B-cell antigens within normal and activated human T cells

Mature B‐ and plasma‐cell flow cytometric analysis: A review of the impact of targeted therapy

Flow cytometry has been indispensable in diagnosing B cell lymphoma and plasma cell neoplasms. The advances in novel multicolor flow cytometry have also made this technology a robust tool for monitoring minimal/measurable residual disease in chronic lymphocytic leukemia and multiple myeloma. However, challenges using conventional gating strategies to isolate neoplastic B or plasma cells are emerging due to the rapidly increasing number of antibody therapeutics targeting single or multiple classic B/plasma cell-lineage markers, such as CD19, CD20, and CD22 in B cells and CD38 in plasma cells. This review is the first of a two-part series that summarizes the most current targeted therapies used in B and plasma cell neoplasms and proposes detailed alternative approaches to overcome post-targeted therapy analysis challenges by flow cytometry. The second review in this series (Chen et al.) focuses on challenges encountered in the use of targeted therapy in precursor B cell neoplasms.

CD8+ T cell-associated genes MS4A1 and TNFRSF17 are prognostic markers and inhibit the progression of colon cancer

Background

Colon cancer (CC) is among the top three diseases with the highest morbidity and mortality rates worldwide. Its increasing incidence imposes a major global health burden. Immune checkpoint inhibitors, such as anti-PD-1 and anti-PD-L1, can be used for the treatment of CC; however, most patients with CC are resistant to immunotherapy. Therefore, identification of biomarkers that can predict immunotherapy sensitivity is necessary for selecting patients with CC who are eligible for immunotherapy.

Methods

Differentially expressed genes associated with the high infiltration of CD8+ T cells were identified in CC and para-cancerous samples via bioinformatic analysis. Kaplan–Meier survival analysis revealed that MS4A1 and TNFRSF17 were associated with the overall survival of patients with CC. Cellular experiments were performed for verification, and the protein expression of target genes was determined via immunohistochemical staining of CC and the adjacent healthy tissues. The proliferation, migration and invasion abilities of CC cells with high expression of target genes were determined via in vitro experiments.

Results

Differential gene expression, weighted gene co-expression and survival analyses revealed that patients with CC with high expression of MS4A1 and TNFRSF17 had longer overall survival. The expression of these two genes was lower in CC tissues than in healthy colon tissues and was remarkably associated with the infiltration of various immune cells, including CD8+ T cells, in the tumour microenvironment (TME) of CC. Patients with CC with high expression of MS4A1 and TNFRSF17 were more sensitive to immunotherapy. Quantitative reverse transcription-polymerase chain reaction, western blotting and immunohistochemical staining validated the differential expression of MS4A1 and TNFRSF17. In addition, Cell Counting Kit-8, wound healing and transwell assays revealed that the proliferation, migration and invasion abilities of CC cells were weakened after overexpression of MS4A1 and TNFRSF17.

Conclusions

The core genes MS4A1 and TNFRSF17 can be used as markers to predict the sensitivity of patients with CC to immunotherapy and have potential applications in gene therapy to inhibit CC progression.

MS4A1 expression and function in T cells in the colorectal cancer tumor microenvironment

The majority of human colorectal cancer remains resistant to immune checkpoint inhibitor (ICI) immunotherapy, but the underlying mechanism is incompletely understood. We report here that MS4A1, the gene encoding B cell surface marker CD20, is significantly downregulated in human colorectal carcinoma. Furthermore, MS4A1 expression level in colorectal carcinoma is positively correlated with patient survival. Analysis of scRNA-Seq dataset from public database revealed that MS4A1 is also expressed in subsets of T cells. A CD8⁺CD20⁺ subset of T cells exists in the neighboring non-neoplastic colon but disappears in tumor in human colorectal carcinoma. Furthermore, analysis of a published nivolumab treatment dataset indicated that nivolumab-bound T cells from human patients during anti-PD-1 immunotherapy exhibit significantly higher MS4A1 expression. Our findings indicate that CD8⁺CD20⁺ T subset functions in host cancer immunosurveillance and tumor microenvironment suppresses this T subset through a PD-L1-dependent mechanism.

