T follicular helper cells in space-time

Germinal centers B-cell reaction and T follicular helper cells in response to HIV-1 infection

PURPOSE OF REVIEW

This review aims to summarize the recent findings on germinal center B-cell reaction and Tfh cells in HIV-1 infection, with particular emphasis on the spatial organization of the germinal center, follicular cell regulation, and cellular alterations resulting from HIV infection.

RECENT FINDINGS

HIV-specific bNAbs are generated by iterative cycles of B-cell maturation supported by GC environment. Recent observations underline that germinal center structural alterations at the earliest stages of HIV infection could impact Tfh cell and germinal center B-cell homeostasis, thus preventing the rise of efficient humoral immunity. Moreover, despite ART treatment, HIV-derived antigens persist, particularly in follicular CD4+ T cells. Antigenic persistence and variability lead to unregulated chronic stimulation. In this context, regulation of the germinal center appears of special interest. In addition to follicular T-regulatory cells (Tfr), new potent regulators of germinal center reaction, such as follicular CD8 T and NK cells have been recently identified.

SUMMARY

Altogether these new data provide a better understanding on how HIV infection severely impacts germinal center reaction. Here we propose several therapeutic approaches to promote the bNAb development in HIV-infected patients by improving the preservation of germinal center architecture and its regulation.

Inhibition of IL-2 responsiveness by IL-6 is required for the generation of GC-TFH cells

Sustained T cell receptor (TCR) stimulation is required for maintaining germinal center T follicular helper (GC-T_FH) cells. Paradoxically, TCR activation induces interleukin-2 receptor (IL-2R) expression and IL-2 production, thereby initiating a feedback loop of IL-2 signaling that normally inhibits T_FH cells. It is unclear how GC-T_FH cells can receive prolonged TCR signaling without succumbing to the detrimental effects of IL-2. Using an influenza infection model, we show here that GC-T_FH cells secreted large amounts of IL-2 but responded poorly to it. To maintain their IL-2 hyporesponsiveness, GC-T_FH cells required intrinsic IL-6 signaling. Mechanistically, we found that IL-6 inhibited up-regulation of IL-2Rβ (CD122) by preventing association of STAT5 with the Il2rb locus, thus allowing GC-T_FH cells to receive sustained TCR signaling and produce IL-2 without initiating a TCR/IL-2 inhibitory feedback loop. Collectively, our results identify a regulatory mechanism that controls the generation of GC-T_FH cells.

Unexpected enhancement of FVIII immunogenicity by endothelial expression in lentivirus-transduced and transgenic mice

Factor VIII (FVIII) replacement therapy for hemophilia A is complicated by development of inhibitory antibodies (inhibitors) in ∼30% of patients. Because endothelial cells (ECs) are the primary physiologic expression site, we probed the therapeutic potential of genetically restoring FVIII expression selectively in ECs in hemophilia A mice (FVIIInull). Expression of FVIII was driven by the Tie2 promoter in the context of lentivirus (LV)-mediated in situ transduction (T2F8LV) or embryonic stem cell-mediated transgenesis (T2F8Tg). Both endothelial expression approaches were associated with a strikingly robust immune response. Following in situ T2F8LV-mediated EC transduction, all FVIIInull mice developed inhibitors but had no detectable plasma FVIII. In the transgenic approach, the T2F8Tg mice had normalized plasma FVIII levels, but showed strong sensitivity to developing an FVIII immune response upon FVIII immunization. A single injection of FVIII with incomplete Freund adjuvant led to high titers of inhibitors and reduction of plasma FVIII to undetectable levels. Because ECs are putative major histocompatibility complex class II (MHCII)-expressing nonhematopoietic, "semiprofessional" antigen-presenting cells (APCs), we asked whether they might directly influence the FVIII immune responses. Imaging and flow cytometric studies confirmed that both murine and human ECs express MHCII and efficiently bind and take up FVIII protein in vitro. Moreover, microvascular ECs preconditioned ex vivo with inflammatory cytokines could functionally present exogenously taken-up FVIII to previously primed CD4+/CXCR5+ T follicular helper (Tfh) cells to drive FVIII-specific proliferation. Our results show an unanticipated immunogenicity of EC-expressed FVIII and suggest a context-dependent role for ECs in the regulation of inhibitors as auxiliary APCs for Tfh cells.

Effects of sleep on the splenic milieu in mice and the T cell receptor repertoire recruited into a T cell dependent B cell response

Sleep is known to improve immune function ranging from cell distribution in the naïve state to elevated antibody titers after an immune challenge. The underlying mechanisms still remain unclear, partially because most studies have focused on the analysis of blood only. Hence, we investigated the effects of sleep within the spleen in female C57BL/6J mice with normal sleep compared to short-term sleep-deprived animals both in the naïve state and after an antigen challenge. Lack of sleep decreased the expression of genes associated with immune cell recruitment into and antigen presentation within the spleen both in the naïve state and during a T cell dependent B cell response directed against sheep red blood cells (SRBC). However, neither T cell proliferation nor formation of SRBC-specific antibodies was affected. In addition, the T cell receptor repertoire recruited into the immune response within seven days was not influenced by sleep deprivation. Thus, sleep modulated the molecular milieu within the spleen whereas we could not detect corresponding changes in the primary immune response against SRBC. Further studies will show whether sleep influences the secondary immune response against SRBC or the development of the B cell receptor repertoire, and how this can be compared to other antigens.

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Sleep deprivation (SD) decreases expression of genes involved in T cell function.

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SD induces those changes in the milieu of both lymph nodes and spleen.

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SD dampens the expression of several genes in the spleen during an immune response.

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SD does not alter the T cell receptor repertoire recruited into the immune response.

The Way Forward: Potentiating Protective Immunity to Novel and Pandemic Influenza Through Engagement of Memory CD4 T Cells

Potentially pandemic strains of influenza pose an undeniable threat to human populations. Therefore, it is essential to develop better strategies to enhance vaccine design and predict parameters that identify susceptible humans. CD4 T cells are a central component of protective immunity to influenza, delivering direct effector function and potentiating responses of other lymphoid cells. Humans have highly diverse influenza-specific CD4 T-cell populations that vary in stimulation history, specificity, and functionality. These complexities constitute a formidable obstacle to predicting immune responses to pandemic strains of influenza and derivation of optimal vaccine strategies. We suggest that more precise efforts to identify and enumerate both the positive and negative contributors of immunity in the CD4 T-cell compartment will aid in both predicting susceptible hosts and in development of vaccination strategies that will poise most human subjects to respond to pandemic influenza strains with protective immune responses.

