Plasma Cell Longevity Research Articles

New insights into the ontogeny, diversity, maturation and survival of long-lived plasma cells.

Plasma cells are unique immune effectors, capable of producing large amounts of high-affinity antibodies that protect against pathogenic infections. Although most plasma cells have short lifespans, certain conditions or vaccinations can give rise to long-lived plasma cells (LLPCs) that provide individuals with lifelong protection against pathogen exposure. The nature of these LLPCs is poorly understood; however, recent studies have shed new light on the ontogeny, diversity, maturation and survival of these unique cells. Whereas LLPCs had been thought to arise preferentially from germinal centres, novel genetic tools have revealed that they can originate from various stages throughout the humoral response. Furthermore, new single-cell analyses have shown that mouse and human plasma cells are heterogeneous and may undergo further maturation in situ in the bone marrow niche. Finally, plasma cells were previously considered to be sessile cells maintained in fixed survival niches, but new data show that plasma cell subsets can differentially migrate and organize into clusters that may be associated with survival niches. These descriptive findings provide new insights into how cell-intrinsic programmes and extrinsic factors may regulate the longevity of plasma cells in various contexts, which suggest new research avenues for their functional validation.

Tissues of origin matter to plasma cell longevity.

Tissues of origin matter to plasma cell longevity.

Progressive differentiation toward the long-lived plasma cell compartment in the bone marrow.

The longevity of plasma cells is dependent on their ability to access and reside in so-called niches that are predominantly located in the bone marrow. Here, by employing a traceable method to label recently generated plasma cells, we showed that homeostatic plasma cells in the bone marrow and spleen were continuously replenished by newly generated B220hiMHC-IIhi populations that progressively differentiated into B220loMHC-IIlo long-lived plasma cell (LLPC) populations. We also found that, in the bone marrow, germinal center (GC)-independent and GC-dependent plasma cells decayed similarly upon NP-CGG engagement, and both entered the B220loMHC-IIlo LLPC pool. Compared with NP+B220hiMHC-IIhi plasma cells, NP+B220loMHC-IIlo cells were more immobilized in the bone marrow niches and showed better survival potential. Thus, our results suggest that the adhesion status of bone marrow plasma cells is dynamically altered during their differentiation and is associated with provision of survival signals.

APRIL Drives a Coordinated but Diverse Response as a Foundation for Plasma Cell Longevity.

Ab-secreting cells survive in niche microenvironments, but cellular responses driven by particular niche signals are incompletely defined. The TNF superfamily member a proliferation-inducing ligand (APRIL) can support the maturation of transitory plasmablasts into long-lived plasma cells. In this study, we explore the biological programs established by APRIL in human plasmablasts. Under conditions allowing the maturation of ex vivo- or in vitro-generated plasmablasts, we find that APRIL drives activation of ERK, p38, and JNK, accompanied by a classical NF-κB response and activation of the AKT/FOXO1 pathway. Time-course gene expression data resolve coordinated transcriptional responses propagated via immediate early genes and NF-κB targets and converging onto modules of genes enriched for MYC targets and metabolism/cell growth-related pathways. This response is shared between APRIL and an alternate TNF superfamily member CD40L but is not a feature of alternative niche signals delivered by IFN-α or SDF1. However, APRIL and CD40L responses also diverge. CD40L drives expression of genes related to the activated B cell state whereas APRIL does not. Thus, APRIL establishes a broad foundation for plasma cell longevity with features of cellular refueling while being uncoupled from support of the B cell state.

Persistence of Virus-Specific Antibody after Depletion of Memory B Cells.

