CD4+ CD7- T cells: a separate subpopulation of memory T cells?

Genomic Regions Associated with Resistance to Gastrointestinal Nematode Parasites in Sheep-A Review

Gastrointestinal nematodes (GINs) can be a major constraint and global challenge to the sheep industry. These nematodes infect the small intestine and abomasum of grazing sheep, causing symptoms such as weight loss, diarrhea, hypoproteinemia, and anemia, which can lead to death. The use of anthelmintics to treat infected animals has led to GIN resistance, and excessive use of these drugs has resulted in residue traced in food and the environment. Resistance to GINs can be measured using multiple traits, including fecal egg count (FEC), Faffa Malan Chart scores, hematocrit, packed cell volume, eosinophilia, immunoglobulin (Ig), and dagginess scores. Genetic variation among animals exists, and understanding these differences can help identify genomic regions associated with resistance to GINs in sheep. Genes playing important roles in the immune system were identified in several studies in this review, such as the CFI and MUC15 genes. Results from several studies showed overlapping quantitative trait loci (QTLs) associated with multiple traits measuring resistance to GINs, mainly FEC. The discovery of genomic regions, positional candidate genes, and QTLs associated with resistance to GINs can help increase and accelerate genetic gains in sheep breeding programs and reveal the genetic basis and biological mechanisms underlying this trait.

Feasibility and preclinical efficacy of CD7-unedited CD7 CAR T cells for T cell malignancies

Chimeric antigen receptor (CAR)-mediated targeting of T lineage antigens for the therapy of blood malignancies is frequently complicated by self-targeting of CAR T cells or their excessive differentiation driven by constant CAR signaling. Expression of CARs targeting CD7, a pan-T cell antigen highly expressed in T cell malignancies and some myeloid leukemias, produces robust fratricide and often requires additional mitigation strategies, such as CD7 gene editing. In this study, we show fratricide of CD7 CAR T cells can be fully prevented using ibrutinib and dasatinib, the pharmacologic inhibitors of key CAR/CD3ζ signaling kinases. Supplementation with ibrutinib and dasatinib rescued the ex vivo expansion of unedited CD7 CAR T cells and allowed regaining full CAR-mediated cytotoxicity in vitro and in vivo on withdrawal of the inhibitors. The unedited CD7 CAR T cells persisted long term and mediated sustained anti-leukemic activity in two mouse xenograft models of human T cell acute lymphoblastic leukemia (T-ALL) by self-selecting for CD7-, fratricide-resistant CD7 CAR T cells that were transcriptionally similar to control CD7-edited CD7 CAR T cells. Finally, we showed feasibility of cGMP manufacturing of unedited autologous CD7 CAR T cells for patients with CD7+ malignancies and initiated a phase I clinical trial (ClinicalTrials.gov: NCT03690011) using this approach. These results indicate pharmacologic inhibition of CAR signaling enables generating functional CD7 CAR T cells without additional engineering.

Engineering naturally occurring CD7- T cells for the immunotherapy of hematological malignancies

Chimeric antigen receptor (CAR) T-cell therapy targeting T-cell acute lymphoblastic leukemia (T-ALL) faces limitations such as antigen selection and limited T-cell persistence. CD7 is an attractive antigen for targeting T-ALL, but overlapping expression on healthy T cells leads to fratricide of CD7-CAR T cells, requiring additional genetic modification. We took advantage of naturally occurring CD7- T cells to generate CD7-CAR (CD7-CARCD7-) T cells. CD7-CARCD7- T cells exhibited a predominantly CD4+ memory phenotype and had significant antitumor activity upon chronic antigen exposure in vitro and in xenograft mouse models. Based on these encouraging results, we next explored the utility of CD7- T cells for the immunotherapy of CD19+ hematological malignancies. Direct comparison of nonselected (bulk) CD19-CAR and CD19-CARCD7- T cells revealed that CD19-CARCD7- T cells had enhanced antitumor activity compared with their bulk counterparts in vitro and in vivo. Lastly, to gain insight into the behavior of CD19-CAR T cells with low levels of CD7 gene expression (CD7lo) in humans, we mined single-cell gene and T-cell receptor (TCR) expression data sets from our institutional CD19-CAR T-cell clinical study. CD19-CARCD7lo T cells were present in the initial CD19-CAR T-cell product and could be detected postinfusion. Intriguingly, the only functional CD4+ CD19-CAR T-cell cluster observed postinfusion exhibited CD7lo expression. Additionally, samples from patients responsive to therapy had a higher proportion of CD7lo T cells than nonresponders (NCT03573700). Thus, CARCD7- T cells have favorable biological characteristics and may present a promising T-cell subset for adoptive cell therapy of T-ALL and other hematological malignancies.

Synthesis of an Anti-CD7 Recombinant Immunotoxin Based on PE24 in CHO and E. coli Cell-Free Systems

Recombinant immunotoxins (RITs) are an effective class of agents for targeted therapy in cancer treatment. In this article, we demonstrate the straight-forward production and testing of an anti-CD7 RIT based on PE24 in a prokaryotic and a eukaryotic cell-free system. The prokaryotic cell-free system was derived from Escherichia coli BL21 StarTM (DE3) cells transformed with a plasmid encoding the chaperones groEL/groES. The eukaryotic cell-free system was prepared from Chinese hamster ovary (CHO) cells that leave intact endoplasmic reticulum-derived microsomes in the cell-free reaction mix from which the RIT was extracted. The investigated RIT was built by fusing an anti-CD7 single-chain variable fragment (scFv) with the toxin domain PE24, a shortened variant of Pseudomonas Exotoxin A. The RIT was produced in both cell-free systems and tested for antigen binding against CD7 and cell killing on CD7-positive Jurkat, HSB-2, and ALL-SIL cells. CD7-positive cells were effectively killed by the anti-CD7 scFv-PE24 RIT with an IC50 value of 15 pM to 40 pM for CHO and 42 pM to 156 pM for E. coli cell-free-produced RIT. CD7-negative Raji cells were unaffected by the RIT. Toxin and antibody domain alone did not show cytotoxic effects on either CD7-positive or CD7-negative cells. To our knowledge, this report describes the production of an active RIT in E. coli and CHO cell-free systems for the first time. We provide the proof-of-concept that cell-free protein synthesis allows for on-demand testing of antibody−toxin conjugate activity in a time-efficient workflow without cell lysis or purification required.

HTLV-1-related adult T-cell leukemia/lymphoma: insights in early detection and management

PURPOSE OF REVIEW

Adult T-cell leukemia-lymphoma (ATL) is an aggressive mature T-cell malignancy that arises in approximately 5% of carriers of human T-lymphotropic virus type 1 (HTLV-1), but this risk is not random among carriers. We describe recent advance in pathogenesis, risk factors and for early detection of ATL.

