The Role of the Immune System in the Course of Hashimoto's Thyroiditis: The Current State of Knowledge.

The process of thyroid autoimmunization develops against the background of genetic predispositions associated with class II human leukocyte antigens (HLA-DR), as well as cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), protein tyrosine phosphatase non-receptor type 22 (PTPN22), and forkhead transcription box protein P3 (FOXP3). Environmental factors, such as vitamin D deficiency, Zn, Se, and Mg, as well as infections, chronic stress, pregnancy, smoking, alcohol, medications, intestinal dysbiosis, and malnutrition, also play an important role. The first stage of autoimmunization involves the accumulation of macrophages and dendritic cells, as well as plasma cells. In the second stage, the mutual interactions of individual cells in the immune system lead to a decrease in the level of CD8+ in favor of CD4+, which intensifies the synthesis of T lymphocyte derivatives, especially Th1, Th17, Tfh, and Tc, reducing the level of Treg. Consequently, the number of the anti-inflammatory cytokines IL10 and IL2 decreases, and the synthesis of the pro-inflammatory cytokines IL-2, Il-12, Il-17, IL-21, IL-22, IFN-γ, and TNF-α increases. The latter two especially trigger the pyroptosis process involving the inflammasome. Activation of the inflammasome by IL-ß and IL-18 produced by macrophages is one of the mechanisms of pyroptosis in the course of Hashimoto's thyroiditis, involving Gram-negative bacteria and NLRC4. In the next step, the apoptosis of thyroid cells is initiated by the intensification of perforin, granzyme, and proteoglycan synthesis by Tc and NK cells. The current findings raise many possibilities regarding interventions related to the inhibition of pro-inflammatory cytokines and the stimulation of anti-inflammatory cytokines produced by both T and B lymphocytes. Furthermore, since there is currently no effective method for treating thyroid autoimmunity, a summary of the review may provide answers regarding the treatment of not only Hashimoto's thyroiditis, but also other autoimmune diseases associated with autoimmunity.

Mechanical regulation of lymphocyte activation and function.

Mechanosensing, or how cells sense and respond to the physical environment, is crucial for many aspects of biological function, ranging from cell movement during development to cancer metastasis, the immune response and gene expression driving cell fate determination. Relevant physical stimuli include the stiffness of the extracellular matrix, contractile forces, shear flows in blood vessels, complex topography of the cellular microenvironment and membrane protein mobility. Although mechanosensing has been more widely studied in non-immune cells, it has become increasingly clear that physical cues profoundly affect the signaling function of cells of the immune system. In this Review, we summarize recent studies on mechanical regulation of immune cells, specifically lymphocytes, and explore how the force-generating cytoskeletal machinery might mediate mechanosensing. We discuss general principles governing mechanical regulation of lymphocyte function, spanning from the molecular scale of receptor activation to cellular responses to mechanical stimuli.

Genomic and immunocyte characterisation of bloodstream infection caused by Klebsiella pneumoniae.

OBJECTIVES: The aim of this study was to evaluate the characteristics of immunocyte associated with bloodstream infection (BSI) caused by Klebsiella pneumoniae (Kpn). METHODS: Patients with BSI-Kpn were included from 2015 to 2022 in our hospital. Immunocyte subpopulations of enrolled BSI-Kpn patients were tested on the same day of blood culture using multicolor flow cytometry analysis. Antibiotic susceptibility test was determined by agar dilution or broth dilution method. All included isolates were subjected to whole genome sequencing and comparative genomics analysis. Clinical and genetic data were integrated to investigate the risk factors associated with clinical outcome. RESULTS: There were 173 patients with non-duplicate BSI-Kpn, including 81 carbapenem-resistant Kpn (CRKP), 30 extended-spectrum ß-lactamases producing Kpn (ESBL-Kpn), 62 none CRKP or ESBL-Kpn (S-Kpn). Among 68 ST11-CRKP isolates, ST11-O2v1:KL64 was the most common serotypes cluster (77.9%, 53/68), followed by ST11-OL101: KL47 (13.2%, 9/68). Compared with CSKP group, subpopulations of immunocyte in patients with CRKP were significantly lower (P < 0.01). In patients with ST11-O2v1:KL64 BSI-Kpn, the level of cytotoxic T lymphocytes (CD3 + CD8 +) is the highest, while the B lymphocytes (CD3-CD19 +) was the least. In addition, the level of immunocyte in patients with Kpn co-harbored clpV-ybtQ-qacE were lower than that in patients with Kpn harbored one of clpV, ybtQ or qacE and without these three genes. Furthermore, co-existence of clpV-ybtQ-qacE was independently associated with a higher risk for 30-day mortality. CONCLUSIONS: The results demonstrate that patients with BSI-CRKP, especially for ST11-O2v1:KL64, exhibit lower leukomonocyte counts. In addition, BSI-Kpn co-harbored clpV-ybtQ-qacE is correlated to higher 30-day mortality.