Structure and function of the immune system in the spleen

The spleen is the largest secondary lymphoid organ in the body and, as such, hosts a wide range of immunologic functions alongside its roles in hematopoiesis and red blood cell clearance. The physical organization of the spleen allows it to filter blood of pathogens and abnormal cells and facilitate low-probability interactions between antigen-presenting cells (APCs) and cognate lymphocytes. APCs specific to the spleen regulate the T and B cell response to these antigenic targets in the blood. This review will focus on cell types, cell organization, and immunologic functions specific to the spleen and how these affect initiation of adaptive immunity to systemic blood-borne antigens. Potential differences in structure and function between mouse and human spleen will also be discussed.

CD4+ T cell phenotypes in the pathogenesis of immune thrombocytopenia

Immune thrombocytopenia (ITP) is an autoimmune disorder characterized by low platelet counts due to enhanced platelet clearance and compromised production. Traditionally, ITP was regarded a B cell mediated disorder as anti-platelet antibodies are detected in most patients. The very nature of self-antigens, evident processes of isotype switching and the affinity maturation of anti-platelet antibodies indicate that B cells in order to mount anti-platelet immune response require assistance of auto-reactive CD4⁺ T cells. For a long time, ITP pathogenesis has been exclusively reviewed through the prism of the disturbed balance between Th1 and Th2 subsets of CD4⁺ T cells, however, more recently new subsets of these cells have been described including Th17, Th9, Th22, T follicular helper and regulatory T cells. In this paper, we review the current understanding of the role and immunological mechanisms by which CD4⁺ T cells contribute to the pathogenesis of ITP.

T and B-cell signaling in activated PI3K delta syndrome: From immunodeficiency to autoimmunity

Phosphatidylinositol 3 kinases (PI3K) are a family of lipid kinases that are activated by a variety of cell-surface receptors, and regulate a wide range of downstream readouts affecting cellular metabolism, growth, survival, differentiation, adhesion, and migration. The importance of these lipid kinases in lymphocyte signaling has recently been highlighted by genetic analyses, including the recognition that both activating and inactivating mutations of the catalytic subunit of PI3Kδ, p110δ, lead to human primary immunodeficiencies. In this article, we discuss how studies on the human genetic disorder "Activated PI3K-delta syndrome" and mouse models of this disease (Pik3cd^E1020K/+ mice) have provided fundamental insight into pathways regulated by PI3Kδ in T and B cells and their contribution to lymphocyte function and disease, including responses to commensal bacteria and the development of autoimmunity and tumors. We highlight critical roles of PI3Kδ in T follicular helper cells and the orchestration of the germinal center reaction, as well as in CD8⁺ T-cell function. We further  present data demonstrating the ability of the AKT-resistant FOXO1^AAA mutant to rescue IgG1 class switching defects in Pik3cd^E1020K/+ B cells, as well as data supporting a role for PI3Kδ in promoting multiple T-helper effector cell lineages.

Regulation of immune system development and function by Cbl-mediated ubiquitination

Ubiquitination is a form of posttranslational protein modification that affects the activity of target proteins by regulating their intracellular degradation, trafficking, localization, and association with other regulators. Recent studies have placed protein ubiquitination as an important regulatory mode to control immune system development, function, and pathogenesis. In this review, we will mainly update the research progress from our laboratory on the roles of the Cbl family of E3 ubiquitin ligases in the development and function of lymphocytes and non-lymphoid cells. In addition, we will highlight our current understanding of the mechanisms used by this family of proteins, especially Cbl and Cbl-b, to co-ordinately regulate the function of various receptors and transcription factors in the context of immune regulation and diseases.

T follicular helper and T follicular regulatory cells in colorectal cancer: A complex interplay

Colorectal cancer is considered to be one of the major causes of morbidity and mortality all over the world. T Follicular helper (T_FH) and T follicular regulatory (T_FR) cells are specialized providers of T-cells to help B-cells and shaping germinal centers (GC) response. Recent researches reported a high percentage of T_FH and T_FR in different infectious diseases and certain malignancies. However, their functional role in human colorectal cancer (CRC) is relatively unknown. Furthermore, recent studies show that the interaction of both T_FH cells and T_FR cells are essential to promote several diseases. Under the control of specific cytokines and B-cell lymphoma 6 transcription factor (Bcl-6), the major transcription factor of T_FH cells, T_FH, can expand to the other distinct CD4 + T helper cells (TH1, TH2, and TH17) which exert a different role in the development of CRC. This review aims to discuss these suggested roles of the two-opposite subset of follicular T cells in colorectal cancer immune pathogenesis.

How to dissect the plasticity of antigen-specific immune response: a tissue perspective

Generation of antigen-specific humoral responses following vaccination or infection requires the maturation and function of highly specialized immune cells in secondary lymphoid organs (SLO), such as lymph nodes or tonsils. Factors that orchestrate the dynamics of these cells are still poorly understood. Currently, experimental approaches that enable a detailed description of the function of the immune system in SLO have been mainly developed and optimized in animal models. Conversely, methodological approaches in humans are mainly based on the use of blood-associated material because of the challenging access to tissues. Indeed, only few studies in humans were able to provide a discrete description of the complex network of cytokines, chemokines and lymphocytes acting in tissues after antigenic challenge. Furthermore, even fewer data are currently available on the interaction occurring within the complex micro-architecture of the SLO. This information is crucial in order to design particular vaccination strategies, especially for patients affected by chronic and immune compromising medical conditions who are under-vaccinated or who respond poorly to immunizations. Analysis of immune cells in different human tissues by high-throughput technologies, able to obtain data ranging from gene signature to protein expression and cell phenotypes, is needed to dissect the peculiarity of each immune cell in a definite human tissue. The main aim of this review is to provide an in-depth description of the current available methodologies, proven evidence and future perspectives in the analysis of immune mechanisms following immunization or infections in SLO.

