Immune Aging and Its Implication for Age-Related Disease Progression

As life expectancy increases globally, the prevalence and severity of age-related diseases have risen, significantly impacting patients' quality of life and increasing dependency on the healthcare system. Age-related diseases share several pathological commonalities, and emerging evidence suggests that targeting these biological processes ameliorates multiple age-related diseases. Immune aging plays a critical role in the pathogenesis of age-related diseases, given its involvement not only in controlling infection and cancer but also in facilitating tissue homeostasis and repair. Aging causes compositional and functional changes in both innate and adaptive immune cells, thereby significantly contributing to the pathogenesis of age-related disease and systemic low-grade inflammation, termed "inflammaging." This review article aims to describe the current understanding of immune aging and its impact on age-related diseases with particular emphasis on kidney and autoimmune diseases. In addition, this review highlights tertiary lymphoid structures (TLS) as a hallmark of immune aging, exploring their roles in inflammation, tissue damage, and potential therapeutic targeting.

Aberrant B cell receptor signaling responses in circulating double-negative 2 B cells from radiographic axial spondyloarthritis patients

Objective

Radiographic axial spondyloarthritis (r-axSpA) is a chronic rheumatic disease in which innate immune cells and T cells are thought to play a major role. However, recent studies also hint at B cell involvement. Here, we performed an in-depth analysis on alterations within the B-cell compartment from r-axSpA patients.

Methods

We performed immune gene expression profiling on total peripheral blood B cells from 8 r-axSpA patients and 8 healthy controls (HCs). Next, we explored B cell subset distribution and B-cell receptor (BCR) signaling responses in circulating B cells from 28 r-axSpA patients and 15 HCs, by measuring spleen tyrosine kinase, phosphoinositide 3-kinase and extracellular signal regulated kinase 1/2 phosphorylation upon α-Ig stimulation using phosphoflow cytometry.

Results

Immune gene expression profiling indicated an elevated pathway score for BCR signaling in total B cells from r-axSpA patients compared with HCs. Flow cytometric analysis revealed an increase in frequency of both total and double-negative 2 (DN2) B cells in r-axSpA patients compared with HCs. In r-axSpA patients, DN2 B cells displayed an isotype shift towards IgA. Remarkably, where DN2 B cells from HCs were hyporesponsive, these cells displayed significant proximal BCR signaling responses in r-axSpA patients. Enhanced BCR signaling responses were also observed in the transitional and naïve B cell population from r-axSpA patients compared with HCs. The enhanced BCR signaling responses in DN2 B cells correlated with clinical disease parameters.

Conclusion

In r-axSpA patients, circulating DN2 B cells are expanded and, together with transitional and naïve B cells, display significantly enhanced BCR signaling responses upon stimulation. Together, our data suggest B cell involvement in the pathogenesis of r-axSpA.

Auto-antibodies against interferons are common in people living with chronic hepatitis B virus infection and associate with PegIFNα non-response

Background & Aims

Type one (T1) and three interferons (T3IFNs) are implicated in chronic hepatitis B (CHB) immunopathogenesis. IFN remains the only licenced immune modulating therapy for CHB. We measured the prevalence of auto-antibodies (auto-Abs) against T1 and T3IFNs to examine the hypothesis that they impact HBV control and treatment response, as highlighted by COVID-19.

Methods

Our multi-centre retrospective longitudinal study accessed two CHB cohorts; auto-Ab levels and neutralisation status were measured against T1IFN and T3IFN. Associations were tested against HBV clinical parameters.

Results

Overall, 16.7% (46/276) of patients with CHB had any detectable anti-IFN auto-Abs at any time and 6.5% (18/276) anti-T3IFN auto-Abs, with a high incidence of PegIFNα-induced de novo auto-Abs (31.4%, 11/35). However, only a minority of auto-Ab-positive sera demonstrated neutralisation in vitro (4/46, 8.7%). Auto-Ab positivity correlated with higher median HBsAg levels (p = 0.0110). All individuals with detectable anti-T1IFN auto-Abs were PegIFNα non-responders.

Conclusions

Non-neutralising anti-IFN auto-Abs are common in CHB and associate with higher median HBsAg levels. Further prospective study of anti-cytokine auto-Abs in CHB are required to characterise the association with long-term outcomes.

Impact and implications

HBV and PegIFNα individually may induce broad autoreactivity associated with dysregulated antiviral immune responses. Auto-Ab screening prior to PegIFNα treatment or other immunotherapies may play a critical role in predicting treatment responses.

Two distinct durable human class-switched memory B cell populations are induced by vaccination and infection

Memory lymphocytes are durable cells that persist in the absence of antigen, but few human B cell subsets have been characterized in terms of durability. The relative durability of eight non-overlapping human B cell sub-populations covering 100% of all human class-switched B cells was interrogated. Only two long-lived B cell populations persisted in the relative absence of antigen. In addition to canonical germinal center-derived switched-memory B cells with an IgD-CD27+CXCR5+ phenotype, a second, non-canonical, but distinct memory population of IgD-CD27-CXCR5+ DN1 B cells was also durable, exhibited a unique TP63-linked transcriptional and anti-apoptotic signature, had low levels of somatic hypermutation, but was more clonally expanded than canonical switched-memory B cells. DN1 B cells likely evolved to preserve immunological breadth and may represent the human counterparts of rodent extrafollicular memory B cells that, unlike canonical memory B cells, can enter germinal centers and facilitate B cell and antibody evolution.

Critical roles of chronic BCR signaling in the differentiation of anergic B cells into age-associated B cells in aging and autoimmunity

Age-associated B cells (ABCs) with autoreactive properties accumulate with age and expand prematurely in autoimmune diseases. However, the mechanisms behind ABC generation and maintenance remain poorly understood. We show that continuous B cell receptor (BCR) signaling is essential for ABC development from anergic B cells in aged and autoimmune mice. ABCs exhibit constitutive BCR activation, with surface BCRs being internalized. Notably, anergic B cells, but not nonautoreactive B cells, contributed to ABC formation in these models. Anergic B cells also showed a greater propensity for in vitro differentiation into ABCs, which was inhibited by the expression of the transcription factor Nr4a1. Bruton's tyrosine kinase (Btk), a key BCR signaling component, was constitutively activated in ABCs from aged and autoimmune mice as well as patients with lupus. Inhibiting Btk reduced ABC numbers and ameliorated the pathogenicity of lupus mice. Our findings reveal critical mechanisms underlying ABC development and offer previously unrecognized therapeutic insights for autoimmune diseases.

Obesity-associated Inflammation and Alloimmunity

Obesity is a worldwide health problem with a rapidly rising incidence. In organ transplantation, increasing numbers of patients with obesity accumulate on waiting lists and undergo surgery. Obesity is in general conceptualized as a chronic inflammatory disease, potentially impacting alloimmune response and graft function. Here, we summarize our current understanding of cellular and molecular mechanisms that control obesity-associated adipose tissue inflammation and provide insights into mechanisms affecting transplant outcomes, emphasizing on the beneficial effects of weight loss on alloimmune responses.

Early decrease of T-bet+ B cells during subcutaneous belimumab predicts response to therapy in systemic lupus erythematosus patients

Systemic lupus erythematosus (SLE) is characterized by B cell dysregulation and expansion of atypical B cells that may correlate with disease manifestations and activity. This study investigated the impact of subcutaneous (sc) Belimumab (BLM) on the peripheral B cell compartment and on the functional properties of CD21low, T-bet+ and CD11c+ atypical B cells, in 21 active SLE patients over a 12-month period. At baseline, active SLE patients displayed reduced unswitched IgM memory B cells and expansion of atypical B cells, compared to healthy donors and to SLE patients in remission. sc BLM therapy promptly restored B cell homeostasis with a reduction of T-bet+ B cells, observed early in patients responsive to therapy. These findings highlight the pathogenic role of T-bet+ B cells in SLE disease and suggest their potential utility as biomarker of clinical response.

