Memory B and memory plasma cells

Autoantibodies from long-lived 'memory' plasma cells of NZB/W mice drive immune complex nephritis

OBJECTIVES

We have previously shown that both short- and long-lived plasma cells (PCs) significantly contribute to autoantibody production in NZB/W mice as a model of lupus nephritis. The aim of this study was to determine the role of autoreactive long-lived (memory) PCs refractory to immunosuppression and B cell depletion in the pathogenesis of systemic lupus erythematosus.

METHODS

Splenic CD138+ antibody-secreting cells (ASCs) from >6-month-old NZB/W mice with high titres of anti-dsDNA autoantibodies or from Balb/c mice 5 days after secondary immunisation with ovalbumin (OVA) were adoptively transferred to immunodeficient Rag1(-/-) mice, in which the development of nephritis was investigated by measuring proteinuria. Total IgG and IgM as well as anti-dsDNA and anti-OVA antibody levels were followed up by ELISA. After 21 weeks the recipient mice were sacrificed so that PCs in spleen and bone marrow could be analysed using ELISPOT and flow cytometry and renal immunohistology performed.

RESULTS

The adoptive transfer of NZB/W and anti-OVA ASCs resulted in the continuous generation of anti-dsDNA antibodies and anti-OVA antibodies, respectively, exclusively by long-lived PCs that had homed to the spleen and bone marrow of recipient Rag1(-/-) mice. Rag1(-/-) mice generating autoantibodies including anti-dsDNA had reduced survival, proteinuria and immune complex nephritis with C1q, C3, IgG and IgM deposits 21 weeks after transfer.

CONCLUSIONS

These findings demonstrate that autoantibodies exclusively secreted by long-lived (memory) PCs contribute to autoimmune pathology and should be considered as candidate targets for future therapeutic strategies.

Memory B cells in mouse models

One of the principles behind vaccination, as shown by Edward Jenner in 1796, and host protection is immunological memory, and one of the cells central to this is the antigen-experienced memory B cell that responds rapidly upon re-exposure to the initiating antigen. Classically, memory B cells have been defined as progenies of germinal centre (GC) B cells expressing isotype-switched and substantially mutated B cell receptors (BCRs), that is, membrane-bound antibodies. However, it has become apparent over the last decade that this is not the only pathway to B cell memory. Here, we will discuss memory B cells in mice, as defined by (1) cell surface markers; (2) multiple layers; (3) formation in a T cell-dependent and either GC-dependent or GC-independent manner; (4) formation in a T cell-independent fashion. Lastly, we will touch upon memory B cells in; (5) mouse models of autoimmune diseases.

Analysis of cross-reactive antibodies recognizing the fusion loop of envelope protein and correlation with neutralizing antibody titers in Nicaraguan dengue cases

Dengue virus (DENV) is the leading cause of arboviral diseases in humans worldwide. The envelope (E) protein of DENV is the major target of neutralizing antibodies (Abs). Previous studies have shown that a significant proportion of anti-E Abs in human serum after DENV infection recognize the highly conserved fusion loop (FL) of E protein. The role of anti-FL Abs in protection against subsequent DENV infection versus pathogenesis remains unclear. A human anti-E monoclonal Ab was used as a standard in a virion-capture ELISA to measure the concentration of anti-E Abs, [anti-E Abs], in dengue-immune sera from Nicaraguan patients collected 3, 6, 12 and 18 months post-infection. The proportion of anti-FL Abs was determined by capture ELISA using virus-like particles containing mutations in FL, and the concentration of anti-FL Abs, [anti-FL Abs], was calculated. Neutralization titers (NT₅₀) were determined using a previously described flow cytometry-based assay. Analysis of sequential samples from 10 dengue patients revealed [anti-E Abs] and [anti-FL Abs] were higher in secondary than in primary DENV infections. While [anti-FL Abs] did not correlate with NT₅₀ against the current infecting serotype, it correlated with NT₅₀ against the serotypes to which patients had likely not yet been exposed (“non-exposed” serotypes) in 14 secondary DENV3 and 15 secondary DENV2 cases. These findings demonstrate the kinetics of anti-FL Abs and provide evidence that anti-FL Abs play a protective role against “non-exposed” serotypes after secondary DENV infection.

The four serotypes of dengue virus (DENV) are the leading cause of mosquito-borne viral diseases in humans. Whereas infection with one DENV serotype is thought to confer protection against re-infection with that serotype, it can be either protective or enhance disease severity upon subsequent (“secondary”) infection with a different serotype. The envelope (E) protein of DENV is the major target of neutralizing antibodies. Previously, we and others reported that a significant proportion of anti-E antibodies in human dengue-immune sera recognize the fusion loop (FL) of E protein. The role of anti-FL antibodies in protection against subsequent DENV infections versus pathogenesis remains unclear. In this study, we developed capture ELISAs to measure the concentrations of anti-E and anti-FL antibodies in sera of Nicaraguan dengue patients collected 3, 6, 12 and 18 months post-illness, and investigated the kinetics of these antibodies and their relationship to neutralization activity. While the concentrations of anti-FL antibodies did not correlate with 50% neutralization titers (NT₅₀) against the current infecting serotype, it correlated with NT₅₀ against serotypes to which patients had likely not yet been exposed (“non-exposed” serotypes) in secondary DENV infections. These findings provide evidence that anti-FL antibodies play a protective role against “non-exposed” serotypes after secondary DENV infection.

The hierarchical process of differentiation of long-lived antibody-secreting cells is dependent on integrated signals derived from antigen and IL-17A

Switched CD19-positive memory B cells purified from mice with chronic immune response against Thalassophrynenattereri venom proteins were cultured with venom or cytokines. Our results confirm the existence of a hierarchic process of differentiation: activated memory B cells progressively acquire increasing levels of CD138 and decreasing levels of CD45R/B220 to finally arrive at ASC with B220^neg phenotype, which are IgG1-secreting cells. Only Bmem from peritoneal cavity or bone marrow of VTn immunized mice presented the capacity to generate ASC functionally active. IL-17A or IL-21/IL-23/IL-33 improves the ability of venom to induce intracellular IgG of peritoneal derived-ASC. Cognate stimulation with venom and IL-17A is sufficient to down-regulate the expression of CD45R/B220. BAFF-R is up-regulated in splenic or medullar derived-ASC stimulated by venom, CpG or cytokines. Only splenic derived-ASC up-regulate Bcl-2 expression after CpG or the combination of IL-21/IL-23/IL-33 stimulation. Finally, the activation of ASC for IgG1 secretion is triggered by venom proteins in peritoneal cavity and by IL-17A in medullar niche. These results show the importance of the integration of signals downstream of BCR and IL17-A receptors in modulating ASC differentiation, focusing in the microenvironment niche of their generation.

Murine marginal zone B cells play a role in Vibrio cholerae LPS antibody responses

The emergence of Vibrio cholerae (Vc) lipopolysaccharide (LPS) as a lead protective antigen for a cholera subunit vaccine has increased the interest in what type of B cell is best suited to generate anti-Vc LPS antibodies. A related question is what form of LPS is the most immunogenic. C57Bl/6 (B6) neonatal mice (10 days old) whose marginal zone (MZ) B cell compartment is still maturing and two lines of knockout mice that either lack the signaling mechanism required for the maturation of MZ B cells or that lack a receptor required for MZ B cell retention in the MZ were used to determine the role of MZ B cells in anti-Vc LPS antibody responses. Data support the conclusion that MZ B cells play a significant role in the anti-Vc LPS antibody response. Serum and vibriocidal antibody titers also depend on whether the Vc LPS is purified or bacterial cell-associated.