Cardamonin induces immune responses and enhances survival rate in WEHI-3 cell-generated mouse leukemia in vivo

Cardamonin, a monomeric alkaloid, is isolated from Alpinia conchigera Griff and other natural plants. Recently, it has been focused on its anticancer activities, and no information showing its immune effects on leukemia mice was reported. In this study, we investigated the immune effects of cardamonin on WEHI-3 cell-generated leukemia mice. Forty BALB/c mice were randomly divided into four groups: Group I mice were normal animals and groups II-IV were leukemia. Group II mice, as a positive control, were administered with normal diet, and group III and IV mice were treated with 1 and 5 mg/kg of cardamonin, respectively, by intraperitoneal injection every 2 days for 14 days. The population of white blood cells, macrophage phagocytosis, and the proliferations of T and B cells were analyzed by flow cytometry. Another forty mice were also separated randomly into four groups for the determination of survival rate. Results showed that cardamonin did not affect body weight. Cardamonin decreased CD3, CD11b, and Mac-3 cell populations but increased CD19 number. Cardamonin enhanced phagocytic abilities of macrophages from the peripheral blood mononuclear cells of leukemia mice. Furthermore, cardamonin at 1 mg/kg treatment improved the survival rate of leukemia mice in vivo. Therefore, cardamonin could be applied for a leukemia therapeutic reagent at a defined dose.

Diagnostic and prognostic roles of soluble CD22 in patients with Gram-negative bacterial sepsis

BACKGROUND

Soluble CD22 (sCD22) is a fragment of CD22, a B cell-specific membrane protein that negatively regulates B-cell receptor signaling. To date, sCD22 has only been regarded as a tumor marker of B-cell malignancies. Its expression in infectious diseases has not yet been assessed.

METHODS

Serum concentrations of sCD22, procalcitonin (PCT) and interleukin-6 (IL-6) were measured by enzyme-linked immunosorbent assays in patients with intra-abdominal Gram-negative bacterial infection. Receiver operating characteristic curve analysis was performed to evaluate the diagnostic accuracy of these biomarkers in this type of infection. The correlations between biomarkers and the Acute Physiology and Chronic Health Evaluation (APACHE) II scores were also analyzed.

RESULTS

Concentrations of sCD22 were significantly elevated in patients with sepsis and the elevation is correlated with the severity of sepsis. sCD22 was also slightly elevated in patients with non-infected systemic inflammatory response syndrome or local infection. The diagnostic accuracy of sCD22 for sepsis was equivalent to that of PCT or IL-6. In addition, the correlation of sCD22 with APACHE II scores was stronger than that of PCT or IL-6.

CONCLUSIONS

Serum sCD22 is a novel inflammatory mediator released during infection. This soluble biomarker plays a potential role in the diagnosis of Gram-negative bacterial sepsis, with a diagnostic accuracy as efficient as that of PCT or IL-6. Furthermore, sCD22 is more valuable to predict the outcomes in patients with sepsis than PCT or IL-6. The present study suggested that sCD22 might be potentially useful in supplementing current criteria for sepsis.

Bifunctional antibody fragment-based fusion proteins for the targeted elimination of pathogenic T-cell subsets

Pathogenic effector T cells are key contributors to autoimmune diseases such as systemic lupus erythematosus (SLE). General inhibition of T cells using, e.g., methotrexate, prednisolone, or TNF blockers, has prominent therapeutic effects frequently at the cost of severe long-term side effects and toxicity. Therefore, targeted strategies that can selectively inhibit or eliminate pathogenic T cells are sought after as a new approach to safely block perpetual inflammatory T-cell responses and inhibit concomitant progressive tissue destruction. Of particular interest in this respect is the use of the so-called single-chain fragments of variable region (scFv) antibody fragments for the targeted reactivation of Fas-dependent activation-induced cell death (AICD). Recently, we demonstrated that a recombinant fusion protein comprising a T-cell-targeted anti-CD7 scFv antibody fragment genetically fused to soluble FasL (sFasL) can eliminate synovial fluid T cells in the absence of activity toward resting peripheral blood cells. Here, we describe a detailed protocol for construction and preclinical evaluation of such scFv:FasL fusion proteins that may be used to selectively eliminate pathogenic immune cells.

Frequency of Th17 CD20+ cells in the peripheral blood of rheumatoid arthritis patients is higher compared to healthy subjects

Introduction

Rheumatoid arthritis (RA) is considered a T cell driven autoimmune disease, therefore, the ability of B cell depleting biologics, e.g., anti-CD20 antibodies, to alleviate RA is unclear. This study examined the proportions of IL-17-secreting lymphocytes in the blood of healthy subjects and RA patients and determined if Th17 cells belong to a CD20+ subset of T cells.

Methods

Fluorescence-activated cell sorting and confocal microscopy verified CD3, CD4/CD8 and CD20-staining of T cells. IL-17 secretion was determined using a commercial assay.