Compromised B-cell homeostasis: Unraveling the link between major depression, infection and autoimmune disorders

BACKGROUND

Major depression can increase susceptibility to viral infections and autoimmune diseases. B cell responses are crucial for immune defense against infections but can trigger autoimmunity when deregulated. However, it remains unclear whether compromised B-cell homeostasis in major depression contributes to an increased risk of infection and autoimmunity.

METHODS

Chronic unpredictable mild stress (CUMS) procedure was applied to adult C57BL/6 J mice to generate a reliable depression model. Mice were immunized with (4-hydroxy-3-nitrophenyl) acetyl (NP) keyhole limpet hemocyanin (NP-KLH) to elicit B-cell-mediated humoral immune responses. CUMS mice were subjected to a collagen-induced arthritis model or a Bm12-induced systemic lupus erythematosus model to assess the contribution of major depression to autoimmunity. RNA sequencing was performed to understand the effects of CUMS on B-cell homeostasis at the transcriptomic level.

RESULTS

CUMS mice exhibited an impaired humoral immune response, as evidenced by reduced germinal centers (GCs), plasma cells, and antigen-specific antibodies. Unimmunized CUMS mice displayed aberrant spontaneous expansion of GC B cells, plasma cells, age-associated B cells and autoantibody production. CUMS mice also demonstrated a greater exacerbation of autoimmune manifestations. RNA sequencing revealed that genes involved in B-cell-mediated immune response were downregulated in B cells from CUMS mice, while the pathways related to autoimmunity seem to be upregulated.

LIMITATIONS

Further research is needed to understand the specific targets, mechanisms, and role of B cell dysfunction in major depression.

CONCLUSIONS

Our results provide novel insights into B-cell-dependent mechanisms that involve the association of increased susceptibility to infections and autoimmunity in major depression.

Aberrations in peripheral B lymphocytes and B lymphocyte subsets levels in Parkinson disease: a systematic review

Objective

The association of B lymphocytes and B lymphocyte subsets and Parkinson's disease (PD) is increasingly acknowledged. However, there is inconsistence in the alterations of B lymphocytes or B lymphocyte subsets in peripheral blood of PD patients. To comprehensively understand its changes in PD patients,it is necessary to conduct a systematic review on this subject.

Methods

PubMed, Cochrane Library, and MEDLINE databases were searched until 3rd February 2024.

Results

We included 20 studies (n=2658) to conduct this systematic review. We conducted a qualitative analysis to assess the alterations of B lymphocytes and B lymphocyte subsets in the peripheral blood of individuals with PD. And studies reviewed demonstrated a significant decrease in the number of B cells, as well as immune dysregulation in the B lymphocyte subsets of these patients' peripheral blood.

Conclusion

Studies reviewed demonstrated that PD is linked to abnormalities in B lymphocytes and/or B lymphocytes subsets in peripheral blood. This study provides a novel perspective into the pathogenesis of PD, and future investigations into the B lymphocytes and/or B lymphocyte subsets as biomarkers and therapeutic targets for PD is warranted.

T-bet+CD11c+ age-associated B cells resist BLyS- and CD20-targeted ablation in murine lupus models

OBJECTIVE

B cell ablation strategies show promise for treating humoral autoimmune diseases, but their impact on pathogenic tissue-localized T-bet+CD11c+ age-associated B cells (ABCs) is poorly defined. We assessed whether mAb-mediated B cell depletion impacts ABCs and other splenic B cell subsets in two mouse models of lupus.

METHODS

Following disease onset, we injected NZBxNZWF1 mice (NZBWF1; n = 72) or bm12 chronic graft versus host disease mice (cGVHD; n = 59) with 0.2 mg or 1 mg of anti-BLyS (10F4), anti-CD20 (18B12), combined treatment, or saline. Spleens were harvested after two weeks and B cell subset representation was analyzed via flow cytometry.

RESULTS

In the NZBWF1 model, lymphopenia and resistance to 10F4 and 18B12 that arose concomitant with disease onset complicated interpretation, as ablative activity was partial and variable in the follicular (FO) and marginal zone (MZ) pools. Conversely, the T-bet+CD11c+ ABC pool was unchanged or enlarged versus controls and was entirely refractory to antibody treatments. In the cGVHD model, both 10F4 and 18B12 treatments ablated nearly all FO B cells. MZ B cells were profoundly ablated by 10F4 but spared by 18B12 treatment, whereas 10F4 treatment spared a small, undefined subset of splenic B cells that was ablated by 18B12. In contrast, T-bet+CD11c+ ABCs were minimally impacted by either reagent alone or combined, regardless of dose.

CONCLUSION

The spleen-resident T-bet+CD11c+ ABC pool resists anti-BLyS and anti-CD20 ablative treatment. These findings have implications for antibody-mediated ablative strategies in patients with autoimmune diseases.

Immunosenescence in autoimmune diseases

Autoimmune diseases (AIDs) are a group of disorders in which the immune system mistakenly attacks the body's own tissues, characterized by the loss of tolerance to self-antigens and destruction of tissues. Aging is a natural process of physiological decline that also alters the immune system, a condition known as immunosenescence. During immunosenescence, the immune system undergoes various changes, including modifications and antigenicity of self-antigens, abnormalities in the quantity, phenotype, and function of lymphocytes and antibodies, as well as a narrowing of the B and T cell receptor repertoire, changes that may increase susceptibility to AIDs. Additionally, senescent immune cells and the senescence-associated secretory phenotype (SASP) contribute to target organ involvement in AIDs, exacerbating chronic inflammation and tissue damage. Mitochondrial dysfunction and metabolic imbalances in AIDs lead to the accumulation of senescent cells, which act as upstream drivers of immunosenescence. In this review, we summarize the bidirectional relationship between AIDs and immunosenescence, as well as its potential mechanisms. Therapeutic approaches targeting immunosenescence in AIDs remain at an early stage. Strategies aimed at resetting or reversing the aging immune system are expected to become a novel direction in the future.

T-bet+ CXCR3+ B cells drive hyperreactive B-T cell interactions in multiple sclerosis

Multiple sclerosis (MS) is an autoimmune disease of the central nervous system (CNS). Self-peptide-dependent autoproliferation (AP) of B and T cells is a key mechanism in MS. Here, we show that pro-inflammatory B-T cell-enriched cell clusters (BTECs) form during AP and mirror features of a germinal center reaction. T-bet+CXCR3+ B cells are the main cell subset amplifying and sustaining their counterpart Th1 cells via interferon (IFN)-γ and are present in highly inflamed meningeal tissue. The underlying B cell activation signature is reflected by epigenetic modifications and receptor-ligand interactions with self-reactive T cells. AP+ CXCR3+ B cells show marked clonal evolution from memory to somatically hypermutated plasmablasts and upregulation of IFN-γ-related genes. Our data underscore a key role of T-bet+CXCR3+ B cells in the pathogenesis of MS in both the peripheral immune system and the CNS compartment, and thus they appear to be involved in both early relapsing-remitting disease and the chronic stage.

Know Your ABCs: Discovery, Differentiation, and Targeting of T-Bet+ B Cells

Since their first description in 2008, T-bet+ B cells have emerged as a clinically important B cell subset. Now commonly known as ABCs (Age-associated B Cells), they are uniquely characterized by their expression of the transcription factor T-bet. Indeed, this singular factor defines this B cell subset. This review will describe the discovery of T-bet+ B cells, their role in bacterial infection as T cell-independent (TI) plasmablasts, as well as long-term follicular helper T cell-dependent (TD) IgM+ and switched memory cells (i.e., T-bet+ ABCs), and later discoveries of their role(s) in diverse immunological responses. These studies highlight a critical, although limited, role of T-bet in IgG2a class switching, a function central to the cells' role in immunity and autoimmunity. Given their association with autoimmunity, pharmacological targeting is an attractive strategy for reducing or eliminating the B cells. T-bet+ ABCs express a number of characteristic cell surface markers, including CD11c, CD11b, CD73, and the adenosine 2a receptor (A2aR). Accordingly, A2aR agonist administration effectively targeted T-bet+ ABCs in vivo. Moreover, agonist treatment of lupus-prone mice reduced autoantibodies and disease symptoms. This latter work highlights the potential therapeutic use of adenosine agonists for treating autoimmune diseases involving T-bet+ ABCs.