RECENT FINDINGS

Unraveling ATL molecular genetics has shed light on pathogenesis and provides insights into novel therapeutic targets. Moreover, an important step in improving outcomes is identifying asymptomatic carriers who are at high risk of progression to ATL, which has traditionally relied on quantifying the proviral load (PVL). This can be done by quantifying oligoclonality- and in particular the expanded clone- with molecular and flow cytometric techniques, that can be applied to a clinical setting. Studies using these methods have shown that carriers with oligoclonal populations are at an increased risk of transformation, beyond that that predicted by PVL alone.

SUMMARY

There is an urgent unmet need for developing novel therapies in ATL in order to improve survival. Recent advances in the molecular and epigenetic landscape of ATL, and the early detection of disease offer the potential to intervene early, before disease becomes aggressive, and to offer tailored therapeutic strategies.

Current and Emerging Targeted Therapies for Acute Graft-Versus-Host Disease

Acute graft-versus-host disease (GVHD), the major complication after allogeneic hematopoietic cell transplant (HCT), develops in approximately 50% of patients. The primary treatment is high-dose systemic steroids, but treatment failure is common, and steroid-refractory (SR) GVHD is the leading cause of non-relapse mortality after allogeneic HCT. Ruxolitinib became the first treatment for SR GVHD to obtain US Food and Drug Administration approval, and other new treatments are actively being studied. We searched the literature using the PubMed database and clinical trials using ClinicalTrials.gov to identify the most promising new treatments for GVHD. In this review, we categorize potential new treatments for GVHD by their mechanism of action (e.g., antibodies that deplete T cells or prevent their trafficking to target tissues, proteasome inhibitors, tyrosine kinase inhibitors, and other agents) and summarize the results from clinical trials.

SCHNEL: scalable clustering of high dimensional single-cell data

MOTIVATION

Single cell data measures multiple cellular markers at the single-cell level for thousands to millions of cells. Identification of distinct cell populations is a key step for further biological understanding, usually performed by clustering this data. Dimensionality reduction based clustering tools are either not scalable to large datasets containing millions of cells, or not fully automated requiring an initial manual estimation of the number of clusters. Graph clustering tools provide automated and reliable clustering for single cell data, but suffer heavily from scalability to large datasets.

RESULTS

We developed SCHNEL, a scalable, reliable and automated clustering tool for high-dimensional single-cell data. SCHNEL transforms large high-dimensional data to a hierarchy of datasets containing subsets of data points following the original data manifold. The novel approach of SCHNEL combines this hierarchical representation of the data with graph clustering, making graph clustering scalable to millions of cells. Using seven different cytometry datasets, SCHNEL outperformed three popular clustering tools for cytometry data, and was able to produce meaningful clustering results for datasets of 3.5 and 17.2 million cells within workable time frames. In addition, we show that SCHNEL is a general clustering tool by applying it to single-cell RNA sequencing data, as well as a popular machine learning benchmark dataset MNIST.

AVAILABILITY AND IMPLEMENTATION

Implementation is available on GitHub (https://github.com/biovault/SCHNELpy). All datasets used in this study are publicly available.

SUPPLEMENTARY INFORMATION

Supplementary data are available at Bioinformatics online.

The Spectrum of Hypereosinophilia and Associated Clonal Disorders - A Real-World Data Based on Combined Retrospective and Prospective Analysis from a Tropical Setting

OBJECTIVE

To determine the frequency, etiological spectrum and treatment outcome of hypereosinophilia (HE) and hypereosinophilic syndromes (HES) in a tropical setting.

METHODS

A retrospective analysis of hospital data of five years (January 2009 to December 2013) and a comprehensive prospective evaluation of patients presenting with HE/HES over a period of 33 months (January 2014 to September 2016) was performed.

RESULTS

HE/HES was diagnosed in a total of 125 patients during the study period with an estimated prevalence of 0.5-1 case per 100,000 population in our hospital settings. 41 patients were excluded from the final analysis due to lack of sufficient data. Infections, especially helminths were the commonest cause (34%) followed by primary/clonal HE/HES (24%) and reactive HE/HES secondary to various clonal disorders (14.3%). A lymphocytic variant of HES and FIP1L1-PDGFRA positive HES were diagnosed in 3.6% each. Imatinib-responsive BCR-ABL1 negative HE/HES constitute 7.1% in our patients. None of the clinical or routine laboratory features including the age of patients, duration of HE, presence or absence of organomegaly, hemoglobin levels, eosinophil %, absolute eosinophil count, total leukocyte count, platelet counts, serum IgE levels or presence of myelofibrosis could predict or exclude malignancy in patients with HE/HES. The absence of blasts in peripheral blood or the absence of >5% blasts in bone marrow does not exclude primary/clonal HES.

CONCLUSIONS

An underlying malignancy (Primary HE/HES and neoplasms leading to reactive HES; 35.7%) is diagnosed with nearly equal frequency compared to infections (34.5%) in tropical settings. There are no hematological or serological parameters, which can reliably be used to exclude an underlying malignancy, necessitating a thorough follow-up and comprehensive work-up in patients with HE/HES.

The clinical importance of CD4+ CD7- in human diseases

The CD7 antigen is a member of the immunoglobulin superfamily that expresses on the surface of all thymocytes, a majority of mature T cells, and also natural killer cells. Interestingly, under physiological and different pathological conditions, the loss of CD7 antigen occurred in the subset of CD4⁺ memory T cells. Various functions have been proposed for CD7, including its role in the activation and intercellular adhesiveness of T cells. Several studies indicate that the number of CD4⁺ CD7^- T cells increases in diseases such as chronic inflammation and T-cell malignancies, these being skin inflammatory lesions. Therefore, this can be useful for the diagnosis of cancer cells, especially with reference to blood origin, treatment monitoring, and establishment of new therapies. Therefore, a comprehensive review could be useful to increase our knowledge about the clinical importance of these cells in human disease.

