The relationship between CD27 negative and positive B cell populations in human peripheral blood

Double Negative B Cell Is Associated With Renal Impairment in Systemic Lupus Erythematosus and Acts as a Marker for Nephritis Remission

Objective: Recent studies on double negative B cells (DN B cells) suggested that they have potential pathogenic roles in systemic lupus erythematosus (SLE). This study aimed to determine the circulating DN B cells in SLE patients and analyzed the clinical significance of this cell subset. Methods: Fifty-seven SLE patients and fifty healthy controls (HCs) were recruited in this study. Among the 57 SLE patients, 25 had lupus nephritis (LN). All patients were followed up for 24 weeks. Peripheral B cell subsets were analyzed by flow cytometry. Results: DN B cells were significantly elevated in the SLE patients, especially in the patients with LN (p < 0.01). DN B showed a positive correlation with 24-h urine protein excretion (24 h-UPE) levels (r = 0.444, p = 0.034) in LN patients, and inversely correlated with evaluated glomerular filtration rate (eGFR) (r = -0.351, p = 0.011). DN B cells had a positive correlation with plasma cells (r = 0.484, p < 0.001) and memory B cells (r = 0.703, p < 0.001). After treatment, decreased DN B cells were associated with LN alleviation (p = 0.002). In the follow-up, the remission rate of LN patients with decreased DN B cells was significantly higher than LN patients with increased DN B cells (83.33 vs. 25.00%, p = 0.030) at week 24. Conclusions: This study suggests that the peripheral DN B cells are positively correlated with the severity of renal damage in LN patients and may potentially be used as a prognostic marker in LN.

sumrep: A Summary Statistic Framework for Immune Receptor Repertoire Comparison and Model Validation

The adaptive immune system generates an incredible diversity of antigen receptors for B and T cells to keep dangerous pathogens at bay. The DNA sequences coding for these receptors arise by a complex recombination process followed by a series of productivity-based filters, as well as affinity maturation for B cells, giving considerable diversity to the circulating pool of receptor sequences. Although these datasets hold considerable promise for medical and public health applications, the complex structure of the resulting adaptive immune receptor repertoire sequencing (AIRR-seq) datasets makes analysis difficult. In this paper we introduce sumrep, an R package that efficiently performs a wide variety of repertoire summaries and comparisons, and show how sumrep can be used to perform model validation. We find that summaries vary in their ability to differentiate between datasets, although many are able to distinguish between covariates such as donor, timepoint, and cell type for BCR and TCR repertoires. We show that deletion and insertion lengths resulting from V(D)J recombination tend to be more discriminative characterizations of a repertoire than summaries that describe the amino acid composition of the CDR3 region. We also find that state-of-the-art generative models excel at recapitulating gene usage and recombination statistics in a given experimental repertoire, but struggle to capture many physiochemical properties of real repertoires.

Guidelines for the use of flow cytometry and cell sorting in immunological studies (second edition)

These guidelines are a consensus work of a considerable number of members of the immunology and flow cytometry community. They provide the theory and key practical aspects of flow cytometry enabling immunologists to avoid the common errors that often undermine immunological data. Notably, there are comprehensive sections of all major immune cell types with helpful Tables detailing phenotypes in murine and human cells. The latest flow cytometry techniques and applications are also described, featuring examples of the data that can be generated and, importantly, how the data can be analysed. Furthermore, there are sections detailing tips, tricks and pitfalls to avoid, all written and peer-reviewed by leading experts in the field, making this an essential research companion.

Phenotypic and Ig Repertoire Analyses Indicate a Common Origin of IgD-CD27- Double Negative B Cells in Healthy Individuals and Multiple Sclerosis Patients

IgD^-CD27^- double negative (DN) B cells with proinflammatory characteristics are abnormally elevated in a proportion of multiple sclerosis (MS) patients. In this study, the origin and selection characteristics of DN B cells were studied in MS patients and healthy controls (HC). Expression of developmental markers on peripheral blood DN, IgD^-CD27⁺ class-switched memory (CSM) and IgD⁺CD27^- naive B cells of HC (n = 48) and MS patients (n = 96) was determined by flow cytometry. High-throughput adaptive immune receptor repertoire sequencing was performed on peripheral blood DN and CSM B cells of HC and MS patients (n = 3 each). DN B cells from HC and MS patients showed similar phenotypic and Ig repertoire characteristics. Phenotypic analysis indicated a mature state of DN B cells by low CD5, CD10, and CD38 expression. However, the frequency of CD95⁺ and IgA⁺ cells was lower in DN versus CSM B cells. DN B cells are Ag experienced, as shown by somatic hypermutation of their Ig genes in adaptive immune receptor repertoire sequencing, although they showed a lower mutation load than CSM B cells. Shared clones were found between DN and CSM B cells, although >95% of the clones were unique to each population, and differences in V(D)J usage and CDR3 physicochemical properties were found. Thus, DN B cells arise in HC and MS patients via a common developmental pathway that is probably linked to immune aging. However, DN and CSM B cells develop through unique differentiation pathways, with most DN B cells representing an earlier maturation state.

Activation Dynamics and Immunoglobulin Evolution of Pre-existing and Newly Generated Human Memory B cell Responses to Influenza Hemagglutinin

Vaccine-induced memory B cell responses to evolving viruses like influenza A involve activation of pre-existing immunity and generation of new responses. To define the contribution of these two types of responses, we analyzed the response to H7N9 vaccination in H7N9-naive adults. We performed comprehensive comparisons at the single-cell level of the kinetics, Ig repertoire, and activation phenotype of established pre-existing memory B cells recognizing conserved epitopes and the newly generated memory B cells directed toward H7 strain-specific epitopes. The recall response to conserved epitopes on H7 HA involved a transient expansion of memory B cells with little observed adaptation. However, the B cell response to newly encountered epitopes was phenotypically distinct and generated a sustained memory population that evolved and affinity matured months after vaccination. These findings establish clear differences between newly generated and pre-existing memory B cells, highlighting the challenges in achieving long-lasting, broad protection against an ever-evolving virus.

Phenotypic and functional alterations of regulatory B cell subsets in adult allergic asthma patients

BACKGROUND

IL-10-producing regulatory B cells (Bregs) are widely ascribed immune regulatory functions. However, Breg subsets in human asthma have not been fully investigated.

OBJECTIVE

We studied Breg subsets in adult allergic asthma patients by assessing two major parameters, frequency and IL-10 expression. We then investigated factors that affect these two parameters in patients.

METHODS

Peripheral blood mononuclear cells (PBMCs) of adult allergic asthma patients (N = 26) and non-asthmatic controls (N = 28) were used to assess the frequency of five subsets of transitional B cells (TBs), three subsets of CD24^high CD27⁺ B cells and B1 cells. In addition to clinical data, IL-10 expression by individual Breg subsets was assessed by flow cytometry.

RESULTS

Asthma patients had decreases of CD5⁺ and CD1d⁺ CD5⁺ , but an increase of CD27⁺ TBs which was significant in patients with moderate asthma (60 < FEV1 < 80). Regardless of asthma severity, there was no significant alteration in the frequencies of 6 other Breg subsets tested. However, we found that oral corticosteroid (OCS) significantly affected the frequency of Bregs in Breg subset-specific manners. OCS decreased CD5⁺ and CD1d⁺ CD5⁺ TBs, but increased CD27⁺ TBs and CD10⁺ CD24^high CD27⁺ cells. Furthermore, OCS decreased IL-10 expression by CD27⁺ TBs, all 3 CD24^high CD27⁺ B cell subsets (CD5⁺ , CD10⁺ and CD1d⁺ ) and B1 cells. OCS-mediated inhibition of IL-10 expression was not observed in the other Breg subsets tested.

CONCLUSION & CLINICAL RELEVANCE

Alterations in the frequency of Bregs and their ability to express IL-10 are Breg subset-specific. OCS treatment significantly affects the frequency as well as their ability to express IL-10 in Breg subset-specific manners.