The Aging Immune System: A Critical Attack on Ischemic Stroke

Ischemic stroke caused by cerebrovascular embolism is an age-related disease with high rates of disability and mortality. Although the mechanisms of immune and inflammatory development after stroke have been of great interest, most studies have neglected the critical and unavoidable factor of age. As the global aging trend intensifies, the number of stroke patients is constantly increasing, emphasizing the urgency of finding effective measures to address the needs of elderly stroke patients. The concept of "immunosenescence" appears to explain the worse stroke outcomes in older individuals. Immune remodeling due to aging involves dynamic changes at all levels of the immune system, and the overall consequences of central (brain-resident) and peripheral (non-brain-resident) immune cells in stroke vary according to the age of the individual. Lastly, the review outlines recent strategies aimed at immunosenescence to improve stroke prognosis.

Integrated analyses uncover new features of atypical memory B cells and novel targets for intervention

BACKGROUND

Atypical memory B (AMB) is a novel subset of B lymphocytes, but its immune features and pathogenetic roles in systemic rheumatic diseases are still largely elusive. This study aimed to characterize transcriptomic features, immune phenotypes and potential signaling pathways of AMB, and also to confirm its alternations in systemic rheumatic diseases via combined transcriptome analyses.

METHOD

B cell subsets and their transcriptomic signatures were identified via analyses of single cell RNA-sequencing (scRNA-seq) data. Functional characterization of AMB was performed with bioinformatics and CyTOF-based phenotyping. Alternation of AMB in systemic lupus erythematosus (SLE), rheumatoid arthritis (RA) and Sjögren's syndrome (SjS) was evaluated via bioinformatic approaches.

RESULT

A total of 11 B cell subsets including AMB were identified through scRNA-seq transcriptome analyses. Both transcriptome analyses and CyTOF-based immune phenotyping confirmed that AMB had increased levels of TBX21 (T-bet), ITGAX (CD11c), CD19, CD20 and CXCR3 (P < 0.05), and it had decreased expressions of CD27, CD38, CXCR4, CXCR5 and CD62L (P < 0.05). More than 50 % of T-bet+ B cells did not express CD11c, and more than 30 % expressed CD27. AMB was characterized by activated mTORC1 signaling and increased p-P38 level (P < 0.05). AMB transcriptional signature was significantly enriched in the peripheral blood and disease tissues of patients of SLE, RA and SjS (P < 0.05), suggesting the expanded AMB cells in those patients.

CONCLUSION

This study defines the transcriptomic signature, immune phenotypes and potential signaling pathways of AMB, and also confirms the involvement of AMB in systemic rheumatic diseases including SLE, RA and SjS via transcriptomic approaches. mTORC1 signaling and P38/MAPK signaling are promising therapeutic targets for systemic rheumatic diseases mediated by AMB.

Signaling Activation and Modulation in Extrafollicular B Cell Responses

The differentiation of naive follicular B cells into either the germinal center (GC) or extrafollicular (EF) pathway plays a critical role in shaping the type, affinity, and longevity of effector B cells. This choice also governs the selection and survival of autoreactive B cells, influencing their potential to enter the memory compartment. During the first 2-3 days following antigen encounter, initially activated B cells integrate activating signals from T cells, Toll-like receptors (TLRs), and cytokines, alongside inhibitory signals mediated by inhibitory receptors. This integration modulates the intensity of signaling, particularly of the PI3K/AKT/mTOR pathway, which plays a central role in guiding developmental decisions. These early signaling events determine whether B cells undergo GC maturation or differentiate rapidly into antibody-secreting cells (ASCs) via the EF pathway. Dysregulation of these signaling pathways-whether through excessive activation or defective regulatory mechanisms-can disrupt the balance between GC and EF fates, predisposing individuals to autoimmunity. Accordingly, aberrant PI3K/AKT/mTOR signaling has been implicated in the defective selection of autoreactive B cells, increasing the risk of autoimmune disease. This review focuses on the signaling events in newly activated B cells, with an emphasis on the induction and regulation of the PI3K/AKT/mTOR pathway. It also highlights gaps in our understanding of how alternative B cell fates are regulated. Both the physiological context and the implications of inborn errors of immunity (IEIs) and complex autoimmune conditions will be discussed in this regard.

Aligning cellular and molecular components in age-dependent tertiary lymphoid tissues of kidney and liver

Tertiary lymphoid tissues (TLTs) are ectopic lymphoid structures induced by multiple stimuli, including infection and tissue injuries; however, their clinical relevance in disease progression has remained unclear. We demonstrated previously that TLTs develop in mouse and human kidneys with aging and can be a potential marker of kidney injury and prognosis, and therapeutic targets. In addition, we found that two types of unique lymphocytes that emerge with aging, senescence-associated T cells and age-associated B cells, are essential for TLT formation in the kidney. Although TLTs develop with aging in other organs as well, their cellular and molecular components, and clinical significance remain unclear. In the present study, we found that TLTs developed in the liver with aging, and that their cellular and molecular components were similar to those in the kidneys. Notably, senescence-associated T cells and age-associated B cells were also present in hepatic TLTs. Furthermore, analysis of publicly available data on human liver biopsy transcriptomes revealed that the expression of TLT-related genes was elevated in the liver biopsy samples from hepatitis C virus (HCV)-infected patients compared with those without HCV infection and was associated with liver injury and fibrosis. Therefore, we analyzed liver biopsy samples from 47 HCV patients and found that TLTs were present in 87.2% of cases and that the numbers and stages of TLTs were higher in aged patients and cellular and molecular components of TLTs in humans were similar to those in mice. Our findings suggesting that age-dependent TLT formation is a systemic phenomenon across the tissues and aging is also a predisposing factor for TLT formation across organs.

T-bet-expressing B cells promote atherosclerosis in apolipoprotein E-deficient mice

The humoral immune system influences the development of atherosclerosis, but the contributions of specific memory B cell subsets and IgG isotypes are poorly understood. We assessed the relationship between atherosclerosis and age-associated B cells (ABCs), a T-bet-expressing memory B cell subset that is enriched for IgG2c production and implicated in humoral autoimmunity. We found increased numbers of splenic CD11c+ ABCs in 6-mo-old, chow-fed Apoe-/- mice versus C57BL/6 control mice, which were exacerbated by high-fat diet. Deletion of T-bet in the B lineage in high-fat diet-fed Apoe-/- mice reduced aortic lesion area, and this correlated with decreased splenic CD11c+ B cells and reduced serum oxidized low-density lipoprotein-specific IgG2c. Our findings suggest that T-bet-expressing B cells are atherogenic agents in the Apoe-/- model and indicate that interventions to inhibit a T-bet-driven humoral response may improve atherosclerotic disease.