High-avidity and potently neutralizing cross-reactive human monoclonal antibodies derived from secondary dengue virus infection

The envelope (E) protein of dengue virus (DENV) is the major target of neutralizing antibodies (Abs) and vaccine development. Previous studies of human dengue-immune sera reported that a significant proportion of anti-E Abs, known as group-reactive (GR) Abs, were cross-reactive to all four DENV serotypes and to one or more other flaviviruses. Based on studies of mouse anti-E monoclonal antibodies (MAbs), GR MAbs were nonneutralizing or weakly neutralizing compared with type-specific MAbs; a GR response was thus not regarded as important for vaccine strategy. We investigated the epitopes, binding avidities, and neutralization potencies of 32 human GR anti-E MAbs. In addition to fusion loop (FL) residues in E protein domain II, human GR MAbs recognized an epitope involving both FL and bc loop residues in domain II. The neutralization potencies and binding avidities of GR MAbs derived from secondary DENV infection were stronger than those derived from primary infection. GR MAbs derived from primary DENV infection primarily blocked attachment, whereas those derived from secondary infection blocked DENV postattachment. Analysis of the repertoire of anti-E MAbs derived from patients with primary DENV infection revealed that the majority were GR, low-avidity, and weakly neutralizing MAbs, whereas those from secondary infection were primarily GR, high-avidity, and potently neutralizing MAbs. Our findings suggest that the weakly neutralizing GR anti-E Abs generated from primary DENV infection become potently neutralizing MAbs against the four serotypes after secondary infection. The observation that the dengue immune status of the host affects the quality of the cross-reactive Abs generated has implications for new strategies for DENV vaccination.

Detection of influenza A virus homo- and heterosubtype-specific memory B-cells using a novel protein microarray-based analysis tool

The emergence of the A(H1N1) 2009 pandemic influenza virus was initially seen as a major world-wide health concern since a low degree of immunity to this virus strain was anticipated. However, age-specific infection attack rates and age-specific differences in seroresponse indicate that pre-existing immunity may have played a significant role in protection especially in older age groups. This study describes the use of a protein microarray as a multiplex analysis tool for detection of influenza virus H1 strain-specific memory B-cells before and after infection with A(H1N1)pdm09. The discrimination was based on detection of specific antibodies in culture supernatants from polyclonally stimulated B-cells against recombinant influenza virus HA1 proteins representing influenza virus subtypes H1 through H9. The protein microarray proved sensitive and specific for antibody detection in culture supernatants of B-cells, and with the potential to deduce a person's history of infection with particular influenza virus variants, including A(H1N1)pdm09. Blood samples obtained from different age groups prior to the pandemic in 2009 partly showed the presence of B-cells producing antibodies binding to the closely related A(H1N1) 1918 pandemic influenza virus, and of which the magnitude increased with age. These cross-reactive antibodies were produced by single memory B-cells present in these donors, and either bind to epitopes on HA1 which are shared within different H1 strains (homosubtypic response) or shared between different subtypes (heterosubtypic response).

Noncoordinate expression of J-chain and Blimp-1 define nurse shark plasma cell populations during ontogeny

B-lymphocyte-induced maturation protein 1 (Blimp-1) is the master regulator of plasma cell development, controlling genes such as those encoding J-chain and secretory Ig heavy chain. However, some mammalian plasma cells do not express J-chain, and mammalian B1 cells secrete "natural" IgM antibodies without upregulating Blimp-1. While these results have been controversial in mammalian systems, here we describe subsets of normally occurring Blimp-1(-) antibody-secreting cells in nurse sharks, found in lymphoid tissues at all ontogenic stages. Sharks naturally produce large amounts of both pentameric (classically "19S") and monomeric (classically "7S") IgM, the latter an indicator of adaptive immunity. Consistent with the mammalian paradigm, shark Blimp-1 is expressed in splenic 7S IgM-secreting cells, though rarely detected in the J-chain(+) cells producing 19S IgM. Although IgM transcript levels are lower in J-chain(+) cells, these cells nevertheless secrete 19S IgM in the absence of Blimp-1, as demonstrated by ELISPOT and metabolic labeling. Additionally, cells in the shark BM equivalent (epigonal) are Blimp-1(-). Our data suggest that, in sharks, 19S-secreting cells and other secreting memory B cells in the epigonal are maintained for long periods without Blimp-1, but like in mammals, Blimp-1 is required for terminating the B-cell program following an adaptive immune response in the spleen.

TLR2, TLR4 and the MyD88 signaling are crucial for the in vivo generation and the longevity of long-lived antibody-secreting cells

This study was undertaken to gain better insights into the role of TLRs and MyD88 in the development and differentiation of memory B cells, especially of ASC, during the Th2 polarized memory response induced by Natterins. Our in vivo findings demonstrated that the anaphylactic IgG1 production is dependent on TLR2 and MyD88 signaling, and that TLR4 acts as adjuvant accelerating the synthesis of high affinity-IgE. Also, TLR4 (MyD88-independent) modulated the migration of innate-like B cells (B1a and B2) out of the peritoneal cavity, and the emigration from the spleen of B1b and B2 cells. TLR4 (MyD88-independent) modulated the emigration from the spleen of Bmem as well as ASC B220^pos. TLR2 triggered to the egress from the peritoneum of Bmem (MyD88-dependent) and ASC B220^pos (MyD88-independent). We showed that TLR4 regulates the degree of expansion of Bmem in the peritoneum (MyD88-dependent) and in BM (MyD88-independent) as well as of ASC B220^neg in the spleen (MyD88-independent). TLR2 regulated the intensity of the expansion of Bmem (MyD88-independent) and ASC B220^pos (MyD88-dependent) in BM. Finally, TLR4 signals sustained the longevity of ASC B220^pos (MyD88-independent) and ASC B220^neg into the peritoneum (MyD88-dependent) and TLR2 MyD88-dependent signaling supported the persistence of B2 cells in BM, Bmem in the spleen and ASC B220^neg in peritoneum and BM. Terminally differentiated ASC B220^neg required the cooperation of both signals through TLR2/TLR4 via MyD88 for longevity in peritoneum, whereas Bmem required only TLR2/MyD88 to stay in spleen, and ASC B220^pos rested in peritoneum dependent on TLR4 signaling. Our data sustain that earlier events on memory B cells differentiation induced in secondary immune response against Natterins, after secondary lymph organs influx and egress, may be the key to determining peripheral localization of innate-like B cells and memory B cells as ASC B220^pos and ASC B220^neg.