Human umbilical cord-derived mesenchymal stem cell transplantation improves the long COVID.

No effective treatments can ameliorate symptoms of long COVID patients. Our study assessed the safety and efficacy of human umbilical cord-derived mesenchymal stem cells (UC-MSCs) in the treatment of long COVID patients. Ten long COVID patients were enrolled and received intravenous infusions of UC-MSCs on Days 0, 7, and 14. Adverse events and clinical symptoms were recorded, and chest-high-resolution CT (HRCT) images and laboratory parameters were analyzed. During UC-MSCs treatment and follow-up, we did not observe serious adverse events, the symptoms of long COVID patients were significantly relieved in a short time, especially sleep difficulty, depression or anxiety, memory issues, and so forth, and the lung lesions were also repaired. The routine laboratory parameters did not exhibit any significant abnormalities following UC-MSCs transplantation (UMSCT). The proportion of regulatory T cells gradually increased, but it was not statistically significant until 12 months. The proportion of naive B cells was elevated, while memory B cells, class-switched B-cells, and nonswitched B-cells decreased at 1 month after infusion. Additionally, we observed a transient elevation in circulating interleukin (IL)-6 after UMSCT, while tumor necrosis factor (TNF)-α, IL-17A, and IL-10 showed no significant changes. The levels of circulating immunoglobulin (Ig) M increased significantly at month 2, while IgA increased significantly at month 6. Furthermore, the SARS-CoV-2 IgG levels remained consistently high in all patients at Month 6, and there was no significant decrease during the subsequent 12-month follow-up. UMSCT was safe and tolerable in long COVID patients. It showed potential in alleviating long COVID symptoms and improving interstitial lung lesions.

Making a Monkey out of Human Immunodeficiency Virus/Simian Immunodeficiency Virus Pathogenesis: Immune Cell Depletion Experiments as a Tool to Understand the Immune Correlates of Protection and Pathogenicity in HIV Infection.

Understanding the underlying mechanisms of HIV pathogenesis is critical for designing successful HIV vaccines and cure strategies. However, achieving this goal is complicated by the virus's direct interactions with immune cells, the induction of persistent reservoirs in the immune system cells, and multiple strategies developed by the virus for immune evasion. Meanwhile, HIV and SIV infections induce a pandysfunction of the immune cell populations, making it difficult to untangle the various concurrent mechanisms of HIV pathogenesis. Over the years, one of the most successful approaches for dissecting the immune correlates of protection in HIV/SIV infection has been the in vivo depletion of various immune cell populations and assessment of the impact of these depletions on the outcome of infection in non-human primate models. Here, we present a detailed analysis of the strategies and results of manipulating SIV pathogenesis through in vivo depletions of key immune cells populations. Although each of these methods has its limitations, they have all contributed to our understanding of key pathogenic pathways in HIV/SIV infection.

Neuroinflammation in Alzheimer's disease: insights from peripheral immune cells.