Higher expression of human telomerase reverse transcriptase in productively-infected CD4 cells possibly indicates a mechanism for persistence of the virus in HIV infection

Mechanisms involved in survival of productively-infected memory CD4+cells after initial antigenic stimulation and their subsequent reversion to the resting state are critical for the development of a predominant replication-competent HIV reservoir. These mechanisms may also counter their elimination after HIV reactivation through latency-reversing agents (LRA). Thus, their evaluation is critical when using an appropriate HIV latency model that recapitulates the predominant replication-competent HIV reservoir to develop strategies for HIV eradication. The model for evaluating the possible survival mechanisms after T cell receptor (TCR) stimulation was developed by infecting memory CD4+cells with an HIV-1C primary isolate and cytokine secretion and gene expression patterns determined. Infected cells showed compromised functionality as evident from 6.8-fold lower secretion of IL-2 than from uninfected control cells. After TCR stimulation, the infected cells showed significantly higher fold increases in CD27 and CCR5 and smaller increases in CD5 mRNA over baseline values. Because CD27 expression may influence telomerase activity through AKT phosphorylation, CD27, human telomerase reverse transcriptase (hTERT) and pAKT expression in productively-infected cells from HIV-infected patients was evaluated by flow cytometry. HIV harbored in memory CD4+ cells was reactivated by HIV-1 envelope peptides, which have been shown to act as effective LRA. P24+CD4+cell showed significantly higher expression of CD27, hTERT and pAKT than P24-CD4+cells. These findings indicate compromised functionality of HIV-infected cells after TCR stimulation, which may interfere with their elimination by the immune system. They also indicate that pAKT and hTERT induction are possible survival mechanisms of productively-infected CD4+cells.

T Cell Receptor Vβ Staining Identifies the Malignant Clone in Adult T cell Leukemia and Reveals Killing of Leukemia Cells by Autologous CD8+ T cells

There is growing evidence that CD8+ cytotoxic T lymphocyte (CTL) responses can contribute to long-term remission of many malignancies. The etiological agent of adult T-cell leukemia/lymphoma (ATL), human T lymphotropic virus type-1 (HTLV-1), contains highly immunogenic CTL epitopes, but ATL patients typically have low frequencies of cytokine-producing HTLV-1-specific CD8+ cells in the circulation. It remains unclear whether patients with ATL possess CTLs that can kill the malignant HTLV-1 infected clone. Here we used flow cytometric staining of TCRVβ and cell adhesion molecule-1 (CADM1) to identify monoclonal populations of HTLV-1-infected T cells in the peripheral blood of patients with ATL. Thus, we quantified the rate of CD8+-mediated killing of the putative malignant clone in ex vivo blood samples. We observed that CD8+ cells from ATL patients were unable to lyse autologous ATL clones when tested directly ex vivo. However, short in vitro culture restored the ability of CD8+ cells to kill ex vivo ATL clones in some donors. The capacity of CD8+ cells to lyse HTLV-1 infected cells which expressed the viral sense strand gene products was significantly enhanced after in vitro culture, and donors with an ATL clone that expressed the HTLV-1 Tax gene were most likely to make a detectable lytic CD8+ response to the ATL cells. We conclude that some patients with ATL possess functional tumour-specific CTLs which could be exploited to contribute to control of the disease.

CADM1 expression and stepwise downregulation of CD7 are closely associated with clonal expansion of HTLV-I-infected cells in adult T-cell leukemia/lymphoma

PURPOSE

Cell adhesion molecule 1 (CADM1), initially identified as a tumor suppressor gene, has recently been reported to be ectopically expressed in primary adult T-cell leukemia-lymphoma (ATL) cells. We incorporated CADM1 into flow-cytometric analysis to reveal oncogenic mechanisms in human T-cell lymphotrophic virus type I (HTLV-I) infection by purifying cells from the intermediate stages of ATL development.

EXPERIMENTAL DESIGN

We isolated CADM1- and CD7-expressing peripheral blood mononuclear cells of asymptomatic carriers and ATLs using multicolor flow cytometry. Fluorescence-activated cell sorted (FACS) subpopulations were subjected to clonal expansion and gene expression analysis.

RESULTS

HTLV-I-infected cells were efficiently enriched in CADM1(+) subpopulations (D, CADM1(pos)CD7(dim) and N, CADM1(pos)CD7(neg)). Clonally expanding cells were detected exclusively in these subpopulations in asymptomatic carriers with high proviral load, suggesting that the appearance of D and N could be a surrogate marker of progression from asymptomatic carrier to early ATL. Further disease progression was accompanied by an increase in N with a reciprocal decrease in D, indicating clonal evolution from D to N. The gene expression profiles of D and N in asymptomatic carriers showed similarities to those of indolent ATLs, suggesting that these subpopulations represent premalignant cells. This is further supported by the molecular hallmarks of ATL, that is, drastic downregulation of miR-31 and upregulation of abnormal Helios transcripts.

CONCLUSION

The CADM1 versus CD7 plot accurately reflects disease progression in HTLV-I infection, and CADM1(+) cells with downregulated CD7 in asymptomatic carriers have common properties with those in indolent ATLs.

Splenic lymphoid subsets with less well-recognized phenotypes mimic aberrant antigen expression

OBJECTIVES

Flow cytometry can assist in the diagnosis of lymphoma by identifying aberrant antigen expression. Recognition of aberrancy requires knowledge of the phenotype of normal lymphoid cells.

METHODS

Lymphoid subsets were characterized in 20 spleens removed for traumatic rupture, using 8-color flow cytometry.

RESULTS

Normal variation in splenic lymphoid subsets was highlighted and several well-recognized subsets were identified: CD5+ B cells (20/20 specimens), CD7- T cells (20/20), and CD3 brightγδT cells (16/20). In addition, less well-recognized lymphoid subsets that resemble those described in lymphoma were identified in all specimens: CD5- T cells (4.5 ± 5.1% of T cells), CD2- natural killer (NK) cells (38 ± 7% of NK cells), and CD7dim+ NK cells. Similar populations were identified in 20 control peripheral blood specimens, where they represented a smaller proportion of total lymphoid cells.

CONCLUSIONS

Familiarity with the phenotype of normal lymphoid subsets can help prevent misinterpreting flow cytometric data. Furthermore, in the context of neoplastic cells, the phenotype may suggest expanded normal subsets rather than aberrant antigen expression.

The CD3 versus CD7 plot in multicolor flow cytometry reflects progression of disease stage in patients infected with HTLV-I

PURPOSE

In a recent study to purify adult T-cell leukemia-lymphoma (ATL) cells from acute-type patients by flow cytometry, three subpopulations were observed in a CD3 versus CD7 plot (H: CD3(high)CD7(high); D: CD3(dim)CD7(dim); L: CD3(dim)CD7(low)). The majority of leukemia cells were enriched in the L subpopulation and the same clone was included in the D and L subpopulations, suggesting clonal evolution. In this study, we analyzed patients with indolent-type ATL and human T-cell leukemia virus type I (HTLV-I) asymptomatic carriers (ACs) to see whether the CD3 versus CD7 profile reflected progression in the properties of HTLV-I-infected cells.

EXPERIMENTAL DESIGN

Using peripheral blood mononuclear cells from patient samples, we performed multi-color flow cytometry. Cells that underwent fluorescence-activated cell sorting were subjected to molecular analyses, including inverse long PCR.