T cell-dependent IgM memory B cells generated during bacterial infection are required for IgG responses to antigen challenge

Immunological memory has long considered to be harbored in B cells that express high-affinity class-switched IgG. IgM-positive memory B cells can also be generated following immunization, although their physiological role has been unclear. In this study, we show that bacterial infection elicited a relatively large population of IgM memory B cells that were uniquely identified by their surface expression of CD11c, CD73, and programmed death-ligand 2. The cells lacked expression of cell surface markers typically expressed by germinal center B cells, were CD138 negative, and did not secrete Ab ex vivo. The population was also largely quiescent and accumulated somatic mutations. The IgM memory B cells were located in the region of the splenic marginal zone and were not detected in blood or other secondary lymphoid organs. Generation of the memory cells was CD4 T cell dependent and required IL-21R signaling. In vivo depletion of the IgM memory B cells abrogated the IgG recall responses to specific Ag challenge, demonstrating that the cell population was required for humoral memory, and underwent class-switch recombination following Ag encounter. Our findings demonstrate that T cell-dependent IgM memory B cells can be elicited at high frequency and can play an important role in maintaining long-term immunity during bacterial infection.

CD49b/CD69-Dependent Generation of Resting T Helper Cell Memory

In the absence of antigen, memory T helper (Th) cells are maintained in a resting state. Recently it has been shown that bone marrow (BM) is a major reservoir of resting memory Th cells. In a given immune response, less than 10% of the activated CD4 T cells are recruited to the pool of resting BM memory Th cells. Here we review recent evidence that CD69 and CD49b control homing of memory Th cell precursors to the BM. During the effector phase of an immune response, about 10% of activated CD4 T cells in the spleen express both CD69 and CD49b, and thus qualify as precursors of resting memory Th cells of BM. Loss or blockade of CD69 and CD49b expression on CD4 T cells impairs the generation of resting memory Th cells in the BM. Moreover, in the absence of BM memory Th cells in CD69-deficient mice, T-cell help for B cells is impaired, confirming the central role of BM memory Th cells in the maintenance of immunological memory.

Utilizing poxviral vectored vaccines for antibody induction-progress and prospects

•

Poxviral vectors are now regarded as robust tools for B cell and antibody induction.

•

Antibody responses can be induced against the vector as well as a transgene.

•

Increasing application is seen in heterologous prime–boost immunization regimes.

•

Effective veterinary poxviral vaccine products are now licensed.

•

Promising results of antibody induction are being reported in human clinical trials.

Over the last decade, poxviral vectors emerged as a mainstay approach for the induction of T cell-mediated immunity by vaccination, and their suitability for human use has led to widespread clinical testing of candidate vectors against infectious intracellular pathogens and cancer. In contrast, poxviruses have been widely perceived in the vaccine field as a poor choice of vector for the induction of humoral immunity. However, a growing body of data, from both animal models and recent clinical trials, now suggests that these vectors can be successfully utilized to prime and boost B cells and effective antibody responses. Significant progress has been made in the context of heterologous prime–boost immunization regimes, whereby poxviruses are able to boost responses primed by other vectors, leading to the induction of high-titre antigen-specific antibody responses. In other cases, poxviral vectors have been shown to stimulate humoral immunity against both themselves and encoded transgenes, in particular viral surface proteins such as influenza haemagglutinin. In the veterinary field, recombinant poxviral vectors have made a significant impact with numerous vectors licensed for use against a variety of animal viruses. On-going studies continue to explore the potential of poxviral vectors to modulate qualitative aspects of the humoral response, as well as their amenability to adjuvantation seeking to improve quantitative antibody immunogenicity. Nevertheless, the underlying mechanisms of B cell induction by recombinant poxviruses remain poorly defined, and further work is necessary to help guide the rational optimization of future poxviral vaccine candidates aiming to induce antibodies.

Carbon nanotube-protein carriers enhance size-dependent self-adjuvant antibody response to haptens

Carbon nanotubes (CNTs) are nanomaterials with interesting emerging applications. Their properties make CNTs excellent candidates for use as new nanovehicles in drug delivery, immunization and diagnostics. In the current study, we assessed the immune-response-amplifying properties of CNTs to haptens by using azoxystrobin, the first developed strobilurin fungicide, as a model analyte. An azoxystrobin derivative bearing a carboxylated spacer arm (hapten AZc6) was covalently coupled to bovine serum albumin (BSA), and the resulting BSA-AZc6 conjugate was covalently linked to four functionalized CNTs of different shapes and sizes, varying in diameter and length. These four types of CNT-based constructs were obtained using efficient, fast, and easy functionalization procedures based on microwave-assisted chemistry. New Zealand rabbits and BALB/c mice were immunized with BSA-AZc6 alone and with the four CNT-BSA-AZc6 constructs, both with and without Freund's adjuvant. The IgG-type antibody responses were assessed in terms of the titer and affinity, paying special attention to the relationship between the immune response and the size and shape of the employed CNTs. Immunization with CNT-BSA-AZc6 resulted in enhanced titers and excellent affinities for azoxystrobin. More important, remarkable IgG responses were obtained even in the absence of an adjuvant, thus proving the self-adjuvanting capability of CNTs. Immunogens were able to produce strong anti-azoxystrobin immune responses in rabbits even when administered at a BSA-AZc6 conjugate dose as low as 0.05 μg. The short and thick CNT-BSA-AZc6 construct produced the best antibody response under all tested conditions.

A functional BCR in human IgA and IgM plasma cells

IgA and IgM human plasma cells express a functional BCR on their cell surface and can therefore respond to antigenic stimulation.

Activation of the B cell antigen receptor triggers reactivation of latent Kaposi's sarcoma-associated herpesvirus in B cells

Kaposi's sarcoma-associated herpesvirus (KSHV) is an oncogenic herpesvirus and the cause of Kaposi's sarcoma, primary effusion lymphoma (PEL) and multicentric Castleman's disease. Latently infected B cells are the main reservoir of this virus in vivo, but the nature of the stimuli that lead to its reactivation in B cells is only partially understood. We established stable BJAB cell lines harboring latent KSHV by cell-free infection with recombinant virus carrying a puromycin resistance marker. Our latently infected B cell lines, termed BrK.219, can be reactivated by triggering the B cell receptor (BCR) with antibodies to surface IgM, a stimulus imitating antigen recognition. Using this B cell model system we studied the mechanisms that mediate the reactivation of KSHV in B cells following the stimulation of the BCR and could identify phosphatidylinositol 3-kinase (PI3K) and X-box binding protein 1 (XBP-1) as proteins that play an important role in the BCR-mediated reactivation of latent KSHV.

B-cell subset alterations and correlated factors in HIV-1 infection

OBJECTIVES

During HIV-1 infection, the development, phenotype, and functionality of B cells are impaired. Transitional B cells and aberrant B-cell populations arise in blood, whereas a declined percentage of resting memory B cells is detected. Our study aimed at pinpointing the demographic, immunological, and viral factors driving these pathological findings, and the role of antiretroviral therapy in reverting these alterations.

DESIGN

B-cell phenotype and correlating factors were evaluated.

METHODS

Variations in B-cell subsets were evaluated by flow cytometry in HIV-1-infected individuals naive to therapy, elite controllers, and patients treated with antiretroviral drugs (virological control or failure). Multivariable analysis was performed to identify variables independently associated with the B-cell alterations.