Alzheimer's disease (AD) is a serious brain disorder characterized by the presence of beta-amyloid plaques, tau pathology, inflammation, neurodegeneration, and cerebrovascular dysfunction. The presence of chronic neuroinflammation, breaches in the blood-brain barrier (BBB), and increased levels of inflammatory mediators are central to the pathogenesis of AD. These factors promote the penetration of immune cells into the brain, potentially exacerbating clinical symptoms and neuronal death in AD patients. While microglia, the resident immune cells of the central nervous system (CNS), play a crucial role in AD, recent evidence suggests the infiltration of cerebral vessels and parenchyma by peripheral immune cells, including neutrophils, T lymphocytes, B lymphocytes, NK cells, and monocytes in AD. These cells participate in the regulation of immunity and inflammation, which is expected to play a huge role in future immunotherapy. Given the crucial role of peripheral immune cells in AD, this article seeks to offer a comprehensive overview of their contributions to neuroinflammation in the disease. Understanding the role of these cells in the neuroinflammatory response is vital for developing new diagnostic markers and therapeutic targets to enhance the diagnosis and treatment of AD patients.

Identification of prognostic risk model based on plasma cell markers in hepatocellular carcinoma through single-cell sequencing analysis.

Hepatocellular carcinoma (HCC) represents a substantial global health burden. Tumorinfiltrating B lymphocytes (TIL-Bs) contribute to tumor progression and significantly impact the efficacy of tumor therapy. However, the characteristics of TIL-Bs in HCC and their effect on HCC therapy remain elusive. Single-cell RNA sequencing (scRNAseq) was applied to investigate the heterogeneity, cellular differentiation and cell-cell communication of TIL-Bs in HCC. Further, the Cancer Genome Atlas-liver hepatocellular carcinoma (TCGA-LIHC) and liver cancer institutes (LCI) cohorts were applied to construct and validate the plasma cell marker-based prognostic risk model. The relationship between the prognostic risk model and the responsiveness of immunotherapy and chemotherapy in patients with HCC were estimated by OncoPredict and tumor immune dysfunction and exclusion (TIDE) algorithm. Finally, we established nomogram and calibration curves to evaluate the precision of the risk score in predicating survival probability. Our data identified five subtypes of TIL-Bs in HCC, each exhibiting varying levels of infiltration in tumor tissues. The interactions between TIL-Bs and other cell types contributed to shaping distinct tumor microenvironments (TME). Moreover, we found that TIL-Bs subtypes had disparate prognostic values in HCC patients. The prognostic risk model demonstrated exceptional predictive accuracy for overall survival and exhibited varying sensitivities to immunotherapy and chemotherapy among patients with HCC. Our data demonstrated that the risk score stood as an independent prognostic predictor and the nomogram results further affirmed its strong prognostic capability. This study reveals the heterogeneity of TIL-Bs and provides a prognostic risk model based on plasma cell markers in HCC, which could prove valuable in predicting prognosis and guiding the choice of suitable therapies for patients with HCC.

Defects in B-lymphopoiesis and B-cell maturation underlie prolonged B-cell depletion in ANCA-associated vasculitis.

OBJECTIVES: B-cell depletion time after rituximab (RTX) treatment is prolonged in antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) compared with other autoimmune diseases. We investigated central and peripheral B-cell development to identify the causes for the defect in B-cell reconstitution after RTX therapy. METHODS: We recruited 91 patients with AAV and performed deep phenotyping of the peripheral and bone marrow B-cell compartment by spectral flow and mass cytometry. B-cell development was studied by in vitro modelling and the role of BAFF receptor by quantitative PCR, western blot analysis and in vitro assays. RESULTS: Treatment-naïve patients with AAV showed low transitional B-cell numbers, suggesting impaired B-lymphopoiesis. We analysed bone marrow of treatment-naïve and RTX-treated patients with AAV and found reduced B-lymphoid precursors. In vitro modelling of B-lymphopoiesis from AAV haematopoietic stem cells showed intact, but slower and reduced immature B-cell development. In a subgroup of patients, after RTX treatment, the presence of transitional B cells did not translate in replenishment of naïve B cells, suggesting an impairment in peripheral B-cell maturation. We found low BAFF-receptor expression on B cells of RTX-treated patients with AAV, resulting in reduced survival in response to BAFF in vitro. CONCLUSIONS: Prolonged depletion of B cells in patients with AAV after RTX therapy indicates a B-cell defect that is unmasked by RTX treatment. Our data indicate that impaired bone marrow B-lymphopoiesis results in a delayed recovery of peripheral B cells that may be further aggravated by a survival defect of B cells. Our findings contribute to the understanding of AAV pathogenesis and may have clinical implications regarding RTX retreatment schedules and immunomonitoring after RTX therapy.