RESULTS

In the D(%) versus L(%) plot, patient data could largely be categorized into three groups (Group 1: AC; Group 2: smoldering- and chronic-type ATL; and Group 3: acute-type ATL). Some exceptions, however, were noted (e.g., ACs in Group 2). In the follow-up of some patients, clinical disease progression correlated well with the CD3 versus CD7 profile. In clonality analysis, we clearly detected a major clone in the D and L subpopulations in ATL cases and, intriguingly, in some ACs in Group 2.

CONCLUSION

We propose that the CD3 versus CD7 plot reflects progression of disease stage in patients infected with HTLV-I. The CD3 versus CD7 profile will be a new indicator, along with high proviral load, for HTLV-I ACs in forecasting disease progression.

Clinical end points and response criteria in mycosis fungoides and Sézary syndrome: a consensus statement of the International Society for Cutaneous Lymphomas, the United States Cutaneous Lymphoma Consortium, and the Cutaneous Lymphoma Task Force of the European Organisation for Research and Treatment of Cancer

Mycosis fungoides (MF) and Sézary syndrome (SS), the major forms of cutaneous T-cell lymphoma, have unique characteristics that distinguish them from other types of non-Hodgkin's lymphomas. Clinical trials in MF/SS have suffered from a lack of standardization in evaluation, staging, assessment, end points, and response criteria. Recently defined criteria for the diagnosis of early MF, guidelines for initial evaluation, and revised staging and classification criteria for MF and SS now offer the potential for uniform staging of patients enrolled in clinical trials for MF/SS. This article presents consensus recommendations for the general conduct of clinical trials of patients with MF/SS as well as methods for standardized assessment of potential disease manifestations in skin, lymph nodes, blood, and visceral organs, and definition of end points and response criteria. These guidelines should facilitate collaboration among investigators and collation of data from sponsor-generated or investigator-initiated clinical trials involving patients with MF or SS.

Leukemic T cells are specifically enriched in a unique CD3(dim) CD7(low) subpopulation of CD4(+) T cells in acute-type adult T-cell leukemia

The morphological discrimination of leukemic from non-leukemic T cells is often difficult in adult T-cell leukemia (ATL) as ATL cells show morphological diversity, with the exception of typical "flower cells." Because defects in the expression of CD3 as well as CD7 are common in ATL cells, we applied multi-color flow cytometry to detect a putative leukemia-specific cell population in the peripheral blood from ATL patients. CD4(+) CD14(-) cells subjected to two-color analysis based on a CD3 vs CD7 plot clearly demonstrated the presence of a CD3(dim) CD7(low) subpopulation in each of nine patients with acute-type ATL. The majority of sorted cells from this fraction showed a flower cell-like morphology and carried a high proviral load for the human T-cell leukemia virus type 1 (HTLV-I). Genomic integration site analysis (inverse long-range PCR) and analysis of the T cell receptor Vβ repertoire by flow cytometry indicated that the majority of leukemia cells were included in the CD3(dim) CD7(low) subpopulation. These results suggest that leukemic T cells are specifically enriched in a unique CD3(dim) CD7(low) subpopulation of CD4(+) T cells in acute-type ATL.

Induced Sézary syndrome PBMCs poorly express immune response genes up-regulated in stimulated memory T cells

BACKGROUND

Dysfunctions in memory T cells contribute to various inflammatory autoimmune diseases and neoplasms. We hypothesize that investigating the differences of genetic profiles between resting and activated naïve and memory T cells may provide insight into the characterization of abnormal memory T cells in diseases, such as Sézary syndrome (SS), a neoplasm composed of CD4(+) CD45RO(+) cells.

OBJECTIVE

We determined genes distinctively expressed between resting and activated naive and memory cells. Levels of up-regulated genes in resting and activated memory cells were measured in SS PBMCs, which were largely comprised of CD4(+) CD45RO(+) cells, to quantitatively assess how different Sézary cells were from memory cells.

METHODS

We compared gene expression profiles using high-density oligo-microarrays between resting and activated naïve and memory CD4(+) T cells. Differentially expressed genes were confirmed by qRT-PCR and immunoblotting. Levels of genes up-regulated in activated and resting memory T cells were determined in SS PBMCs by qRT-PCR.

RESULTS

Activated memory cells expressed greater numbers of immune-mediated genes involved in effector function compared to naïve cells in our microarray analysis and qRT-PCR. Nine out of 14 genes with enhanced levels in activated memory cells had reduced levels in SS PBMCs (p<0.05).

CONCLUSIONS

Activation of memory and naïve CD4(+) T cells revealed a diverging gap in gene expression between these subsets, with memory cells expressing immune-related genes important for effector function. Many of these genes were markedly depressed in SS patients, implying Sézary cells are markedly impaired in mounting immune responses compared to memory cells.

Skewed T-cell maturation and function in HIV-infected patients failing CD4+ recovery upon long-term virologically suppressive HAART

OBJECTIVE

Analysis of functionally defined T-cell differentiation in HIV-infected patients with low CD4(+) on virologically suppressive HAART is crucial to design clinically efficacious treatments.

METHODS

We cross-sectionally investigated the maturation (CD45RA/CCR7, CD7) and function [antigen-specific enzyme-linked immunosorbent spot assay (ELISPOT), interleukin-2 (IL-2)/interferon-gamma-producing cells] of CD4(+) and CD8(+) T cells in 34 HIV-infected immunological nonresponders (INRs): CD4(+) cell count less than or equal to 200 cells/microl, HIV-RNA 50 copies/ml or less, as compared to 20 full responders (CD4(+) > 500 cells/microl, HIV-RNA < 50 copies/ml).

RESULTS

We describe skewed T-cell maturation in INRs with outgrowth of effector memory CD45RA(-)CCR7(-) CD4(+)/CD8(+) and Th2-committed CD7(-)CD4(+), and reduced unprimed-naive T cells (P = 0.001). Functionally, INRs display reduced Gag-specific ELISPOT (P = 0.04) and IL-2-secreting CD8(+) (P = 0.08) while showing CMV-specific responses comparable to full responders.

CONCLUSION

CD4 lymphopenia on HAART results in skewed, senescent T-cell maturation profile, inefficient T-helper function and poor HIV-specific CD8(+) response. This delineates a functional/phenotypic T-cell pattern that correlates to unfavourable clinical outcome.

CD7(-) T cells are late memory cells generated from CD7(+) T cells

CD7(-) T cells constitute a distinct subset within the CD4(+) and CD8(+) T cell populations; their developmental and functional relationship to the majority of CD7(+) T cells, however, remained so far unresolved. We here elucidate that CD7(-) cells represent aging T cells in late memory cell development characterized by a high activation threshold, low effector capacities, and high sensitivity to activation-induced cell death (AICD). In this regard, CD7(-) T cells highly express killer cell lectin-like receptor G1 (KLRG-1), harbor telomeres of shorter lengths, a decreased telomerase expression per cell, and less amounts of T cell receptor rearrangement excision circles (TRECs) compared to CD7(+) cells. CD7(-) T cells are generated in vitro from naive CD7(+) T cells upon repetitive TCR/CD28 engagement, a process that is unidirectional and requires multiple cell divisions. Consequently, clonal expansions of CD7(-) T cells in vivo are less frequent than of CD7(+) T cells, the former can be traced back to those of CD7(+) T cells.