RESULTS

Significant differences were observed among patients' groups in relation to all B-cell subsets. Resting memory B cells were preserved in patients naive to therapy and elite controllers, but reduced in treated patients. Individuals naive to therapy and experiencing multidrug failure, as well as elite controllers, had significantly higher levels of activated memory B cells compared to healthy controls. In the multivariate analysis, plasma viral load and nadir CD4 T cells independently correlated with major B-cell alterations. Coinfection with hepatitis C but not hepatitis B virus also showed an impact on specific B-cell subsets. Successful protracted antiretroviral treatment led to normalization of all B-cell subsets with exception of resting memory B cells.

CONCLUSION

Our results indicate that viremia and nadir CD4 T cells are important prognostic markers of B-cell perturbations and provide evidence that resting memory B-cell depletion during chronic infection is not reverted upon successful antiretroviral therapy.

Why do we need IgM memory B cells?

Immunological memory is our reservoir of ready-to-use antibodies and memory B cells. Because of immunological memory a secondary infection will be very light or not occur at all. Antibodies and cells, generated in the germinal center in response to the first encounter with antigen, are highly specific, remain in the organism virtually forever and are mostly of IgG isotype. Long lived plasma cells homing to the bone marrow ensure the constant production of protective antibodies, whereas switched memory B cells proliferate and differentiate in response to secondary challenge. IgM memory B cells represent our first-line defense against infections. They are generated by a T-cell independent mechanism probably triggered by Toll-like receptor-9. They produce natural antibodies with anti-bacterial specificity and the spleen is indispensable for their maintenance. We will review the characteristics and functions of IgM memory B cells that explain their importance in the immediate protection from pathogens. IgM memory B cells, similar to mouse B-1a B cells, may be a remnant of a primitive immune system that developed in the spleen of cartilaginous fish and persisted throughout evolution notwithstanding the sophisticated tools of the adaptive immune system.

Adaptive immunity in rheumatic diseases: bystander or pathogenic player?

Rheumatic diseases comprise a wide spectrum of different conditions. Some are caused by disturbances of the adaptive immune system, while defects in innate immune responses have been identified for others. In between are a variety of multifactorial diseases for which the evidence for a causative involvement of the adaptive immune system is still controversial. In these cases, availability of novel drugs that target key players of the adaptive immune system have improved our understanding of the relevance of adaptive immunity to the disease process, but it has also generated unprecedented findings. Rheumatoid arthritis (RA) is a prototypic example of a disease in which the relative contribution of adaptive immunity to disease pathogenesis is incompletely understood. Although numerous markers have been identified that reflect an activated adaptive immune system, several caveats render interpretation of these findings difficult. For one, the very early immune responses initiating disease are likely to take place before an individual is identified as a patient, and are thus difficult to study in the human. Furthermore, increasing evidence points to pathogenetically distinct subgroups within the clinical diagnosis RA, offering the possibility that adaptive immune responses might be relevant to one subgroup but not the other. In addition, many indications for an adaptive immune system involvement are based on associations for which the underlying mechanism is often unknown. Finally, therapeutic interventions targeting the adaptive immune system have generated heterogeneous results. The present review addresses these issues by placing adaptive immune responses in the context of rheumatic diseases, and by reviewing the evidence for a contribution of adaptive immunity to RA.

Maintenance of anti-Sm/RNP autoantibody production by plasma cells residing in ectopic lymphoid tissue and bone marrow memory B cells

Although ectopic lymphoid tissue formation is associated with many autoimmune diseases, it is unclear whether it serves a functional role in autoimmune responses. 2,6,10,14-Tetramethylpentadecane causes chronic peritoneal inflammation and lupus-like disease with autoantibody production and ectopic lymphoid tissue (lipogranuloma) formation. A novel transplantation model was used to show that transplanted lipogranulomas retain their lymphoid structure over a prolonged period in the absence of chronic peritoneal inflammation. Recipients of transplanted lipogranulomas produced anti-U1A autoantibodies derived exclusively from the donor, despite nearly complete repopulation of the transplanted lipogranulomas by host lymphocytes. The presence of ectopic lymphoid tissue alone was insufficient, as an anti-U1A response was not generated by the host in the absence of ongoing peritoneal inflammation. Donor-derived anti-U1A autoantibodies were produced for up to 2 mo by plasma cells/plasmablasts recruited to the ectopic lymphoid tissue by CXCR4. Although CD4(+) T cells were not required for autoantibody production from the transplanted lipogranulomas, de novo generation of anti-U1A plasma cells/plasmablasts was reduced following T cell depletion. Significantly, a population of memory B cells was identified in the bone marrow and spleen that did not produce anti-U1A autoantibodies unless stimulated by LPS to undergo terminal differentiation. We conclude that 2,6,10,14-tetramethylpentadecane promotes the T cell-dependent development of class-switched, autoreactive memory B cells and plasma cells/plasmablasts. The latter home to ectopic lymphoid tissue and continue to produce autoantibodies after transplantation and in the absence of peritoneal inflammation. However, peritoneal inflammation appears necessary to generate autoreactive B cells de novo.

B cell depletion in immune thrombocytopenia reveals splenic long-lived plasma cells

Primary immune thrombocytopenia (ITP) is a disorder caused by autoantibody-mediated platelet destruction and decreased platelet production. Rituximab, a B cell-depleting agent, has become the first-line treatment for ITP; however, patients with refractory disease usually require splenectomy. We identified antibody-secreting cells as the major splenic B cell population that is resistant to rituximab. The phenotype, antibody specificity, and gene expression profile of these cells were characterized and compared to those of antibody-secreting cells from untreated ITP spleens and from healthy tissues. Antiplatelet-specific plasma cells (PC) were detected in the spleens of patients with ITP up to 6 months after rituximab treatment, and the PC population displayed a long-lived program similar to the one of bone marrow PC, thus explaining for most of these patients the absence of response to rituximab and the response to splenectomy. When analyzed by multiplex PCR at the single-cell level, normal splenic PC showed a markedly different gene expression profile, with an intermediate signature, including genes characteristic of both long-lived PC and proliferating plasmablasts. Surprisingly, long-lived PC were not detected in untreated ITP spleens. These results suggest that the milieu generated by B cell depletion promotes the differentiation and settlement of long-lived PC in the spleen.

Gastrointestinal B-cell lymphomas: From understanding B-cell physiology to classification and molecular pathology

The gut is the most common extranodal site where lymphomas arise. Although all histological lymphoma types may develop in the gut, small and large B-cell lymphomas predominate. The sometimes unexpected finding of a lymphoid lesion in an endoscopic biopsy of the gut may challenge both the clinician (who is not always familiar with lymphoma pathogenesis) and the pathologist (who will often be hampered in his/her diagnostic skill by the limited amount of available tissue). Moreover, the past 2 decades have spawned an avalanche of new data that encompasses both the function of the reactive B-cell as well as the pathogenic pathways that lead to its neoplastic counterpart, the B-cell lymphoma. Therefore, this review aims to offer clinicians an overview of B-cell lymphomas in the gut, and their pertinent molecular features that have led to new insights regarding lymphomagenesis. It addresses the question as how to incorporate all presently available information on normal and neoplastic B-cell differentiation, and how this knowledge can be applied in daily clinical practice (e.g., diagnostic tools, prognostic biomarkers or therapeutic targets) to optimalise the managment of this heterogeneous group of neoplasms.

