The BAFF/APRIL system at the crossroads of B cell memory and autoimmune relapse: Implication into the therapeutic strategies.

Paeoniae Radix Alba polysaccharides: Structural characterization, macrophage immunomodulation, and potent vaccine adjuvant activity.

Follicular dendritic cell sarcoma (FDCS) is a rare neoplasm with morphologic and phenotypic features resembling those of normal follicular dendritic cells (FDCs). FDCS has been classified into two distinct entities based on their association with Epstein-Barr Virus (EBV): classic FDCS (cFDCS) and EBV-positive inflammatory FDCS (EBV + IFDCS). Diagnosis relies on characteristic histopathology and immunohistochemistry using FDC markers and EBV in situ hybridization (EBER). This study aimed to compare the clinical presentations, histologic features, and immunoprofiles between these two entities in a Taiwanese cohort. We retrospectively reviewed histological features of in-house and consultation cases of FDCS. Immunohistochemistry with novel markers including serglycin (SRGN), FDC-secreted protein (FDCSP) was applied, together with conventional FDC markers (CD21, CD23, CD35) and EBER. Programmed death ligand-1 (PD-L1), a potential therapeutic marker, was additionally evaluated and scored. Clinical and histological parameters, inflammatory cell infiltration, mitotic rate, and PD-L1 tumor proportion score (TPS) were compared statistically. We identified 30 patients including 16 cFDCS and 14 EBV + IFDCS. The median age was 56years old (range, 22-80), with a female preponderance in EBV + IFDCS. EBV + IFDCS occurred exclusively in extra-nodal sites, while cFDCS more commonly involved lymph nodes. EBV + IFDCS showed significantly higher PD-L1 TPS (p = 0.012), more prominent inflammatory cell infiltration (90.0% vs. 12.5%, p < 0.001) in the presence of germinal centers (50% vs. 6%, p = 0.012), and lower mitotic activity (0.5 vs. 2.5/10 HPFs, p = 0.002). We identified distinct clinical and histologic features, as well as differential PD-Ll expression between cFDCS and EBV + IFDCS, supporting their classification as separate entities. Further molecular studies are needed to investigate their pathogenesis.

Abstract Hypertrophied adenoids in children can impair breathing and lead to obstructive sleep apnea (OSA), often accompanied by abnormal growth and weakened stamina and immunity. However, the cause of the pathological transformation in these originally immune-enhancing lymphoid tissues remains unclear. Our study provides the first single cell transcriptomic and immune repertoire atlas of adenoids from normal snoring to mild, moderate, and severe OSA, and identified markedly asynchronous functional modules, transcriptional regulatory networks and intercellular communications during the progression of OSA. Children with severe OSA exhibited exhibit active Hippo, Notch, and Wnt signaling, alongside significant downregulation of energy synthesis. Analysis revealed compromised T-cell and B-cell immunity, as well as reduced antigen processing by innate immune cells, coupled with diminished cell-cell communication in severe OSA group. T-cell receptor and B-cell receptor sequencing results also support more infection imprints and abnormal germinal centers and antibody class switching. Mechanistically, HIF1A-mediated hypoxic signaling likely drives the downregulation of key immune components (including HLA and interferon molecules), positioning it as a promising therapeutic target for OSA.

Multiple roads to IgE memory: A pluralistic model of IgE immunity.

The induction of long-term humoral immune responses depends upon the interaction between T follicular helper (Tfh) and B cells in germinal centers, leading to development of memory B cells (MBCs) and class-switched antibodies. Expansion and activation of circulating Tfh2 (cTfh2) cells were detected in both vivax and falciparum malaria subjects. However, how these cells help B cells generate anti-malarial immunity is still unclear. Here, we assessed the breadth and competency of antibody responses from P. vivax subjects and related them to the frequency and activation status of cTfh2 subset. We also demonstrated the ability of P. vivax antigen to trigger cTfh2 cell activation and the function of cTfh2 cells to help MBCs secrete antibodies. Of 40 subjects with acute P. vivax malaria, 23 were seropositive for anti-PvDBPII antibodies (High and Low responders). Three High Responders (HRs) produced inhibitory antibodies against PvDBPII-human erythrocyte binding. An expansion of cTfh2 cells was detected in seropositive subjects. While their frequency did not differ significantly between High and Low Responders (LRs), the expression of co-stimulatory molecule ICOS in cTfh2 cells was higher in HRs. Activation of cTfh2 cells was specifically stimulated by PvDBPII antigen. In cTfh2-MBC co-cultures, proliferation and activation of cTfh2 cells were detected after receiving signal from MBCs. These activated cTfh2 cells then promoted MBC differentiation into antibody secreting cells (ASCs) which secreted anti-PvDBPII IgG. A decrease in cTfh2 cell activation was observed upon the addition of IFN-γ to the co-cultures. Importantly, cTfh2 cells played a role in producing anti-malarial specific antibodies. This study demonstrated that activation of cTfh2 cells, marked by the upregulation of ICOS molecules, was notably observed in subjects who produced high titers of anti-PvDBPII antibodies in response to P. vivax infection. This was also seen in a few subjects who produced high levels of antibody with inhibitory function. The PvDBPII antigen specifically stimulated cTfh2 cell proliferation and activation. Additionally, interactions between cTfh2 cells and MBCs promoted both cTfh2 activation and anti-PvDBPII antibody secretion.