Epstein-Barr Virus Negative Clonal Plasma Cell Proliferations and Lymphomas in Peripheral T-cell Lymphomas

Clonal B-cell populations have been described in peripheral T-cell lymphomas (PTCL) as secondary Epstein-Barr virus (EBV) driven B-cell expansions that may evolve to an overt B-cell lymphoma. EBV-negative B-cell proliferations associated with T-cell lymphomas are uncommon and not well characterized. We studied 15 patients who developed an EBV-negative B-cell proliferation or malignant lymphoma associated with PTCL. The T-cell tumors were 8 PTCL, not otherwise specified, 4 angioimmunoblastic T-cell lymphomas, and 3 cutaneous PTCL. The B-cell component was intermingled with the PTCL in all patients and it was classified as clonal/monotypic plasma cell proliferation in 8 lesions, clonal/monotypic large B-cell proliferation in 4 patients, and B-cell lymphoma with plasmacytic/plasmablastic differentiation in 3 patients. Two patients had 2 clonally unrelated plasma cell proliferations associated with the same PTCL. All cases showed cytoplasmic Ig light chain restriction. Clonal IgH and T-cell receptor rearrangements were detected in 11/12 and 11/13 cases examined, respectively. EBV, cytomegalovirus, and HHV-8 were not observed in any of the examined cases. Sequential samples in 7 patients showed persistence of the PTCL and the B-cell component in 4, the PTCL without the B-cell lymphoma in 2, and progression of the B-cell neoplasm in 1. Patients followed an aggressive clinical course similar to conventional PTCL. In conclusion, EBV-negative clonal or mononotypic B-cell proliferations in patients with PTCL present with a spectrum of lesions ranging from plasma cell proliferations to overt lymphomas with plasmacytic/plasmablastic features. The distinctive features of these patients suggest that these lesions represent a specific phenomenon in PTCL.

Proteomic analysis of the inflamed intestinal mucosa reveals distinctive immune response profiles in Crohn's disease and ulcerative colitis

Although Crohn's disease (CrD) and ulcerative colitis (UC) share several clinical features, the mechanisms of tissue injury differ. Because the global cellular function depends upon the protein network environment as a whole, we explored changes in the distribution and association of mucosal proteins to define key events involved in disease pathogenesis. Endoscopic biopsies were taken from CrD, UC, and control colonic mucosa, and Multi-Epitope-Ligand-Cartographie immunofluorescence microscopy with 32 different Abs was performed. Multi-Epitope-Ligand-Cartographie is a novel, highly multiplexed robotic imaging technology which allows integrating cell biology and biomathematical tools to visualize dozens of proteins simultaneously in a structurally intact cell or tissue. In CrD, the number of CD3+CD45RA+ naive T cells was markedly increased, but only activated memory, but not naive, T cells expressed decreased levels of Bax, active caspase-3 or -8. In UC, only CD4+ T cells coexpressing NF-kappaB were caspase-8 and poly(ADP-ribose)-polymerase positive. Furthermore, the number of CD4+CD25+ T cells was elevated only in UC, whereas in CrD and controls, the number of these cells was similar. By using hub analysis, we also identified that the colocalization pattern with NF-kappaB+ and poly(ADP-ribose)-polymerase+ as base motifs distinguished CrD from UC. High-content proteomic analysis of the intestinal mucosa demonstrated for the first time that different T cell populations within the intestinal mucosa express proteins translating distinct biological functions in each form of inflammatory bowel disease. Thus, topological proteomic analysis may help to unravel the pathogenesis of inflammatory bowel disease by defining distinct immunopathogenic profiles in CrD and UC.

High prevalence of circulating CD4+CD28- T-cells in patients with small abdominal aortic aneurysms

OBJECTIVE

To assess the possible role of proinflammatory CD28- T cells in abdominal aortic aneurysms (AAAs). Animal studies and human tissue studies suggest a role for interferon (IFN)-gamma-producing T cells in the development and progression of AAAs.

METHODS AND RESULTS

Fluorescence-activated cells sorter analysis of peripheral blood samples and measurement of AAA size using sonography were performed in 101 AAA patients and 38 healthy controls. Peripheral percentages of CD28- T cells of the CD3+CD4+ and the CD3+CD8+ were enriched in AAA patients with 7.8+/-8.8% and 41.9+/-15.7% compared with healthy controls with 2.2+/-6.1% and 24.9+/-15.5%, respectively (P=0.002 and P<0.001, respectively). Both CD4+CD28- and CD8+CD28- T cells produced large amounts of IFN-[gamma] and perforin. Patients with small AAAs (<4 cm) showed higher peripheral levels of CD4+CD28- T cells than those with larger AAAs (P=0.025). Immunohistological examinations revealed 39.1+/-17.2% CD4+CD28- and 44.0+/-13.8% CD8+CD28- in AAA tissue specimens with inflammatory infiltratestes.

CONCLUSIONS

IFN-gamma- and perforin-producing CD28- T cells are present in the periphery and the vessel wall of a majority of AAAs. This observation in humans favors the concept of a T cell-mediated pathophysiology of AAAs, especially during the early development of AAAs.

Phenotypic heterogeneity of antigen-specific CD4 T cells under different conditions of antigen persistence and antigen load

The factors responsible for the phenotypic heterogeneity of memory CD4 T cells are unclear. In the present study, we have identified a third population of memory CD4 T cells characterized as CD45RA⁺CCR7^– that, based on its replication history and the homeostatic proliferative capacity, was at an advanced stage of differentiation. Three different phenotypic patterns of memory CD4 T cell responses were delineated under different conditions of antigen (Ag) persistence and load using CD45RA and CCR7 as markers of memory T cells. Mono‐phenotypic CD45RA^–CCR7⁺ or CD45RA^–CCR7^– CD4 T cell responses were associated with conditions of Ag clearance (tetanus toxoid‐specific CD4 T cell response) or Ag persistence and high load (chronic HIV‐1 and primary CMV infections), respectively. Multi‐phenotypic CD45RA^–CCR7⁺, CD45RA^–CCR7^– and CD45RA⁺CCR7^– CD4 T cell responses were associated with protracted Ag exposure and low load (chronic CMV, EBV and HSV infections and HIV‐1 infection in long‐term nonprogressors). The mono‐phenotypic CD45RA^–CCR7⁺ response was typical of central memory (T_CM) IL‐2‐secreting CD4 T cells, the mono‐phenotypic CD45RA^–CCR7^– response of effector memory (T_EM) IFN‐γ‐secreting CD4 T cells and the multi‐phenotypic response of both IL‐2‐ and IFN‐γ‐secreting cells. The present results indicate that the heterogeneity of different Ag‐specific CD4 T cell responses is regulated by Ag exposure and Ag load.