Kinetics of antibody and memory B cell responses after MMR immunization in children and young adults

The persistence of antigen-specific memory B-cells (MBCs) in children and young adults long time after vaccination against measles, mumps and rubella (MMR) is not known. Here we have looked at the Swedish immunization program and examined children 1-10 years after the first MMR dose in early childhood, as well as young adults 7-18 years after the second dose of MMR. We show that Ab titers and MBCs against measles and rubella have different kinetics, indicating that the MBC pool and the corresponding Ab titers are regulated independently. These data fit well with other findings that continuous IgG secretion comes from long-lived plasma cells and not MBCs. We also demonstrate that individuals with low post-vaccination Ab titers might have an adequate MBC response. It remains to be shown if memory B-cells provide the same protection as specific antibodies, but our data is a valuable complement to the incomplete knowledge about correlates of protection after vaccination.

In vitro generation of long-lived human plasma cells

Plasma cells (PCs), the terminal effectors of humoral immunity, are short-lived unless supported by niche environments in which they may persist for years. No model system has linked B cell activation with niche function to allow the in vitro generation of long-lived PCs. Thus, the full trajectory of B cell terminal differentiation has yet to be investigated in vitro. In this article, we describe a robust model for the generation of polyclonal long-lived human PCs from peripheral blood B cells. After a proliferative plasmablast phase, PCs persist in the absence of cell division, with viability limited only by elective culture termination. Conservative predictions for PC life expectancy are 300 d, but with the potential for significantly longer life spans for some cells. These long-lived PCs are preferentially derived from memory B cells, and acquire a CD138(high) phenotype analogous to that of human bone marrow PCs. Analysis of gene expression across the system defines clusters of genes with related dynamics and linked functional characteristics. Importantly, genes in these differentiation clusters demonstrate a similar overall pattern of expression for in vitro and ex vivo PCs. In vitro PCs are fully reprogrammed to a secretory state and are adapted to their secretory load, maintaining IgG secretion of 120 pg/cell/day in the absence of XBP1 mRNA splicing. By establishing a set of conditions sufficient to allow the development and persistence of mature human PCs in vitro, to our knowledge, we provide the first platform with which to sequentially explore and manipulate each stage of human PC differentiation.

Rationale of anti-CD19 immunotherapy: an option to target autoreactive plasma cells in autoimmunity

Anti-CD20 therapy using rituximab directly targeting B cells has been approved for treatment of non-Hodgkin lymphoma, rheumatoid arthritis and anti-neutrophil cytoplasmic antibody-associated vasculitides and has led to reappreciation of B-lineage cells for anti-rheumatic treatment strategies. Moreover, blocking B-cell activating factor with belimumab, a drug that is licensed for treatment of active, seropositive systemic lupus erythematosus (SLE), represents an alternative, indirect anti-B-cell approach interfering with proper B-cell development. While these approaches apparently have no substantial impact on antibody-secreting plasma cells, challenges to improve the treatment of difficult-to-treat patients with SLE remain. In this context, anti-CD19 antibodies have the promise to directly target autoantibody-secreting plasmablasts and plasma cells as well as early B-cell differentiation stages not covered by anti-CD20 therapy. Currently known distinct expression profiles of CD19 by human plasma cell subsets, experiences with anti-CD19 therapies in malignant conditions as well as the rationale of targeting autoreactive plasma cells in patients with SLE are discussed in this review.

New concepts in the generation and functions of IgA

The intestinal mucosa contains the largest population of antibody-secreting plasma cells in the body, and in humans several grams of secretory immunoglobulin A (SIgA) are released into the intestine each day. In the gut lumen, SIgA serves as a first-line barrier that protects the epithelium from pathogens and toxins. Recently, next-generation sequencing has revolutionized our understanding of the nature of the intestinal microbiota and has also shed new light on the important roles of SIgA in the regulation of host-commensal homeostasis. Here, I discuss pathways of IgA induction in the context of SIgA specificity and function.

How the interval between prime and boost injection affects the immune response in a computational model of the immune system

The immune system is able to respond more vigorously to the second contact with a given antigen than to the first contact. Vaccination protocols generally include at least two doses, in order to obtain high antibody titers. We want to analyze the relation between the time elapsed from the first dose (priming) and the second dose (boost) on the antibody titers. In this paper, we couple in vivo experiments with computer simulations to assess the effect of delaying the second injection. We observe that an interval of several weeks between the prime and the boost is necessary to obtain optimal antibody responses.

Immunopathological events initiated and maintained by pathogenic IgG autoantibodies in an experimental autoimmune kidney disease

The experimental models of Heymann nephritis (HN) and slowly progressive Heymann nephritis (SPHN) give us rare opportunities to investigate the etiologies and pathogenesis of two immunopathological processes in rats leading to: (1) autoimmune disease, where the autoimmune disease HN and SPHN is initiated and maintained by cross-reactive pathogenic IgG autoantibodies (aabs) directed against the renal proximal convoluted tubules' brush border (BB) cells - where the nephritogenic antigen (ag) is produced and localized - damaging and releasing BB associated nephritogenic ag into the circulation which in turn contributes to continuation of the autoimmune disease; and (2) immune complex glomerulonephritis, where the glomerular injury is initiated, proceeding into a chronic progressive disease by depositing immune complexes (ICs) - made up of a glomerular epithelial cell produced endogenous nephritogenic ag and the developing pathogenic IgG aab directed against the nephritogenic ag, and complement components - on the epithelial side of the glomerular basement membrane. We also observed how the normally functioning immune system is able to avert autoimmune disease developments by circulating specific non-pathogenic IgM aabs clearing the system of intracytoplasmic ags released from cells at the end of their life spans or following damage by toxic agents. We also described how an autoimmune disease SPHN can be prevented and when present terminated by the implementation of a new vaccination technique we have developed and call modified vaccination technique. By increasing the specific IgM aab production against the native nephritogenic ag - by injecting ICs made up of: [nephritogenic ag X homologous anti-nephritogenic ag IgM ab] in slight ag excess into SPHN rats - pathogenic IgG aab producing native and modified nephritogenic ags were removed from the circulation and termination of the autoimmune disease causing immune events was achieved. Even though HN and SPHN are not well-known disease models, their studies are important because the etiologies and pathogenesis of two conditions - that can also occur in humans, namely autoimmune diseases and membranous glomerulonephritis - can be simultaneously investigated.

Bone marrow of NZB/W mice is the major site for plasma cells resistant to dexamethasone and cyclophosphamide: implications for the treatment of autoimmunity

Antibodies contribute to the pathogenesis of many chronic inflammatory diseases, including autoimmune disorders and allergies. They are secreted by proliferating plasmablasts, short-lived plasma cells and non-proliferating, long-lived memory plasma cells. Memory plasma cells refractory to immunosuppression are critical for the maintenance of both protective and pathogenic antibody titers. Here, we studied the response of plasma cells in spleen, bone marrow and inflamed kidneys of lupus-prone NZB/W mice to high-dose dexamethasone and/or cyclophosphamide. BrdU+, dividing plasmablasts and short-lived plasma cells in the spleen were depleted while BrdU- memory plasma cells survived. In contrast, all bone marrow plasma cells including anti-DNA secreting cells were refractory to both drugs. Unlike bone marrow and spleen, which showed a predominance of IgM-secreting plasma cells, inflamed kidneys mainly accommodated IgG-secreting plasma cells, including anti-DNA secreting cells, some of which survived the treatments. These results indicate that the bone marrow is the major site of memory plasma cells resistant to treatment with glucocorticoids and anti-proliferative drugs, and that inflamed tissues and secondary lymphoid organs can contribute to the autoreactive plasma cell memory. Therefore, new strategies targeting autoreactive plasma cell memory should be considered. This could be the key to finding a curative approach to the treatment of chronic inflammatory autoantibody-mediated diseases.