Mass cytometry reveals systemic and local immune signatures that distinguish inflammatory bowel diseases

Inflammatory bowel disease (IBD) includes Crohn's disease and ulcerative colitis. Each disease is characterized by a diverse set of potential manifestations, which determine patients' disease phenotype. Current understanding of phenotype determinants is limited, despite increasing prevalence and healthcare costs. Diagnosis and monitoring of disease requires invasive procedures, such as endoscopy and tissue biopsy. Here we report signatures of heterogeneity between disease diagnoses and phenotypes. Using mass cytometry, we analyze leukocyte subsets, characterize their function(s), and examine gut-homing molecule expression in blood and intestinal tissue from healthy and/or IBD subjects. Some signatures persist in IBD despite remission, and many signatures are highly represented by leukocytes that express gut trafficking molecules. Moreover, distinct systemic and local immune signatures suggest patterns of cell localization in disease. Our findings highlight the importance of gut tropic leukocytes in circulation and reveal that blood-based immune signatures differentiate clinically relevant subsets of IBD.

Production of IgG2 Antibodies to Pneumococcal Polysaccharides After Vaccination of Treated HIV Patients May Be Augmented by IL-7Rα Signaling in ICOS+ Circulating T Follicular-Helper Cells

Greater understanding of factors influencing the maturation of antibody responses against pneumococcal polysaccharides (PcPs) may improve pneumococcal vaccination strategies. Although PcPs are type 2 T cell-independent antigens thought not to induce follicular immune responses, we have previously shown that IgG2 antibody responses against antigens in the 23-valent unconjugated PcP vaccine (PPV23) are associated with expansion of ICOS⁺ circulating T follicular helper (cT_FH) cells in HIV seronegative subjects but not HIV patients. As IL-7Rα signaling in CD4⁺ T cells may affect T_FH cell function and is adversely affected by HIV-1 infection, we have examined the relationship of IL-7Rα expression on ICOS⁺ cT_FH cells with PcP-specific IgG2 antibody responses. PPV23 vaccination was undertaken in HIV patients receiving antiretroviral therapy (n = 25) and HIV seronegative subjects (n = 20). IL-7Rα expression on ICOS⁺ and ICOS⁻ cT_FH cells was assessed at day(D) 0, 7, and 28. Fold increase between D0 and D28 in serum IgG1 and IgG2 antibodies to PcP serotypes 4, 6B, 9V, and 14 and the frequency of IgG1⁺ and IgG2⁺ antibody secreting cells (ASCs) at D7 were also assessed. Decline in IL-7Rα expression on ICOS⁺ cT_FH cells between D0 and D7 occurred in 75% of HIV seronegative subjects and 60% of HIV patients (Group A), with changes in IL-7Rα expression being more pronounced in HIV patients. Group A patients exhibited abnormally high IL-7Rα expression pre-vaccination, an association of serum IgG2, but not IgG1, antibody responses with a decline of IL-7Rα expression on ICOS⁺ cT_FH cells between D0 and D7, and an association of higher IgG2⁺ ASCs with lower IL-7Rα expression on ICOS⁺ cT_FH cells at D7. As decline of IL-7Rα expression on CD4⁺ T cells is an indicator of IL-7Rα signaling, our findings suggest that utilization of IL-7 by cT_FH cells affects production of IgG2 antibodies to PPV23 antigens in some HIV patients.

B cell profiling in malaria reveals expansion and remodelling of CD11c+ B cell subsets

Humoral immunity is important in limiting clinical disease in malaria, yet the longitudinal B cell response to infection remains unclear. We performed a 1-year prospective study in patients treated for acute P. falciparum malaria for the first time, or with previous exposure to the disease. Using an unbiased exploratory approach with mass cytometry, followed by targeted flow cytometry, we found that ~80% of mature B cells that proliferated in response to acute infection expressed CD11c. Only ~40% of CD11c+ B cells displayed an atypical B cell phenotype, with the remaining cells primarily made up of activated- and resting memory B cells. The CD11c+ B cells expanded rapidly following infection, with previous exposure to malaria resulting in a significantly larger increase compared to individuals with primary infection. This was attributed to an expansion of switched CD11c+ B cells that was absent in primary infected individuals. The rate of contraction of the CD11c+ B cell compartment was independent of previous exposure to malaria and displayed a slow decay with a half-life of ~300 days. Collectively, these results identify CD11c as a marker of B cells responding to malaria and further highlight differences in primary- and secondary B cell responses during infection.

Are B cells altered in the decidua of women with preterm or term labor?

PROBLEM

The immunophenotype of B cells at the maternal-fetal interface (decidua) in labor at term and preterm labor is poorly understood.

METHOD OF STUDY

Decidual tissues were obtained from women with preterm or term labor and from non-labor gestational age-matched controls. Immunophenotyping of decidual B cells was performed using multicolor flow cytometry.

RESULTS

(a) In the absence of acute or chronic chorioamnionitis, total B cells were more abundant in the decidua parietalis of women who delivered preterm than in those who delivered at term, regardless of the presence of labor; (b) decidual transitional and naïve B cells were the most abundant B-cell subsets; (c) decidual B1 B cells were increased in women with either labor at term or preterm labor and chronic chorioamnionitis compared to those without this placental lesion; (d) decidual transitional B cells were reduced in women with preterm labor compared to those without labor; (e) naïve, class-switched, and non-class-switched B cells in the decidual tissues underwent mild alterations with the process of preterm labor; (f) decidual plasmablasts seemed to increase in women with either labor at term or preterm labor with chronic chorioamnionitis; and (g) decidual B cells expressed high levels of interleukin (IL)-12, IL-6, and/or IL-35.

CONCLUSION

Total B cells are not increased with the presence of preterm or term labor; yet, specific subsets (B1 and plasmablasts) undergo alterations in women with chronic chorioamnionitis. Therefore, B cells are solely implicated in the pathological process of preterm labor in a subset of women with chronic inflammation of the placenta. These findings provide insight into the immunology of the maternal-fetal interface in preterm and term labor.

Systematic comparison of respiratory syncytial virus-induced memory B cell responses in two anatomical compartments

Respiratory syncytial virus (RSV) is a leading cause of hospitalization in infants and young children. Although it is widely agreed that an RSV vaccine should induce both mucosal and systemic antibody responses, little is known about the B cell response to RSV in mucosa-associated lymphoid tissues. Here, we analyze this response by isolating 806 RSV F-specific antibodies from paired adenoid and peripheral blood samples from 4 young children. Overall, the adenoid-derived antibodies show higher binding affinities and neutralization potencies compared to antibodies isolated from peripheral blood. Approximately 25% of the neutralizing antibodies isolated from adenoids originate from a unique population of IgM⁺ and/or IgD⁺ memory B cells that contain a high load of somatic mutations but lack expression of classical memory B cell markers. Altogether, the results provide insight into the local B cell response to RSV and have implications for the development of vaccines that stimulate potent mucosal responses.

Reduced CD27-IgD- B Cells in Blood and Raised CD27-IgD- B Cells in Gut-Associated Lymphoid Tissue in Inflammatory Bowel Disease

The intestinal mucosa in inflammatory bowel disease (IBD) contains increased frequencies of lymphocytes and a disproportionate increase in plasma cells secreting immunoglobulin (Ig)G relative to other isotypes compared to healthy controls. Despite consistent evidence of B lineage cells in the mucosa in IBD, little is known of B cell recruitment to the gut in IBD. Here we analyzed B cells in blood of patients with Crohn's disease (CD) and ulcerative colitis (UC) with a range of disease activities. We analyzed the frequencies of known B cell subsets in blood and observed a consistent reduction in the proportion of CD27^-IgD^- B cells expressing all Ig isotypes in the blood in IBD (independent of severity of disease and treatment) compared to healthy controls. Successful treatment of patients with biologic therapies did not change the profile of B cell subsets in blood. By mass cytometry we demonstrated that CD27^-IgD^- B cells were proportionately enriched in the gut-associated lymphoid tissue (GALT) in IBD. Since production of TNFα is a feature of IBD relevant to therapies, we sought to determine whether B cells in GALT or the CD27^-IgD^- subset in particular could contribute to pathology by secretion of TNFα or IL-10. We found that donor matched GALT and blood B cells are capable of producing TNFα as well as IL-10, but we saw no evidence that CD27^-IgD^- B cells from blood expressed more TNFα compared to other subsets. The reduced proportion of CD27^-IgD^- B cells in blood and the increased proportion in the gut implies that CD27^-IgD^- B cells are recruited from the blood to the gut in IBD. CD27^-IgD^- B cells have been implicated in immune responses to intestinal bacteria and recruitment to GALT, and may contribute to the intestinal inflammatory milieu in IBD.