Results

In healthy subjects and RA patients blood, the median percentage of total CD20+ lymphocytes was similar (7.5%; n = 6 and 10.3%; n = 9, respectively) and comprised predominantly of B cells (~ 86%). However, 2-4% of CD3+ T cells from both healthy subjects (n = 7) and RA (n = 8) individuals co-expressed CD20. The peripheral blood of healthy subjects contained few IL-17-secreting CD20+ T cells (< 0.1%; n = 6). In contrast, in RA blood a median and interquartile range % of, 24.2%; IQR 28.5 of IL-17-secreting T cells were CD20+ (n = 9; p = 0.02).

Conclusions

In the blood of RA patients, a greater proportion of Th17 cells are of a CD20+ phenotype compared to healthy individuals. These cells may represent an additional target for anti-CD20 therapies.

Extensive complement-dependent enhancement of HIV-1 by autologous non-neutralising antibodies at early stages of infection

BACKGROUND

Non-neutralising antibodies to the envelope glycoprotein are elicited during acute HIV-1 infection and are abundant throughout the course of disease progression. Although these antibodies appear to have negligible effects on HIV-1 infection when assayed in standard neutralisation assays, they have the potential to exert either inhibitory or enhancing effects through interactions with complement and/or Fc receptors. Here we report that non-neutralising antibodies produced early in response to HIV-1 infection can enhance viral infectivity.

RESULTS

We investigated this complement-mediated antibody-dependent enhancement (C'-ADE) of early HIV infection by carrying out longitudinal studies with primary viruses and autologous sera derived sequentially from recently infected individuals, using a T cell line naturally expressing the complement receptor 2 (CR2; CD21). The C'-ADE was consistently observed and in some cases achieved infection-enhancing levels of greater than 350-fold, converting a low-level infection to a highly destructive one. C'-ADE activity declined as a neutralising response to the early virus emerged, but later virus isolates that had escaped the neutralising response demonstrated an increased capacity for enhanced infection by autologous antibodies. Moreover, sera with autologous enhancing activity were capable of C'ADE of heterologous viral isolates, suggesting the targeting of conserved epitopes on the envelope glycoprotein. Ectopic expression of CR2 on cell lines expressing HIV-1 receptors was sufficient to render them sensitive to C'ADE.

CONCLUSIONS

Taken together, these results suggest that non-neutralising antibodies to the HIV-1 envelope that arise during acute infection are not 'passive', but in concert with complement and complement receptors may have consequences for HIV-1 dissemination and pathogenesis.

Immunosuppressive therapy modulates T lymphocyte gene expression in patients with systemic lupus erythematosus

To evaluate the T-cell large-scale differential gene expression in systemic lupus erythematosus (SLE) patients presenting with glomerulonephritis we studied SLE patients before and after immunosuppressive treatment. Large-scale gene expression of peripheral blood mononuclear T cells was evaluated using cDNA microarray nylon membranes containing 5184 cDNAs. Data were analysed using the SAM and Cluster and Treeview software. When untreated patients were compared to healthy individuals, 38 genes, most of them located on chromosomes 1, 3, 6, 17 and 19, were repressed, and when untreated patients were compared to treated ones, 154 genes, located on chromosomes 1, 6, 7, 12 and 17, were induced. In terms of biological function of coded proteins, the differentially expressed genes were associated with apoptosis, cell cycle, chromosomal scaffold, cytokine/chemokine, DNA repair/replication, Golgi/mitochondrial proteins, mRNA processing, signalling molecules and tumour suppressors. Two autoantigen genes related to RNA splicing (small nuclear riboprotein 70,000 MW-U1 SNR, and splicing factor 3a, 60,000 MW), and the tetranectin-plasminogen-binding protein were repressed. The Fc fragment of immunoglobulin G low affinity IIb, apoptotic protease activating factor-1, two subunits of cytochrome c, caspase 8, complement C5a, HLA-DRA, HLA-DQB1, transforming growth factor-beta receptor II, small nuclear ribonucleoprotein polypeptide N (Sm protein N) genes, heterogeneous nuclear riboprotein-C, and argininosuccinate lyase genes, among others, were induced. A total of 10 genes were repressed in untreated patients and induced in treated ones, among them tumour necrosis factor (ligand) superfamily member 9, tumour protein p53, mannosidase alpha class IA, and CD22. Although some of these differentially expressed genes are typically expressed in B cells, CD22 and CD32 have also been reported in T cells and may provide regulatory signals to B cells. Assessment of differential gene expression may provide hybridization signatures that may identify susceptibility, diagnostic and prognostic markers of SLE.