Humoral immunity is a major component of the adaptive immune response against viruses and other pathogens with pathogen-specific antibody acting as the first line of defense against infection. Virus-specific antibody levels are maintained by continual secretion of antibody by plasma cells residing in the bone marrow. This raises the important question of how the virus-specific plasma cell population is stably maintained and whether memory B cells are required to replenish plasma cells, balancing their loss arising from their intrinsic death rate. In this study, we examined the longevity of virus-specific antibody responses in the serum of mice following acute viral infection with three different viruses: lymphocytic choriomeningitis virus (LCMV), influenza virus, and vesicular stomatitis virus (VSV). To investigate the contribution of memory B cells to the maintenance of virus-specific antibody levels, we employed human CD20 transgenic mice, which allow for the efficient depletion of B cells with rituximab, a human CD20-specific monoclonal antibody. Mice that had resolved an acute infection with LCMV, influenza virus, or VSV were treated with rituximab starting at 2 months after infection, and the treatment was continued for up to a year postinfection. This treatment regimen with rituximab resulted in efficient depletion of B cells (>95%), with virus-specific memory B cells being undetectable. There was an early transient drop in the antibody levels after rituximab treatment followed by a plateauing of the curve with virus-specific antibody levels remaining relatively stable (half-life of 372 days) for up to a year after infection in the absence of memory B cells. The number of virus-specific plasma cells in the bone marrow were consistent with the changes seen in serum antibody levels. Overall, our data show that virus-specific plasma cells in the bone marrow are intrinsically long-lived and can maintain serum antibody titers for extended periods of time without requiring significant replenishment from memory B cells. These results provide insight into plasma cell longevity and have implications for B cell depletion regimens in cancer and autoimmune patients in the context of vaccination in general and especially for COVID-19 vaccines. IMPORTANCE Following vaccination or primary virus infection, virus-specific antibodies provide the first line of defense against reinfection. Plasma cells residing in the bone marrow constitutively secrete antibodies, are long-lived, and can thus maintain serum antibody levels over extended periods of time in the absence of antigen. Our data, in the murine model system, show that virus-specific plasma cells are intrinsically long-lived but that some reseeding by memory B cells might occur. Our findings demonstrate that, due to the longevity of plasma cells, virus-specific antibody levels remain relatively stable in the absence of memory B cells and have implications for vaccination.

To build a plasma cell.

To build a plasma cell.

Spatial Map of Human B Cell and Plasma Cell Compartments

Abstract Naive B cells differentiate into antibody secreting plasma cells (PC) and memory B cells (MBC) that together dictate the quality and persistence of the humoral immune response. However, a comprehensive analysis of human B lineage population structure that integrates surface phenotype and intracellular functional status is lacking. One reason for this knowledge gap is the difficulty of obtaining diverse tissues from normal individuals. Here we have performed a comprehensive analysis of human lymphoid tissue from relatively inaccessible sites including SPL, BM and LN to visualize B cell organization across diverse tissues from normal donors. We exploited a novel algorithmic pipeline for unbiased analysis. Further, we are aligning findings across mouse and man. Here we report the identification of select markers that are involved in a shared BM precursor/PC program including CD28, CLEC12A, CCR2, CD7 and CD79b by LEGENDScreening. We have validated these markers by RNA-seq analysis of murine splenic PC and conventional flow cytometry analysis of human gut PC. We hypothesize that long-lived PCs returning to BM extinguish the B cell program and re-engage with the ancestral long-lived program. Overall, our findings constitute the basis for a geographic understanding of human B lineage population structure that will inform studies on the human humoral immune response and the mechanisms of PC longevity.

Longevity, clonal relationship, and transcriptional program of celiac disease-specific plasma cells.

Disease-specific plasma cells (PCs) reactive with transglutaminase 2 (TG2) or deamidated gluten peptides (DGPs) are abundant in celiac disease (CeD) gut lesions. Their contribution toward CeD pathogenesis is unclear. We assessed expression of markers associated with PC longevity in 15 untreated and 26 treated CeD patients in addition to 13 non-CeD controls and performed RNA sequencing with clonal inference and transcriptomic analysis of 3,251 single PCs. We observed antigen-dependent V-gene selection and stereotypic antibodies. Generation of recombinant DGP-specific antibodies revealed a key role of a heavy chain residue that displays polymorphism, suggesting that immunoglobulin gene polymorphisms may influence CeD-specific antibody responses. We identified transcriptional differences between CeD-specific and non-disease-specific PCs and between short-lived and long-lived PCs. The short-lived CD19+CD45+ phenotype dominated in untreated and short-term-treated CeD, in particular among disease-specific PCs but also in the general PC population. Thus, the disease lesion of untreated CeD is characterized by massive accumulation of short-lived PCs that are not only directed against disease-specific antigens.

ZBTB38 is dispensable for antibody responses.