Homing and adhesion patterns determine the cellular composition of the bone marrow plasma cell niche

According to commonly held concepts, plasma cell (PC) longevity in bone marrow (BM) depends upon their access to survival niches. These are thought to exist in nursery cell types, which support PCs by secreting PC survival factors. To better define PC survival niches and their functioning, we adoptively transferred traceable Blimp-1-(GFP) PCs into recipient mice lacking a proliferation-inducing ligand (APRIL), IL-6, or macrophage migration inhibitory factor. Transferred BMPCs were preferentially associated with Ly-6C(high) monocytes (normalized colocalization index: 9.84), eosinophils (4.29), and megakaryocytes (2.12). Although APRIL was essential for BMPC survival, PC recruitment into the proximity of nursery cells was unimpaired in APRIL-deficient mice, questioning the concept that the same factors account for attraction/retention of PCs as for their local survival. Rather, the order of colocalization with BMPCs (monocytes > eosinophils > megakaryocytes) reflected these cells' relative expression of CXCR4, VLA-4, and LFA-1, the homing and adhesion molecules that direct/retain PCs in the BM. This suggests a scenario wherein the cellular composition of the BMPC niche is defined by a common pattern of attraction/retention on CXCL12-abundant reticular docking cells. Thereby, PCs are directed to associate in a functional BM niche with hematopoietic CXCR4(+)VLA-4(+)LFA-1(+) nursery cells, which provide PC survival factors.

Recruitment of memory B cells to lymph nodes remote from the site of immunization requires an inflammatory stimulus

Successful recall Ab responses require recruitment of quiescent memory B cells to secondary lymphoid organs. However, the cellular dynamics of memory cells responding to local antigenic challenge at lymphoid sites distal from the initial Ag encounter are not well understood. We show in this study that memory B cells generated following s.c. immunization in one footpad generate secondary responses to soluble Ag given i.p. but not to Ag given s.c. in the contralateral footpad unless LPS is coadministered. Memory B cells do not express CD62L, and CD62L(-ve) cells cannot enter lymph nodes unless LPS-mediated inflammation is induced there. Functional TLR4 is required on the B cells, as well as on non-B cells, in the lymph node to achieve full recruitment. Furthermore, splenectomized mice fail to respond to such inflammatory s.c. challenge in contralateral footpads, unlike lymphadenectomized mice lacking the original draining lymph nodes. Splenectomized mice also fail to respond to i.p. challenge with soluble Ag. Together, these data indicate that, unlike the central memory pool of T cells, which circulates through resting lymph nodes, the majority of long-lived memory B cells are spleen resident and require inflammatory signals for mounting recall responses at distal challenge sites.

DOCK8 functions as an adaptor that links TLR-MyD88 signaling to B cell activation

The adaptors DOCK8 and MyD88 have been linked to serological memory. Here we report that DOCK8-deficient patients had impaired antibody responses and considerably fewer CD27(+) memory B cells. B cell proliferation and immunoglobulin production driven by Toll-like receptor 9 (TLR9) were considerably lower in DOCK8-deficient B cells, but those driven by the costimulatory molecule CD40 were not. In contrast, TLR9-driven expression of AICDA (which encodes the cytidine deaminase AID), the immunoglobulin receptor CD23 and the costimulatory molecule CD86 and activation of the transcription factor NF-κB, the kinase p38 and the GTPase Rac1 were intact. DOCK8 associated constitutively with MyD88 and the tyrosine kinase Pyk2 in normal B cells. After ligation of TLR9, DOCK8 became tyrosine-phosphorylated by Pyk2, bound the Src-family kinase Lyn and linked TLR9 to a Src-kinase Syk-transcription factor STAT3 cascade essential for TLR9-driven B cell proliferation and differentiation. Thus, DOCK8 functions as an adaptor in a TLR9-MyD88 signaling pathway in B cells.

B cell analysis of ethnic groups in Mali with differential susceptibility to malaria

BACKGROUND

Several studies indicate that people of the Fulani ethnic group are less susceptible to malaria compared to those of other ethnic groups living sympatrically in Africa, including the Dogon ethnic group. Although the mechanisms of this protection remain unclear, the Fulani are known to have higher levels of Plasmodium falciparum-specific antibodies of all Ig classes as compared to the Dogon. However, the proportions of B cell subsets in the Fulani and Dogon that may account for differences in the levels of Ig have not been characterized.

METHODS

In this cross-sectional study, venous blood was collected from asymptomatic Fulani (n = 25) and Dogon (n = 25) adults in Mali during the malaria season, and from P. falciparum-naïve adults in the U.S. (n = 8). At the time of the blood collection, P. falciparum infection was detected by blood-smear in 16% of the Fulani and 36% of the Dogon volunteers. Thawed lymphocytes were analysed by flow cytometry to quantify B cell subsets, including immature and naïve B cells; plasma cells; and classical, activated, and atypical memory B cells (MBCs).

RESULTS

The overall distribution of B cell subsets was similar between Fulani and Dogon adults, although the percentage of activated MBCs was higher in the Fulani group (Fulani: 11.07% [95% CI: 9.317 - 12.82]; Dogon: 8.31% [95% CI: 6.378 - 10.23]; P = 0.016). The percentage of atypical MBCs was similar between Fulani and Dogon adults (Fulani: 28.3% [95% CI: 22.73 - 34.88]; Dogon: 29.3% [95% CI: 25.06 - 33.55], but higher than U.S. adults (U.S.: 3.0% [95% CI: -0.21 - 6.164]; P < 0.001). Plasmodium falciparum infection was associated with a higher percentage of plasma cells among Fulani (Fulani infected: 3.3% [95% CI: 1.788 - 4.744]; Fulani uninfected: 1.71% [95% CI: 1.33 - 2.08]; P = 0.011), but not Dogon adults.

CONCLUSION

These data show that the malaria-resistant Fulani have a higher percentage of activated MBCs compared to the Dogon, and that P. falciparum infection is associated with a higher percentage of plasma cells in the Fulani compared to the Dogon, findings that may account for the higher levels of P. falciparum antibodies in the Fulani.

Signals controlling rest and reactivation of T helper memory lymphocytes in bone marrow

Established views on the maintenance of immunological memory have been challenged recently by the description of memory plasma cells and memory T helper (Th) lymphocytes residing in the bone marrow (BM) in dedicated survival niches, resting in terms of proliferation and migration. While memory plasma cells are no longer reactive to antigen, memory Th lymphocytes are in a state of attentive rest, and can be reactivated fast and efficiently. Here, we discuss the signals controlling these resting states, which the memory lymphocytes receive from their microenvironment.