Toll-like receptor 7 agonist imiquimod prevents the progression of SLE in MRL/lpr mice via inhibiting the differentiation of T follicular helper cells

Previous research has recently indicated that TLR7 is able to induce CD4⁺T cell anergy, which is the opposite of the role it plays in innate immune cells. Therefore, TLR7 ligands may be used as a manner in which to induce CD4⁺T cells "tolerance" in autoimmune diseases. T follicular helper (Tfh) cells were demonstrated to be a subset of CD4⁺T cells that help B cells produce antibodies. The abnormal activity of Tfh cells, though, is their function as a primary pathogenic factor in systemic lupus erythematosus (SLE). However, the role of TLR7 in Tfh cells is not clear. Our study was aimed at determining the influence of TLR7 on Tfh cells in a murine model of SLE (MRL/lpr mice). We were surprised to find that the frequency of Tfh cells and germinal center (GC) B cells was significantly reduced after treatment with the TLR7 agonist imiquimod. Imiquimod also significantly reduced the expression of inducible costimulatory molecule (ICOS) and programmed death 1(PD-1) in Tfh cells and decreased IL-21 secretion. Moreover, imiquimod significantly reduced the mRNA expression of several transcription factors, including Bcl-6, c-Maf, Batf3, Nfatc2 and Stat3, and enhanced the expression of Prdm1 and Stat5b in CD4⁺T cells. Imiquimod also ameliorated the progression of SLE in MRL/lpr mice by inhibiting anti-dsDNA antibodies and antinuclear antibody (ANA) secretion in the serum. Our findings indicated that TLR7 inhibited the development of Tfh cells both in vivo and ex vivo, which depended on many transcription factors aside from Bcl-6. Our results demonstrated that a TLR7 agonist has the potential to be used to inhibit Tfh cell responses during SLE.

Concepts of GPCR-controlled navigation in the immune system

G‐protein–coupled receptor (GPCR) signaling is essential for the spatiotemporal control of leukocyte dynamics during immune responses. For efficient navigation through mammalian tissues, most leukocyte types express more than one GPCR on their surface and sense a wide range of chemokines and chemoattractants, leading to basic forms of leukocyte movement (chemokinesis, haptokinesis, chemotaxis, haptotaxis, and chemorepulsion). How leukocytes integrate multiple GPCR signals and make directional decisions in lymphoid and inflamed tissues is still subject of intense research. Many of our concepts on GPCR‐controlled leukocyte navigation in the presence of multiple GPCR signals derive from in vitro chemotaxis studies and lower vertebrates. In this review, we refer to these concepts and critically contemplate their relevance for the directional movement of several leukocyte subsets (neutrophils, T cells, and dendritic cells) in the complexity of mouse tissues. We discuss how leukocyte navigation can be regulated at the level of only a single GPCR (surface expression, competitive antagonism, oligomerization, homologous desensitization, and receptor internalization) or multiple GPCRs (synergy, hierarchical and non‐hierarchical competition, sequential signaling, heterologous desensitization, and agonist scavenging). In particular, we will highlight recent advances in understanding GPCR‐controlled leukocyte navigation by intravital microscopy of immune cells in mice.

The frequency of Tim-3 on circulating Tfh cells was increased in type 2 diabetes mellitus patients

Type 2 diabetes mellitus (T2DM) is a chronic, low-grade inflammation disease. T follicular helper (Tfh) cells and T cell immunoglobulin and mucin domain 3 (Tim-3) are implicated in many immune diseases. This study aims to explore whether Tim-3 expression on Tfh cells is associated with T2DM progression. White blood cells (WBCs) were harvested from 30 patients with T2DM and 20 healthy donors. The abundance of circulating Tfh cells (cTfh) and the frequency of Tim-3 were analyzed by flow cytometry. Levels of fasting plasma glucose (FPG), insulin, hemoglobin A1C (HbA1C), and fasting plasma C-peptide were measured. Body mass index (BMI) and diabetes duration were also recorded. Patients with T2DM had higher numbers of cTfh cells. In addition, cTfh cells showed a negative correlation with HbA1C and diabetes duration, a positive correlation with fasting plasma C-peptide. The frequency of Tim-3 on cTfh cells was higher among T2DM patients compared with healthy donors. The in vitro experiment showed that high glucose levels increased the abundance cTfh cells but had no effect on Tim-3 expression. Our results suggest that cTfh cells and associated Tim-3 frequency may contribute to the progression of T2DM, and high glucose levels may influence cTfh cells directly.

The Critical Role of Bach2 in Shaping the Balance between CD4+ T Cell Subsets in Immune-Mediated Diseases

The transcription factor Bach2 which is predominantly expressed in B and T lymphocytes represses the expression of genes by forming heterodimers with small Maf and Batf proteins and binding to the corresponding sequence on the DNA. In this way, Bach2 serves as a highly conserved repressor which controls the terminal differentiation and maturation of both B and T lymphocytes. It is required for class switch recombination (CSR) and somatic hypermutation (SHM) of immunoglobulin genes in activated B cells, and its function in B cell differentiation has been well-described. Furthermore, emerging data show that Bach2 regulates transcriptional activity in T cells at super enhancers or regions of high transcriptional activity, thus stabilizing immunoregulatory capacity and maintaining T cell homeostasis. Bach2 is also critical for the formation and function of CD4⁺ T cell lineages (Th1, Th2, Th9, Th17, T follicular helper (Tfh), and regulatory T (Treg) cells). Genetic variations within Bach2 locus are associated with numerous immune-mediated diseases including multiple sclerosis (MS), rheumatoid arthritis (RA), chronic pancreatitis (CP), type 2 chronic airway inflammation, inflammatory bowel disease (IBD), and type 1 diabetes. Here, we reveal a critical role of Bach2 in regulating T cell biology and the correlation with these immune-mediated diseases.

T follicular helper cell heterogeneity: Time, space, and function

T follicular helper (Tfh) cells play a crucial role in orchestrating the humoral arm of adaptive immune responses. Mature Tfh cells localize to follicles in secondary lymphoid organs (SLOs) where they provide help to B cells in germinal centers (GCs) to facilitate immunoglobulin affinity maturation, class-switch recombination, and generation of long-lived plasma cells and memory B cells. Beyond the canonical GC Tfh cells, it has been increasingly appreciated that the Tfh phenotype is highly diverse and dynamic. As naive CD4⁺ T cells progressively differentiate into Tfh cells, they migrate through a variety of microanatomical locations to obtain signals from other cell types, which in turn alters their phenotypic and functional profiles. We herein review the heterogeneity of Tfh cells marked by the dynamic phenotypic changes accompanying their developmental program. Focusing on the various locations where Tfh and Tfh-like cells are found, we highlight their diverse states of differentiation. Recognition of Tfh cell heterogeneity has important implications for understanding the nature of T helper cell identity specification, especially the plasticity of the Tfh cells and their ontogeny as related to conventional T helper subsets.