Members of the broad complex, tram track, bric-a-brac and zinc finger (BTB-ZF) family of transcription factors, such as BCL-6, ZBTB20, and ZBTB32, regulate antigen-specific B cell differentiation, plasma cell longevity, and the duration of antibody production. We found that ZBTB38, a different member of the BTB-ZF family that binds methylated DNA at CpG motifs, is highly expressed by germinal center B cells and plasma cells. To define the functional role of ZBTB38 in B cell responses, we generated mice conditionally deficient in this transcription factor. Germinal center B cells lacking ZBTB38 dysregulated very few genes relative to wild-type and heterozygous littermate controls. Accordingly, mice with hematopoietic-specific deletion of Zbtb38 showed normal germinal center B cell numbers and antibody responses following immunization with hapten-protein conjugates. Memory B cells from these animals functioned normally in secondary recall responses. Despite expression of ZBTB38 in hematopoietic stem cells, progenitors and mature myeloid and lymphoid lineages were also present in normal numbers in mutant mice. These data demonstrate that ZBTB38 is dispensable for hematopoiesis and antibody responses. These conditional knockout mice may instead be useful in defining the functional importance of ZBTB38 in other cell types and contexts.

Do plasma cells contribute to the determination of their lifespan?

Longevity of plasma cells is dependent on their ability to access and reside in so-called survival niches that are predominantly located in the bone marrow. It is proposed that by some process a small fraction of the plasma cells generated in response to new antigen challenges can enter into the long-lived repertoire by displacing existing plasma cells. Several lines of research show that this process is not stochastic as not all resident, long-lived plasma cells appear equally likely to be displaced. The basis of these differences might reside in the niches, the plasma cells or a combination of both factors that intersect to create a distribution of susceptibility to replacement and lifespans. In this review, I consider factors that might vary in plasma cells and thus influence their access to niches and the ability of newly generated plasma cells to survive over the long term.

The Presence and Persistence of Pregnancy-Associated Red Blood Cell Alloantibodies in Blood Donors

Background: Females have higher RBC alloantibody prevalence than males, presumably due to exposure to non-self RBC antigens through pregnancy as well as transfusion. Given the lack of routinely available and longitudinal data on lifelong pregnancy and transfusion histories, few studies have been able to distinguish pregnancy versus transfusion as contributing risk factors for RBC alloantibody induction or for the persistence of RBC alloantibody detectability. We hypothesized that pregnancy would be an important source of persistently detected RBC alloantibodies and investigated this in a longitudinal blood donor database. Study Design and Methods: Donor/donation data were obtained from 4 US blood centers from 2012-2016. RBC antibody screen results and antibody identification (using tube, gel, or solid phase), donor demographics, pregnancy history, and transfusion history were evaluated. Blood donors were included in this analysis if they had an RBC alloantibody detected at any given donation as long as they had at least one subsequent blood donation and antibody screen. Anti-D antibodies detected, but present for < 6 months in females <50 years old were presumed due to passive RhIg and were excluded from this analysis. RBC alloantibody persistence was defined as an RBC alloantibody detected at each subsequent donation following its initial identification and RBC alloantibody evanescence was defined as one or more subsequent donations without re-detection of the alloantibody. Rates of donor alloantibody persistence were calculated as blood donors with persistent alloantibodies divided by blood donors with any alloantibody, and patterns of persistence were characterized by donor sex and presumed alloantibody source exposure. Results: 503 blood donors had a detectable RBC alloantibody and a follow-up antibody screen; 374 (74%) were female and 130 (26%) were male. Of the 374 alloimmunized females, 210 (56%) reported prior pregnancy and no transfusion, 124 (33%) reported prior pregnancy and transfusion, 26 (7%) reported no pregnancy or transfusion, and 12 (3%) reported prior transfusion and no pregnancy. 215/334 (64%) of previously pregnant females had RBC alloantibodies that remained detectable throughout the duration of the study. The mean duration of detectability for persistent antibodies in previously pregnant females was 640 days, compared to a mean time to disappearance of 183 days for evanescent antibodies. In contrast, males and all never-pregnant females were less likely to have persistently detectable antibodies, with 52% (87/167) being in this category (chi square p = 0.008). The mean duration of detectability for persistent antibodies in males and never-pregnant females was 576 days, compared to a mean time to disappearance of 290 days for evanescent antibodies. Previously pregnant females with a reported history of prior transfusion (n=124) had the highest rate (77%) of RBC alloantibody persistence. The alloantibody specificities of previously pregnant females included E (96), D (81), K (78), Fy (21), C (47), MNS (38), and Jk (18). Of these, Fy and non-passive D were most likely to be persistent (each 86%), followed by C (79%), K (74%), E (59%), Jk (55%), and MNS (34%). Conclusion: Data from this multi-center blood donor database, with documented life-long pregnancy and transfusion histories, highlight the role that pregnancy plays in RBC alloimmunization. Importantly, pregnancy was an exposure source in almost all studied RBC alloimmunized female healthy blood donors and was the sole reported exposure in the majority of donors. Although these data cannot definitively identify the source of non-self blood group antigen exposure in blood donors with both pregnancy and transfusion histories, they show that antibodies in previously pregnant females are long lasting. It is possible that length of exposure to non-self RBC antigens, the relatively young age of females during childbearing, long standing fetal white blood cell microchimerism in the maternal circulation, or other variables may impact plasma cell longevity and/or antibody production, and thus the persistence of pregnancy (versus transfusion) associated RBC alloantibodies. Given the numbers and persistence of such RBC alloantibodies, we recommend that pregnancy history be taken into consideration in all RBC alloimmunization studies involving females at or beyond childbearing age. Disclosures Spencer: HemaStrat, LLC: Membership on an entity's Board of Directors or advisory committees.

