Chronic viral infection impairs immune memory to a different pathogen.

Chronic viral infections cause T cell dysfunction in both animal models and human clinical settings, thereby affecting the ability of the host immune system to clear viral pathogens and develop proper virus-specific immune memory. However, the impact of chronic viral infections on the host's immune memory to other pathogens has not been well described. In this study, we immunized mice with recombinant Listeria monocytogenes expressing OVA (Lm-OVA) to generate immunity to Lm and allow analysis of OVA-specific memory T (Tm) cells. We then infected these mice with lymphocytic choriomeningitis virus (LCMV) strain Cl-13 which establishes a chronic infection. We found that chronically infected mice were unable to protect against Listeria re-challenge. OVA-specific Tm cells showed a progressive loss in total numbers and in their ability to produce effector cytokines in the context of chronic LCMV infection. Unlike virus-specific T cells, OVA-specific Tm cells from chronically infected mice did not up-regulate the expression of inhibitory receptors, a hallmark feature of exhaustion in virus-specific T cells. Finally, OVA-specific Tm cells failed to mount a robust recall response after bacteria re-challenge both in the chronically infected and adoptively transferred naïve hosts. These results show that previously established bacteria-specific Tm cells become functionally impaired in the setting of an unrelated bystander chronic viral infection, which may contribute to poor immunity against other pathogens in the host with chronic viral infection.

CD8+ T cells in fetal membranes display a unique phenotype, and their activation is involved in the pathophysiology of spontaneous preterm birth.

Preterm labor/birth is the leading cause of perinatal mortality and morbidity worldwide. Previous studies demonstrated that T cells were crucial for maintaining maternal-fetal immune tolerance during the first trimester of pregnancy; however, their phenotypes and functions in labor and delivery remain largely unknown. We recruited three cohorts of women at delivery for T-cell immunophenotyping in the placentas, fetal membranes, umbilical cord blood, and maternal peripheral blood. Our data showed a differential enrichment of T cells during the third trimester of human pregnancy, with CD4+ T cells being more observable within the umbilical cord blood, whereas CD8+ T cells became relatively more abundant in fetal membranes. CD4+ and CD8+ T cells derived from fetal membranes were dominated by effector memory T cells and exhibited extensive expression of activation markers but decreased expression of homing receptor. In comparison with term births, fetal membrane CD8+ T cells, especially the central memory subset, were significantly increased in frequency and showed more profound activation in spontaneous preterm birth patients. Finally, using an allogeneic mouse model, we found that T-cell-activation-induced preterm birth could be alleviated by the depletion of CD8+ T but not CD4+ T cells in vivo. Collectively, we showed that CD8+ T cells in fetal membranes displayed a unique phenotype, and their activation was involved in the pathophysiology of spontaneous preterm birth, which provides novel insights into the immune mechanisms of preterm birth and potential targets for the prevention of this syndrome. © 2023 The Pathological Society of Great Britain and Ireland.

ICAM-1 mediated cell-cell adhesion exerts dual roles on human B cell differentiation and IgG production.

Intercellular adhesion molecule 1 (ICAM-1) plays prominent roles in mediating cell-cell adhesion which also facilitates B cell activation and differentiation with the help from CD4+ T cells. Here, we have reported a unique phenomenon that increased ICAM-1 on purified human CD4+ T cells upon anti-CD3/CD28 stimulation enhanced CD4+ T-B cell adhesion whereas induced less B cell differentiation and IgG production. This was largely due to increased PD-1 expression on CD19hi B cells after coculturing with hyperactivated CD4+ T cells. Consequently, ICAM-1 blockade during CD4+ T cell-B cell coculture promoted IgG production with the activation of ERK1/2 and Blimp-1/IRF4 upregulation. Consistently, CD4+ T cells from moderate-to-severe SLE patients with high ICAM-1 expression mediated less IgG production after T-B coculture. Therefore, ICAM-1-mediated human CD4+ T-B cell adhesion provides dual roles on B cell differentiation and IgG production partially depending on expression levels of PD-1 on B cells, supporting cell adhesion and subsequent PD-1 induction as an alternative intrinsic checkpoint for B cell differentiation.

Distinct roles of ICOS and CD40L in human T-B cell adhesion and antibody production.