Atypical memory B cells acquire Breg phenotypes in hepatocellular carcinoma

The functional plasticity of tumor-infiltrating lymphocyte B-cells (TIL-B) spans from antitumor responses to noncanonical immune suppression. Yet, how the tumor microenvironment (TME) influences TIL-B development is still underappreciated. Our current study integrated single-cell transcriptomics and B cell receptor (BCR) sequencing to profile TIL-B phenotypes and clonalities in hepatocellular carcinoma (HCC). Using trajectory and gene regulatory network analysis, we were able to characterize plasma cells and memory and naive B cells within the HCC TME and further revealed a downregulation of BCR signaling genes in plasma cells and a subset of inflammatory TNF+ memory B cells. Within the TME, a nonswitched memory B cell subset acquired an age-associated B cell phenotype (TBET+CD11c+) and expressed higher levels of PD-L1, CD25, and granzyme B. We further demonstrated that the presence of HCC tumor cells could confer suppressive functions on peripheral blood B cells that in turn, dampen T cell costimulation. To the best of our knowledge, these findings represent novel mechanisms of noncanonical immune suppression in HCC. While previous studies identified atypical memory B cells in chronic hepatitis and across several solid cancer types, we further highlighted their potential role as regulatory B cells (Bregs) within both the TME and peripheral blood of HCC patients.

Age-Associated B Cells in Autoimmune Diseases: Pathogenesis and Clinical Implications

As a heterogeneous B cell subset, age-associated B cells (ABCs) exhibit distinct transcription profiles, extrafollicular differentiation processes, and multiple functions in autoimmunity. TLR7 and TLR9 signals, along with IFN-γ and IL-21 stimulation, are both essential for ABC differentiation, which is also regulated by chemokine receptors including CXCR3 and CCR2 and integrins including CD11b and CD11c. Given their functions in antigen uptake and presentation, autoantibody and proinflammatory cytokine secretion, and T helper cell activation, ABCs display potential in the prognosis, diagnosis, and therapy for autoimmune diseases, including systemic lupus erythematosus, rheumatoid arthritis, Sjögren's syndrome, multiple sclerosis, neuromyelitis optica spectrum disorders, and ankylosing spondylitis. Specifically targeting ABCs by inhibiting T-bet and CD11c and activating CD11b and ARA2 represents potential therapeutic strategies for SLE and RA. Although single-cell sequencing technologies have recently revealed the heterogeneous characteristics of ABCs, further investigations to explore and validate ABC-target therapies are still warranted.

Cellular and molecular determinants mediating the dysregulated germinal center immune dynamics in systemic lupus erythematosus

Introduction

Systemic lupus erythematosus (SLE) is characterized by dysregulated humoral immunity, leading to the generation of autoreactive B cells that can differentiate both within and outside of lymph node (LN) follicles.

Methods

Here, we employed spatial transcriptomics and multiplex imaging to investigate the follicular immune landscaping and the in situ transcriptomic profile in LNs from SLE individuals.

Results

Our spatial transcriptomic analysis revealed robust type I IFN and plasma cell signatures in SLE compared to reactive, control follicles. Cell deconvolution revealed that follicular T cell subsets are mainly affected by the type I IFN fingerprint of SLE follicles. Dysregulation of TFH differentiation was documented by i) the significant reduction of Bcl6hi TFH cells, ii) the reduced cell density of potential IL-4 producing TFH cell subsets associated with the impaired transcriptomic signature of follicular IL-4 signaling and iii) the loss of their correlation with GC-B cells. This profile was accompanied by a marked reduction of Bcl6hi B cells and an enrichment of extrafollicular CD19hiCD11chiTbethi, age-associated B cells (ABCs), known for their autoreactive potential. The increased prevalence of follicular IL-21hi cells further reveals a hyperactive microenvironment in SLE compared to control.

Discussion

Taken together, our findings highlight the altered immunological landscape of SLE follicles, likely fueled by potent inflammatory signals such as sustained type I IFN and/or IL-21 signaling. Our work provides novel insights into the spatial molecular and cellular signatures of SLE follicular B and TFH cell dynamics, and points to druggable targets to restore immune tolerance and enhance vaccine responses in SLE patients.

Everything everywhere all at once: Unraveling the waves of aging

In a recent work reported in Science, Zhang et al. untangle dynamic changes arising across aging in multiple cell populations within thirteen organs using single-cell transcriptomics and identify four distinct dynamic waves in which immune cells are the most affected populations.

B cells in non-lymphoid tissues

B cells have long been understood to be drivers of both humoral and cellular immunity. Recent advances underscore this importance but also indicate that in infection, inflammatory disease and cancer, B cells function directly at sites of inflammation and form tissue-resident memory populations. The spatial organization and cellular niches of tissue B cells have profound effects on their function and on disease outcome, as well as on patient response to therapy. Here we review the role of B cells in peripheral tissues in homeostasis and disease, and discuss the newly identified cellular and molecular signals that are involved in regulating their activity. We integrate emerging data from multi-omic human studies with experimental models to propose a framework for B cell function in tissue inflammation and homeostasis.

Senescence-associated T cells in immunosenescence and diseases

Age-related changes in the immune system, referred to as immunosenescence, appear to evolve with rather paradoxical manifestations, a diminished adaptive immune capacity, and an increased propensity for chronic inflammation often with autoimmunity, which may underlie the development of diverse disorders with age. Immunosenescent phenotypes are associated with the emergence of unique lymphocyte subpopulations of both T and B lineages. We report that a CD153+ programmed cell death protein 1 (PD-1)+ CD4+ T-cell subpopulation with severely attenuated T-cell receptor (TCR)-responsiveness, termed senescence-associated T (SAT) cells, co-evolve with potentially autoreactive CD30+ B cells, such as spontaneous germinal center B cells and age-associated B cells, in aging mice. SAT cells and CD30+ B cells are reciprocally activated with the aid of the interaction of CD153 with CD30 in trans and with the TCR complex in cis, resulting in the restoration of TCR-mediated proliferation and secretion of abundant pro-inflammatory cytokines in SAT cells and the activation and production of autoantibodies by CD30+ B cells. Besides normal aging, the development of SAT cells coupled with counterpart B cells may be robustly accelerated and accumulated in the relevant tissues of lymphoid or extra-lymphoid organs under chronic inflammatory conditions, including autoimmunity, and may contribute to the pathogenesis and aggravation of the disorders. This review summarizes and discusses recent advances in the understanding of SAT cells in the contexts of immunosenescent phenotypes, as well as autoimmune and chronic inflammatory diseases, and it provides a novel therapeutic clue.

Impact of Fli1 deletion on B cell populations: A focus on age-associated B cells and transcriptional dynamics

BACKGROUND

Altered Fli1 expression is associated with various autoimmune diseases, yet its impact on B cells remains unexplored.

OBJECTIVE

This study investigated the direct effects of Fli1 depletion on B cell populations, focusing on age-associated B cells (ABCs).

METHODS

Splenocytes of Fli1 BcKO (Cd19-Cre+/-; Fli1flox/flox) and Cd19-Cre+/- mice were analyzed flow cytometrically. Transcriptional/epigenetic profiles of Cd11b+Cd11c+ ABCs were examined by RNA-sequencing and ATAC-sequencing.

RESULTS

Fli1 BcKO mice displayed a notable reduction in follicular and marginal zone B cells, with a concurrent rise in newly formed B cells compared to Cd19-Cre+/- mice. Additionally, a striking increase in B-1 B cells, as well as Cd11b+Cd11c+ or T-bet+Cd11c+ ABCs, was observed in Fli1 BcKO mice. Furthermore, these mice exhibited elevated Cd138 levels in follicular B cells. Conducting transcriptional analyses of Fli1-depleted ABCs unveiled upregulated genes associated with cell-cell adhesion, coupled with downregulated genes linked to cell activation or immune responses. Exploring the chromatin landscape found that Fli1 depletion dysregulated the chromatin accessibility of the interferon regulatory factor family, implying potential roles in autoimmunity.

CONCLUSION

These findings suggest complex modulations of B cell populations and immune-related gene expression due to Fli1 deficiency, shedding light on its involvement in autoimmune processes.