BLIMP1 tunes germinal center B cell responses to limit clonal dominance.

Disrupted sleep is increasingly recognized as a factor influencing vaccine efficacy, yet the mechanisms by which sleep disruption affects vaccine-induced immunity remain incompletely understood. Sleep fragmentation, a hallmark of several common sleep disorders, may interfere with immune processes required for effective vaccination. Here, we show that chronic sleep fragmentation (CSF) markedly impairs immune responses to influenza vaccination. In a mouse model, two weeks of CSF before and during influenza vaccination significantly compromises antibody responses and reduces protection against lethal challenge, with lower neutralizing antibody titers, diminished IgG subclass responses, and decreased survival despite preserved antibody avidity. Single-cell RNA sequencing revealed transcriptional signatures associated with altered B cell maturation, impaired germinal center programs, and stress in antibody-producing plasma cells, including activation of unfolded protein response and oxidative stress pathways, alongside altered interactions between B and T cells. Clinically, analysis of 916,307 influenza-vaccinated adults shows that obstructive sleep apnea, a disorder characterized by recurrent sleep fragmentation, is associated with a higher risk of influenza infection than matched controls (0.7% vs. 0.4%; risk ratio 1.70). Taken together, this study demonstrates that CSF compromises vaccine-induced immune responses and highlights sleep health as a modifiable determinant of vaccine-associated protection.

Conventional subunit vaccines, typically formulated as a simple antigen and adjuvant mixture, suffer from premature clearance and poor synchronization of antigen and adjuvant, resulting in suboptimal immune activation. Here, we develop an amphipathic polymer, YAXA, featuring acid-labile imine bonds for pH-responsive degradation and terminal NHS-activated esters for covalent conjugation of protective antigen. Through hydrophilic-hydrophobic co-assembly with the hydrophobic TLR7 agonist 3M-052, followed by antigen conjugation, YAXA forms an inhalable nanoparticle vaccine, YM3.7, in which the antigen is displayed on the hydrophilic surface while the adjuvant is encapsulated in the hydrophobic core. Following aerosolized intratracheal inoculation into the lung, YM3.7 is efficiently internalized by antigen-presenting cells and trafficked into the lysosome, where acidic conditions trigger its dissociation and co-release of antigen and adjuvant. This lysosome-targeted, spatiotemporally synchronized delivery couples antigen presentation with TLR7/NF-κB activation, driving robust immune responses, including antigen-presenting cell maturation, germinal center formation, systemic and lung-resident B/T cell response, and IgG/sIgA production. In lethal pneumonia models induced by Pseudomonas aeruginosa or Staphylococcus aureus, YM3.7 markedly improves survival over a conventional antigen and adjuvant mixture. This research establishes a paradigm for developing next-generation inhalable nanoparticle vaccines, capable of spatiotemporally coordinating innate immunity, humoral immunity, mucosal immunity, and cell-mediated immunity to provide enhanced immunoprotection.