CD40-CD40L and inducible co-stimulatory molecule (ICOS)-ICOSL ligations are demonstrated to play critical roles in CD4+T-B interaction for B cell activation and differentiation in mouse models. Herein, by using a micropipette adhesion assay and an in vitro CD4+T-B cell coculture system simultaneously, we intended to dissect their roles in human CD4+T-B adhesion and IgG/IgM production. With the upregulation of CD40L and ICOS expressions on CD4+ T cells upon TCR/CD28 stimulation in vitro, activated CD4+ T cells exhibited enhanced adhesion with autologous B cells at a single cell level when compared to the resting counterparts. Blockade of ICOS dramatically damped the adhesion between CD4+ T and B cells whereas less effect of CD40L blockade was observed. On the contrary, blockade of CD40L led to the dramatic decrease in IgG/IgM production when B cells were cocultured with activated CD4+ T cells together with the decrease in the induction of CD19hi B cells. However, ICOS blockade displayed less attenuation on IgG/IgM production. Distinct roles of CD40-CD40L and ICOS-ICOSL in cell adhesion and IgG/IgM production were also observed in CD4+T-B cell interaction in system lupus erythematosus patients. The blockade of CD40L, rather than ICOS, led to the dramatic decrease in the phosphorylation of Pyk2 in CD19hi B cells and total B cells. Our study thus provides the evidence that CD40L and ICOS on activated CD4+ T cells either upon in vitro activation or at the pathogenic state function diversely during CD4+T-B cell interactions. While ICOS-ICOSL ligation is more likely to be engaged in cell adhesion, CD40-CD40L provides indispensable signal for B cell differentiation and IgG/IgM production. Our results are thus indicative for the segregating costimulation of CD40-CD40L and ICOS-ICOSL on CD4+ T cells for B cell activation and differentiation, which might be helpful for the dissection of SLE pathogenesis.

Four novel compound heterozygous mutations in C5orf42 gene in patients with pure and mild Joubert syndrome.

Joubert syndrome (JS) is a rare clinically and genetically heterogeneous disease. Using whole or targeted exome sequencing, we identified four novel compound heterozygous mutations in chromosome 5 open reading frame 42 gene (C5orf42), including c.2876C>T (missense mutation) and c.3921+1G>A (splicing mutation), c.2292 -2delA (splicing mutation) and c.4067C>T (missense mutation), c.6997_6998insT (frameshift mutation) and c.8710C>T (nonsense mutation), c.3981G>C (nonsense mutation) and c.230 _233del (frameshift mutation), in four Chinese JS families. They were all inherited from their heterozygosis parents in the autosomal recessive inheritance mode. Pure JS clinical manifestations and mild neuroimaging findings were found in these patients. These verified the previous findings that C5orf42 mutations generally resulted in a purely neurological Joubert phenotype, and neuroimaging findings were mild in JS with C5orf42 mutations. Our report analyzed these C5orf42 mutations-associated phenotypes and neuroimaging findings in JS and updated the genetic variation spectrum of JS caused by C5orf42.These will help clinicians and geneticists reach a more accurate diagnosis for JS.

Autoreactive B Cell Differentiation in Diffuse Ectopic Lymphoid-Like Structures of Inflamed Pemphigus Lesions.

Pemphigus is an organ-specific autoimmune disease that targets skin and/or mucous membranes. Our previous study showed that infiltrating lymphocytes in pemphigus vulgaris (PV) lesions produce anti-desmoglein (Dsg) 1/3 antibodies after in vitro culture. In this study, we found diffuse ectopic lymphoid-like structures (ELSs) commonly present in the lesions of both PV and pemphigus foliaceus. Notably, pemphigus lesions contained centroblasts, plasmablasts, and plasma cells, which recapitulated the different stages of B cell differentiation. Elevated mRNA expression levels of the differentiation-related transcription factors BLIMP-1, IRF4, and BCL-6 were observed in pemphigus lesions. Moreover, B cell receptor repertoire analysis revealed the clonal expansion of the lesional B cells. Lesional B cells might recirculate among lesions, lymph nodes, and peripheral blood. Increased mRNA expression levels of multiple chemokines in pemphigus lesions and elevated expression levels of chemokine receptors on lesional B cells were also observed. Collectively, these results show that the ELSs in pemphigus lesions might act as a niche, supporting in situ B cell differentiation and clonal expansion.

Construction of a lncRNA-miRNA-mRNA network to determine the regulatory roles of lncRNAs in psoriasis.