Immunosenescence and age-related immune cells: causes of age-related diseases

Immunosenescence is a weakening of the immune system due to aging, characterized by changes in immune cells and dysregulated immune function. Age-related immune cells are increasing with aging. They are associated with chronic prolonged inflammation, causing tissue dysfunction and age-related diseases. Here, we discuss increased pro-inflammatory activity of aged macrophages, accumulation of lymphocytes with an age-associated phenotype, and specific alterations in both functions and characteristics of these immune cells. These cellular changes are associated with development of age-related diseases. Additionally, we reviewed various therapeutic strategies targeting age-related immunosenescence, providing pathways to mitigate effects of age-related diseases.

Autoantibodies against phosphatidylserine and DNA during canine Dirofilaria immitis infection

Heartworm infection caused by Dirofilaria immitis induces a devastating disease that greatly affects the global canine population. The mechanism leading to heartworm pathology has been attributed to be mostly by mechanical damage of the worm to the dog´s vascular system and immune-mediated, but the latter processes are not completely understood. Autoantibodies targeting host molecules such as lipids and nucleic acids have been described with pathological roles during malaria and COVID-19 and mediating anemia and thrombocytopenia. We hypothesized that autoantibodies could be present and have a pathological role during canine heartworm disease caused by D. immitis. In this study, we analyzed the levels of autoantibodies (IgM and IgG) against membrane lipid phosphatidylserine (PS) and DNA in the serum of 169 canine samples based on D. immitis infection. First, our results found significant levels of anti-PS IgM and IgG autoantibodies that were associated with D. immitis-positive when compared to D. immitis-negative samples. Second, we found that autoantibodies, particularly anti-PS, are correlated with hematological parameters such as low platelet count suggesting an association with pathologies such as thrombocytopenia. Altogether, these findings elucidate the understudied presence and pathological role of autoantibodies during canine heartworm disease by D. immitis with implications as biomarkers of disease.

Immune Aging in Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a life-long autoimmune disease caused by the confluence of genetic and environmental variables that lead to loss of self-tolerance and persistent joint inflammation. RA occurs at the highest incidence in individuals >65 years old, implicating the aging process in disease susceptibility. Transformative approaches in molecular immunology and in functional genomics have paved the way for pathway paradigms underlying the replacement of immune homeostasis with autodestructive immunity in affected patients, including the process of immune aging. Patients with RA have a signature of premature immune aging, best understood for CD4+ T cells, which function as pathogenic effectors in this HLA class II-associated disease. Premature immune aging is present in healthy HLA-DRB1*04+ individuals, placing accelerated immune aging before joint inflammation. Aging-related molecular abnormalities directly implicated in turning RA CD4+ T cells into proinflammatory effector cells are linked to malfunction of subcellular organelles, such as mitochondria, lysosomes, lipid droplets, and the endoplasmic reticulum. Resulting changes in T cell behavior include cellular hypermobility, tissue invasiveness, unopposed mammalian target of rapamycin complex (mTORC)1 activation, excessive release of tumor necrosis factor, lysosomal failure, clonal expansion, and immunogenic cell death. Aged and metabolically reprogrammed T cells in patients with RA are accompanied by age-associated B cells, which specialize in autoantibody production. Clonal hematopoiesis drives myeloid cell aging by producing aged monocytes and hypermetabolic macrophages, which sustain the process of inflammaging. Here, we synthesize insights into the relationship of RA risk and immune aging and discuss mechanisms through which immune aging can cause autoimmunity.

Function and Regulation of Age-Associated B Cells in Diseases

The aging process often leads to immune-related diseases, including infections, tumors, and autoimmune disorders. Recently, researchers identified a special subpopulation of B cells in elderly female mice that increases with age and accumulates prematurely in mouse models of autoimmune diseases or viral infections; these B cells are known as age-related B cells (ABCs). These cells possess distinctive cell surface phenotypes and transcriptional characteristics, and the cell population is widely recognized as CD11c+CD11b+T-bet+CD21-CD23- cells. Research has shown that ABCs are a heterogeneous group of B cells that originate independently of the germinal center and are insensitive to B-cell receptor (BCR) and CD40 stimulation, differentiating and proliferating in response to toll-like receptor 7 (TLR7) and IL-21 stimulation. Additionally, they secrete self-antibodies and cytokines to regulate the immune response. These issues have aroused widespread interest among researchers in this field. This review summarizes recent research progress on ABCs, including the functions and regulation of ABCs in aging, viral infection, autoimmune diseases, and organ transplantation.

Immune senescence: A key player in cancer biology

With the rapid development of immunological techniques in recent years, our understanding of immune senescence has gradually deepened, but the role of immune senescence in cancer biology remains incompletely elucidated. Understanding these mechanisms and interactions is crucial for the development of tumor biology. This review examines five key areas: the classification and main features of immune senescence, factors influencing immune cell senescence in cancer, the reciprocal causal cycle between immune senescence and malignancy, and the potential of immune senescence as a target for cancer immunotherapy.

Single-Cell Analysis Provides New Insights into the Roles of Tertiary Lymphoid Structures and Immune Cell Infiltration in Kidney Injury and Chronic Kidney Disease

Chronic kidney disease (CKD) is a global health concern with high morbidity and mortality. Acute kidney injury (AKI) is a pivotal risk factor for the progression of CKD, and the rate of AKI-to-CKD progression increases with aging. Intrarenal inflammation is a fundamental mechanism underlying AKI-to-CKD progression. Tertiary lymphoid structures (TLSs), ectopic lymphoid aggregates formed in nonlymphoid organs, develop in aged injured kidneys, but not in young kidneys, with prolonged inflammation and maladaptive repair, which potentially exacerbates AKI-to-CKD progression in aged individuals. Dysregulated immune responses are involved in the pathogenesis of various kidney diseases, such as IgA nephropathy, lupus nephritis, and diabetic kidney diseases, thereby deteriorating kidney function. TLSs also develop in several kidney diseases, including transplanted kidneys and renal cell carcinoma. However, the precise immunologic mechanisms driving AKI-to-CKD progression and development of these kidney diseases remain unclear, which hinders the development of novel therapeutic approaches. This review aims to describe recent findings from single-cell analysis of cellular heterogeneity and complex interactions among immune and renal parenchymal cells, which potentially contribute to the pathogenesis of AKI-to-CKD progression and other kidney diseases, highlighting the mechanisms of formation and pathogenic roles of TLSs in aged injured kidneys.

In-depth human immune cellular profiling from newborn to frail

Immune functional decline and remodeling accompany aging and frailty. It is still largely unknown how changes in the immune cellular composition differentiate healthy individuals from those who become frail at a relatively early age. Our aim in this exploratory study was to investigate immunological changes from newborn to frailty and the association between health statute and various immune cell subtypes. The participants analyzed in this study covered human cord blood cells and peripheral blood cells collected from young adults and healthy and frail old individuals. A total of 30 immune cell subsets were performed by flow cytometry based on the surface markers of immune cells. Furthermore, frailty was investigated for its relations with various leukocyte subpopulations. Frail individuals exhibited a higher CD4/CD8 ratio; a higher proportion of CD4+ central memory T cells, CD8+ effector memory T cells, CD27- switched memory B (BSM) cells, CD27+ BSM cells, age-associated B cells, and CD38-CD24- B cells; and a lower proportion of naïve CD8+ T cells and progenitor B cells. The frailty index score was found to be associated with naïve T cells, CD4/CD8 ratio, age-associated B cells, CD27- BSM cells, and CD4+ central memory T cells. Our findings conducted a relatively comprehensive and extensive atlas of age- and frailty-related changes in peripheral leukocyte subpopulations from newborn to frailty. The immune phenotypes identified in this study can contribute to a deeper understanding of immunosenescence in frailty and may provide a rationale for future interventions and diagnosis.

