺CD25⁺ population in synovial fluid of juvenile idiopathic arthritis (JIA) patients comprises both regulatory and effector T cells that can be distinguished by expression of CD27. CD4⁺CD25⁺CD27⁺ cells expressed high amounts of FoxP3 (43% of them being FoxP3⁺), did not produce interleukin (IL)-2, interferon-γ, or tumor necrosis factor, and suppressed T cell proliferation in vitro, being, on a per cell basis, fourfold more potent than the corresponding peripheral blood population. In contrast, CD4⁺CD25⁺CD27⁻ cells expressed low amounts of FoxP3, produced effector cytokines and did not suppress T cell proliferation. After in vitro activation and expansion, regulatory but not conventional T cells maintained high expression of CD27. IL-7 and IL-15 were found to be present in synovial fluid of JIA patients and, when added in vitro, abrogated the suppressive activity of regulatory T cells. Together, these results demonstrate that, when used in conjunction with CD25, CD27 is a useful marker to distinguish regulatory from effector T cells in inflamed tissues and suggest that at these sites IL-7 and IL-15 may interfere with regulatory T cell function.