Psoriasis is a chronic inflammatory skin disorder that impairs the quality of life of affected patients. Emerging studies indicate that certain long non-coding RNAs (lncRNAs) have important roles in psoriasis. However, the exact functions of lncRNAs and their regulatory mechanisms as competitive endogenous RNAs (ceRNAs) in psoriasis have remained to be fully elucidated. In the present study, differentially expressed lncRNAs, microRNAs (miRNAs) and mRNAs were identified by analyzing public datasets, and a psoriasis-associated lncRNA-miRNA-mRNA network was constructed based on the ceRNA theory. Furthermore, previously validated abnormally expressed miRNAs in psoriasis were identified by a systematic literature search in the PubMed and Web of Science databases, and a specific miRNA-associated lncRNA-miRNA-mRNA sub-network was extracted. Furthermore, Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses were performed using DAVID 6.8. A total of 253 lncRNAs, 106 miRNAs and 1,156 mRNAs were identified as being differentially expressed between psoriasis skin and healthy control skin. The present study identified two key lncRNAs that may potentially have a role in the pathogenesis of psoriasis: AL035425.3 and Prader Willi/Angelman region RNA 6. This integrative analysis enhances the understanding of the molecular mechanism of psoriasis and may provide novel therapeutic targets for the treatment of psoriasis.

Deep Surveying of the Transcriptional and Alternative Splicing Signatures for Decidual CD8+ T Cells at the First Trimester of Human Healthy Pregnancy.

Decidual CD8+ (dCD8) T cells have been proposed to play important roles in immune protection against the invading pathogens and in tolerance toward the growing semi-allogeneic fetus during early pregnancy. However, their phenotypic and functional characteristics remain poorly defined. Here, we performed the first analysis of the transcriptional and alternative splicing (AS) signatures for human first-trimester dCD8 T cells using high-throughput mRNA sequencing. Our data revealed that dCD8 T cells have distinct transcriptional and AS landscapes when compared with their autologous peripheral blood CD8+ (pCD8) T counterparts. Furthermore, human dCD8 T cells were observed to contain CD8-Treg and effector-memory T-cell subsets, and display enhanced functionality in terms of degranulation and cytokine production on a per-cell basis. Additionally, we have identified the novel splice junctions that use a high ratio of the non-canonical splicing motif GC-AG and found that AS is not a major contributor to the gene expression-level changes between paired pCD8 and dCD8 T cells. Together, our findings not only provide a comprehensive framework of the transcriptional and AS landscapes but also reveal the functional feature of human dCD8 T cells, which are of great importance in understanding the biology of these cells and the physiology of human healthy pregnancy.

Peripheral CD19hi B cells exhibit activated phenotype and functionality in promoting IgG and IgM production in human autoimmune diseases.

Systemic Lupus Erythematosus (SLE) and pemphigus are two representative autoimmune diseases driven by pathogenic autoantibody systemically and organ-specifically, respectively. Given the involvement of antibody in the pathogenesis, B cells are inclined to differentiate and function in an abnormal activation model. Here we defined a unique CD19hi B cell population existing in the periphery of SLE and pemphigus patients as well as in human tonsils. CD19hi B cells could be induced in vitro after co-culturing fully activated CD4+ T cells with autologous B cells. They expressed high levels of HLA-DR, IgG, IgM and multiple ligands of costimulatory molecules with the capacity to produce extra IgG and IgM. Transcirptome assay revealed that genes involved in B-cell activation and differentiation were up-regulated in CD19hi B cells. Antibody blockade experiments showed that the interactions between costimulatory molecules contributed to CD19hi B-cell generation and IgG/IgM production. What is more, frequencies of peripheral CD19hi B cells from SLE and pemphigus patients were correlated with serum total IgG and IgM, but not with autoantigen-specific antibodies and disease severity. Therefore, our investigation demonstrates that CD19hi B cells might contain B cell precursors for terminal differentiation and contribute to total IgG/IgM production in human autoimmune diseases.

Distinct Transcriptional and Alternative Splicing Signatures of Decidual CD4+ T Cells in Early Human Pregnancy.

Decidual CD4+ T (dCD4 T) cells are crucial for the maternal-fetal immune tolerance required for a healthy pregnancy outcome. However, their molecular and functional characteristics are not well elucidated. In this study, we performed the first analysis of transcriptional and alternative splicing (AS) landscapes for paired decidual and peripheral blood CD4+ T (pCD4 T) cells in human early pregnancy using high throughput mRNA sequencing. Our data showed that dCD4 T cells are endowed with a unique transcriptional signature when compared to pCD4 T cells: dCD4 T cells upregulate 1,695 genes enriched in immune system process whereas downregulate 1,011 genes mainly related to mRNA catabolic process and the ribosome. Moreover, dCD4 T cells were observed to be at M phase, and show increased activation, proliferation, and cytokine production, as well as display an effector-memory phenotype and a heterogenous nature containing Th1, Th17, and Treg cell subsets. However, dCD4 T cells undergo a comparable number of upregulated and downregulated AS events, both of which are enriched in the genes related to cellular metabolic process. And the changes at the AS event level do not reflect measurable differences at the gene expression level in dCD4 T cells. Collectively, our findings provide a comprehensive portrait of the unique transcriptional signature and AS profile of CD4+ T cells in human decidua and help us gain more understanding of the functional characteristic of these cells during early pregnancy.