Immunometabolism In Brain Aging and Neurodegeneration: Bridging Metabolic Pathways and Immune Responses

The complex set of interactions between the immune system and metabolism, known as immunometabolism, has emerged as a critical regulator of disease outcomes in the central nervous system. Numerous studies have linked metabolic disturbances to impaired immune responses in brain aging, neurodegenerative disorders, and brain injury. In this review, we will discuss how disruptions in brain immunometabolism balance contribute to the pathophysiology of brain dysfunction. The first part of the review summarizes the contributions of critical immune cell populations such as microglia, astrocytes, and infiltrating immune cells in mediating inflammation and metabolism in CNS disorders. The remainder of the review addresses the impact of metabolic changes on immune cell activation and disease progression in brain aging, Alzheimer's disease, Parkinson's disease, multiple sclerosis, stroke, spinal cord injury, and traumatic brain injury. Furthermore, we also address the therapeutic potential of targeting immunometabolic pathways to reduce neuroinflammation and slow disease progression. By focusing on the interactions among brain immune cells and the metabolic mechanisms they recruit in disease, we present a comprehensive overview of brain immunometabolism in human health and disease.

Immune aging and infectious diseases

ABSTRACT

The rise in global life expectancy has led to an increase in the older population, presenting significant challenges in managing infectious diseases. Aging affects the innate and adaptive immune systems, resulting in chronic low-grade inflammation (inflammaging) and immune function decline (immunosenescence). These changes would impair defense mechanisms, increase susceptibility to infections and reduce vaccine efficacy in older adults. Cellular senescence exacerbates these issues by releasing pro-inflammatory factors, further perpetuating chronic inflammation. Moreover, comorbidities, such as cardiovascular disease and diabetes, which are common in older adults, amplify immune dysfunction, while immunosuppressive medications further complicate responses to infections. This review explores the molecular and cellular mechanisms driving inflammaging and immunosenescence, focusing on genomic instability, telomere attrition, and mitochondrial dysfunction. Additionally, we discussed how aging-associated immune alterations influence responses to bacterial, viral, and parasitic infections and evaluated emerging antiaging strategies, aimed at mitigating these effects to improve health outcomes in the aging population.

The essential roles of memory B cells in the pathogenesis of systemic lupus erythematosus

Emerging evidence indicates that memory B cells are dysfunctional in systemic lupus erythematosus (SLE). They are hyporesponsive to signalling through the B cell receptor (BCR) but retain responsiveness to Toll-like receptor (TLR) and type I interferon signalling, as well as to T cell-mediated activation via CD40-CD154. Chronic exposure to immune complexes of ribonucleoprotein (RNP)-specific autoantibodies and TLR-engaging or BCR-engaging cargo is likely to contribute to this partially anergic phenotype. TLR7 or TLR8 signalling and the resulting production of type I interferon, as well as the sustained activation by bystander T cells, fuel a positive feedforward loop in memory B cells that can evade negative selection and permit preferential expansion of anti-RNP autoantibodies. Clinical trials of autologous stem cell transplantation or of B cell-targeted monoclonal antibodies and chimeric antigen receptor (CAR) T cells have correlated replenishment of the memory B cell population with relapse of SLE. Moreover, the BCR hyporesponsiveness of memory B cells might explain the failure of non-depleting B cell-targeting approaches in SLE, including BTK inhibitors and anti-CD22 monoclonal antibodies. Thus, targeting of dysfunctional memory B cells might prove effective in SLE, while also avoiding the adverse events of broad-spectrum targeting of B cell and plasma cell subsets that are not directly involved in disease pathogenesis.

Extrafollicular CD19lowCXCR5-CD11c- double negative 3 (DN3) B cells are significantly associated with disease activity in females with systemic lupus erythematosus

Objective

B cells play a major role in the development and maintenance of systemic lupus erythematosus (SLE). Double negative (DN) B cells defined by the lack of surface expression of IgD and CD27 have attracted recent interest for their sensitivity to Toll-like receptor 7 (TLR7) ligands and their potential role in the production of autoantibodies. Here we aimed at investigating the possible association of DN B cells and their subsets with SLE disease activity specifically in female patients, in which TLR7 gene has been reported to escape X chromosome inactivation.

Methods

Peripheral blood mononuclear cells were purified from woman participating to the clinically well-characterized Swiss SLE Cohort Study (SSCS). PBMC from age-matched healthy females were used as controls. PBMC were stained for cell surface markers, intracellular Tbet and analyzed by multicolor cytofluorimetry. Single nucleotide TLR7 polymorphisms were assessed by polymerase chain reaction.

Results

The median SLE disease activity index of the 86 females was 2, IQR [0-6], all but 8 were under chronic SLE treatment. B cells co-expressing CD11c and Tbet were increased, the mean fluorescence intensity (MFI) of CD19 was considerably reduced and we observed a large increase in CD11c + CXCR5-and CD11c-CXCR5-concomitantly with a reduction of CD11c-CXCR5+ B cells in SLE compared to 40 healthy donors (HD). When focusing on the DN B cell subset, we found a reduction of DN1 (CD11c-CXCR5+) and an increase of DN2 (CD11c + CXCR5-) and most impressively of DN3 (CD11c-CXCR5-) cells. The DN subset, particularly DN3, showed the lowest level of CD19 expression. Both DN1 and DN3 percentages as well as the CD19 MFI of DN cells were associated with SLE disease activity. The use of glucocorticoids, immunosuppressants, and antimalarials impacted differentially on the frequencies of DN B cell subsets. CD19 MFI in B cells and the percentage of DN3 were the strongest biomarkers of disease activity. The TLR7 snp3858384 G allele was associated with increased percentages of B cells and CD19+CD11c-CXCR5+ and decreased CD19+CD11c-CXCR5-.

Conclusions

DN3 B cells are strongly associated with SLE clinical activity pointing to their potential involvement in disease pathogenesis, and CD19 expression level performs accurately as disease activity biomarker.

Relation of CMV and brain atrophy to trajectories of immunosenescence in diverse populations

Immunosenescence (ISC), the aging of the immune system, has largely been studied in populations of European descent. Here, circulating immune cell cytometric data from African-American, Hispanic, and non-Hispanic White participants were generated. Known and novel age effects were identified using either a meta-analysis approach or a parallel genetic approach. Most results are consistent across the three populations, but some cell populations display evidence of heterogeneity, such as a PD-L1 + CD56 + NK cell subset. The study estimated "Immunological Age" (IA) during physiologic aging. While we found no relation of IA to Multiple Sclerosis, IA is associated with entorhinal cortex atrophy, a presymptomatic feature of Alzheimer's disease, linking neurodegeneration and peripheral immunity. ISC trajectories were also inferred, highlighting age, CMV status, and genetic ancestry as key influences. Our assessment offers reference ISC trajectories for personalization of assessments of immune function over the life course in diverse populations.

Flow cytometry identifies changes in peripheral and intrathecal lymphocyte patterns in CNS autoimmune disorders and primary CNS malignancies

BACKGROUND

Immune dysregulation is a hallmark of autoimmune diseases of the central nervous system (CNS), characterized by an excessive immune response, and primary CNS tumors (pCNS-tumors) showing a highly immunosuppressive parenchymal microenvironment.

METHODS

Aiming to provide novel insights into the pathogenesis of CNS autoimmunity and cerebral tumor immunity, we analyzed the peripheral blood (PB) and cerebrospinal fluid (CSF) of 81 autoimmune limbic encephalitis (ALE), 148 relapsing-remitting multiple sclerosis (RRMS), 33 IDH-wildtype glioma, 9 primary diffuse large B cell lymphoma of the CNS (CNS-DLBCL), and 110 controls by flow cytometry (FC). Additionally, an in-depth immunophenotyping of the PB from an independent cohort of 20 RRMS and 18 IDH-wildtype glioblastoma patients compared to 19 controls was performed by FC combined with unsupervised computational approaches.