Insights From Analysis of Human Antigen-Specific Memory B Cell Repertoires

Memory B cells that are generated during an infection or following vaccination act as sentinels to guard against future infections. Upon repeat antigen exposure memory B cells differentiate into new antibody-secreting plasma cells to provide rapid and sustained protection. Some pathogens evade or suppress the humoral immune system, or induce memory B cells with a diminished ability to differentiate into new plasma cells. This leaves the host vulnerable to chronic or recurrent infections. Single cell approaches coupled with next generation antibody gene sequencing facilitate a detailed analysis of the pathogen-specific memory B cell repertoire. Monoclonal antibodies that are generated from antibody gene sequences allow a functional analysis of the repertoire. This review discusses what has been learned thus far from analysis of diverse pathogen-specific memory B cell compartments and describes major differences in their repertoires. Such information may illuminate ways to advance the goal of improving vaccine and therapeutic antibody design.

Older Human B Cells and Antibodies

B cells have a number of different roles in the immune response. Their excellent antigen presentation potential can contribute to the activation of other cells of the immune system, and evidence is emerging that specialized subsets of these cells, that may be increased with age, can influence the cell-mediated immune system in antitumor responses. They can also regulate immune responses, to avoid autoreactivity and excessive inflammation. Deficiencies in regulatory B cells may be beneficial in cancer but will only exacerbate the inflammatory environment that is a hallmark of aging. The B cell role as antibody producers is particularly important, since antibodies perform numerous different functions in different environments. Although studying tissue responses in humans is not as easy as in mice, we do know that certain classes of antibodies are more suited to protecting the mucosal tissues (IgA) or responding to T-independent bacterial polysaccharide antigens (IgG₂) so we can make some inference with respect to tissue-specific immunity from a study of peripheral blood. We can also make inferences about changes in B cell development with age by looking at the repertoire of different B cell populations to see how age affects the selection events that would normally occur to avoid autoreactivity, or increase specificity, to antigen.

ASAP - A Webserver for Immunoglobulin-Sequencing Analysis Pipeline

Reproducible and robust data on antibody repertoires are invaluable for basic and applied immunology. Next-generation sequencing (NGS) of antibody variable regions has emerged as a powerful tool in systems immunology, providing quantitative molecular information on antibody polyclonal composition. However, major computational challenges exist when analyzing antibody sequences, from error handling to hypermutation profiles and clonal expansion analyses. In this work, we developed the ASAP (A webserver for Immunoglobulin-Seq Analysis Pipeline) webserver (https://asap.tau.ac.il). The input to ASAP is a paired-end sequence dataset from one or more replicates, with or without unique molecular identifiers. These datasets can be derived from NGS of human or murine antibody variable regions. ASAP first filters and annotates the sequence reads using public or user-provided germline sequence information. The ASAP webserver next performs various calculations, including somatic hypermutation level, CDR3 lengths, V(D)J family assignments, and V(D)J combination distribution. These analyses are repeated for each replicate. ASAP provides additional information by analyzing the commonalities and differences between the repeats (“joint” analysis). For example, ASAP examines the shared variable regions and their frequency in each replicate to determine which sequences are less likely to be a result of a sample preparation derived and/or sequencing errors. Moreover, ASAP clusters the data to clones and reports the identity and prevalence of top ranking clones (clonal expansion analysis). ASAP further provides the distribution of synonymous and non-synonymous mutations within the V genes somatic hypermutations. Finally, ASAP provides means to process the data for proteomic analysis of serum/secreted antibodies by generating a variable region database for liquid chromatography high resolution tandem mass spectrometry (LC-MS/MS) interpretation. ASAP is user-friendly, free, and open to all users, with no login requirement. ASAP is applicable for researchers interested in basic questions related to B cell development and differentiation, as well as applied researchers who are interested in vaccine development and monoclonal antibody engineering. By virtue of its user-friendliness, ASAP opens the antibody analysis field to non-expert users who seek to boost their research with immune repertoire analysis.

Robust B Cell Responses Predict Rapid Resolution of Lyme Disease

Lyme disease (Borrelia burgdorferi infection) is increasingly recognized as a significant source of morbidity worldwide. Here, we show that blood plasmablasts and CD27⁻ memory B cells are elevated in untreated Lyme disease, with higher plasmablast levels associated with more rapid resolution of clinical symptoms. Stronger serum reactivity to surface proteins and peptides from B. burgdorferi was also associated with faster resolution of clinical symptoms. Through molecular identifier-enabled antibody heavy-chain sequencing of bulk B cells and single-cell paired-chain antibody sequencing of blood plasmablasts, we characterized immunoglobulin gene usage patterns specific to B. burgdorferi infection. Recombinantly expressed antibodies from expanded lineages bound B. burgdorferi antigens, confirming that these clones are driven by the infection. Furthermore, recombinant sequence-derived antibodies were functional, inhibiting growth of B. burgdorferi in vitro. Elevations and clonal expansion of blood plasmablasts were associated with rapid return to health, while poor plasmablast responses were associated with a longer duration of symptoms following treatment. Plasmablasts induced by B. burgdorferi infection showed preferential antibody gene segment usage, while bulk sequencing of total B cells revealed convergent CDR3 motifs specific to B. burgdorferi-infected patients. Our results show that robust plasmablast responses encoding Bb-static antibodies are associated with more rapid resolution of Lyme disease, and these antibodies could provide the basis for next-generation therapeutics for Lyme disease.

Immunoglobulin gene analysis as a tool for investigating human immune responses

The human immunoglobulin repertoire is a hugely diverse set of sequences that are formed by processes of gene rearrangement, heavy and light chain gene assortment, class switching and somatic hypermutation. Early B cell development produces diverse IgM and IgD B cell receptors on the B cell surface, resulting in a repertoire that can bind many foreign antigens but which has had self-reactive B cells removed. Later antigen-dependent development processes adjust the antigen affinity of the receptor by somatic hypermutation. The effector mechanism of the antibody is also adjusted, by switching the class of the antibody from IgM to one of seven other classes depending on the required function. There are many instances in human biology where positive and negative selection forces can act to shape the immunoglobulin repertoire and therefore repertoire analysis can provide useful information on infection control, vaccination efficacy, autoimmune diseases, and cancer. It can also be used to identify antigen-specific sequences that may be of use in therapeutics. The juxtaposition of lymphocyte development and numerical evaluation of immune repertoires has resulted in the growth of a new sub-speciality in immunology where immunologists and computer scientists/physicists collaborate to assess immune repertoires and develop models of immune action.

Chronic Lymphocytic Leukemia B-Cell Normal Cellular Counterpart: Clues From a Functional Perspective

Chronic lymphocytic leukemia (CLL) is characterized by the clonal expansion of small mature-looking CD19+ CD23+ CD5+ B-cells that accumulate in the blood, bone marrow, and lymphoid organs. To date, no consensus has been reached concerning the normal cellular counterpart of CLL B-cells and several B-cell types have been proposed. CLL B-cells have remarkable phenotypic and gene expression profile homogeneity. In recent years, the molecular and cellular biology of CLL has been enriched by seminal insights that are leading to a better understanding of the natural history of the disease. Immunophenotypic and molecular approaches (including immunoglobulin heavy-chain variable gene mutational status, transcriptional and epigenetic profiling) comparing the normal B-cell subset and CLL B-cells provide some new insights into the normal cellular counterpart. Functional characteristics (including activation requirements and propensity for plasma cell differentiation) of CLL B-cells have now been investigated for 50 years. B-cell subsets differ substantially in terms of their functional features. Analysis of shared functional characteristics may reveal similarities between normal B-cell subsets and CLL B-cells, allowing speculative assignment of a normal cellular counterpart for CLL B-cells. In this review, we summarize current data regarding peripheral B-cell differentiation and human B-cell subsets and suggest possibilities for a normal cellular counterpart based on the functional characteristics of CLL B-cells. However, a definitive normal cellular counterpart cannot be attributed on the basis of the available data. We discuss the functional characteristics required for a cell to be logically considered to be the normal counterpart of CLL B-cells.