Molecular cloning and sequencing of feline CD7

Human CD7 is one of the earliest molecules to appear in T cell development. In this study, putative feline CD7 cDNA was identified based on its similarities with human and mouse CD7 genes. The feline CD7 cDNA contained an open reading frame consisting of 630 nucleotides. The amino acid sequence of feline CD7 had 47.7% identity with that of human CD7, and 52.9% with that of mouse CD7. In addition, the feline CD7 protein fused with histidine tag was expressed in 293T cells. The expression was confirmed by indirect immunofluorescence assay.

The Sézary syndrome: hematologic criteria

The hematologic criteria for Sézary syndrome that were recently proposed by the International Society on Cutaneous Lymphomas are critically evaluated. Based on the experience at two institutions, revisions to the definition for Sézary syndrome are proposed.

Preserved immune system in long-term asymptomatic vertically HIV-1 infected children

The objective of this study was to study immune system status in long-term asymptomatic (LTA) HIV-1-infected children. A cross-sectional study was used, involving HIV-1-infected children over 7 years of age who were rated into two groups according to their clinical and immunological classification: (a) LTA: 7 asymptomatic HIV-1-infected children in A1; (b) Rapid progressor (RP): 14 age-matched C3 HIV-1-infected children. The control group consisted of 17 age-matched uninfected children. The characterization of CD4+ T-cell subsets was determined by three-colour flow cytometry. The proliferative response and cytokine production by activated peripheral blood T-cells were also measured. IL-7 levels were measured in serum. Thymic production of T-cells was quantified by TCR rearrangement excision circles (TRECs). The LTA children showed similar proliferative responses to PHA, PWM and anti-CD3+ anti-CD28, but lower responses to tetanus toxoid and streptokinase, in comparison with the controls but always higher responses in comparison with the RP group. The production of TNF-alpha and IFN-gamma was similar in the LTA and control groups, and both were higher than the levels in the RP group. The LTA group showed a lower percentage of memory CD4+ T-cells (CD4+ CD45RO+, CD4+ CD45RA-CD62L+) than the control and RP groups. The LTA group also showed lower percentages of CD4+ CD7- cells than the controls. As for naïve CD4+ T-cells (CD4+ CD45RA+ CD62L+), CD4+ CD45RA+ and CD4+ CD62L+ cells, the LTA group showed higher values than the control and RP groups. The LTA group showed higher percentages of CD4+ HLA-DR+ CD38+ than the controls, but lower values than the RP group. In contrast, the LTA group had percentages of CD4+ HLA-DR-CD38+ T-cells higher than both the control and RP groups, whereas CD4+ CD38+ levels were only higher in the LTA group in comparison with the controls. CD4+ HLA-DR+ CD38- and CD4+ HLA-DR+ cell numbers were lower in the LTA group in comparison with the RP group. We found almost normal values of TRECs and IL-7 in the LTA group, but lower values in the RP group. Moreover, we found an inverse relation between TREC levels and IL-7 in plasma from HIV-infected children. Asymptomatic HIV-1 infected children have a well preserved immune system similar to that of control uninfected children in spite of HIV-infection for more than 7 years. Moreover, our results identified new markers of HIV disease, such as TRECs and IL-7, that could be used to monitor disease.

CD7 is a differentiation marker that identifies multiple CD8 T cell effector subsets

The adaptive immune response of human CD8 T cells to invading pathogens involves the differentiation of naive cells into memory and effector cells. However, the lineage relationship between memory and effector cells and the differentiation of CD8 T cells into distinct subsets of effector cell subpopulations are subjects of considerable debate. CD7 identifies three populations of CD8 T cells: CD7 high (CD7(high)), low (CD7(low)), and negative (CD7(neg)) that translate into subsets with distinct functional properties. The CD7(high) subset contains naive and memory cells and the CD7(low) and CD7(neg) subsets contain effector cells. The effector cells can functionally be divided into cytokine-secreting effector CD8 T cells and lytic effector CD8 T cells. These data provide a model of human CD8 T cell differentiation in which specialized distinct subpopulations can be identified by expression of CD7.

Prevalence, clinical relevance and characterization of circulating cytotoxic CD4+CD28- T cells in ankylosing spondylitis

Circulating CD3+CD4+CD28- cells exhibit reduced apoptosis and were found to be more enriched in patients with ankylosing spondylitis than in age-matched healthy control individuals (7.40 +/- 6.6% versus 1.03 +/- 1.0%; P < 0.001). Levels of CD4+CD28- T cells correlate with disease status as measured using a modified metrology score, but they are independent of age and duration of ankylosing spondylitis. CD4+CD28- T cells produce IFN-gamma and perforin, and thus they must be considered proinflammatory and cytotoxic. These T cells share phenotypic and functional properties of natural killer cells, strongly expressing CD57 but lacking the lymphocyte marker CD7. MHC class I recognizing and activating natural killer cell receptors on the surface of CD4+CD28- T cells may be involved in a HLA-B27 mediated co-stimulation of these proinflammatory and cytotoxic cells.

CD4+CD7- leukemic T cells from patients with Sézary syndrome are protected from galectin-1-triggered T cell death

In early stages of cutaneous T cell lymphoma (Sézary syndrome) both CD4+CD7- and CD4+CD7+ T cells clonally expand whereas in late stages of the disease CD7- cells are predominant in number, giving rise to the question whether CD7- T cells have a survival advantage in the skin. Galectin-1, a cell-bound lectin, was recently reported to trigger apoptosis in activated CD7+ T cells. Here, we demonstrate that in contrast to activated CD7(+) T cells, quiescent and activated CD69+ CD7- T cells from healthy donors and from Sézary patients are resistant to galectin-1-mediated cell death. CD7- T cells are apoptosis-resistant even during coculture with IFN-gamma-stimulated endothelial cells that constitutively express galectin-1 in high amounts. These data imply that resistance of CD7- T cells to galectin-1-induced apoptosis may contribute to the accumulation of CD7- Sézary T cells during progression of the disease.