RESULTS

We identified alterations in peripheral and intrathecal adaptive immunity, mainly affecting the T cell (Tc) but also the B cell (Bc) compartment in ALE, RRMS, and pCNS-tumors compared to controls. ALE, RRMS, and pCNS-tumors featured higher expression of the T cell activation marker HLA-DR, which was even more pronounced in pCNS-tumors than in ALE or RRMS. Glioblastoma patients showed signs of T cell exhaustion that were not visible in RRMS patients. In-depth characterization of the PB revealed differences mainly in the T effector and memory compartment between RRMS and glioblastoma patients and similar alterations in the Bc compartment, including atypical Bc, CD19+CD20- double negative Bc, and plasma cells. PB and CSF mFC together with CSF routine parameters could reliably differentiate ALE and RRMS from pCNS-tumors facilitating early diagnosis and treatment.

CONCLUSIONS

ALE, RRMS, and pCNS-tumors show distinct but partially overlapping changes mainly in HLA-DR+ Tc, memory Tc, exhausted Tc, and Bc subsets providing insights into disease pathogenesis. Moreover, mFC shows diagnostic potential facilitating early diagnosis and treatment.

N6-methyladenosine and its epitranscriptomic effects on hematopoietic stem cell regulation and leukemogenesis

N6-methyladenosine (m6A) RNA modification orchestrates cellular epitranscriptome through tuning the homeostasis of transcript stability, translation efficiency, and the transcript affinity toward RNA-binding proteins (RBPs). An aberrant m6A deposition on RNA can lead toward oncogenic expression profile (mRNA), impaired mitochondrial metabolism (mtRNA), and translational suppression (rRNA) of tumor suppressor genes. In addition, non-coding RNAs (ncRNAs), such as X-inactive specific transcript (XIST), miRNAs, and α-ketoglutarate-centric metabolic transcripts are also regulated by the m6A epitranscriptome. Notably, recent studies had uncovered a myriad of m6A-modified transcripts the center of hematopoietic stem cell (HSC) regulation, in which m6A modification act as a context dependent switch to the on and off of hematopoietic stem cell (HSC) maintenance, lineage commitment and terminal differentiation. In this review, we sequentially unfold the m6A mediated epithelial-to-hematopoietic transition in progenitor blood cell production, lymphocytic lineage expansion (T cells, B cells, NK cells, and non-NK ILCs), and the m6A crosstalk with the onco-metabolic prospects of leukemogenesis. Together, an encompassing body of evidence highlighted the emerging m6A significance in the regulation of HSC biology and leukemogenesis.

A guide to adaptive immune memory

Immune memory - comprising T cells, B cells and plasma cells and their secreted antibodies - is crucial for human survival. It enables the rapid and effective clearance of a pathogen after re-exposure, to minimize damage to the host. When antigen-experienced, memory T cells become activated, they proliferate and produce effector molecules at faster rates and in greater magnitudes than antigen-inexperienced, naive cells. Similarly, memory B cells become activated and differentiate into antibody-secreting cells more rapidly than naive B cells, and they undergo processes that increase their affinity for antigen. The ability of T cells and B cells to form memory cells after antigen exposure is the rationale behind vaccination. Understanding immune memory not only is crucial for the design of more-efficacious vaccines but also has important implications for immunotherapies in infectious disease and cancer. This 'guide to' article provides an overview of the current understanding of the phenotype, function, location, and pathways for the generation, maintenance and protective capacity of memory T cells and memory B cells.

B cell-intrinsic IFN-γ promotes excessive CD11c+ age-associated B cell differentiation and compromised germinal center selection in lupus mice

CD11c+ age-associated B cells (ABCs) have emerged as a key component in protective and autoreactive B cell responses. Lupus is an autoimmune disorder linked to reduced efficacy of vaccines and increased susceptibility to infections. Previously, we reported that excessive CD11c+ ABCs not only significantly contribute to autoantibody production but also promote aberrant T cell activation and compromised affinity-based germinal center selection in response to immunization in lupus mice. Yet, the regulation of CD11c+ ABC differentiation is not fully understood. In this study, we show that B cell-intrinsic IFN-γ is required for excessive CD11c+ ABC differentiation in lupus mice. B cell-intrinsic IFN-γ is mainly produced by CD11c+ ABCs. IFN-γ-deficiency leads to decreased expression of ABC characteristic genes. We further show that ablating IFN-γ can normalize T cell overactivation and rescue antigen-specific GC responses in lupus mice. Our study offers insight into the crucial role of B cell-intrinsic IFN-γ in promoting excessive CD11c+ ABC differentiation, which compromises affinity-based germinal center selection and affinity maturation in lupus, providing a potential strategy to normalize vaccine responses in lupus.

Antibody levels versus vaccination status in the outcome of older adults with COVID-19

BACKGROUNDDespite the currently prevailing, milder Omicron variant of COVID-19, older adults remain at elevated risk of hospital admission, critical illness, and death. Loss of efficacy of the immune system, including reduced strength, quality, and durability of antibody responses, may render generalized recommendations on booster vaccinations inadequate. There is a lack of data on the efficacy of antibody levels in older adults and on the utility of vaccination status versus antibody levels as a correlate of protection. It is further unclear whether antibody levels may be used to guide the timing of booster vaccinations in older adults.METHODSWe conducted a prospective multicenter cohort study comprising hospitalized patients with COVID-19. Anti-SARS-CoV-2 spike antibodies were measured on hospital admission. The primary endpoint was in-hospital mortality. Patients were stratified by age, antibody levels, and vaccination status. Multiple logistic regression and Cox regression analyses were conducted.RESULTSIn total, 785 older patients (≥60 years of age [a]) and 367 controls (<60a) were included. After adjusting for confounders, risk of mortality, ICU admission, endotracheal intubation, and oxygen administration was 4.9, 2.6, 6.5, and 2.3 times higher, respectively, if antibody levels were < 1,200 BAU/mL (aOR, 4.92 [95%CI, 2.59-9.34], P < 0.0001; aOR, 2.64 [95%CI, 1.52-4.62], P = 0.0006; aOR, 6.50 [95%CI, 1.48-28.47], P = 0.013; aOR, 2.34 [95%CI, 1.60-3.343], P < 0.0001). Older adults infected with the Omicron variant were approximately 6 times more likely to die if antibody levels were < 1,200 BAU/mL (aOR, 6.3 [95% CI, 2.43-16.40], P = 0.0002).CONCLUSIONAntibody levels were a stronger predictor of in-hospital mortality than vaccination status. Monitoring antibody levels may constitute a better and more direct approach for safeguarding older adults from adverse COVID-19 outcomes.

Prevalence and clinical significance of anti-SSA antibody in the Chinese health screening population