Inhibition of GRK2 ameliorates the pristane-induced mouse SLE model by suppressing plasma cells differentiation.

Systemic lupus erythematosus (SLE) is a multifaceted autoimmune disorder characterized by diverse clinical manifestations and organ damage. Despite its elusive etiology, dysregulated subsets and functions of B cells are pivotal in SLE pathogenesis. Peoniflorin-6'-O-benzene sulfonate (CP-25), an esterification modification of Paeoniflorin, exhibits potent anti-inflammatory and immunomodulatory properties in autoimmune diseases (AID). However, the involvement of CP-25 and its target, GRK2, in SLE development has not been explored. In this study, we demonstrate that both genetic deficiency and pharmacological inhibition of GRK2 attenuate autoantibodies production, reduce systemic inflammation, and mitigate histopathological alterations in the spleen and kidney in the pristane-induced mouse SLE model. Importantly, our findings highlight that both genetic deficiency and pharmacological inhibition of GRK2 suppress plasma cells generation and restore dysregulated B-cell subsets by modulating two crucial transcription factors, Blimp1 and IRF4. Collectively, targeting GRK2 with CP-25 emerges as a promising therapeutic approach for SLE.

Rab GTPases, Active Members in Antigen-Presenting Cells, and T Lymphocytes.

Processes such as cell migration, phagocytosis, endocytosis, and exocytosis refer to the intense exchange of information between the internal and external environment in the cells, known as vesicular trafficking. In eukaryotic cells, these essential cellular crosstalks are controlled by Rab GTPases proteins through diverse adaptor proteins like SNAREs complex, coat proteins, phospholipids, kinases, phosphatases, molecular motors, actin, or tubulin cytoskeleton, among others, all necessary for appropriate mobilization of vesicles and distribution of molecules. Considering these molecular events, Rab GTPases are critical components in specific biological processes of immune cells, and many reports refer primarily to macrophages; therefore, in this review, we address specific functions in immune cells, concretely in the mechanism by which the GTPase contributes in dendritic cells (DCs) and, T/B lymphocytes.

Stromal B Lymphocytes Affecting Prognosis in Triple-Negative Breast Cancer by Opal/TSA Multiplexed Immunofluorescence.

Objective: Immune cells play a key role in tumor microenvironment. The purpose of this study was to investigate the infiltration and clinical indication of immune cells including their combined prognostic value in microenvironment of triple negative breast cancer. Methods: We investigated 100 patients with triple negative breast cancer by Opal/Tyramide Signal Amplification multispectral immunofluorescence between 2003 and 2017 at Zhejiang Provincial people's Hospital. Intratumoral and stromal immune cells of triple negative breast cancer were classified and quantitatively analyzed. Survival outcomes were compared using the Kaplan-Meier method and further analyzed with multivariate analysis. Results: Infiltration level of stromal B lymphocytes, stromal and intratumoral CD8+ T cells, stromal CD4+ T cells, stromal PD-L1 and intratumoral tumor associated macrophages 2 cells were shown as independent factors affecting disease-free survival and overall survival in univariate analysis. Stromal B lymphocytes, T stage, N stage and pathological type were independent predictive factors for both DFS and OS in multivariate analysis. We firstly found that patients with B lymphocytes-enriched subtypes have a better prognosis than those with T lymphocytes-enriched subtypes and tumor-associated macrophage-enriched subtypes. Conclusion: The present study identified a bunch of immune targets and subtypes, which could be exploited in future combined immunotherapy/chemotherapy strategies for triple negative breast cancer patients.