Double-negative (CD27-IgD-) B cells are expanded in NSCLC and inversely correlate with affinity-matured B cell populations

BACKGROUND

The presence of B cells in early stage non-small cell lung cancer (NSCLC) is associated with longer survival, however, the role these cells play in the generation and maintenance of anti-tumor immunity is unclear. B cells differentiate into a variety of subsets with differing characteristics and functions. To date, there is limited information on the specific B cell subsets found within NSCLC. To better understand the composition of the B cell populations found in NSCLC we have begun characterizing B cells in lung tumors and have detected a population of B cells that are CD79A+CD27-IgD-. These CD27-IgD- (double-negative) B cells have previously been characterized as unconventional memory B cells and have been detected in some autoimmune diseases and in the elderly population but have not been detected previously in tumor tissue.

METHODS

A total of 15 fresh untreated NSCLC tumors and 15 matched adjacent lung control tissues were dissociated and analyzed by intracellular flow cytometry to detect the B cell-related markers CD79A, CD27 and IgD. All CD79A+ B cells subsets were classified as either naïve (CD27-IgD+), affinity-matured (CD27+IgD-), early memory/germinal center cells (CD27+IgD+) or double-negative B cells (CD27-IgD-). Association of double-negative B cells with clinical data including gender, age, smoking status, tumor diagnosis and pathologic differentiation status were also examined using the logistic regression analysis for age and student's t-test for all other variables. Associations with other B cell subpopulations were examined using Spearman's rank correlation.

RESULTS

We observed that double-negative B cells were frequently abundant in lung tumors compared to normal adjacent controls (13 out of 15 cases), and in some cases made up a substantial proportion of the total B cell compartment. The presence of double-negative cells was also found to be inversely related to the presence of affinity-matured B cells within the tumor, Spearman's coefficient of - 0.76.

CONCLUSIONS

This study is the first to observe the presence of CD27-IgD- double-negative B cells in human NSCLC and that this population is inversely correlated with traditional affinity-matured B cell populations.

In-Depth Analysis of Human Neonatal and Adult IgM Antibody Repertoires

Although high-throughput sequencing and associated bioinformatics technologies have enabled the in-depth, sequence-based characterization of human immune repertoires, only a few studies on a relatively small number of sequences explored the characteristics of antibody repertoires in neonates, with contradictory conclusions. To gain a more comprehensive understanding of the human IgM antibody repertoire, we performed Illumina sequencing and IMGT/HighV-QUEST analysis of IgM heavy chain repertoire of the B lymphocytes from the cord blood (CB) of neonates, as well as the repertoire from peripheral blood of healthy human adults (HH). The comparative study revealed unexpectedly high levels of similarity between the neonatal and adult repertoires. In both repertoires, the VDJ gene usage showed no significant difference, and the most frequently used VDJ gene was IGHV4-59, IGHD3-10, and IGHJ3. The average amino acid (aa) length of CDR1 (CB: 8.5, HH: 8.4) and CDR2 (CB: 7.6, HH: 7.5), as well as the aa composition and the average hydrophobicity of the CDR3 demonstrated no significant difference between the two repertories. However, the average aa length of CDR3 was longer in the HH repertoire than the CB repertoire (CB: 14.5, HH: 15.5). Besides, the frequencies of aa mutations in CDR1 (CB: 19.33%, HH: 25.84%) and CDR2 (CB: 9.26%, HH: 17.82%) were higher in the HH repertoire compared to the CB repertoire. Interestingly, the most prominent difference between the two repertoires was the occurrence of N2 addition (CB: 64.87%, HH: 85.69%), a process that occurs during V-D-J recombination for introducing random nucleotide additions between D- and J-gene segments. The antibody repertoire of healthy adults was more diverse than that of neonates largely due to the higher occurrence of N2 addition. These findings may lead to a better understanding of antibody development and evolution pathways and may have potential practical value for facilitating the generation of more effective antibody therapeutics and vaccines.

Pilot Study of Delayed ICOS/ICOS-L Blockade With αCD40 to Modulate Pathogenic Alloimmunity in a Primate Cardiac Allograft Model

Supplemental digital content is available in the text.

Background

Inducible costimulator (ICOS) is rapidly upregulated with T-cell stimulation and may represent an escape pathway for T-cell costimulation in the setting of CD40/CD154 costimulation blockade. Induction treatment exhibited no efficacy in a primate renal allograft model, but rodent transplant models suggest that the addition of delayed ICOS/ICOS-L blockade may prolong allograft survival and prevent chronic rejection. Here, we ask whether ICOS-Ig treatment, timed to anticipate ICOS upregulation, prolongs NHP cardiac allograft survival or attenuates pathogenic alloimmunity.

Methods

Cynomolgus monkey heterotopic cardiac allograft recipients were treated with αCD40 (2C10R4, d0-90) either alone or with the addition of delayed ICOS-Ig (d63-110).

Results

Median allograft survival was similar between ICOS-Ig + αCD40 (120 days, 120-125 days) and αCD40 (124 days, 89-178 days) treated animals, and delayed ICOS-Ig treatment did not prevent allograft rejection in animals with complete CD40 receptor coverage. Although CD4⁺ T_EM cells were decreased in peripheral blood (115 ± 24) and mLNs (49 ± 1.9%) during ICOS-Ig treatment compared with monotherapy (214 ± 27%, P = 0.01; 72 ± 9.9%, P = 0.01, respectively), acute and chronic rejection scores and kinetics of alloAb elaboration were similar between groups.

Conclusions

Delayed ICOS-Ig treatment with the reagent tested is probably ineffective in modulating pathogenic primate alloimmunity in this model.

Biased IGH VDJ gene repertoire and clonal expansions in B cells of chronically hepatitis C virus–infected individuals

Chronic HCV infection leads to extensive BCR immunoglobulin gene repertoire alterations with pathological features even in absence of MC. Many large B-cell clones are consistently found, mainly among IgM+ memory B cells, showing a massive influence of HCV on this compartment.

Proinflammatory B-cell profile in the early phases of MS predicts an active disease

Objective:

To assess whether any alteration of B-cell subset distribution and/or the cytokine production capacities of B cells could be associated with any stage of MS and could be predictive of MS evolution.

Methods:

We prospectively enrolled radiologically isolated syndrome (RIS), clinically isolated syndrome (CIS), naive patients with relapsing remitting MS (RRMS) of any disease modifying drug, and healthy controls (HCs). Peripheral blood B-cell subset distributions and the interleukin (IL)-6/IL-10–producing B-cell ratio were assessed by flow cytometry to evaluate their proinflammatory and anti-inflammatory functional properties.

Results:

Twelve RIS, 46 CIS, 31 RRMS patients, and 36 HCs were enrolled. We observed that a high IL-6/IL-10–producing B-cell ratio in patients with RIS/CIS was associated with the evolution of the disease in the short term (6 months). This imbalance in cytokine production was mainly explained by an alteration of the production of IL-10 by B cells, especially for the transitional B-cell subset. In addition, a significant increase in IgD⁻/CD27⁻ B cells was detected in patients with CIS and RRMS compared with HCs (p = 0.01). Apart from this increase in exhausted B cells, no other variation in B-cell subsets was observed.

Conclusions:

The association between a high IL-6/IL-10–producing B-cell ratio and the evolution of patients with RIS/CIS suggest a skew of B cells toward proinflammatory properties that might be implicated in the early phases of MS disease.