Origin and Function of Circulating Plasmablasts during Acute Viral Infections

Activated B cells proliferate and differentiate into antibody-producing cells, long-lived plasma cells, and memory B cells after immunization or infection. Repeated encounter of the same antigen triggers the rapid re-activation of pre-existing specific memory B cells, which then potentially enter new germinal center reactions and differentiate into short-lived plasmablasts or remain in the system as memory B cells. Short-lived class-switched IgG and IgA plasmablasts appear in the circulation transiently and the frequency of these cells can be remarkably high. The specificities and affinities of single plasmablasts in humans have been reported for several viral infections, so far most extensively for influenza and HIV. In general, the immunoglobulin variable regions of plasmablasts are highly mutated and diverse, suggesting that plasmablasts are derived from memory B cells, yet it is unclear which memory B cell subsets are activated and whether activated memory B cells adapt or mature before differentiation. This review summarizes what is known about the phenotype and the origin of human plasmablasts in the context of viral infections and whether these cells can be predictors of long-lived immunity.

IgA synthesis: a form of functional immune adaptation extending beyond gut

Immunoglobulin A (IgA) is the most abundantly produced antibody isotype in mammals. The primary function of IgA is to maintain homeostasis at mucosal surfaces. IgA is generated in specialized gut associated lymphoid tissues (GALT) by T cell-dependent and T cell-independent mechanisms. Studies in mice have demonstrated that IgA diversification has an essential role in the regulation of gut microbiota. Aberrant bacterial growth, by activating innate and adaptive immune cells, has emerged as a risk factor for inflammatory diseases such as metabolic disorders and autoimmune diseases. Dynamic diversification of IgA shields bacterial antigens preventing inflammatory responses, but when IgA regulation is suboptimal aberrant bacterial growth and inflammation can ensue.

Re-engaging cross-reactive memory B cells: the influenza puzzle

The emergence of a novel influenza A virus strain into humans poses a continuous public health threat. Vaccination is the most effective means of protection against influenza. The generation of memory B cells and long-lived plasma cells that can maintain protective levels of influenza-specific antibodies for protracted periods of time is the foundation for the success of such vaccines. Influenza vaccines elicit an antibody response that is primarily targeting viral surface glycoproteins. However, frequent amino acid mutations within the immunodominant epitopes allow the virus to efficiently escape neutralization by pre-existing antibodies and consequently cause annual epidemics and occasional pandemics. Recently, monoclonal antibodies (mAbs) that target subdominant influenza epitopes have been extensively characterized. These epitopes are immunogenic, can mediate virus neutralization, and most importantly are conserved among different influenza strains. It remains puzzling, however, that despite being repeatedly exposed to such conserved domains of influenza hemagglutinin (HA) either in the form of vaccination or natural infection, most humans do not develop immunological memory that can provide broad protection against emerging virus strains. Here we will discuss the conditions that may be required for engaging such cross-reactive memory B cells in the immune response to influenza infection and vaccination in humans.

Activation-induced cytidine deaminase expression in CD4+ T cells is associated with a unique IL-10-producing subset that increases with age

Activation-induced cytidine deaminase (AID), produced by the Aicda gene, is essential for the immunoglobulin gene (Ig) alterations that form immune memory. Using a Cre-mediated genetic system, we unexpectedly found CD4⁺ T cells that had expressed Aicda (exAID cells) as well as B cells. ExAID cells increased with age, reaching up to 25% of the CD4⁺ and B220⁺ cell populations. ExAID B cells remained IgM⁺, suggesting that class-switched memory B cells do not accumulate in the spleen. In T cells, AID was expressed in a subset that produced IFN-γ and IL-10 but little IL-4 or IL-17, and showed no evidence of genetic mutation. Interestingly, the endogenous Aicda expression in T cells was enhanced in the absence of B cells, indicating that the process is independent from the germinal center reaction. These results suggest that in addition to its roles in B cells, AID may have previously unappreciated roles in T-cell function or tumorigenesis.

Elicitation of anti-1918 influenza virus immunity early in life prevents morbidity and lower levels of lung infection by 2009 pandemic H1N1 influenza virus in aged mice

The Spanish influenza virus pandemic of 1918 was responsible for 40 million to 50 million deaths and is antigenically similar to the swine lineage 2009 pandemic influenza virus. Emergence of the 2009 pandemic from swine into humans has raised the possibility that low levels of cross-protective immunity to past shared epitopes could confer protection. In this study, influenza viruslike particles (VLPs) were engineered to express the hemagglutinin (HA) and genes from the 1918 influenza virus to evaluate the duration of cross-protection to the H1N1 pandemic strain by vaccinating young mice (8 to 12 weeks) and then allowing the animals to age to 20 months. This immunity was long lasting, with homologous receptor-blocking antibodies detected throughout the lifespan of vaccinated mice. Furthermore, the 1918 VLPs fully protected aged mice from 2009 pandemic H1N1 virus challenge 16 months after vaccination. Histopathological assessment showed that aged vaccinated mice had significant protection from alveolar infection but less protection of the bronchial tissue than adult vaccinated mice. Additionally, passive transfer of immune serum from aged vaccinated mice resulted in protection from death but not morbidity. This is the first report describing the lifelong duration of cross-reactive immune responses elicited by a 1918 VLP vaccine in a murine model. Importantly, these lifelong immune responses did not result in decreased total viral replication but did prevent infection of the lower respiratory tract. These findings show that immunity acquired early in life can restrict the anatomical location of influenza viral replication, rather than preventing infection, in the aged.

Genetic variations in multiple myeloma I: effect on risk of multiple myeloma

Few risk factors have been established for the plasma cell disorder multiple myeloma, but some of these like African American ethnicity and a family history of B-cell lymphoproliferative diseases suggest a genetic component for the disease. Genetic variation represents the genetic basis of variability in a population. The complex interplay between environment and genes for the development of cancer may therefore be influenced by genetic variations. A genetic variation may change the function of the gene, and if the genetic variation is associated with the risk of disease, that particular gene may be involved in the pathogenesis of disease. Genes of interest are genes involved in the normal development and function of the plasma cell and genes that protect us against exposures from the environment, for example, genes involved in the metabolism of xenobiotics, metabolism of folate and methionine, as well as genes involved in inflammation and DNA repair. Identification of genes with potential influence on cancer risk may help us to establish relevant laboratory studies on exposure and dose-response assessment and may help us to test the hypothesis in epidemiological studies. Knowledge of individual at high risk of cancer may offer promising insight for the prevention of cancer.