B-cell depletion in autoimmune diseases.

B cells have a pivotal function in the pathogenesis of autoimmune diseases, such as rheumatoid arthritis, multiple sclerosis and systemic lupus erythematosus. In autoimmune disease, B cells orchestrate antigen presentation, cytokine production and autoantibody production, the latter via their differentiation into antibody-secreting plasmablasts and plasma cells. This article addresses the current therapeutic strategies to deplete B cells in order to ameliorate or potentially even cure autoimmune disease. It addresses the main target antigens in the B-cell lineage that are used for therapeutic approaches. Furthermore, it summarises the current evidence for successful treatment of autoimmune disease with monoclonal antibodies targeting B cells and the limitations and challenges of these approaches. Finally, the concept of deep B-cell depletion and immunological reset by chimeric antigen receptor T cells is discussed, as well as the lessons from this approach for better understanding the role of B cells in autoimmune disease.

Potential role of IGF-1R in the interaction between orbital fibroblasts and B lymphocytes: an implication for B lymphocyte depletion in the active inflammatory phase of thyroid-associated ophthalmopathy.

BACKGROUND: Thyroid eye disease (TED) is an inflammatory process involving lymphocyte-mediated immune response and orbital tissue damage. The anti-insulin-like growth factor-1 receptor (IGF-1R) antibodies produced by B lymphocytes are involved in the activation of orbital fibroblasts and the inflammatory process of orbital tissue damage in TED. The purpose of this study was to explore the role of IGF-1R in the mechanistic connection between orbital fibroblasts and B lymphocytes in TED. METHODS: Orbital fibroblasts sampled from orbital connective tissues and peripheral B lymphocytes isolated from peripheral blood, which were obtained from 15 patients with TED and 15 control patients, were co-cultured at a ratio of 1:20. The level of IGF-1R expression in orbital fibroblasts was evaluated by flow cytometry and confocal microscopy. Transient B lymphocyte depletion was induced with anti-CD20 monoclonal antibody rituximab, while the IGF-1R pathway was blocked by the IGF-1R binding protein. The expression levels of interleukin-6 (IL-6) and regulated upon activation, normal T cell expressed and secreted (RANTES) in the co-culture model were quantified via ELISA. RESULTS: IGF-1R expression was significantly elevated in TED orbital fibroblasts compared to that of controls. A 24-h co-culture of orbital fibroblasts with peripheral B lymphocytes induced elevated expression levels of IL-6 and RANTES in each group (TED patients and controls), with the highest levels occurring in TED patients (T + T group). Rituximab and IGF-1R binding protein significantly inhibited increased levels of IL-6 and RANTES in the co-culture model of TED patients. CONCLUSIONS: IGF-1R may mediate interaction between orbital fibroblasts and peripheral B lymphocytes; thus, blocking IGF-1R may reduce the local inflammatory response in TED. Rituximab-mediated B lymphocyte depletion played a role in inhibiting inflammatory responses in this in vitro co-culture model, providing a theoretical basis for the clinical application of anti-CD20 monoclonal antibodies in TED.

Safety of Obinutuzumab in Children With Autoimmune Encephalitis and Early B-Cell Repopulation on Rituximab.