Low CD7 expression in benign and malignant cutaneous lymphocytic infiltrates: experience with an antibody reactive with paraffin-embedded tissue

Loss of CD7 expression by neoplastic lymphocytes is considered a distinguishing characteristic of mycosis fungoides (MF) and cutaneous T-cell lymphoma. Reports to date examining for the CD7 immunophenotype in MF have been performed on fresh-frozen tissue. In this study, we used a paraffin-reactive antibody directed against CD7 to determine its range of expression in MF and to compare these results with those in controls. Examining 22 cases of MF and 61 controls, we found minimal CD7 expression by lymphocytes in MF and in a few cases of benign inflammatory dermatosis (BID). The lowest mean CD7 counts (as a percentage of total lymphocytes) were found in MF (patch stage: 5% +/- 5%, range: 0-10; plaque and tumor stages: 15% +/- 5%, range: 5-25), and these counts were significantly lower than those for BID (35% +/- 20%, range: 5-80; p = 0.001). By logistic regression analysis, low CD7 expression (<10% lymphocytes labeling) had sensitivity and positive predictive values of 80% and 72%, respectively, and specificity and negative predictive values of 93% and 96%, respectively, for the diagnosis of patch stage MF. False-positive results were found for spongiotic dermatitis. Moreover, spongiotic dermatitides exhibited a progressive decrease in mean CD7 counts from acute to subacute to chronic stages (50% versus 35% versus 30%, respectively). In conclusion, minimal CD7 expression is a specific finding for MF. Benign inflammatory infiltrates can also show low CD7 expression, however, which rarely matches that of patch stage MF. Progressive loss of CD7 expression in BID is the likely consequence of expansion of antigen-selected CD3+CD4+CD7- T cells. These inflammatory CD4+CD7- T cells may represent the physiologic counterpart to the neoplastic lymphocyte of MF.

Proliferation of T-cell subsets that contact tumour cells in colorectal cancer

We have investigated the proliferation rates of T-cell subsets in colorectal carcinomas using immunohistochemistry. It was found that the tumour-infiltrating T cells in contact with the tumour cells have a significantly higher frequency of proliferation than those in the stroma. In particular, the CD8+ intraepithelial lymphocytes (T-IEL) within the tumours have a significantly higher frequency of proliferation in comparison with CD8+ T cells in the stromal compartment or in any normal mucosal lymphoid tissues. It is possible that the proliferation of the CD8+ T-IEL may be driven by self-antigens expressed on the tumour cells. The proportion of CD3+ CD7- T cells is increased within carcinomas compared with the normal colon, and a population of CD57+ T cells was observed which is absent from the normal colon. It is possible that these phenotypes are acquired in situ due to repeated stimulation of the T cells by tumour antigens. Intact colorectal carcinoma explants were cultured, and the presence of tumour-infiltrating T cells analysed after 3 days of culture in isolation from the systemic compartments. CD3+ T cells were proliferating (at a low rate) within the explants after 3 days of culture, indicating that they may be sustained by factors present in the tumour microenvironment.

A new monoclonal anti-CD7 antibody reactive on paraffin sections

CBC.37 monoclonal antibody (mAb) was generated using balb/c mice immunized with CEM T cell line. It was selected because of its strong reactivity on T lymphocytes on paraffin tissue sections. The anti-CD7 specificity of CBC.37 mAb was assessed by immunohistochemistry, cross-blocking, and cross-immunoprecipitation experiments using CBC.37 and the anti-CD7 mAb DK24. CBC.37 mAb immunoprecipitated a 40-kDa protein. Cross-blocking and cross-immunoprecipitation experiments demonstrated that the two antibodies recognized the same molecule. Immunostaining of a large number of reactive lymph nodes and B and T cell lymphomas confirms that CBC.37 mAb was directed against T cells. As expected, on reactive lymph nodes the staining pattern was comparable to that of CD3. Among the 110 T cell lymphomas examined, all T lymphoblastic lymphomas were positive (15+/15; 100%). As a result of the frequent loss of CD7 antigen, only 25+/95 (26%) of peripheral T cell neoplasms were found to be positive for CBC.37. A marked reduction in the number of CBC.37-positive T cells was observed in 7 of the 60 cases of benign inflammatory dermatoses studied (approximately 12%). CBC.37 was unreactive with all healthy and neoplastic non-lymphoid samples examined. Because the lack of CD7 expression in T cell lymphomas is of diagnostic value, CBC.37 mAb in association with other anti-T cell antibodies working on paraffin sections could be of particular value in asserting the diagnosis of T cell lymphomas in routine histopathology.

Immunophenotypic analysis of peripheral T-cell neoplasms. A multiparameter flow cytometric approach

We retrospectively reviewed multiparameter flow cytometric analyses in 50 peripheral T-cell neoplasms (PTCNs). Results were interpreted within the context of a large cohort of nonneoplastic T-cell populations. All PTCN diagnoses were confirmed with morphologic and/or molecular analysis. Aberrant populations were defined as discrete immunophenotypic clusters exhibiting loss of or increased or diminished expression of T-cell antigens relative to internal immunophenotypically normal T-cell populations. An antigenic pattern was considered abnormal if it exceeded ranges for T-cell subsets in specific anatomic sites or was not normally encountered. Forty-six of 50 and 41 of 50 demonstrated 1 or more and 2 or more aberrations, respectively. The most common abnormally expressed antigen was CD3, followed by CD7, CD5, and CD2. Except for CD7, abnormally dim or bright antigen expression was more common than deletion. Only 3 cases were abnormal solely based on expansion of an otherwise immunophenotypically normal population; the remainder had patterns of antigen expression not seen in nonneoplastic populations. These data indicate that most PTCNs are aberrant by multiparameter flow analysis. However, results must be interpreted within the context of thorough knowledge of the immunophenotypic spectrum of nonneoplastic T cells.

Variable CD7 expression on T cells in the leukemic phase of cutaneous T cell lymphoma (Sézary syndrome)

CD7, a molecule normally expressed on 90% of normal CD4+ T cells, is often deficient on the malignant T cells of cutaneous T cell lymphoma. To investigate the clinical and biologic implications of CD7 expression, blood lymphocytes from 42 patients with the leukemic phase of cutaneous T cell lymphoma (CD4/CD8 ratio of 10 or more with evidence of a T cell clone in the blood) were analyzed for level of expression of CD7 by flow cytometry. CD7 expression by cells did not clearly segregate into two distinct subgroups that are either CD7 positive or CD7 negative as generally thought; however, nine of 17 patients with a predominantly CD4+CD7+ tumor population on early studies became CD4+CD7- over time whereas the converse situation was not observed. In addition, of three patients with evidence of large tumor cells in the blood coexisting with smaller cells, discordant CD7 expression was observed in one instance. In lymph node specimens, the percentage of cells expressing CD7 and other T cell markers did not correlate with histologic evidence of involvement. CD7 expression on blood lymphocytes also did not correlate with patients' survival nor to serum IgE levels or blood eosinophil counts, a finding suggesting that this marker does not identify functional cell subsets that produce serum interleukin-4 or -5, respectively. We speculate that the level of CD7 expression on malignant T cells may be the effect of sustained antigen stimulation in vivo analogous to what has been proposed to occur with normal T cells during aging.