Comprehensive T-cell immunophenotyping and next-generation sequencing of human papillomavirus (HPV)-positive and HPV-negative head and neck squamous cell carcinomas

The success of programmed cell death 1 (PD-1) inhibition in achieving a clinical response in a subset of head and neck squamous cell carcinoma (HNSCC) patients emphasizes the need to better understand the immunobiology of HNSCC. Immunophenotyping was performed for 30 HCSCC patients [16 human papillomavirus (HPV)-positive; 14 HPV-negative] on matched tissue from the primary tumour site, locally metastatic cervical lymph nodes (LNs), uninvolved local cervical LNs, and peripheral blood. CD4⁺ and CD8⁺ T-cell lymphocytes obtained from tissue were analysed for expression levels of the inhibitory receptors PD-1, TIM-3 and CTLA-4. Next-generation sequencing of the T-cell receptor (TCR) β chain was performed on patients (n = 9) to determine receptor repertoire diversity and for clonality analysis. HPV-negative HNSCC patients, particularly those with stage IV disease, had significantly higher proportions of CD8⁺ T cells expressing CTLA-4 in tumour tissue (P = 0.0013) and in peripheral blood (P = 0.0344) than HPV-positive patients, as well as higher expression levels of TIM-3⁺ PD-1⁺ CD8⁺ T cells (P = 0.0072) than controls. For all patients, PD-1 expression on CD8⁺ T cells - particularly in HPV-negative HNSCC cases - strongly correlated (r = 0.63, P = 0.013) with tumour size at the primary site. The top CD8⁺ TCR clones from tumour tissue significantly overlapped with circulating peripheral blood TCR clones (r = 0.946), and HPV-positive patients had frequently expanded TCR clones that were more hydrophobic - and potentially more immunogenic - than those from HPV-negative patients. Collectively, our findings demonstrate, for the first time, that high-stage HPV-negative HNSCC patients with primary tumours at different sites in the head and neck have elevated peripheral CTLA-4⁺ CD8⁺ T-cell levels, that tumour-familiar CD8⁺ T cells are detectable in peripheral blood from HNSCC patients, and that TCRs from HPV-positive HNSCC patients potentially recognize distinctly immunogenic cognate antigens. However, our findings are preliminary, and need to be further confirmed in a larger patient cohort; also, how these factors affect patient response to immunotherapy needs to be determined. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Circulating B cells in type 1 diabetics exhibit fewer maturation-associated phenotypes

Although autoantibodies have been used for decades as diagnostic and prognostic markers in type 1 diabetes (T1D), further analysis of developmental abnormalities in B cells could reveal tolerance checkpoint defects that could improve individualized therapy. To evaluate B cell developmental progression in T1D, immunophenotyping was used to classify circulating B cells into transitional, mature naïve, mature activated, and resting memory subsets. Then each subset was analyzed for the expression of additional maturation-associated markers. While the frequencies of B cell subsets did not differ significantly between patients and controls, some T1D subjects exhibited reduced proportions of B cells that expressed transmembrane activator and CAML interactor (TACI) and Fas receptor (FasR). Furthermore, some T1D subjects had B cell subsets with lower frequencies of class switching. These results suggest circulating B cells exhibit variable maturation phenotypes in T1D. These phenotypic variations may correlate with differences in B cell selection in individual T1D patients.

B-cell phenotype and IgD-CD27- memory B cells are affected by TNF-inhibitors and tocilizumab treatment in rheumatoid arthritis

Background

The use of TNF-inhibitors and/or the IL-6 receptor antagonist, tocilizumab, in rheumatoid arthritis (RA) have pleiotropic effects that also involve circulating B-cells. The main goal of this study was to assess the effect of TNF-inhibitors and tocilizumab on B-cell phenotype and gene expression in RA.

Methods

Blood samples were collected from untreated early RA (ERA) patients, established RA patients under methotrexate treatment, established RA patients before and after treatment with TNF-inhibitors and tocilizumab, and healthy donors. B-cell subpopulations were characterized by flow cytometry and B-cell gene expression was analyzed by real-time PCR on isolated B-cells. Serum levels of BAFF, CXCL13 and sCD23 were determined by ELISA.

Results

The frequency of total CD19+ B cells in circulation was similar between controls and all RA groups, irrespective of treatment, but double negative (DN) IgD-CD27- memory B cells were significantly increased in ERA and established RA when compared to controls. Treatment with TNF-inhibitors and tocilizumab restored the frequency of IgD-CD27- B-cells to normal levels, but did not affect other B cell subpopulations. TACI, CD95, CD5, HLA-DR and TLR9 expression on B-cells significantly increased after treatment with either TNF-inhibitors and/ or tocilizumab, but no significant changes were observed in BAFF-R, BCMA, CD69, CD86, CXCR5, CD23, CD38 and IgM expression on B-cells when comparing baseline with post-treatment follow-ups. Alterations in B-cell gene expression of BAFF-R, TACI, TLR9, FcγRIIB, BCL-2, BLIMP-1 and β2M were found in ERA and established RA patients, but no significant differences were observed after TNF-inhibitors and tocilizumab treatment when comparing baseline and follow-ups. Serum levels of CXCL13, sCD23 and BAFF were not significantly affected by treatment with TNF-inhibitors and tocilizumab.

Conclusions

In RA patients, the use of TNF-inhibitors and/ or tocilizumab treatment affects B-cell phenotype and IgD-CD27- memory B cells in circulation, but not B-cell gene expression levels.

Comparative Evaluation of αCD40 (2C10R4) and αCD154 (5C8H1 and IDEC-131) in a Nonhuman Primate Cardiac Allotransplant Model

BACKGROUND

Specific blockade of T cell costimulation pathway is a promising immunomodulatory approach being developed to replace our current clinical immunosuppression therapies. The goal of this study is to compare results associated with 3 monoclonal antibodies directed against the CD40/CD154 T cell costimulation pathway.

METHODS

Cynomolgus monkey heterotopic cardiac allograft recipients were treated with either IDEC-131 (humanized αCD154, n = 9), 5C8H1 (mouse-human chimeric αCD154, n = 5), or 2C10R4 (mouse-rhesus chimeric αCD40, n = 6) monotherapy using a consistent, comparable dosing regimen for 3 months after transplant.

RESULTS

Relative to the previously reported IDEC-131-treated allografts, median survival time (35 ± 31 days) was significantly prolonged in both 5C8H1-treated (142 ± 26, P < 0.002) and 2C10R4-treated (124 ± 37, P < 0.020) allografts. IDEC-131-treated grafts had higher cardiac allograft vasculopathy severity scores during treatment relative to either 5C8H1 (P = 0.008) or 2C10R4 (P = 0.0002). Both 5C8H1 (5 of 5 animals, P = 0.02) and 2C10R4 (6/6, P = 0.007), but not IDEC-131 (2/9), completely attenuated IgM antidonor alloantibody (alloAb) production during treatment; 5C8H1 (5/5) more consistently attenuated IgG alloAb production compared to 2C10R4 (4/6) and IDEC-131 (0/9). All evaluable explanted grafts experienced antibody-mediated rejection. Only 2C10R4-treated animals exhibited a modest, transient drop in CD20 lymphocytes from baseline at day 14 after transplant (-457 ± 152 cells/μL) compared with 5C8H1-treated animals (16 ± 25, P = 0.037), and the resurgent B cells were primarily of a naive phenotype.

CONCLUSIONS

In this model, CD154/CD40 axis blockade using IDEC-131 is an inferior immunomodulatory treatment than 5C8H1 or 2C10R4, which have similar efficacy to prolong graft survival and to delay cardiac allograft vasculopathy development and antidonor alloAb production during treatment.

Aiolos Overexpression in Systemic Lupus Erythematosus B Cell Subtypes and BAFF-Induced Memory B Cell Differentiation Are Reduced by CC-220 Modulation of Cereblon Activity

BAFF is a B cell survival and maturation factor implicated in the pathogenesis of systemic lupus erythematosus (SLE). In this in vitro study, we describe that soluble BAFF in combination with IL-2 and IL-21 is a T cell contact-independent inducer of human B cell proliferation, plasmablast differentiation, and IgG secretion from circulating CD27⁺ memory and memory-like CD27^-IgD^- double-negative (DN) B cells, but not CD27^-IgD⁺ naive B cells. In contrast, soluble CD40L in combination with IL-2 and IL-21 induces these activities in both memory and naive B cells. Blood from healthy donors and SLE patients have similar circulating levels of IL-2, whereas SLE patients exhibit elevated BAFF and DN B cells and reduced IL-21. B cell differentiation transcription factors in memory, DN, and naive B cells in SLE show elevated levels of Aiolos, whereas Ikaros levels are unchanged. Treatment with CC-220, a modulator of the cullin ring ligase 4-cereblon E3 ubiquitin ligase complex, reduces Aiolos and Ikaros protein levels and BAFF- and CD40L-induced proliferation, plasmablast differentiation, and IgG secretion. The observation that the soluble factors BAFF, IL-2, and IL-21 induce memory and DN B cell activation and differentiation has implications for extrafollicular plasmablast development within inflamed tissue. Inhibition of B cell plasmablast differentiation by reduction of Aiolos and Ikaros may have utility in the treatment of SLE, where elevated levels of BAFF and Aiolos may prime CD27⁺ memory and DN memory-like B cells to become Ab-producing plasmablasts in the presence of BAFF and proinflammatory cytokines.