Cancer vaccines and carbohydrate epitopes

Tumor-associated carbohydrate antigens (TACA) result from the aberrant glycosylation that is seen with transformation to a tumor cell. The carbohydrate antigens that have been found to be tumor-associated include the mucin related Tn, Sialyl Tn, and Thomsen-Friedenreich antigens, the blood group Lewis related Lewis(Y), Sialyl Lewis(X) and Sialyl Lewis(A), and Lewis(X) (also known as stage-specific embryonic antigen-1, SSEA-1), the glycosphingolipids Globo H and stage-specific embryonic antigen-3 (SSEA-3), the sialic acid containing glycosphingolipids, the gangliosides GD2, GD3, GM2, fucosyl GM1, and Neu5GcGM3, and polysialic acid. Recent developments have furthered our understanding of the T-independent type II response that is seen in response to carbohydrate antigens. The selection of a vaccine target antigen is based on not only the presence of the antigen in a variety of tumor tissues but also on the role this antigen plays in tumor growth and metastasis. These roles for TACAs are being elucidated. Newly acquired knowledge in understanding the T-independent immune response and in understanding the key roles that carbohydrates play in metastasis are being applied in attempts to develop an effective vaccine response to TACAs. The role of each of the above mentioned carbohydrate antigens in cancer growth and metastasis and vaccine attempts using these antigens will be described.

Identification of Epstein–Barr virus-infected CD27+ memory B-cells in liver or stem cell transplant patients

To analyse the phenotype of Epstein–Barr virus (EBV)-infected lymphocytes in EBV-associated infections, cells from eight haematopoietic stem cell/liver transplantation recipients with elevated EBV viral loads were examined by a novel quantitative assay designed to identify EBV-infected cells by using a flow cytometric detection of fluorescent in situ hybridization (FISH) assay. By this assay, 0.05–0.78 % of peripheral blood lymphocytes tested positive for EBV, and the EBV-infected cells were CD20+ B-cells in all eight patients. Of the CD20+ EBV-infected lymphocytes, 48–83 % of cells tested IgD positive and 49–100 % of cells tested CD27 positive. Additionally, the number of EBV-infected cells assayed by using FISH was significantly correlated with the EBV-DNA load, as determined by real-time PCR (r 2 = 0.88, P<0.0001). The FISH assay enabled us to characterize EBV-infected cells and perform a quantitative analysis in patients with EBV infection after stem cell/liver transplantation.

Staying alive: regulation of plasma cell survival

On describing the catastrophic effect of the plague during the Peloponnesian War, Greek historian Thucydides (c ∼450 BC) made the prescient observation that the "same man was never attacked twice - never at least fatally". This is probably the first description of the mammalian immune systems' remarkable ability to elicit a pathogen-specific response that potentially protects the host for its lifetime. This protection is largely mediated by plasma cells (PCs) that produce copious quantities of antibodies for extended periods of time, even after pathogen clearance. Here, I review the requirements for PC longevity in mice and humans, in particular the roles of survival niches in bone marrow and other tissues, and the "dialogue" between PCs and other cells that are crucial for long-lived humoral immunity.

Evidence for intranasal antinuclear autoantibodies in patients with chronic rhinosinusitis with nasal polyps

BACKGROUND

Chronic rhinosinusitis (CRS) with nasal polyps is an inflammatory condition of the nasal passage and paranasal sinuses characterized by T(H)2-biased inflammation with increased levels of B-cell activating factor of the TNF family (BAFF), B lymphocytes, and immunoglobulins. Because high levels of BAFF are associated with autoimmune diseases, we assessed for evidence of autoimmunity in patients with CRS.

OBJECTIVES

The objective of this study was to investigate the presence of autoantibodies in sinonasal tissue from patients with CRS.

METHODS

Standardized nasal tissue specimens were collected from patients with CRS and control subjects and assayed for immunoglobulin production, autoantibody levels, tissue distribution of immunoglobulins, and binding potential of antibodies in nasal tissue with a multiplexed autoantibody microarray, ELISA, and immunofluorescence.

RESULTS

Increased levels of several specific autoantibodies were found in nasal polyp tissue in comparison with levels seen in control tissue and inflamed tissue from patients with CRS without nasal polyps (P < .05). In particular, nuclear-targeted autoantibodies, such as anti-dsDNA IgG and IgA antibodies, were found at increased levels in nasal polyps (P < .05) and particularly in nasal polyps from patients requiring revision surgery for recurrence. Direct immunofluorescence staining demonstrated diffuse epithelial and subepithelial deposition of IgG and increased numbers of IgA-secreting plasma cells not seen in control nasal tissue.

CONCLUSIONS

Autoantibodies, particularly those against nuclear antigens, are present at locally increased levels in nasal polyps. The presence of autoantibodies suggests that the microenvironment of a nasal polyp promotes the expansion of self-reactive B-cell clones. Although the pathogenicity of these antibodies remains to be elucidated, the presence of increased anti-dsDNA antibody levels is associated with a clinically more aggressive form of CRS with nasal polyps requiring repeated surgery.

Current understanding of the role of B cell subsets and intimal and adventitial B cells in atherosclerosis

PURPOSE OF REVIEW

Inflammation, in addition to high cholesterol is a major factor contributing to atherosclerosis-associated adverse cardiovascular events. Thus, there is a pressing need for additional therapeutic strategies to reduce inflammation, by targeting immune cells and cytokines. Here we review B cell subsets and adventitial and intimal B cells in atherosclerosis development and discuss potential B cell-targeted anti-inflammatory therapies for atherosclerosis.

RECENT FINDINGS

B cell subsets can have opposing proatherogenic and atheroprotective roles in atherosclerosis. CD-20-targeted B cell depletion has been shown to decrease murine atherosclerotic lesions. The accumulation of intimal and adventitial B cells associated with atherosclerotic lesions is consistent with their participation in local inflammatory responses. As B2 B cells are proatherogenic, blocking its survival factor B cell activating factor may selectively delete this proatherogenic subset.

SUMMARY

Both intimal and adventitial B cells appear important in atherosclerosis. B2 B cells are proatherogenic and other subsets such as regulatory B cells are antiatherogenic. Future B cell-targeted therapy for atherosclerosis should be customized to selectively deplete damaging B2 B cells while sparing or expanding protective B cell subsets.

SIV infection of rhesus macaques results in dysfunctional T- and B-cell responses to neo and recall Leishmania major vaccination

HIV infection is characterized by immune system dysregulation, including depletion of CD4+ T cells, immune activation, and abnormal B- and T-cell responses. However, the immunologic mechanisms underlying lymphocytic dysfunctionality and whether it is restricted to immune responses against neo antigens, recall antigens, or both is unclear. Here, we immunized SIV-infected and uninfected rhesus macaques to induce immune responses against neo and recall antigens using a Leishmania major polyprotein (MML) vaccine given with poly-ICLC adjuvant. We found that vaccinated SIVuninfected animals induced high frequencies of polyfunctional MML-specific CD4+ T cells. However, in SIV-infected animals, CD4+ T-cell functionality decreased after both neo (P = .0025) and recall (P = .0080) MML vaccination. Furthermore, after SIV infection, the frequency of MML-specific antibody-secreting classic memory B cells was decreased compared with vaccinated, SIV-uninfected animals. Specifically, antibody-secreting classic memory B cells that produced IgA in response to either neo (P = .0221) or recall (P = .0356) MML vaccinations were decreased. Furthermore, we found that T-follicular helper cells, which are essential for priming B cells, are preferentially infected with SIV. These data indicate that SIV infection results in dysfunctional T-cell responses to neo and recall vaccinations, and direct SIV infection of T-follicular helper cells, both of which probably contribute to deficient B-cell responses and, presumably, susceptibility to certain opportunistic infections.