The role of actin and myosin in antigen extraction by B lymphocytes

B cells must extract antigens attached to the surface of antigen presenting cells to generate high-affinity antibodies. Antigen extraction requires force, and recent studies have implicated actomyosin-dependent pulling forces generated within the B cell as the major driver of antigen extraction. These actomyosin-dependent pulling forces also serve to test the affinity of the B cell antigen receptor for antigen prior to antigen extraction. Such affinity discrimination is central to the process of antibody affinity maturation. Here we review the evidence that actomyosin-dependent pulling forces generated within the B cell promote affinity discrimination and power antigen extraction. Our take on these critical B cell functions is influenced significantly by the recent identification of formin-generated, myosin-rich, concentric actin arcs in the medial portion of the T cell immune synapse, as B cells appear to contain a similar contractile actomyosin structure.

Peptide Epitope Hot Spots of CD4 T Cell Recognition Within Influenza Hemagglutinin During the Primary Response to Infection

Antibodies specific for the hemagglutinin (HA) protein of influenza virus are critical for protective immunity to infection. Our studies show that CD4 T cells specific for epitopes derived from HA are the most effective in providing help for the HA-specific B cell responses to infection and vaccination. In this study, we asked whether HA epitopes recognized by CD4 T cells in the primary response to infection are equally distributed across the HA protein or if certain segments are enriched in CD4 T cell epitopes. Mice that collectively expressed eight alternative MHC (Major Histocompatibility Complex) class II molecules, that would each have different peptide binding specificities, were infected with an H1N1 influenza virus. CD4 T cell peptide epitope specificities were identified by cytokine EliSpots. These studies revealed that the HA-specific CD4 T cell epitopes cluster in two distinct regions of HA and that some segments of HA are completely devoid of CD4 T cell epitopes. When located on the HA structure, it appears that the regions that most poorly recruit CD4 T cells are sequestered within the interior of the HA trimer, perhaps inaccessible to the proteolytic machinery inside the endosomal compartments of antigen presenting cells.

The regulators of BCR signaling during B cell activation

B lymphocytes produce antibodies under the stimulation of specific antigens, thereby exerting an immune effect. B cells identify antigens by their surface B cell receptor (BCR), which upon stimulation, directs the cell to activate and differentiate into antibody generating plasma cells. Activation of B cells via their BCRs involves signaling pathways that are tightly controlled by various regulators. In this review, we will discuss three major BCR mediated signaling pathways (the PLC-γ2 pathway, PI3K pathway and MAPK pathway) and related regulators, which were roughly divided into positive, negative and mutual-balanced regulators, and the specific regulators of the specific signaling pathway based on regulatory effects.

The Construction and Comprehensive Analysis of ceRNA Networks and Tumor-Infiltrating Immune Cells in Bone Metastatic Melanoma

Background/Aims: As a malignant and melanocytic tumor, cutaneous melanoma is the devastating skin tumor with high rates of recurrence and metastasis. Bone is the common metastatic location, and bone metastasis may result in pathologic fracture, neurologic damage, and severe bone pain. Although metastatic melanoma was reported to get benefits from immunotherapy, molecular mechanisms and immune microenviroment underlying the melanoma bone metastasis and prognostic factors are still unknown.

Methods: Gene expression profiling of 112 samples, including 104 primary melanomas and 8 bone metastatic melanomas from The Cancer Genome Atlas database, was assayed to construct a ceRNA network associated with bone metastases. Besides, we detected the fraction of 22 immune cell types in melanoma via the algorithm of “cell type identification by estimating relative subsets of RNA transcripts (CIBERSORT).” Based on the significant ceRNAs or immune cells, we constructed nomograms to predict the prognosis of patients with melanoma. Ultimately, correlation analysis was implemented to discover the relationship between the significant ceRNA and immune cells to reveal the potential signaling pathways.

Results: We constructed a ceRNA network based on the interaction among 8 pairs of long noncoding RNA–microRNA and 15 pairs of microRNA–mRNA. CIBERSORT and ceRNA integration analysis discovered that AL118506.1 has both significant prognostic value (P = 0.002) and high correlation with T follicular helper cells (P = 0.033). Meanwhile, T cells CD8 and macrophages M2 were negatively correlated (P < 0.001). Moreover, we constructed two satisfactory nomograms (area under curve of 3-year survival: 0.899; 5-year survival: 0.885; and concordance index: 0.780) with significant ceRNAs or immune cells, to predict the prognosis of patients.

Conclusions: In this study, we suggest that bone metastasis in melanoma might be related to AL118506.1 and its role in regulating thrombospondin 2 and T follicular helper cells. Two nomograms were constructed to predict the prognosis of patients with melanoma and demonstrated their value in improving the personalized management.

T cell immune response within B-cell follicles

B-cell follicle represents a functionally dynamic microstructure within second lymphoid tissues, predominantly consisting of B cells, follicular T cells and DCs. Through intimate interactions with cognate B cells, follicular helper T cells (Tfh) initiate and facilitate germinal center (GC) reactions by providing signals required for producing high-affinity antibodies, as well as for the generation of long-lived antibody-secreting plasma cells and memory B cells. Concomitantly, germinal center reaction needs to be fine controlled to avoid autoimmunity or B-cell malignancies. Among immune cells residing in follicles, follicular regulatory T cells (Tfr), converted from naïve Treg cells, are specifically assigned to repress excessive GC responses by suppressing Tfh and GC B cells within GC structure. Hence, through Yin and Yang (positive and negative) regulation of GC reaction, Tfh cells play concert with Tfr cells in maintaining immune homeostasis. Besides CD4⁺ T cells, a small portion of CXCR5 expressing CD8⁺ T cells, regarded as follicular cytotoxic T cells (Tfc), could migrate into B cell follicles during chronic viral infection and several types of cancers, and this population exhibit lower level of exhaustion than its CXCR5^- counterparts. Besides, Tfc cells demonstrate a stem-cell like phenotype during chronic infection which could further differentiate into terminally differentiated CXCR5^-CD8⁺ T cells. Collectively, in this review, we will discuss the recent advances in our understanding of the ontology and differentiation of B-cell follicle resident Tfh, Tfr and Tfc cells.