Evaluation of Antigen-Specific IgM and IgG Production during an In Vitro Peripheral Blood Mononuclear Cell Culture Assay

The recent attention given to diseases associated with memory B-cell (mBC)-produced antibodies (Abs) suggests the need for a similar in vitro assay to evaluate the functions of mBCs. Here, we cultured peripheral blood mononuclear cells (PBMCs) with the intent to collect mBC-derived Abs in vitro and maintain their cell–cell contact-dependent interactions with helper T-cells. PBMCs were cultured with interleukin (IL)-21, CpG-oligodeoxynucleotides (ODN), phorbol myristate acetate (PMA), and phytohemagglutinin/leucoagglutinin (PHA-L) in 24-well flat-bottom plates (5 × 10⁵ cells/well). A culture supernatant analysis of PBMCs from healthy donors (n = 10) indicated that antigen-specific IgM Ab levels in a PBMC culture supernatant might be better able to demonstrate the antigen sensitization status in a smaller peripheral blood sample, compared to IgG because Epstein–Barr virus-specific IgM mBCs circulate peripherally at a significantly higher frequency once antiviral humoral immunity has stabilized. Thus, our in vitro assay demonstrated the potential significance of antigen-specific IgM Ab production in the culture supernatants. Furthermore, an analysis of cultured PBMCs from allograft kidney recipients (n = 16) sensitized with de novo donor-specific human leukocyte antigen (HLA)-specific Abs (DSAs) showed that IgM-type HLA-specific Abs were detected mainly from the culture supernatants from PBMCs of patients with stable graft function, whereas IgG isotype HLA Abs were detectable only from patients with biopsy-proven antibody-mediated rejection. In other words, these IgG isotype Abs also represented an activated humoral immune response in vivo. Additionally, IgM- and IgG-expressing mBCs from healthy donors (n = 5) were cultured with IL-21, CpG-ODN, and a supernatant produced by stimulating CD19⁺ B-cell-depleted PBMCs with PHA-L and PMA in 24-well flat-bottom plates (1 × 10⁵ cells/well), and the resulting in vitro analysis provided some information regarding the biological processes of IgG and IgM mBCs in peripheral blood. Taken together, our findings suggest that antigen-specific Ab subtype analyses of supernatants from cultured PBMCs might more effectively and accurately reflect a patient’s Ab-associated pathological condition vs. than serum IgG and IgM levels.

CNS Aquaporin-4-specific B cells connect with multiple B-cell compartments in neuromyelitis optica spectrum disorder

Objectives

Neuromyelitis optica spectrum disorder (NMOSD) is a severe inflammatory disorder of the central nervous system (CNS) targeted against aquaporin‐4 (AQP4). The origin and trafficking of AQP4‐specific B cells in NMOSD remains unknown.

Methods

Peripheral (n = 7) and splenic B cells (n = 1) recovered from seven NMOSD patients were sorted into plasmablasts, naïve, memory, and CD27‐IgD‐ double negative (DN) B cells, and variable heavy chain (VH) transcriptome sequences were generated by deep sequencing. Peripheral blood (PB) VH repertoires were compared to the same patient's single‐cell cerebrospinal fluid (CSF) plasmablast (PB) VH transcriptome, CSF immunoglobulin (Ig) proteome, and serum Ig proteome. Recombinant antibodies were generated from paired CSF heavy‐ and light chains and tested for AQP4 reactivity.

Results

Approximately 9% of the CSF VH sequences aligned with PB memory B cells, DN B cells, and plasmablast VH sequences. AQP4‐specific VH sequences were observed in each peripheral B‐cell compartment. Lineage analysis of clonally related VH sequences indicates that CSF AQP4‐specific B cells are closely related to an expanded population of DN B cells that may undergo antigen‐specific B‐cell maturation within the CNS. CSF and serum Ig proteomes overlapped with the VH sequences from each B‐cell compartment; the majority of matches occurring between the PB VH sequences and serum Ig proteome.

Interpretation

During an acute NMOSD relapse, a dynamic exchange of B cells occurs between the periphery and CNS with AQP4‐specific CSF B cells emerging from postgerminal center memory B cells and plasmablasts. Expansion of the PB DN B‐cell compartment may be a potential biomarker of NMOSD activity.

Ro52 autoantibodies arise from self-reactive progenitors in a mother of a child with neonatal lupus

The detection of cardiac conduction defects in an 18-24 week old foetus in the absence of structural abnormalities predicts with near certainty the presence of autoantibodies against 60kD and 52kD SSA/Ro in the mother regardless of her health status. Previous studies have emphasized these autoantibodies as key mediators of tissue injury. The aim of this study was to focus on the anti-Ro52 response to determine whether these autoantibodies originate from progenitors that are inherently self-reactive or from B-cells that acquire self-reactivity during an immune response. We traced the evolution of two anti-Ro52 autoantibodies isolated from circulating IgG1-switched B-cells from an asymptomatic mother of a child with third degree congenital heart block. The autoantibodies were expressed as their immune form and as pre-immune ancestors by reverting somatic mutations to germline sequence. The reactivity of pre-immune and immune antibodies for Ro52, Ro60, La and DNA was measured. Both anti-Ro52 autoantibodies exhibited a low frequency of somatic mutations (3-4%) and utilised the same heavy and light chain genes but represented distinct clones based on differing complementarity determining region sequences. Pre- and post-immune antibodies showed specific binding to Ro52 with no measurable reactivity for other autoantigens. Ro52 binding was higher for immune antibodies compared to pre-immune counterparts demonstrating that autoreactivity was enhanced by affinity maturation. These data indicate that Ro52 reactivity is an intrinsic property of the germline antibody repertoire in a mother with a pathogenic antibody defined by cardiac injury in her offspring, and implies defects in both central and peripheral tolerance mechanisms.

Dysregulation of B Cell Repertoire Formation in Myasthenia Gravis Patients Revealed through Deep Sequencing

Myasthenia gravis (MG) is a prototypical B cell-mediated autoimmune disease affecting 20-50 people per 100,000. The majority of patients fall into two clinically distinguishable types based on whether they produce autoantibodies targeting the acetylcholine receptor (AChR-MG) or muscle specific kinase (MuSK-MG). The autoantibodies are pathogenic, but whether their generation is associated with broader defects in the B cell repertoire is unknown. To address this question, we performed deep sequencing of the BCR repertoire of AChR-MG, MuSK-MG, and healthy subjects to generate ∼518,000 unique V_H and V_L sequences from sorted naive and memory B cell populations. AChR-MG and MuSK-MG subjects displayed distinct gene segment usage biases in both V_H and V_L sequences within the naive and memory compartments. The memory compartment of AChR-MG was further characterized by reduced positive selection of somatic mutations in the V_H CDR and altered V_H CDR3 physicochemical properties. The V_L repertoire of MuSK-MG was specifically characterized by reduced V-J segment distance in recombined sequences, suggesting diminished V_L receptor editing during B cell development. Our results identify large-scale abnormalities in both the naive and memory B cell repertoires. Particular abnormalities were unique to either AChR-MG or MuSK-MG, indicating that the repertoires reflect the distinct properties of the subtypes. These repertoire abnormalities are consistent with previously observed defects in B cell tolerance checkpoints in MG, thereby offering additional insight regarding the impact of tolerance defects on peripheral autoimmune repertoires. These collective findings point toward a deformed B cell repertoire as a fundamental component of MG.

The Isolation, Differentiation, and Quantification of Human Antibody-secreting B Cells from Blood: ELISpot as a Functional Readout of Humoral Immunity

The hallmark of humoral immunity is to generate functional ASCs, which synthesize and secrete Abs specific to an antigen (Ag), such as a pathogen, and are used for host defense. For the quantitative determination of the functional status of the humoral immune response of an individual, both serum Abs and circulating ASCs are commonly measured as functional readouts. In humans, peripheral blood is the most convenient and readily accessible sample that can be used for the determination of the humoral immune response elicited by host B cells. Distinct B-cell subsets, including ASCs, can be isolated directly from peripheral blood via selection with lineage-specific Ab-conjugated microbeads or via cell sorting with flow cytometry. Moreover, purified naïve and memory B cells can be activated and differentiated into ASCs in culture. The functional activities of ASCs to contribute to Ab secretion can be quantified by ELISpot, which is an assay that converges enzyme-linked immunoabsorbance assay (ELISA) and western blotting technologies to enable the enumeration of individual ASCs at the single-cell level. In practice, the ELISpot assay has been increasingly used to evaluate vaccine efficacy because of the ease of handling of a large number of blood samples. The methods of isolating human B cells from peripheral blood, the differentiation of B cells into ASCs in vitro, and the employment of ELISpot for the quantification of total IgM- and IgG-ASCs will be described here.