Anti-Sjögren's syndrome type A (anti-SSA) antibodies are non-organ-specific autoantibodies highly prevalent in various autoimmune diseases. This study primarily investigated the prevalence of anti-SSA antibodies in the health screening population. Additionally, we explored the clinical features of the anti-SSA antibody-positive population and evaluated the development of connective tissue diseases (CTD) over the years in individuals with anti-SSA antibodies for whom follow-up was available. A total of, 64 045 individuals without a history of CTD from 2013 to 2022 who visited Peking Union Medical College Hospital for health screening were screened for autoimmune antibodies: 1.7% (1091/64 045) of the Chinese health screening population were positive for anti-SSA antibodies, with a prevalence of 0.9% (290/33 829) in men and 2.7% (801/30 216) in women. Compared with matched autoantibody-negative controls, anti-SSA antibody-positive individuals had higher levels of serological abnormalities, including erythrocyte sedimentation rate (ESR) [10 (6-15) mm/h vs. 7 (4-12) mm/h, P < 0.0001], rheumatoid factor (RF) [7.15 (4.30-16.90) IU/ml vs. 5.00 (3.20-7.90) IU/ml, P < 0.0001], and immunoglobulin G [13.09 (11.20-15.45) g/L vs. 11.34 (9.85-13.18) g/L, P < 0.0001], and lower levels of white blood cells (WBC; 5.49 ± 1.50 × 109/L vs. 5.82 ± 1.49 × 109/L, P < 0.0001). Additionally, they had a higher proportion of coexisting thyroid autoantibodies, including anti-thyroid peroxidase antibodies (TPO-Ab) (17.1% vs. 11.3%, P < 0.0001) and anti-thyroglobulin antibodies (Tg-Ab) (17.8% vs. 11.0%, P < 0.0001). Among the 381 subjects who were anti-SSA positive and followed up for a median of 4.6 years, 146 (38.3%) individuals developed CTD, including 68 (17.8%) cases of primary Sjögren's syndrome (pSS), 10 (2.6%) cases of rheumatoid arthritis (RA), 5 (1.3%) cases of systemic lupus erythematosus (SLE), 4 (1.0%) cases of secondary Sjögren's syndrome (sSS), and 59 (15.5%) cases of undifferentiated connective tissue disease (UCTD). In all, 235 (61.7%) individuals did not develop CTD over a median time of 5.9 (2.9-8.1) years after the earliest autoantibody detection. Elevated ESR (>20 mm/h), RF positivity (>20 IU/ml), and female gender were identified as independent risk factors for CTD among the anti-SSA antibody-positive individuals. Anti-SSA antibodies were found in 17 among approximately 1000 individuals without a history of autoimmune diseases. Anti-SSA antibody-positive individuals are advised to periodically monitor thyroid function. Elevated ESR (>20 mm/h), female gender, and RF positivity may delineate a high-risk cohort for CTDs.

The 3 I's of immunity and aging: immunosenescence, inflammaging, and immune resilience

As we age, our immune system's ability to effectively respond to pathogens declines, a phenomenon known as immunosenescence. This age-related deterioration affects both innate and adaptive immunity, compromising immune function and leading to chronic inflammation that accelerates aging. Immunosenescence is characterized by alterations in immune cell populations and impaired functionality, resulting in increased susceptibility to infections, diminished vaccine efficacy, and higher prevalence of age-related diseases. Chronic low-grade inflammation further exacerbates these issues, contributing to a decline in overall health and resilience. This review delves into the characteristics of immunosenescence and examines the various intrinsic and extrinsic factors contributing to immune aging and how the hallmarks of aging and cell fates can play a crucial role in this process. Additionally, it discusses the impact of sex, age, social determinants, and gut microbiota health on immune aging, illustrating the complex interplay of these factors in altering immune function. Furthermore, the concept of immune resilience is explored, focusing on the metrics for assessing immune health and identifying strategies to enhance immune function. These strategies include lifestyle interventions such as diet, regular physical activity, stress management, and the use of gerotherapeutics and other approaches. Understanding and mitigating the effects of immunosenescence are crucial for developing interventions that support robust immune responses in aged individuals.

Lymphocytes Change Their Phenotype and Function in Systemic Lupus Erythematosus and Lupus Nephritis

Systemic lupus erythematosus (SLE) is a complex autoimmune disease, characterized by considerable changes in peripheral lymphocyte structure and function, that plays a critical role in commencing and reviving the inflammatory and immune signaling pathways. In healthy individuals, B lymphocytes have a major role in guiding and directing defense mechanisms against pathogens. Certain changes in B lymphocyte phenotype, including alterations in surface and endosomal receptors, occur in the presence of SLE and lead to dysregulation of peripheral B lymphocyte subpopulations. Functional changes are characterized by loss of self-tolerance, intra- and extrafollicular activation, and increased cytokine and autoantibody production. T lymphocytes seem to have a supporting, rather than a leading, role in the disease pathogenesis. Substantial aberrations in peripheral T lymphocyte subsets are evident, and include a reduction of cytotoxic, regulatory, and advanced differentiated subtypes, together with an increase of activated and autoreactive forms and abnormalities in follicular T cells. Up-regulated subpopulations, such as central and effector memory T cells, produce pre-inflammatory cytokines, activate B lymphocytes, and stimulate cell signaling pathways. This review explores the pivotal roles of B and T lymphocytes in the pathogenesis of SLE and Lupus Nephritis, emphasizing the multifaceted mechanisms and interactions and their phenotypic and functional dysregulations.

Inflammation of the nasal mucosa is associated with susceptibility to experimental pneumococcal challenge in older adults

Streptococcus pneumoniae colonization in the upper respiratory tract is linked to pneumococcal disease development, predominantly affecting young children and older adults. As the global population ages and comorbidities increase, there is a heightened concern about this infection. We investigated the immunological responses of older adults to pneumococcal-controlled human infection by analyzing the cellular composition and gene expression in the nasal mucosa. Our comparative analysis with data from a concurrent study in younger adults revealed distinct gene expression patterns in older individuals susceptible to colonization, highlighted by neutrophil activation and elevated levels of CXCL9 and CXCL10. Unlike younger adults challenged with pneumococcus, older adults did not show recruitment of monocytes into the nasal mucosa following nasal colonization. However, older adults who were protected from colonization showed increased degranulation of cluster of differentiation 8+ T cells, both before and after pneumococcal challenge. These findings suggest age-associated cellular changes, in particular enhanced mucosal inflammation, that may predispose older adults to pneumococcal colonization.

Atypical B Cells Promote Cancer Progression and Poor Response to Bacillus Calmette-Guérin in Non-Muscle Invasive Bladder Cancer

Poor response to Bacillus Calmette-Guérin (BCG) immunotherapy remains a major barrier in the management of patients with non-muscle invasive bladder cancer (NMIBC). Multiple factors are associated with poor outcomes, including biological aging and female sex. More recently, it has emerged that a B-cell-infiltrated pretreatment immune microenvironment of NMIBC tumors can influence the response to intravesically administered BCG. The mechanisms underlying the roles of B cells in NMIBC are poorly understood. Here, we show that B-cell-dominant tertiary lymphoid structures (TLSs), a hallmark feature of the chronic mucosal immune response, are abundant and located close to the epithelial compartment in pretreatment tumors from BCG non-responders. Digital spatial proteomic profiling of whole tumor sections from male and female patients with NMIBC who underwent treatment with intravesical BCG, revealed higher expression of immune exhaustion-associated proteins within the tumor-adjacent TLSs in both responders and non-responders. Chronic local inflammation, induced by the N-butyl-N-(4-hydroxybutyl) nitrosamine carcinogen, led to TLS formation with recruitment and differentiation of the immunosuppressive atypical B-cell (ABC) subset within the bladder microenvironment, predominantly in aging female mice compared to their male counterparts. Depletion of ABCs simultaneous to BCG treatment delayed cancer progression in female mice. Our findings provide evidence indicating a role for ABCs in BCG response and will inform future development of therapies targeting the B-cell-exhaustion axis.

Inflammatory and Immune Mechanisms in COPD: Current Status and Therapeutic Prospects

Background

Chronic obstructive pulmonary disease (COPD) currently ranks among the top three causes of mortality worldwide, presenting as a prevalent and complex respiratory ailment. Ongoing research has underscored the pivotal role of immune function in the onset and progression of COPD. The immune response in COPD patients exhibits abnormalities, characterized by diminished anti-infection capacity due to immune senescence, heightened activation of neutrophils and macrophages, T cell infiltration, and aberrant B cell activity, collectively contributing to airway inflammation and lung injury in COPD.

Objective

This review aimed to explore the pivotal role of the immune system in COPD and its therapeutic potential.

Methods

We conducted a review of immunity and COPD published within the past decade in the Web of Science and PubMed databases, sorting through and summarizing relevant literature.

Results

This article examines the pivotal roles of the immune system in COPD. Understanding the specific functions and interactions of these immune cells could facilitate the development of novel therapeutic strategies and interventions aimed at controlling inflammation, enhancing immune function, and mitigating the impact of respiratory infections in COPD patients.