Pivotal Role of Lesional and Perilesional T/B Lymphocytes in Pemphigus Pathogenesis.

Pemphigus is a skin and mucosal membrane-targeting autoimmune bullous disease. Previous studies have shown that circulating anti-desmoglein1/3 antibodies are pathogenic and mediate blister formation. However, the role of infiltrating immune cells in lesional skin has not been fully investigated. In this study we showed that there existed a large number of B and T lymphocytes and plasma cells in the skin lesions by immunohistochemistry and immunofluorescence staining. In addition, a significantly increased number of Dsg1- and Dsg3-specific B cells could be identified by flow cytometric analysis or enzyme-linked immunospot technique (i.e., ELISPOT) assay. Furthermore, anti-Dsg1 and Dsg3 antibodies could be detected from the supernatant of in vitro cultures with isolated lymphocytes from lesional skin. We found that most T lymphocytes infiltrating pemphigus vulgaris lesions were CD4+ T helper cells expressing IL-21 and IL-17a but not typical T follicular helper cells expressing CXCR5. Additionally, our microarray assay showed that the level of chemokine CCL19 was significantly elevated, suggesting active T-/B-lymphocyte trafficking and aggregation in the pemphigus vulgaris lesions. Collectively, our results suggest a critical role of locally infiltrating lymphocytes in pemphigus pathogenesis.

Characterization of T follicular helper cells in allogeneic normal pregnancy and PDL1 blockage-induced abortion.

A deeper understanding of the immunological events during pregnancy will provide novel insights into the pathogenesis of pregnancy complications. The fundamental function of T follicular helper (Tfh) cells is to provide cognate help to B cells. Dysregulations of Tfh-cell function and/or development can result in various immunological diseases. However, the role and characteristics of Tfh cells during pregnancy remain unknown. Herein, an allogeneic-normal-pregnant mouse model was used, and we found that the CD4+ T cells residing at the uterus and placenta (UP) displayed a Tfh-like phenotype; and the UP-derived CD4+CXCR5hiPD-1hi and CD4+CXCR5hiICOShi Tfh cells, which showed a memory/activation phenotype, reached their peak at mid-pregnancy. These Tfh cells were located abundantly in the uterus at mid-pregnancy, but greatly increased in the placenta at late-pregnancy. Furthermore, increased foetal resorption by PDL1 blockade correlated with enhanced accumulation of Tfh cells and upregulated expressions of ICOS and PD-1 on these cells. Collectively, our findings are the first to indicate that an adequate and balanced accumulation of Tfh cells during gestation is likely to help maintaining a successful pregnancy, whereas an excessively high level of these cells could lead to abortion.

Long-term exposure to decabrominated diphenyl ether impairs CD8 T-cell function in adult mice.

Polybrominated diphenyl ethers (PBDEs) are ubiquitous environmental pollutants that accumulate to high levels in human populations that are subject to occupational or regional industry exposure. PBDEs have been shown to affect human neuronal, endocrine and reproductive systems, but their effect on the immune system is not well understood. In this study, experimental adult mice were intragastrically administered 2,2',3,3',4,4',5,5',6,6'-decabromodiphenyl ether (BDE-209) at doses of 8, 80 or 800 mg/kg of body weight (bw) at 2-day intervals. Our results showed that continuous exposure to BDE-209 resulted in high levels of BDE-209 in the plasma that approached the levels found in people who work in professions with high risks of PDBE exposure. Reduced leukocytes, decreased cytokine (IFN-γ, IL-2 and TNF-α) production and lower CD8 T-cell proliferation were observed in the mice exposed to BDE-209. Additionally, mice with long-term BDE-209 exposure had lower numbers of antigen-specific CD8 T cells after immunization with recombinant Listeria monocytogenes expressing ovalbumin (rLm-OVA) and the OVA-specific CD8 T cells had reduced functionality. Taken together, our study demonstrates that continuous BDE-209 exposure causes adverse effects on the number and functionality of immune cells in adult mice.