Detection of cytoplasmic CD antigens within normal human peripheral blood leucocytes

Polymorphonuclear neutrophils (PMNs) are capable of synthesizing various pro-inflammatory cytokines which may indirectly influence specific immune responses. PMNs may also have the capacity to present foreign peptides to helper T cells (Th cells). In support of this hypothesis, recent studies have shown that neutrophils, when activated by the correct combination of cytokines, can be induced to express cell surface major histocompatibility complex (MHC) Class II (DR) antigen, CD80 (B7.1) and CD86 (B7.2): molecules required for antigen presentation and subsequent T-cell activation. In this study we have used normal "resting" human peripheral blood neutrophils and demonstrated, using a mild fixation and permeabilization protocol, significant cytoplasmic "stores" of these molecules known to be important in antigen presentation. Cytoplasmic MHC Class II antigen was found with two out of 20 normal donors tested whereas cytoplasmic CD80 and CD86 were found to a variable extent within all normal donors. Surprisingly, we also found several other neutrophil cytoplasmic CD antigens more commonly associated with B cells, i.e. CD20, CD21 (CR2/EBV-R) and CD22 (BL-CAM). All of these antigens were confined to the "resting" cell cytoplasm and were never found to be expressed on the cell surface. To exclude the possibility that these antigens were absorbed from plasma and to provide evidence for active synthesis, we used a novel whole blood in situ hybridization flow cytometry assay method to detect mRNA specific for these antigens within normal PMNs. We also conducted real-time polymerase chain reactions to confirm these findings using CD22 as a good example of an "inappropriately expressed" CD antigen. These observations therefore provide support for the hypothesis that human PMNs have the potential to express molecules required for antigen presentation and cell signalling.

Presence of B220 within thymocytes and its expression on the cell surface during apoptosis

B220 is the full-length splicing isoform of a tyrosine phosphatase CD45 and is predominantly expressed as a transmembrane protein on B cells. Other splicing isoforms of CD45 are yielded by alternative splicing of exons 4, 5 and 6. Recently, the expression of B220 on peripheral T cells during activation-induced cell death has been reported. To investigate whether B220 is implicated in apoptosis of immature T cells, we analysed (by flow cytometry using the anti-B220 monoclonal antibody, RA3-6B2) the expression of B220 on mouse thymocytes undergoing X-irradiation- and dexamethasone (DEX)-induced apoptosis. The expression of B220 on thymocytes positive for Thy-1 was induced by X-irradiation or DEX treatment and increased with length of incubation. The expression of B220 was pronounced on the apoptotic hypodiploid cells in the fraction showing lower forward scattering values. Reverse transcription-polymerase chain reaction detected mRNA containing exons 4, 5 and 6 of CD45 in normal thymocytes as well as those exposed to X-rays or DEX. Surprisingly, cytoplasmic B220 antigens were detected in a considerable fraction of normal thymocytes. Moreover, the expression level of the 220 000-MW protein in normal thymocytes was similar to that in the thymocytes undergoing apoptosis. During apoptosis, the expression level of B220 antigen was reduced in the cytoplasm but, conversely, up-regulated on the surface of thymocytes. These results suggest that B220 is constitutively expressed as a cytoplasmic form within thymocytes and possibly translocated to the cell membrane during apoptosis.

An expressed sequence tag database of T-cell-enriched activated chicken splenocytes: sequence analysis of 5251 clones

The cDNA and gene sequences of many mammalian cytokines and their receptors are known. However, corresponding information on avian cytokines is limited due to the lack of cross-species activity at the functional level or strong homology at the molecular level. To improve the efficiency of identifying cytokines and novel chicken genes, a directionally cloned cDNA library from T-cell-enriched activated chicken splenocytes was constructed, and the partial sequence of 5251 clones was obtained. Sequence clustering indicates that 2357 (42%) of the clones are present as a single copy, and 2961 are distinct clones, demonstrating the high level of complexity of this library. Comparisons of the sequence data with known DNA sequences in GenBank indicate that approximately 25% of the clones match known chicken genes, 39% have similarity to known genes in other species, and 11% had no match to any sequence in the database. Several previously uncharacterized chicken cytokines and their receptors were present in our library. This collection provides a useful database for cataloging genes expressed in T cells and a valuable resource for future investigations of gene expression in avian immunology. A chicken EST Web site (http://udgenome. ags.udel. edu/chickest/chick.htm) has been created to provide access to the data, and a set of unique sequences has been deposited with GenBank (Accession Nos. AI979741-AI982511). Our new Web site (http://www. chickest.udel.edu) will be active as of March 3, 2000, and will also provide keyword-searching capabilities for BLASTX and BLASTN hits of all our clones.