The CD7(-) subset of CD4(+) memory T cells is prone to accelerated apoptosis that is prevented by interleukin-15 (IL-15)

The CD7(-) subset of CD4(+) T cells reflects a stable differentiation state of post-thymic helper T cells with CD45R0(+)CD45RA(-) 'memory' phenotype. Here we report that CD4(+)CD7(-) T cells are prone to increased spontaneous apoptosis in vitro compared to CD4(+)CD7(+) T cells. Spontaneous apoptosis is prevented by IL-15, but not by IL-2. Moreover, IL-15 increases Bcl-2 and decreases CD95/Fas expression of CD7(-), but not of CD7(+) T cells. Because IL-15 is physiologically not secreted but expressed in a membrane-bound form, we cocultured T cells with TNF-alpha stimulated fibroblasts that expose membrane IL-15. TNF-alpha stimulated fibroblasts rescue CD4(+)CD7(-) T cells from apoptosis whereas unstimulated fibroblasts do not. Rescue from apoptosis requires cell-cell contact and is abolished by addition of neutralizing antibodies to IL-15. We conclude that membrane IL-15 prevents accelerated apoptosis of CD4(+)CD7(-) T cells. This mechanism may contribute to accumulation of CD7(-) T cells in chronic inflammatory skin lesions.

CD4(+)CD7(-) T cells compose the dominant T-cell clone in the peripheral blood of patients with Sézary syndrome

BACKGROUND

Absence of CD7 antigen expression in T cells defines a subset of normal CD4(+) CD45RO(+) CD45RA(-) memory cells and is furthermore observed in Sézary syndrome (SS).

OBJECTIVE

Our purpose was to identify circulating T-cell clones in patients with SS and to elucidate whether the dominant T-cell clones express the CD7 antigen.

METHODS

Peripheral blood lymphocytes of patients with SS were analyzed by two-color flow cytometry using antibodies to the V beta region of the T cell receptor (TCR) in combination with an antibody to CD7. In addition, T cells were analyzed for TCR-gamma gene rearrangement by polymerase chain reaction (PCR) techniques.

RESULTS

Clonal T-cell expansion was detected in 7 patients with SS by immunostaining of the TCR V beta regions. PCR analysis confirmed the presence of dominant T cell clones. Double-immunostaining revealed that in each case cells of the clonal V beta TCR rearrangement homogeneously express the CD4(+)CD7(-) phenotype. Furthermore, CD4(+)CD7(-) cells express the CD15s antigen but lack expression of CD26 and CD49d.

CONCLUSION

Expansion of clonal T cells strongly correlates with the expansion of CD4(+)CD7(-) T cells in 7 tested patients with SS. This supports our model that a subset of late differentiated, normal CD4(+)CD7(-) memory T cells may represent the physiologic counterpart of Sézary cells. Monitoring of circulating T cells with the CD4(+)CD7(-)CD15s(+)CD26(-)CD49d(-) phenotype proved to be useful for the identification of clonal T cells in patients with SS.

Reconstitution of lymphocyte subpopulations after paediatric bone marrow transplantation

We prospectively studied the reconstitution of lymphocyte subpopulations in a group of 22 children, who survived disease-free at least 6 months after allogeneic BMT for a haematological malignancy. Absolute counts of total lymphocytes, B lymphocytes, T lymphocytes, and CD4+ helper T lymphocytes reached the 5th percentile (p5) of age-matched reference values within 6 months after BMT in 15, 17, 7 and 2 patients, respectively. In particular, CD4+ helper T lymphocyte reconstitution was very slow. Unexpectedly, CMV reactivation had a profound positive influence upon the number of CD4+ helper T lymphocytes in the children. In five patients, absolute B lymphocyte counts above the 95th percentile were reached from 6 months after BMT onwards, mimicking normal ontogeny. Unlike normal ontogeny, the percentages of helper T lymphocytes expressing the 'naive' CD45RA isoform were low and those expressing the 'memory' CD45RO isoform were high in the first 3 months after BMT, as described before. Thereafter, the CD45RA:CD45RO ratio slowly normalised. Also, CD7 expression was absent on up to 90% of T lymphocytes in the first months after BMT, and on a steadily decreasing percentage thereafter, as recently described in adults. However, the absolute counts of CD45RO+/CD4+ and CD7-/CD4+ helper T lymphocytes did not change significantly. So, we found no evidence of peripheral expansion of previously primed donor-derived 'memory' T lymphocytes during the follow-up period which spanned 1-18 months after BMT. The absolute counts of 'naive' CD45RA+ helper T lymphocytes did not show a faster increase after BMT than in adults, despite the presumed presence of a non-involuted thymus in children. Bone Marrow Transplantation (2000) 25, 267-275.

CD4 + /CD7- T cell frequency and polymerase chain reaction-based clonality assay correlate with stage in cutaneous T cell lymphomas

In cutaneous T cell lymphomas, tumor cells can be found in skin and in other compartments. A precise definition of extracutaneous spread including blood involvement is necessary for staging and treatment design. We investigated peripheral blood in 51 patients with various types of cutaneous T cell lymphomas by the analysis of blood smears for Sézary cells, the CD4 + /CD7- T helper cell frequency in the peripheral blood by fluorescence activated cell sorter analysis and by polymerase chain reaction for the T cell receptor gamma-chain followed by denaturing gradient gel electrophoresis. Eleven polymerase chain reaction products were sequenced. Thirty-five per cent of patients with stage Ia-IIb cutaneous T cell lymphomas presented a peripheral blood T cell clone. In patients with stage III-IVb cutaneous T cell lymphomas 75% were positive for clonality in the peripheral blood by polymerase chain reaction. Interestingly, three of 13 Sézary patients showed a TCR-gamma joining region pseudogene (JgammaP1/JgammaP2) usage. CD4 + /CD7- cell counts were significantly higher in patients with advanced cutaneous T cell lymphomas than in patients with early cutaneous T cell lymphomas. There was a correlation between increased percentage of circulating CD4 + /CD7- cells and detection of clonality by polymerase chain reaction (p = 0.001). There was no significant correlation between the polymerase chain reaction data and the percentage of Sézary cells on blood smears. A significant correlation between CD4 + /CD7- cells and Sézary cells was found, however. Stepwise logistic regression analysis showed that the CD4 + /CD7- cell count and clonal T cell detection in peripheral blood are independently correlated with stage. The combination of both parameters gives more information than each one separately. In conclusion, our data indicate that fluorescence activated cell sorter analysis of peripheral blood and polymerase chain reaction-based clonality assays can improve the accuracy of staging investigations in cutaneous T cell lymphomas patients.