Transitional B Cells in Early Human B Cell Development - Time to Revisit the Paradigm?

The B cell repertoire is generated in the adult bone marrow by an ordered series of gene rearrangement processes that result in massive diversity of immunoglobulin (Ig) genes and consequently an equally large number of potential specificities for antigen. As the process is essentially random, the cells exhibiting excess reactivity with self-antigens are generated and need to be removed from the repertoire before the cells are fully mature. Some of the cells are deleted, and some will undergo receptor editing to see if changing the light chain can rescue an autoreactive antibody. As a consequence, the binding properties of the B cell receptor are changed as development progresses through pre-B ≫ immature ≫ transitional ≫ naïve phenotypes. Using long-read, high-throughput, sequencing we have produced a unique set of sequences from these four cell types in human bone marrow and matched peripheral blood, and our results describe the effects of tolerance selection on the B cell repertoire at the Ig gene level. Most strong effects of selection are seen within the heavy chain repertoire and can be seen both in gene usage and in CDRH3 characteristics. Age-related changes are small, and only the size of the CDRH3 shows constant and significant change in these data. The paucity of significant changes in either kappa or lambda light chain repertoires implies that either the heavy chain has more influence over autoreactivity than light chain and/or that switching between kappa and lambda light chains, as opposed to switching within the light chain loci, may effect a more successful autoreactive rescue by receptor editing. Our results show that the transitional cell population contains cells other than those that are part of the pre-B ≫ immature ≫ transitional ≫ naïve development pathway, since the population often shows a repertoire that is outside the trajectory of gene loss/gain between pre-B and naïve stages.

Multiple Antibody Lineages in One Donor Target the Glycan-V3 Supersite of the HIV-1 Envelope Glycoprotein and Display a Preference for Quaternary Binding

One of the goals of HIV-1 vaccine development is the elicitation of neutralizing antibodies against vulnerable regions on the envelope glycoprotein (Env) viral spike. Broadly neutralizing antibodies targeting the Env glycan-V3 region (also called the N332 glycan supersite) have been described previously, with several single lineages each derived from different individual donors. We used a high-throughput B-cell culture method to isolate neutralizing antibodies from an HIV-1-infected donor with high serum neutralization breadth. Clonal relatives from three distinct antibody lineages were isolated. Each of these antibody lineages displayed modest breadth and potency but shared several characteristics with the well-characterized glycan-V3 antibodies, including dependence on glycans N332 and N301, VH4 family gene utilization, a heavy chain complementarity-determining region 2 (CDRH2) insertion, and a longer-than-average CDRH3. In contrast to previously described glycan-V3 antibodies, these antibodies preferentially recognized the native Env trimer compared to monomeric gp120. These data indicate the diversity of antibody specificities that target the glycan-V3 site. The quaternary binding preference of these antibodies suggests that that their elicitation likely requires the presentation of a native-like trimeric Env immunogen.

IMPORTANCE

Broadly neutralizing antibodies targeting the HIV-1 glycan-V3 region with single lineages from individual donors have been described previously. Here we describe three lineages from a single donor, each of which targets glycan-V3. Unlike previously described glycan-V3 antibodies, these mature antibodies bind preferentially to the native Env trimer and weakly to the gp120 monomer. These data extend our knowledge of the immune response recognition of the N332 supersite region and suggest that the mode of epitope recognition is more complex than previously anticipated.

Age-Associated B Cells with Proinflammatory Characteristics Are Expanded in a Proportion of Multiple Sclerosis Patients

Immune aging occurs in the elderly and in autoimmune diseases. Recently, IgD^-CD27^- (double negative, DN) and CD21^-CD11c⁺ (CD21^low) B cells were described as age-associated B cells with proinflammatory characteristics. This study investigated the prevalence and functional characteristics of DN and CD21^low B cells in multiple sclerosis (MS) patients. Using flow cytometry, we demonstrated a higher proportion of MS patients younger than 60 y with peripheral expansions of DN (8/41) and CD21^low (9/41) B cells compared with age-matched healthy donors (1/33 and 2/33, respectively), which indicates an increase in age-associated B cells in MS patients. The majority of DN B cells had an IgG⁺ memory phenotype, whereas CD21^low B cells consisted of a mixed population of CD27^- naive, CD27⁺ memory, IgG⁺, and IgM⁺ cells. DN B cells showed similar (MS patients) or increased (healthy donors) MHC-II expression as class-switched memory B cells and intermediate costimulatory molecule expression between naive and class-switched memory B cells, indicating their potential to induce (proinflammatory) T cell responses. Further, DN B cells produced proinflammatory and cytotoxic cytokines following ex vivo stimulation. Increased frequencies of DN and CD21^low B cells were found in the cerebrospinal fluid of MS patients compared with paired peripheral blood. In conclusion, a proportion of MS patients showed increased peripheral expansions of age-associated B cells. DN and CD21^low B cell frequencies were further increased in MS cerebrospinal fluid. These cells could contribute to inflammation by induction of T cell responses and the production of proinflammatory cytokines.

Unraveling the Role of Allo-Antibodies and Transplant Injury

Alloimmunity driving rejection in the context of solid organ transplantation can be grossly divided into mechanisms predominantly driven by either T cell-mediated rejection (TCMR) and antibody-mediated rejection (ABMR), though the co-existence of both types of rejections can be seen in a variable number of sampled grafts. Acute TCMR can generally be well controlled by the establishment of effective immunosuppression (1, 2). Acute ABMR is a low frequency finding in the current era of blood group and HLA donor/recipient matching and the avoidance of engraftment in the context of high-titer, preformed donor-specific antibodies. However, chronic ABMR remains a major complication resulting in the untimely loss of transplanted organs (3-10). The close relationship between donor-specific antibodies and ABMR has been revealed by the highly sensitive detection of human leukocyte antigen (HLA) antibodies (7, 11-15). Injury to transplanted organs by activation of humoral immune reaction in the context of HLA identical transplants and the absence of donor specific antibodies (17-24), strongly suggest the participation of non-HLA (nHLA) antibodies in ABMR (25). In this review, we discuss the genesis of ABMR in the context of HLA and nHLA antibodies and summarize strategies for ABMR management.

Targeting B cells in relapsing-remitting multiple sclerosis: from pathophysiology to optimal clinical management

Multiple sclerosis (MS) is a chronic inflammatory demyelinating disease that is caused by an autoimmune response against central nervous system (CNS) structures. Traditionally considered a T-cell-mediated disorder, the contribution of B cells to the pathogenesis of MS has long been debated. Based on recent promising clinical results from CD20-depleting strategies by three therapeutic monoclonal antibodies in clinical phase II and III trials (rituximab, ocrelizumab and ofatumumab), targeting B cells in MS is currently attracting growing interest among basic researchers and clinicians. Many questions about the role of B and plasma cells in MS remain still unanswered, ranging from the role of specific B-cell subsets and functions to the optimal treatment regimen of B-cell depletion and monitoring thereafter. Here, we will assess our current knowledge of the mechanisms implicating B cells in multiple steps of disease pathology and examine current and future therapeutic approaches for the treatment of MS.

The human intestinal B-cell response

The intestinal immune system is chronically challenged by a huge plethora of antigens derived from the lumen. B-cell responses in organized gut-associated lymphoid tissues and regional lymph nodes that are driven chronically by gut antigens generate the largest population of antibody-producing cells in the body: the gut lamina propria plasma cells. Although animal studies have provided insights into mechanisms that underpin this dynamic process, some very fundamental differences in this system appear to exist between species. Importantly, this prevents extrapolation from mice to humans to inform translational research questions. Therefore, in this review we will describe the structures and mechanisms involved in the propagation, dissemination, and regulation of this immense plasma cell population in man. Uniquely, we will seek our evidence exclusively from studies of human cells and tissues.