The Maintenance of Memory Plasma Cells.

It is now well accepted that plasma cells can become long-lived (memory) plasma cells and secrete antibodies for months, years or a lifetime. However, the mechanisms involved in this process of humoral memory, which is crucial for both protective immunity and autoimmunity, still are not fully understood. This article will address a number of open questions. For example: Is longevity of plasma cells due to their intrinsic competence, extrinsic factors, or a combination of both? Which internal signals are involved in this process? What factors provide external support? What survival factors play a part in inflammation and autoreactive disease? Internal and external factors that contribute to the maintenance of memory long-lived plasma cells will be discussed. The aim is to provide useful additional information about the maintenance of protective and autoreactive memory plasma cells that will help researchers design effective vaccines for the induction of life-long protection against infectious diseases and to efficiently target pathogenic memory plasma cells.

Plasma cells: You are what you eat.

Plasma cells are terminally differentiated B lymphocytes that constitutively secrete antibodies. These antibodies can provide protection against pathogens, and their quantity and quality are the best clinical correlates of vaccine efficacy. As such, plasma cell lifespan is the primary determinant of the duration of humoral immunity. Yet dysregulation of plasma cell function can cause autoimmunity or multiple myeloma. The longevity of plasma cells is primarily dictated by nutrient uptake and non-transcriptionally regulated metabolic pathways. We have previously shown a positive effect of glucose uptake and catabolism on plasma cell longevity and function. In this review, we discuss these findings with an emphasis on nutrient uptake and its effects on respiratory capacity, lifespan, endoplasmic reticulum stress, and antibody secretion in plasma cells. We further discuss how some of these pathways may be dysregulated in multiple myeloma, potentially providing new therapeutic targets. Finally, we speculate on the connection between plasma cell intrinsic metabolism and systemic changes in nutrient availability and metabolic diseases.

B cell primary immune responses.

B cell primary immune responses.

Quantification of plasma cell dynamics using mathematical modelling.

Plasma cells (PCs) are the main antibody-producing cells in humans. They are long-lived so that specific antibodies against either pathogens or vaccines are produced for decades. PC longevity is attributed to specific areas within the bone marrow micro-environment, the so-called ‘niche’, providing the cells with required growth and survival factors. With antigen encounters, e.g. infection or vaccination, new PCs are generated and home to the bone marrow where they compete with resident PCs for the niche. We propose a parametrized mathematical model describing healthy PC dynamics in the bone marrow. The model accounts for competition for the niche between newly produced PCs owing to vaccination and resident PCs. Mathematical analysis and numerical simulations of the model allow explanation of the recovery of PC homoeostasis after a vaccine-induced perturbation, and the fraction of vaccine-specific PCs inside the niche. The model enables quantification of the niche-related dynamics of PCs, i.e. the duration of PC transition into the niche and the impact of different rates for PC transitions into and out of the niche on the observed cell dynamics. Ultimately, it provides a potential basis for further investigations in health and disease.

Persistence of long-lived plasma cells and humoral immunity in individuals responding to CD19-directed CAR T-cell therapy