Glioblastoma (GBM) is characterized by aberrant neovascularization and angiogenesis. Bevacizumab (Avastin), a monoclonal antibody targeting vascular endothelial growth factor (VEGF), is clinically used with chemotherapy for patients with GBM, yet its impact on the tumor immune microenvironment remains poorly understood. Transcriptomic profiling of matched pre- and post-treatment tumors from patients with recurrent GBM treated with bevacizumab plus the topoisomerase inhibitor irinotecan revealed significant immune reprogramming in responders, with post-treatment tumors displaying features indicative of tertiary lymphoid structure (TLS) formation and enhanced antitumor immunity. In preclinical orthotopic glioma models, combining αVEGF therapy with intratumoral epidermal growth factor receptor (EGFR)-targeted cytotoxic therapy and αCD40 immunotherapy normalized the tumor vasculature, promoted lymphatic vessel growth, induced tumor cell killing, increased intratumoral T cells, plasma cells, germinal center B cells, and antigen-presenting and tissue-repair-associated macrophages, while reducing immunosuppression and supporting mature TLS formation with an antitumor immune phenotype. Functionally, the tumor-, immune-, and vascular-targeted combination therapy significantly improved tumor control, extended survival, and induced durable antitumor memory in glioma models. Collectively, these results identify VEGF as a central regulator of the vascular-immune axis during cytotoxic EGFR+αCD40 therapy in GBM and provide a strong rationale for combining vascular-, tumor-, and immune-targeted approaches to overcome therapeutic resistance and improve outcomes for patients with GBM.

Memory B cells (MBCs) are an integral part of the humoral immune response with the capacity to both reseed germinal center reactions and rapidly form antibody-secreting plasma cells (ASCs) upon secondary antigen encounter. MBCs arise via both T cell-dependent and -independent routes and while CD4+ T cells are not required for their formation, it is still not clear if or how initial T:B-cell interactions influence the molecular programming and diversity of T cell-independent MBCs. To address this, we characterized MBCs that form in response to influenza infection in major histocompatibility complex class II knockout (MHCII-KO) mice, which lack CD4+ T cells. Consistent with T cell-independent responses, the MBCs that formed in MHCII-KO mice were reduced in number and did not acquire surface expression of CCR6 and class-switched BCR. Transcriptional profiling identified cytokine- and activation-induced genes that were reduced in expression in MHCII-KO MBCs compared to wild type (WT). Adoptive transfer of MHCII-KO B cells into WT hosts, which cannot receive peptide/MHCII-TCR cognate interactions, revealed an ability of MHCII-KO cells to form MBCs and ASCs. Single-cell RNA sequencing revealed minimal transcriptional differences between MHCII-KO and WT MBCs, indicating that cognate CD4+ T-cell interactions provide limited early programming instruction to MBCs. MHCII-KO MBCs were able to clonally expand, class-switch, and form the same diverse transcriptional clusters as WT. These data indicate that early differentiating MBCs can seed a diverse pool of MBC populations in response to influenza infection independent of cognate T-cell help.

Acetylcholine from lymphocytes regulates B cell antibody production within germinal centers.

IL-1β is typically associated with the innate response, often produced following the detection of pathogen associated-molecular patterns (PAMPs) and damage- associated molecular patterns (DAMPs). It is also identified as a cytokine involved in bridging the innate and adaptive immune responses, in which innate cells, like dendritic cells, utilize IL-1β to activate T cells for the adaptive immune response. The role of IL-1 signaling has been established in the context of T cell differentiation and function, particularly in its regulation of T follicular helper (TFH) cells. Recent work has demonstrated that with TFH function primarily acting within the germinal center (GC), a local source of IL-1β must be present, identifying GC B cells as a critical source of IL-1β. Here we discuss the roles of cells within the GC milieu, the cytokines they produce, and their impact on the GC. Additionally, we also discuss the findings from studies examining the molecular mechanisms underlying IL-1β production in B cells and its impact on B cell function. This review is especially relevant as it draws together findings from various disease pathologies to consolidate our current understanding of B cell subsets producing IL-1β and IL-1β signaling within the GC, in both T cells and B cells.

B cells are crucial for adaptive immunity, orchestrating humoral responses by producing antibodies essential for pathogen clearance. Here, we show that Poly(rC) binding protein 1 (Pcbp1), a multifunctional RNA binding protein, is a key regulator of antibody production in B cells. Pcbp1 deficiency in B cells resulted in significant reductions in immunoglobulin M expression at steady state and compromised differentiation of germinal center B cells and production of high-affinity antibodies upon immunization. These effects were caused by defective mitochondrial integrity in Pcbp1-deficient B cells, including impaired mitochondrial electron transport chain complex I and elevated mitochondrial reactive oxygen species production. Mechanistically, Pcbp1 binds to the 3' untranslated region of Fdxr messenger RNA to promote its expression, thereby supporting iron-sulfur cluster biogenesis, the assembly of mitochondrial complex I, and other Fdxr-dependent processes. Our findings reveal a previously unidentified role for Pcbp1 in regulating mitochondrial function, protein synthesis, and antibody responses in B cells, providing insight into posttranscriptional regulation and mitochondrial functions in adaptive immunity.