A Public Database of Memory and Naive B-Cell Receptor Sequences

The vast diversity of B-cell receptors (BCR) and secreted antibodies enables the recognition of, and response to, a wide range of epitopes, but this diversity has also limited our understanding of humoral immunity. We present a public database of more than 37 million unique BCR sequences from three healthy adult donors that is many fold deeper than any existing resource, together with a set of online tools designed to facilitate the visualization and analysis of the annotated data. We estimate the clonal diversity of the naive and memory B-cell repertoires of healthy individuals, and provide a set of examples that illustrate the utility of the database, including several views of the basic properties of immunoglobulin heavy chain sequences, such as rearrangement length, subunit usage, and somatic hypermutation positions and dynamics.

Clonal redemption of autoantibodies by somatic hypermutation away from self-reactivity during human immunization

Clonal anergy is an enigmatic self-tolerance mechanism because no apparent purpose is served by retaining functionally silenced B cells bearing autoantibodies. Human autoantibodies with IGHV4-34*01 heavy chains bind to poly-N-acetyllactosamine carbohydrates (I/i antigen) on erythrocytes and B lymphocytes, cause cold agglutinin disease, and are carried by 5% of naive B cells that are anergic. We analyzed the specificity of three IGHV4-34*01 IgG antibodies isolated from healthy donors immunized against foreign rhesus D alloantigen or vaccinia virus. Each IgG was expressed and analyzed either in a hypermutated immune state or after reverting each antibody to its unmutated preimmune ancestor. In each case, the preimmune ancestor IgG bound intensely to normal human B cells bearing I/i antigen. Self-reactivity was removed by a single somatic mutation that paradoxically decreased binding to the foreign immunogen, whereas other mutations conferred increased foreign binding. These data demonstrate the existence of a mechanism for mutation away from self-reactivity in humans. Because 2.5% of switched memory B cells use IGHV4-34*01 and >43% of these have mutations that remove I/i binding, clonal redemption of anergic cells appears efficient during physiological human antibody responses.

Human Memory B Cells in Healthy Gingiva, Gingivitis, and Periodontitis

The presence of inflammatory infiltrates with B cells, specifically plasma cells, is the hallmark of periodontitis lesions. The composition of these infiltrates in various stages of homeostasis and disease development is not well documented. Human tissue biopsies from sites with gingival health (n = 29), gingivitis (n = 8), and periodontitis (n = 21) as well as gingival tissue after treated periodontitis (n = 6) were obtained and analyzed for their composition of B cell subsets. Ag specificity, Ig secretion, and expression of receptor activator of NF-κB ligand and granzyme B were performed. Although most of the B cell subsets in healthy gingiva and gingivitis tissues were CD19(+)CD27(+)CD38(-) memory B cells, the major B cell component in periodontitis was CD19(+)CD27(+)CD38(+)CD138(+)HLA-DR(low) plasma cells, not plasmablasts. Plasma cell aggregates were observed at the base of the periodontal pocket and scattered throughout the gingiva, especially apically toward the advancing front of the lesion. High expression of CXCL12, a proliferation-inducing ligand, B cell-activating factor, IL-10, IL-6, and IL-21 molecules involved in local B cell responses was detected in both gingivitis and periodontitis tissues. Periodontitis tissue plasma cells mainly secreted IgG specific to periodontal pathogens and also expressed receptor activator of NF-κB ligand, a bone resorption cytokine. Memory B cells resided in the connective tissue subjacent to the junctional epithelium in healthy gingiva. This suggested a role of memory B cells in maintaining periodontal homeostasis.

B cells from African American lupus patients exhibit an activated phenotype

Systemic lupus erythematosus (SLE) is a complex systemic autoimmune disease driven by both innate and adaptive immune cells. African Americans tend to present with more severe disease at an earlier age compared with patients of European ancestry. In order to better understand the immunological differences between African American and European American patients, we analyzed the frequencies of B cell subsets and the expression of B cell activation markers from a total of 68 SLE patients and 69 normal healthy volunteers. We found that B cells expressing the activation markers CD86, CD80, PD1, and CD40L, as well as CD19⁺CD27^-IgD^- double-negative B cells, were enriched in African American patients vs. patients of European ancestry. In addition to increased expression of CD40L, surface levels of CD40 on B cells were lower, suggesting the engagement of the CD40 pathway. In vitro experiments confirmed that CD40L expressed by B cells could lead to CD40 activation and internalization on adjacent B cells. To conclude, these results indicate that, compared with European American patients, African American SLE patients present with a particularly active B cell component, possibly via the activation of the CD40/CD40L pathway. These data may help guide the development of novel therapies.

Distinct TLR-mediated cytokine production and immunoglobulin secretion in human newborn naïve B cells

Neonatal innate immunity is distinct from that of adults, which may contribute to increased susceptibility to infection and limit vaccine responses. B cells play critical roles in protection from infection and detect PAMPs via TLRs, that, when co-activated with CD40, can drive B-cell proliferation and Ab production. We characterized the expression of TLRs in circulating B cells from newborns and adults, and evaluated TLR- and CD40-mediated naïve B-cell class-switch recombination (CSR) and cytokine production. Gene expression levels of most TLRs was similar between newborn and adult B cells, except that newborn naïve B cells expressed more TLR9 than adult naïve B cells. Neonatal naïve B cells demonstrated impaired TLR2- and TLR7- but enhanced TLR9-mediated cytokine production. Significantly fewer newborn naïve B cells underwent CSR to produce IgG, an impairment also noted with IL-21 stimulation. Additionally, co-stimulation via CD40 and TLRs induced greater cytokine production in adult B cells. Thus, while newborn naïve B cells demonstrate adult-level expression of TLRs and CD40, the responses to stimulation of these receptors are distinct. Relatively high expression of TLR9 and impaired CD40-mediated Ig secretion contributes to distinct innate and adaptive immunity of human newborns and may inform novel approaches to early-life immunization.

Large-scale sequence and structural comparisons of human naive and antigen-experienced antibody repertoires

Elucidating how antigen exposure and selection shape the human antibody repertoire is fundamental to our understanding of B-cell immunity. We sequenced the paired heavy- and light-chain variable regions (VH and VL, respectively) from large populations of single B cells combined with computational modeling of antibody structures to evaluate sequence and structural features of human antibody repertoires at unprecedented depth. Analysis of a dataset comprising 55,000 antibody clusters from CD19(+)CD20(+)CD27(-) IgM-naive B cells, >120,000 antibody clusters from CD19(+)CD20(+)CD27(+) antigen-experienced B cells, and >2,000 RosettaAntibody-predicted structural models across three healthy donors led to a number of key findings: (i) VH and VL gene sequences pair in a combinatorial fashion without detectable pairing restrictions at the population level; (ii) certain VH:VL gene pairs were significantly enriched or depleted in the antigen-experienced repertoire relative to the naive repertoire; (iii) antigen selection increased antibody paratope net charge and solvent-accessible surface area; and (iv) public heavy-chain third complementarity-determining region (CDR-H3) antibodies in the antigen-experienced repertoire showed signs of convergent paired light-chain genetic signatures, including shared light-chain third complementarity-determining region (CDR-L3) amino acid sequences and/or Vκ,λ-Jκ,λ genes. The data reported here address several longstanding questions regarding antibody repertoire selection and development and provide a benchmark for future repertoire-scale analyses of antibody responses to vaccination and disease.

Ageing of the B-cell repertoire

Older people are more susceptible to infection, less responsive to vaccination and have a more inflammatory immune environment. Using spectratype analysis, we have previously shown that the B-cell repertoire of older people shows evidence of inappropriate clonal expansions in the absence of challenge, and that this loss of B-cell diversity correlates with poor health. Studies on response to vaccination, using both spectratyping and high-throughput sequencing of the repertoire, indicate that older responses to challenge are lacking in magnitude and/or delayed significantly. Also that some of the biologically significant differences may be in different classes of antibody. We have also previously shown that normal young B-cell repertoires can vary between different phenotypic subsets of B cells. In this paper, we present an analysis of immunoglobulin repertoire in different subclasses of antibody in five different populations of B cell, and show how the repertoire in these different groups changes with age. Although some age-related repertoire differences occur in naive cells, before exogenous antigen exposure, we see indications that there is a general dysregulation of the selective forces that shape memory B-cell populations in older people.