BACKGROUND: Rituximab (RTX) resistance or early B-cells repopulation were observed in children but only few publications reported the use of Obinutuzumab and no recommendations were made concerning the dosage for children. METHODS: This study was a single-center retrospective cohort study of all the children followed-up in the Pediatric Neurology Department of Necker-Enfants malades Hospital in Paris, France, and treated with obinutuzumab, between November 1, 2019, and November 1, 2021. RESULTS: A total of eight children (three females, median age 4.5 years) were treated. Seven patients presented with autoimmune encephalitis and one with myeloradiculitis. The median delay of B-cell repopulation after a course of RTX was 87 days (range 41 to 160). A switch to obinutuzumab (anti-CD20) was performed for eight children. The median duration between the first RTX infusion and obinutuzumab administration was 6.6 months. The dosage regimen for obinutuzumab was one infusion of 1000 mg/1.73 m2, that is to say 580 mg/m2 (maximum 1000 mg/infusion), by extrapolation from the adult dosage. The median delay of B-cell repopulation after one course of obinutuzumab was 230 days (range 66 to 303 days) vs 87 days after one course of RTX (P < 0.01). None of the patients presented side effects with obinutuzumab treatment. All patients had a favorable evolution at the last-follow up. Median follow-up was 1.6 years. CONCLUSIONS: This study reports the use of obinutuzumab in neurological inflammatory diseases in a pediatric population. Obinutuzumab seems to have a better biological efficacy than RTX with a longer time of B-cell repopulation.

Integration of multi-omics analysis reveals metabolic alterations of B lymphocytes in systemic lupus erythematosus.

OBJECTIVE: To link changes in the B-cell transcriptome from systemic lupus erythematosus (SLE) patients with those in their macroenvironment, including cellular and fluidic components. METHODS: Analysis was performed on 363 patients and 508 controls, encompassing transcriptomics, metabolomics, and clinical data. B-cell and whole-blood transcriptomes were analysed using DESeq and GSEA. Plasma and urine metabolomics peak changes were quantified and annotated using Ceu Mass Mediator database. Common sources of variation were identified using MOFA integration analysis. RESULTS: Cellular macroenvironment was enriched in cytokines, stress responses, lipidic synthesis/mobility pathways and nucleotide degradation. B cells shared these pathways, except nucleotide degradation diverted to nucleotide salvage pathway, and distinct glycosylation, LPA receptors and Schlafen proteins. CONCLUSIONS: B cells showed metabolic changes shared with their macroenvironment and unique changes directly or indirectly induced by IFN-α signalling. This study underscores the importance of understanding the interplay between B cells and their macroenvironment in SLE pathology.

Reference values of lymphocyte subsets from healthy Polish adults.

The flow cytometry method could support physicians' decisions in the diagnosis and treatment monitoring of immunodeficient patients. Most clinical recommendations are focused on the search for alterations in T- and B-lymphocyte subsets, less commonly natural killer (NK) cells and granulocytes. While reference values for clinically meaningful lymphocyte subsets have been published ubiquitously among numerous countries, we have not found significant data for a population of adult Polish habitats; thus we determined reference values for T, B, and NK subsets according to sex and age. The female group showed a higher percentage of lymphocytes (CD45++), T helper lymphocytes with a higher absolute count, as well as CD4/CD8 ratio, marginal zone-like B cells, class-switched B cells, and CD21low B cells than the male group. The male group was found to have elevated percentages of naïve B lymphocytes, transitional B cells, and plasmablasts. A weak positive correlation with age was found among double positive T lymphocytes, natural killer T cells (NKT) lymphocytes, and CD21low B cells. A negative correlation with age for double negative T lymphocytes, marginal zone-like B cells, and plasmablasts was noted. The results indicated the importance of creating distinct reference ranges regarding sex and age concerning immunophenotype.

Severe enterovirus infections in patients with immune-mediated inflammatory diseases receiving anti-CD20 monoclonal antibodies.