HIV broadly neutralizing antibodies (bnAbs) are promising reagents for prevention and therapy of disease; however, their elicitation is constrained by genetic limitations of the human B cell antigen-receptor (BCR) repertoire. Precision genome-editing offers a potential solution by enabling bnAb genes to be programmed into the BCR repertoire as IgH-modified B cells. Such cells can be vaccinated to elicit durable bnAb memory responses in mice; however, extending this success to non-human primates (NHPs) would be a major advance towards clinical translation. Here, we show that ex vivo reprogrammed NHP B cells can survive autologous infusion and respond to immunization, differentiating into antibody-secreting cells (ASCs) that can produce up to 1 µg/ml of a bnAb in serum following vaccination prime. Although durable transgenic memory responses were not generated, vaccination of engineered cells in secondary lymphoid organoid (SLO) cultures recapitulated transient ASC responses in vitro. These findings suggest that NHP-derived SLOs could provide a platform to optimize engineering and vaccination conditions that drive germinal center maturation of IgH-reprogrammed B cells in a clinically relevant NHP model, supporting the development of engineered B-cell vaccines that generate durable bnAb responses as a potential functional cure for HIV.

Antibodies against Salmonella Typhimurium (STm) can provide protection against infection. Understanding how antibodies, complement, and leukocytes interact is essential and can help advance vaccine development. To evaluate the in vivo role of STm-specific antibodies, mice were immunized with an outer membrane vesicle (OMV) vaccine and subsequently challenged with STm. Immunohistology and intravital microscopy revealed that OMV-induced antibodies promoted STm uptake by macrophages in the spleen and liver, whereas bacteria were only infrequently associated with neutrophils. Depletion of monocytic cells using clodronate liposomes demonstrated that these cells help prevent antigen dissemination. Immunization and challenge experiments in mice deficient in C1q, C3, C4, or C5 showed that OMV immunization conferred protection in all groups except C3-deficient mice. Mice deficient in C3 failed to develop robust germinal center and plasma cell responses following OMV immunization. Nevertheless, C3-deficient mice that received immune sera by adoptive transfer prior to infection had significantly reduced bacterial burdens compared to mice receiving non-immune control sera. In vitro studies using human sera and THP-1 cells confirmed that antibodies alone are sufficient to promote bacterial capture by macrophages. Complement-particularly C1q and C3, but not C5-further enhanced bacterial uptake. Overall, under the conditions tested, antibodies are sufficient to reduce STm burdens in vivo and facilitate bacterial uptake in vitro, with these processes supported by complement and macrophages.IMPORTANCEBacterial infections remain a significant global challenge, further complicated by the growing issue of antimicrobial resistance (AMR). In this context, vaccination provides a cost-effective means of preventing infections and combating the emergence of AMR strains. Antibodies are key mediators of vaccine-induced protection. However, their mechanisms of action in vivo are not fully understood. In this study, we demonstrate how antibodies enhance the capture of Salmonella by macrophages. Although these cells may be dispensable for controlling bacterial numbers, they are crucial for limiting the spread of bacterial antigens. Additionally, we find that the classical complement cascade is not necessary for bacterial clearance but does facilitate bacterial capture by macrophages. Overall, our findings reveal that multiple antibody-mediated pathways operate in vivo, exhibiting some redundancy in their combined efforts to control infection, underscoring the importance of antibody functions in limiting bacterial spread.

Immunosenescence, the age-associated decline in immune function, is a key feature of human aging. In human lymphoid organs, however, the specific immune cell populations that acquire senescence-associated phenotypes during aging and how they influence the surrounding tissue microenvironment remain poorly understood. A spatially resolved map of these senescence-associated immune states in human lymphoid tissues could help clarify their relationship with aging and their potential contributions to the progressive decline of immune function. Here, we integrated single-cell and spatial multi-omics to systematically characterize age-related senescence in human lymph nodes (LNs). Single-cell transcriptomics of lymphoid tissues from donors aged 18 to 100 years old identified 34 immune and stromal cell types and revealed age-associated upregulation of senescence signatures in specific populations. Spatial proteomic profiling of 99 LN sections from 51 donors (18-86 years) using high-plex immunofluorescence (∼20 million cells) mapped senescence markers (p16, p21, HMGB1, 𝛾 -H2AX) at single-cell resolution, revealing diverse senescent-like cell types ("senotypes") and a stepwise shift from extrafollicular to germinal center (GC) localization with age. Notably, we observed focal clonal-like senescence in GC B cells in older donor LNs. Spatial transcriptomics, epigenomics, and metabolic imaging of selected samples further elucidate the multi-omics signatures and underlying mechanisms of functional impairment, metabolic remodeling, and distinct regulatory programs in senescent-like GC B cells. This study presents a comprehensive spatial atlas of senescence-associated immune states in human lymph nodes, revealing cell-type-specific and spatial heterogeneity that may contribute to immunosenescence and the decline of immune function during aging.