Targeting Antigens to CD180 but Not CD40 Programs Immature and Mature B Cell Subsets to Become Efficient APCs

Targeting Ags to the CD180 receptor activates both B cells and dendritic cells (DCs) to become potent APCs. After inoculating mice with Ag conjugated to an anti-CD180 Ab, B cell receptors were rapidly internalized. Remarkably, all B cell subsets, including even transitional 1 B cells, were programed to process, present Ag, and stimulate Ag-specific CD4⁺ T cells. Within 24-48 hours, Ag-specific B cells were detectable at T-B borders in the spleen; there, they proliferated in a T cell-dependent manner and induced the maturation of T follicular helper (T_FH) cells. Remarkably, immature B cells were sufficient for the maturation of T_FH cells after CD180 targeting: T_FH cells were induced in BAFFR^-/- mice (with only transitional 1 B cells) and not in μMT mice (lacking all B cells) following CD180 targeting. Unlike CD180 targeting, CD40 targeting only induced DCs but not B cells to become APCs and thus failed to efficiently induce T_FH cell maturation, resulting in slower and lower-affinity IgG Ab responses. CD180 targeting induces a unique program in Ag-specific B cells and to our knowledge, is a novel strategy to induce Ag presentation in both DCs and B cells, especially immature B cells and thus has the potential to produce a broad range of Ab specificities. This study highlights the ability of immature B cells to present Ag to and induce the maturation of cognate T_FH cells, providing insights toward vaccination of mature B cell-deficient individuals and implications in treating autoimmune disorders.

Circulating B Cells With Memory and Antibody-Secreting Phenotypes Are Detectable in Pediatric Kidney Transplant Recipients Before the Development of Antibody-Mediated Rejection

Development of anti-human leukocyte antigen donor-specific antibodies (DSAs) is associated with antibody-mediated rejection (AMR) and reduced allograft survival in kidney transplant recipients. Whether changes in circulating lymphocytes anticipate DSA or AMR development is unclear.

METHODS

We used time-of-flight mass cytometry to analyze prospectively collected peripheral blood mononuclear cells (PBMC) from pediatric kidney transplant recipients who developed DSA (DSA-positive recipients [DSAPOS], n = 10). PBMC were obtained at 2 months posttransplant, 3 months before DSA development, and at DSA detection. PBMC collected at the same time points posttransplant from recipients who did not develop DSA (DSA-negative recipients [DSANEG], n = 11) were used as controls.

RESULTS

DSAPOS and DSANEG recipients had similar baseline characteristics and comparable frequencies of total B and T cells. Within DSAPOS recipients, there was no difference in DSA levels (mean fluorescence intensity [MFI]: 13 687 ± 4159 vs 11 375 ± 1894 in DSAPOSAMR-positive recipients (AMRPOS) vs DSAPOSAMR-negative recipients (AMRNEG), respectively; P = 0.630), C1q binding (5 DSAPOSAMRPOS [100%] vs 4 DSAPOSAMRNEG [80%]; P = 1.000), or C3d binding (3 DSAPOSAMRPOS [60%] vs 1 DSAPOSAMRNEG [20%]; P = 0.520) between patients who developed AMR and those who did not. However, DSAPOS patients who developed AMR (n = 5; 18.0 ± 3.6 mo post-DSA detection) had increased B cells with antibody-secreting (IgD-CD27+CD38+; P = 0.002) and memory (IgD-CD27+CD38-; P = 0.003) phenotypes compared with DSANEG and DSAPOSAMRNEG recipients at DSA detection.

CONCLUSIONS

Despite the small sample size, our comprehensive phenotypic analyses show that circulating B cells with memory and antibody-secreting phenotypes are present at DSA onset, >1 year before biopsy-proven AMR in pediatric kidney transplant recipients.

Excessive CD11c+Tbet+ B cells promote aberrant TFH differentiation and affinity-based germinal center selection in lupus

Excessive self-reactive and inadequate affinity-matured antigen-specific antibody responses have been reported to coexist in lupus, with elusive cellular and molecular mechanisms. Here, we report that the antigen-specific germinal center (GC) response-a process critical for antibody affinity maturation-is compromised in murine lupus models. Importantly, this defect can be triggered by excessive autoimmunity-relevant CD11c⁺Tbet⁺ age-associated B cells (ABCs). In B cell-intrinsic Ship-deficient (ShipΔB) lupus mice, excessive CD11c⁺Tbet⁺ ABCs induce deregulated follicular T-helper (T_FH) cell differentiation through their potent antigen-presenting function and consequently compromise affinity-based GC selection. Excessive CD11c⁺Tbet⁺ ABCs and deregulated T_FH cell are also present in other lupus models and patients. Further, over-activated Toll-like receptor signaling in Ship-deficient B cells is critical for CD11c⁺Tbet⁺ ABC differentiation, and blocking CD11c⁺Tbet⁺ ABC differentiation in ShipΔB mice by ablating MyD88 normalizes T_FH cell differentiation and rescues antigen-specific GC responses, as well as prevents autoantibody production. Our study suggests that excessive CD11c⁺Tbet⁺ ABCs not only contribute significantly to autoantibody production but also compromise antigen-specific GC B-cell responses and antibody-affinity maturation, providing a cellular link between the coexisting autoantibodies and inadequate affinity-matured antigen-specific antibodies in lupus models and a potential target for treating lupus.

The critical role of Bach2 in regulating type 2 chronic airway inflammation

Although Bach2 (broad complex-tramtrack-bric a brac and Cap'n'collar homology 2) plays an important role in regulating Th2 cell differentiation and type 2 immune responses, the underlying molecular mechanisms remain unclear. Our current studies demonstrate that Bach2 associates with Batf (basic leucine zipper transcription factor ATF-like) family transcription factors and binds to the regulatory regions of the Th2 cytokine gene loci. The Bach2-Batf complex antagonizes the recruitment of the interferon regulatory factor 4 (Irf4)-containing Batf complex to activator protein 1 (AP-1) motifs in the Th2 cytokine gene locus and suppresses Th2 cytokine production and/or Th2 cell differentiation. The deletion of Batf ameliorated the spontaneous development of type 2 airway inflammation that is found in mice with Bach2 deficiency specifically in T cells. Interestingly, Bach2 regulates Batf and Batf3 expression via two distinct pathways. First, the Bach2-Batf complex directly binds to the Batf and Batf3 gene loci and reduces transcription by interfering with the Batf-Irf4 complex. Second, Bach2 suppresses interleukin 4 (IL-4)-induced augmentation of Batf and Batf3 expression through the regulation of IL-4 production. These findings suggest that IL-4 and Batf family transcription factors form a positive feedback amplification loop to induce Th2 cell differentiation and that Bach2-Batf interactions block the formation of this amplification loop. Furthermore, we found that reductions in Bach2 confer an innate immunological function on CD4 T cells to induce antigen-independent cytokine production. Some Bach2-deficient lung CD4 T cells showed characteristic features similar to pathogenic Th2 cells, including IL-33 receptor expression and IL-33-dependent Th2 cytokine production. These results suggest a critical role for Bach2 in regulating Th2 cell differentiation and the subsequent onset of chronic type 2 inflammation.