AbstractThe mechanisms underlying the maintenance of long-lasting humoral immunity are not well understood. Studies in mice indicate that plasma cells (PCs) can survive up to a lifetime, even in the absence of regeneration by B cells, implying the presence of long-lived PCs as a mechanism for long-lasting immunity. Evidence from humans treated with anti-CD20, which depletes circulating B cells, also suggests B-cell–independent long-term survival of some PCs. On the other hand, antibody responses may be sustained solely by short-lived PCs with repopulation from clonally related memory B cells. To explore PC longevity and humoral immunity in humans, we investigated the fate of PCs and their antibodies in adult and pediatric patients who received chimeric antigen receptor–based adoptive T-cell immunotherapy targeting CD19 to treat B-cell lineage malignancies (CTL019). Treatment with CTL019 is frequently associated with B-cell aplasia that can persist for years. Serum antibody titers to vaccine-related antigens were measured, and quantitative assessment of B cells and PCs in blood and bone marrow was performed at various time points before and after CTL019 therapy. While total serum immunoglobulin concentrations decline following CTL019-induced B-cell aplasia, several vaccine/pathogen-specific serum immunoglobulin G and A (IgG and IgA) titers remain relatively stable for at least 6 and 12 months posttreatment, respectively. Analysis of bone marrow biopsies after CTL019 revealed 8 patients with persistence of antibody-secreting PCs at least 25 months post-CTL019 infusion despite absence of CD19+CD20+ B cells. These results provide strong evidence for the existence of memory B-cell–independent, long-lived PCs in humans that contribute to long-lasting humoral immunity.

Image‐based systems biology

Image‐based systems biology

Quantitative image analysis of cell colocalization in murine bone marrow

Long-term antibody production is a key property of humoral immunity and is accomplished by long-lived plasma cells. They mainly reside in the bone marrow, whose importance as an organ hosting immunological memory is becoming increasingly evident. Signals provided by stromal cells and eosinophils may play an important role for plasma cell maintenance, constituting a survival microenvironment. In this joint study of experiment and theory, we investigated the spatial colocalization of plasma cells, eosinophils and B cells by applying an image-based systems biology approach. To this end, we generated confocal fluorescence microscopy images of histological sections from murine bone marrow that were subsequently analyzed in an automated fashion. This quantitative analysis was combined with computer simulations of the experimental system for hypothesis testing. In particular, we tested the observed spatial colocalization of cells in the bone marrow against the hypothesis that cells are found within available areas at positions that were drawn from a uniform random number distribution. We find that B cells and plasma cells highly colocalize with stromal cells, to an extent larger than in the simulated random situation. While B cells are preferentially in contact with each other, i.e., form clusters among themselves, plasma cells seem to be solitary or organized in aggregates, i.e., loosely defined groups of cells that are not necessarily in direct contact. Our data suggest that the plasma cell bone marrow survival niche facilitates colocalization of plasma cells with stromal cells and eosinophils, respectively, promoting plasma cell longevity.

Plasma cell formation, secretion, and persistence: the short and the long of it.

B cells can be activated by cognate antigen, anti-B-cell receptor antibody, complement receptors, or polyclonal stimulators like lipopolysaccharide; the overall result is a large shift in RNA processing to the secretory-specific form of immunoglobulin (Ig) heavy chain mRNA and an upregulation of Igh mRNA amounts. Associated with this shift is the large-scale induction of Ig protein synthesis and the unfolded protein response to accommodate the massive quantity of secretory Ig that results. Stimulation to secretion also produces major structural accommodations and stress, with extensive generation of endoplasmic reticulum and Golgi as part of the cellular architecture. Reactive oxygen species can lead to either activation or apoptosis based on context and the high or low oxygen tension surrounding the cells. Transcription elongation factor ELL2 plays an important role in the induction of Ig secretory mRNA production, the unfolded protein response, and gene expression during hypoxia. After antigen stimulation, activated B cells from either the marginal zones or follicles can produce short-lived antibody secreting cells; it is not clear whether cells from both locations can become long-lived plasma cells. Autophagy is necessary for plasma cell long-term survival through the elimination of some of the accumulated damage to the ER from producing so much protein. Survival signals from the bone marrow stromal cells also contribute to plasma cell longevity, with BCMA serving a potentially unique survival role. Integrating the various information pathways converging on the plasma cell is crucial to the development of their long-lived, productive immune response.

What Is and What Should Always Have Been: Long-Lived Plasma Cells Induced by T Cell–Independent Antigens

It is well accepted that Ag-induced B cell differentiation often results in the generation of exceptionally long-lived plasma cells. Much of the work supporting this viewpoint stems from studies focused on germinal center-derived plasma cells secreting high-affinity isotype-switched Abs in mice immunized with T cell-dependent Ags. In contrast, less attention has been devoted to understanding Ab responses to T cell-independent Ags and pathogens. In this study, we review recent work showing that T cell-independent Ags consisting of either polysaccharides or LPSs also induce the formation of long-lived plasma cells, despite their general inability to sustain germinal center responses. This new information provides a framework for more fully understanding the forces underlying immunity to pathogens that resist T cell recognition and the extracellular cues governing plasma cell longevity.