OBJECTIVE: Patients with X linked agammaglobulinemia are susceptible to enterovirus (EV) infections. Similarly, severe EV infections have been described in patients with impaired B-cell response following treatment with anti-CD20 monoclonal antibodies (mAbs), mostly in those treated for haematological malignancies. We aimed to describe severe EV infections in patients receiving anti-CD20 mAbs for immune-mediated inflammatory diseases (IMIDs). METHODS: Patients were included following a screening of data collected through the routine surveillance of EV infections coordinated by the National Reference Center and a review of the literature. Additionally, neutralising antibodies were assessed in a patient with chronic EV-A71 meningoencephalitis. RESULTS: Nine original and 17 previously published cases were retrieved. Meningoencephalitis (n=21/26, 81%) associated with EV-positive cerebrospinal fluid (n=20/22, 91%) was the most common manifestation. The mortality rate was high (27%). EV was the only causal agents in all reported cases. Patients received multiple anti-CD20 mAbs infusions (median 8 (5-10)), resulting in complete B-cell depletion and moderate hypogammaglobulinemia (median 4.9 g/L (4.3-6.7)), and had limited concomitant immunosuppressive treatments. Finally, in a patient with EV-A71 meningoencephalitis, a lack of B-cell response to EV was shown. CONCLUSION: EV infection should be evoked in patients with IMIDs presenting with atypical organ involvement, especially meningoencephalitis. Anti-CD20 mAbs may lead to impaired B-cell response against EV, although an underlying primary immunodeficiency should systematically be discussed.

[IgA antibodies against HIV-1]. / Les anticorps IgA contre le VIH-1.

Antibodies, and notably immunoglobulins A (IgA), are paramount in mucosal tissues as protective immune effectors against invading pathogens and immunomodulators of the microbiota. Upon human immunodeficiency virus type 1 (HIV-1) infection, systemic and mucosal IgA antibody responses are triggered. While naturally produced serum HIV-1 envelope protein-specific IgA are quantitatively and qualitatively weaker than their IgG counterparts, they also possess antiviral properties including neutralization and Fc-dependent functions. IgA neutralizers can block HIV-1 mucosal transmission in animal models, indicating that their elicitation by vaccination would be an important component for preventing infection. Moreover, the first genuine IgA broadly HIV-1 neutralizing antibodies (bNAbs) were recently identified in certain individuals living with HIV-1. Vaccine-based induction of IgA bNAbs potentially protective at the mucosal level is therefore conceivable. Hence, research efforts must therefore be undertaken to better understand their development and functions. In this review, we present the general functions of IgA in homeostasis and antimicrobial immunity and discuss their involvement in the antibody responses against HIV-1.

Unravelling humoral immunity in SARS-CoV-2: Insights from infection and vaccination.

Following infection and vaccination against SARS-CoV-2, humoral components of the adaptive immune system play a key role in protecting the host. Specifically, B cells generate high-affinity antibodies against various antigens of the virus. In this review, we discuss the mechanisms of immunity initiation through both natural infection and vaccination, shedding light on the activation of B cell subsets in response to SARS-CoV-2 infection and vaccination. The innate immune system serves as the initial line of primary and nonspecific defence against viruses. However, within several days following infection or a vaccine dose, a virus-specific immune response is initiated, primarily by B cells that produce antibodies. These antibodies contribute to the resolution of the disease. Subsequently, these B cells transition into memory B cells, which play a crucial role in providing long-term immunity against the virus. CD4+ T helper cells initiate a cascade, leading to B cell somatic hypermutation, germinal center memory B cells, and the production of neutralizing antibodies. B-cell dysfunction can worsen disease severity and reduce vaccine efficacy. Notably, individuals with B cell immunodeficiency show lower IL-6 production. Furthermore, this review delves into several aspects of immune responses, such as hybrid immunity, which has shown promise in boosting broad-spectrum protection. Cross-reactive immunity is under scrutiny as well, as pre-existing antibodies can offer protection against the disease. We also decipher breakthrough infection mechanisms, especially with the novel variants of the virus. Finally, we discuss some potential therapeutic solutions regarding B cells including convalescent plasma therapy, B-1 cells, B regulatory cell (Breg) modulation, and the use of neutralizing monoclonal antibodies in combating the infection. Ongoing research is crucial to grasp population immunity trends and assess the potential need for booster doses in maintaining effective immune responses against potential viral threats.