Circulating follicular T helper cells are possibly associated with low levels of serum immunoglobulin G due to impaired immunoglobulin class-switch recombination of B cells in children with primary nephrotic syndrome

Clinically, most patients with primary nephrotic syndrome (PNS) have low serum IgG levels, which is an important factor in infection and in PNS relapse.To some extent, the mechanisms involved remain largely unknown. Here, we aimed to investigate the pathogenesis of the decreased IgG levels in PNS. Peripheral blood was collected from patients with PNS and closely age- and sex-matched healthy individuals. The frequency, phenotype and molecular function of different circulating B cell and T follicular helper cell (TFH) subsets were examined by flow cytometry. The function of the CD40/CD40 L interaction in immunoglobulin class-switch recombination (CSR) was evaluated by assessing the induction of activation-induced deaminase (AID) expression with CD40 L stimulation. We revealed an increase in the levels of circulating total plasmablasts, plasma cells and mature-naive B cells and a decrease in the levels of germinal centre-like B cells and CD19⁺IgG⁺ B cells in PNS. In addition, although the expression of CD86 on the surface of B cells and the expression of the inducible costimulator (ICOS) on the surface of TFH cells both were increased, the expression of CD40 L on the surface of TFH cells was decreased. Moreover, upon stimulation with CD40 L in vitro, the mRNA expression of AID in peripheral blood mononuclear cells (PBMCs) was decreased in patients with PNS compared with that in healthy controls. Our results indicate that the immunoglobulin CSR of B cells was partly dysfunctional and provide insights into the potential involvement of impaired TFH cell-dependent B cell responses in the pathogenesis of low IgG levels through downregulating CD40 L expression on TFH cells in PNS.

T follicular helper cells in human efferent lymph retain lymphoid characteristics

T follicular helper cells (Tfh), a subset of CD4+ T cells, provide requisite help to B cells in the germinal centers (GC) of lymphoid tissue. GC Tfh are identified by high expression of the chemokine receptor CXCR5 and the inhibitory molecule PD-1. Although more accessible, blood contains lower frequencies of CXCR5+ and PD-1+ cells that have been termed circulating Tfh (cTfh). However, it remains unclear whether GC Tfh exit lymphoid tissues and populate this cTfh pool. To examine exiting cells, we assessed the phenotype of Tfh present within the major conduit of efferent lymph from lymphoid tissues into blood, the human thoracic duct. Unlike what was found in blood, we consistently identified a CXCR5-bright PD-1-bright (CXCR5BrPD-1Br) Tfh population in thoracic duct lymph (TDL). These CXCR5BrPD-1Br TDL Tfh shared phenotypic and transcriptional similarities with GC Tfh. Moreover, components of the epigenetic profile of GC Tfh could be detected in CXCR5BrPD-1Br TDL Tfh and the transcriptional imprint of this epigenetic signature was enriched in an activated cTfh subset known to contain vaccine-responding cells. Together with data showing shared TCR sequences between the CXCR5BrPD-1Br TDL Tfh and cTfh, these studies identify a population in TDL as a circulatory intermediate connecting the biology of Tfh in blood to Tfh in lymphoid tissue.

Human lymphoid organ cDC2 and macrophages play complementary roles in T follicular helper responses

CD4+ T follicular helper (Tfh) cells are essential for inducing efficient humoral responses. T helper polarization is classically orientated by dendritic cells (DCs), which are composed of several subpopulations with distinct functions. Whether human DC subsets display functional specialization for Tfh polarization remains unclear. Here we find that tonsil cDC2 and CD14+ macrophages are the best inducers of Tfh polarization. This ability is intrinsic to the cDC2 lineage but tissue dependent for macrophages. We further show that human Tfh cells comprise two effector states producing either IL-21 or CXCL13. Distinct mechanisms drive the production of Tfh effector molecules, involving IL-12p70 for IL-21 and activin A and TGFβ for CXCL13. Finally, using imaging mass cytometry, we find that tonsil CD14+ macrophages localize in situ in the B cell follicles, where they can interact with Tfh cells. Our results indicate that human lymphoid organ cDC2 and macrophages play complementary roles in the induction of Tfh responses.

TLR-2 and TLR-4 agonists favor expansion of CD4+ T cell subsets implicated in the severity of neuromyelitis optica spectrum disorders

BACKGROUND

High frequency of circulating Th17 cell subsets expressing TLR2, TLR4 and TLR9 was observed in Neuromyelitis optica spectrum disorder (NMOSD) patients, a severe humoral autoimmune disease of the central nervous system. Our objective was to evaluate the direct effects of different TLR ligands on CD4⁺ T-cells form those patients.

METHODS

CD4⁺ T-cell cultures from NMOSD and healthy individuals were stimulated with different TLR ligands and the cell proliferation and cytokine profile was analyzed by [³H] TdR up take and ELISA/ cytometry, respectively. The plasma levels of CD14 were determined by ELISA.

RESULTS

Here, Pam3C (TLR2) and LPS (TLR4) induced significant cell proliferation and IL-6, IL-17 and IL-21 production by CD4⁺ T-cells from NMOSD. Additionally, while both TLR ligands were more potent in favoring the expansion of T_FH-like cells, Pam3C reduced the frequency of IL-10-secreting FoxP3⁺and FoxP3^- CD4⁺ T-cells. With regard to disease severity, the levels of IL-6, IL-17 and IL-21 produced by CD4⁺ T-cells, as well as the frequency of T_FH-like cells, in response to TLR2 and TLR4 agonists were positively correlated with neurological disabilities and the occurrence of new acute relapses during follow up. Finally, circulating levels of CD14, an indirect marker of microbial translocation, were positively correlated with IL-6, IL-17 and IL-21 release by Pam3C- and LPS-activated CD4⁺ T-cells.

CONCLUSIONS

In summary, our data suggest that microbial antigens may affect NMOSD outcomes by favoring an imbalance between Th17 and TFH-like cells and regulatory T cell subsets.

Clinical spectrum, evolution, and management of autoimmune cytopenias associated with angioimmunoblastic T-cell lymphoma

OBJECTIVE

Angioimmunoblastic T-cell lymphoma (AITL) is frequently associated with autoimmune cytopenia (AIC). Whether such patients have a particular phenotype and require particular management is unclear.

METHOD

Angioimmunoblastic T-cell lymphoma patients from the multicentric database of the Lymphoma Study Association presenting with AIC during disease course were included and matched to AITL patients without AIC (1/5 ratio).