Antibody-mediated immune responses in mucosal tissues are critical for defending against pathogens while maintaining homeostasis with commensals. Nasal vaccination aims to induce local protection in the upper airway mucosa. Although B cell-driven immunity is well characterized in gut-associated lymphoid tissues such as Peyer's patches and mesenteric LNs, much less is known about analogous processes in the upper airways. Here, we show that B cell receptor (BCR) affinity and CCR6 regulate germinal center (GC) seeding and class-switch recombination (CSR) to IgA in nasal-associated lymphoid tissue (NALT) following nasal vaccination. B cells bearing low-affinity BCRs failed to upregulate CCR6 and did not support T follicular helper cell differentiation or seed GCs in the NALT. CCR6-deficient B cells were unable to migrate to the NALT subepithelial dome or undergo IgA CSR and seed GC effectively in response to nasal vaccination or commensal bacteria signals. Thus, effective targeting of B cell clones to induce CCR6 expression is essential for nasal vaccine design.

Abstract Histological examination of follicular lymphoma (FL) biopsies remains the cornerstone for diagnosis and staging of FL. Single cell sequencing approaches, while transcriptomically rich, require tissue dissociation and therefore lose the native spatial context that may underpin FL progression and transformation to a high-grade lymphoma, typically diffuse large B cell lymphoma (DLBCL). By single cell spatial profiling, we aimed to characterize the spatiotemporal heterogeneity and interplay between malignant B cells and the tumor microenvironment (TME) during transformation from FL to DLBCL histology. Single cell spatial transcriptomics (Nanostring CosMx) and proteomics (Cell DIVE) were performed on FFPE tissue cores of 14 tFL patients with paired FL (tFL-FL) and DLBCL (tFL-DLBCL) timepoints, and 13 FL patients without evidence of progression or transformation (non-tFL; &amp;gt;6y of follow-up). Spatial omics confirmed malignant B cell dominated follicular structures in non-tFL and tFL-FL while absent in tFL-DLBCL, consistent with pathologic classification. Follicles were then delineated (defining intra-follicular, peri-follicular and extra-follicular regions) and enriched proliferation and exhaustion features were observed in intra-follicular regions compared to extra-follicular counterparts. Moreover, differential spatial interaction patterns were observed, amongst which Galectin-9 crosstalk components were identified as being differentially expressed and exhaustion-related pathways were more prevalent in intra-follicular and peri-follicular regions in non-tFL and tFL-FL timepoints. Macrophage phenotypes also markedly shifted across spatial regions with progression: intrafollicular FOLR2+ and IL4I1+ macrophages present in non-tFL progressively diminished, while CD163+, SPP1+, and NLRP3+ macrophages became increasingly enriched in extra-follicular regions in tFL-DLBCL. Cell neighborhood analysis showed differential abundance among non-tFL, tFL-FL, and tFL-DLBCL timepoints. For B-cell-predominant cell neighborhoods (CNs), the germinal center (GC) score was higher in non-tFL than tFL-FL, whereas tFL-FL and tFL-DLBCL shared similar GC score levels. Within CNs of similar cell type compositions, T cells were more exhausted and macrophages were more polarized towards anti-inflammatory phenotypes in the transformed state. Subsequent single cell proteomics validated the differential follicular Galectin-9 signaling and macrophage-related gene expression patterns among spatial regions. In summary, we delineated the spatial landscape of both indolent and transformed FL. We identified a spatiotemporal shift in TME composition, spatial interactions, and cell neighborhoods. This study provides novel insights into the spatial lymphoma architecture associated with FL transformation, contributing to a refined disease evolution model. Citation Format: Shaocheng Wu, Eric Lee, Anne-Sophie Fratzscher, Andrew Lytle, Spencer D. Martin, David G. Huntsman, David W. Scott, Christian Steidl, Andrew Roth. Single cell spatial multi-omic characterization of the tumor microenvironment in transformed follicular lymphoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 6198.

Antibody feedback shapes germinal center selection in an epitope-specific manner, influencing immunodominance and antibody breadth.