RESULTS

At diagnosis, AIC patients (n = 28) had more spleen and bone marrow involvement (54% vs 19% and 71% vs 34%, P < 0.001), Epstein-Barr virus replication (89% vs 39%, P < 0.001), gamma globulin titers (median 23 vs 15 g/L, P = 0.002), and proliferating B cells and plasmablasts in biopsies, as compared to control patients (n = 136). The 28 AIC patients had 41 episodes of AIC, diagnosed concomitantly with AITL in 23 (82%) cases. After a median follow-up of 24 months (range 3-155), 10 patients relapsed, all associated with AITL relapse.

CONCLUSION

Our results provide new insight into AIC associated with AITL by highlighting the significant interplay between AITL and B-cell activation leading to subsequent autoimmunity.

Exploiting CD22 To Selectively Tolerize Autoantibody Producing B-Cells in Rheumatoid Arthritis

Rheumatoid arthritis (RA) is an autoimmune disease that primarily affects the synovial joints and can lead to bone erosion and cartilage damage. One hallmark of RA is anticitrullinated protein autoantibodies (ACPA) and memory citrulline-specific B-cells, which have been implicated in RA pathogenesis. While depletion of B-cells with Rituximab improves clinical responses in RA patients, this treatment strategy leaves patients susceptible to infections. Here we use of Siglec-engaging Tolerance-inducing Antigenic Liposomes (STALs) to selectively target the citrulline-specific B-cells. ACPA production from purified human RA patients' B-cells in vitro was achieved through a set of stimulation conditions, which includes the following: BAFF, anti-CD40, IL-21, and LPS. In vivo generation of citrulline specific B-cells and ACPA production was accomplished by antigenic liposomes consisting of monophosphoryl lipid A (MPLA) and a cyclic citrullinated peptide (CCP) administered to SJL/J mice. We show that STALs that codisplay a high affinity CD22 glycan ligand and synthetic citrullinated antigen (CCP STALs) can prevent ACPA production from RA patients' memory B-cells in vitro. These CCP STALs were also effective in inducing tolerance to citrullinated antigens in SJL/J mice. The results demonstrate that tolerization of the B-cells responsible for ACPA can be achieved by exploiting the inhibitory receptor CD22 with high-affinity glycan ligands. Such a treatment strategy could be beneficial in the treatment of RA.

CD4 T cells in protection from influenza virus: Viral antigen specificity and functional potential

CD4 T cells convey a number of discrete functions to protective immunity to influenza, a complexity that distinguishes this arm of adaptive immunity from B cells and CD8 T cells. Although the most well recognized function of CD4 T cells is provision of help for antibody production, CD4 T cells are important in many aspects of protective immunity. Our studies have revealed that viral antigen specificity is a key determinant of CD4 T cell function, as illustrated both by mouse models of infection and human vaccine responses, a factor whose importance is due at least in part to events in viral antigen handling. We discuss research that has provided insight into the diverse viral epitope specificity of CD4 T cells elicited after infection, how this primary response is modified as CD4 T cells home to the lung, establish memory, and after challenge with a secondary and distinct influenza virus strain. Our studies in human subjects point out the challenges facing vaccine efforts to facilitate responses to novel and avian strains of influenza, as well as strategies that enhance the ability of CD4 T cells to promote protective antibody responses to both seasonal and potentially pandemic strains of influenza.

Immunological abnormalities in patients with primary biliary cholangitis

Primary biliary cholangitis (PBC), an autoimmune liver disease occurring predominantly in women, is characterized by high titers of serum anti-mitochondrial antibodies (AMAs) and progressive intrahepatic cholestasis. The immune system plays a critical role in PBC pathogenesis and a variety of immune cell subsets have been shown to infiltrate the portal tract areas of patients with PBC. Amongst the participating immune cells, CD4 T cells are important cytokine-producing cells that foster an inflammatory microenvironment. Specifically, these cells orchestrate activation of other immune cells, including autoreactive effector CD8 T cells that cause biliary epithelial cell (BEC) injury and B cells that produce large quantities of AMAs. Meanwhile, other immune cells, including dendritic cells (DCs), natural killer (NK) cells, NKT cells, monocytes, and macrophages are also important in PBC pathogenesis. Activation of these cells initiates and perpetuates bile duct damage in PBC patients, leading to intrahepatic cholestasis, hepatic damage, liver fibrosis, and eventually cirrhosis or even liver failure. Taken together, the body of accumulated clinical and experimental evidence has enhanced our understanding of the immunopathogenesis of PBC and suggests that immunotherapy may be a promising treatment option. Herein, we summarize current knowledge regarding immunological abnormalities of PBC patients, with emphasis on underlying pathogenic mechanisms. The differential immune response which occurs over decades of disease activity suggests that different therapies may be needed at different stages of disease.

Programming Isotype-Specific Plasma Cell Function

Helper T cell induced plasma cells (PCs) that secrete class-switched neutralizing antibody are paramount to effective immunity. Following class-switch recombination (CSR), antigen-activated B cells differentiate into extrafollicular PCs or mature in germinal centers (GCs) to produce high-affinity memory B cells and follicular PCs. Many studies focus on the core transcriptional programs that drive central PC functions of longevity and antibody secretion. However, it is becoming clear that these central programs are further subdivided across antibody isotype with separable transcriptional trajectories. Divergent functions emerge at CSR, persist through PC terminal differentiation and further assort memory PC function following antigen recall. Here, we emphasize recent work that assorts divergent isotype-specific PC function across four major modules of immune protection.

Pivotal role for αV integrins in sustained Tfh support of the germinal center response for long-lived plasma cell generation

CD4+ follicular helper T cells (Tfh) are essential for germinal center (GC) reactions in the lymph node that generate high-affinity, long-lived plasma cells (LLPCs). Temporal GC analysis suggests B memory cells (Bmem) are generated early, while LLPCs are generated late in the GC reaction. Distinct roles for Tfh at these temporally different stages are not yet clear. Tfh entry into the GC is highly dynamic and the signals that maintain Tfh within the GC for support of late LLPC production are poorly understood. The GC is marked by inflammation-induced presentation of specific ECM components. To determine if T cell recognition of these ECM components played a role in Tfh support of the GC, we immunized mice with a T cell-restricted deletion of the ECM-binding integrin α_V (α_V-CD4 cKO). T cell integrin α_V deletion led to a striking defect in the number and size of the GCs following immunization with OVA protein in complete Freund's adjuvant. The GC defect was not due to integrin α_V deficiency impeding Tfh generation or follicle entry or the ability of α_V-CD4 cKO Tfh to contact and support B cell activation. Instead, integrin α_V was essential for T cell-intrinsic accumulation within the GC. Altered Tfh positioning resulted in lower-affinity antibodies and a dramatic loss of LLPCs. Influenza A infection revealed that α_V integrin was not required for Tfh support of Bmem but was essential for Tfh support of LLPCs. We highlight an α_V integrin-ECM-guided mechanism of Tfh GC accumulation that selectively impacts GC output of LLPCs but not Bmem.

Molecular Basis of the Differentiation and Function of Virus Specific Follicular Helper CD4+ T Cells

During viral infection, virus-specific follicular helper T cells provide important help to cognate B cells for their survival, consecutive proliferation and mutation and eventual differentiation into memory B cells and antibody-secreting plasma cells. Similar to Tfh cells generated in other conditions, the differentiation of virus-specific Tfh cells can also be characterized as a process involved multiple factors and stages, however, which also exhibits distinct features. Here, we mainly focus on the current understanding of Tfh fate commitment, functional maturation, lineage maintenance and memory transition and formation in the context of viral infection.

Dendritic cell subsets in T cell programming: location dictates function

Dendritic cells (DCs) can be viewed as translators between innate and adaptive immunity. They integrate signals derived from tissue infection or damage and present processed antigen from these sites to naive T cells in secondary lymphoid organs while also providing multiple soluble and surface-bound signals that help to guide T cell differentiation. DC-mediated tailoring of the appropriate T cell programme ensures a proper cascade of immune responses that adequately targets the insult. Recent advances in our understanding of the different types of DC subsets along with the cellular organization and orchestration of DC and lymphocyte positioning in secondary lymphoid organs over time has led to a clearer understanding of how the nature of the T cell response is shaped. This Review discusses how geographical organization and ordered sequences of cellular interactions in lymph nodes and the spleen regulate immunity.

Costimulatory blockade molecules and B-cell-mediated immune response: current knowledge and perspectives

There is an urgent need for therapeutic agents that target humoral alloimmunity in solid organ transplantation. This includes sensitized patients with preformed donor-specific human leukocyte antigen antibodies and patients who develop de novo donor-specific antibodies, both of which are associated with acute and chronic antibody-mediated rejection and allograft loss. In the last decade, both experimental and clinical studies highlighted the major impact of costimulation molecules in the control of immune responses both in the field of transplantation and autoimmune disease. Although these molecules have been initially developed to control the early steps of T-cell activation, recent evidence also supports their influence at several steps of the humoral response. In this review, we aim to provide an overview of the current knowledge of the effects of costimulatory blockade agents on humoral responses in both autoimmune and allogeneic contexts. We first present the effects of costimulatory molecules on the different steps of alloantibody production. We then summarize mechanisms and clinical results observed using cytotoxic T lymphocyte antigen-4 (CTLA4)-Ig molecules both in transplantation and autoimmunity. Finally, we present the potential interest and implications of other costimulatory family members as therapeutic targets, with emphasis on combinatorial approaches, for the optimal control of the alloantigen-specific humoral response.

The expansion of circulating IL-6 and IL-17-secreting follicular helper T cells is associated with neurological disabilities in neuromyelitis optica spectrum disorders

Due to their function in assisting B cells, T_FH cells may be involved in the production of pathogenic IgG in neuromyelitis optica spectrum disorder (NMOSD). In the present study, the proportion of IL-6⁺ and IL-17⁺ T_FH cell subsets was higher in NMOSD patients than healthy individuals. The frequency of both T_FH cell subsets were directly associated with disease activity. By contrast, NMOSD patients with a higher proportion of IL-10⁺ T_FH cell subsets showed a lower neurological disabilities score. In summary, all findings suggest that expansion of peripheral IL-6⁺ and IL-17⁺ T_FH cells may be involved in the severity of NMOSD.

PI3K Orchestrates T Follicular Helper Cell Differentiation in a Context Dependent Manner: Implications for Autoimmunity

T follicular helper (Tfh) cells are a specialized population of CD4⁺ T cells that provide help to B cells for the formation and maintenance germinal centers, and the production of high affinity class-switched antibodies, long-lived plasma cells, and memory B cells. As such, Tfh cells are essential for the generation of successful long-term humoral immunity and memory responses to vaccination and infection. Conversely, overproduction of Tfh cells has been associated with the generation of autoantibodies and autoimmunity. Data from gene-targeted mice, pharmacological inhibitors, as well as studies of human and mice expressing activating mutants have revealed that PI3Kδ is a key regulator of Tfh cell differentiation, acting downstream of ICOS to facilitate inactivation of FOXO1, repression of Klf2 and induction of Bcl6. Nonetheless, here we show that after acute LCMV infection, WT and activated-PI3Kδ mice (Pik3cd^E1020K/+) show comparable ratios of Tfh:Th1 viral specific CD4⁺ T cells, despite higher polyclonal Tfh cells in Pik3cd^E1020K/+ mice. Thus, the idea that PI3K activity primarily drives Tfh cell differentiation may be an oversimplification and PI3K-mediated pathways are likely to integrate multiple signals to promote distinct effector T cell lineages. The consequences of dysregulated Tfh cell generation will be discussed in the context of the human primary immunodeficiency “Activated PI3K-delta Syndrome” (APDS), also known as “p110 delta-activating mutation causing senescent T cells, lymphadenopathy and immunodeficiency” (PASLI). Overall, these data underscore a major role for PI3K signaling in the orchestration of T lymphocyte responses.

Epidemiological characteristics and clinical analysis of 97 AIDS patients

This study is to analyze clinical features of 97 AIDS patients received and treated in our hospital. Clinical data of 97 HIV-infected patients who were admitted between September 2004 and September 2018 were analyzed retrospectively. We found that all patients were in AIDS stage, CD4+ T lymphocytes counts were (210.56 ± 79.31)/µL. After the highly active antiretroviral therapy (HAART) regimens, CD4+ cell number is 315.21 ± 187.90, most patients before clinical symptoms are significantly improved. HIV infections were mainly through intravenous drug injection (51 cases, 52.58%) and sex contact (29 cases, 29.90%). In conclusion, the clinical manifestations of AIDS patients are various, and the main infection route is intravenous drug injection. Multiple measures should be taken to prevent and control HIV transmission, patients should undergo effective antiviral treatment, monitor and follow-up, so as to control opportunistic infection and virus replication.