Reactive Plasmacytoses Are Expansions of Plasmablasts Retaining the Capacity to Differentiate Into Plasma Cells

Evaluation of Regulatory B Cell Subpopulations CD24++CD38++, CD24++CD27+, Plasmablasts and Their Correlation with T Regs CD3+CD4+CD25+FOXP3+ in Dialysis Patients and Early Post-Transplant Rejection-Free Kidney Recipients

Background: B and T regulatory cells, also known as Bregs and Tregs, are involved in kidney transplantation. The purpose of this study is to monitor changes in the frequency and absolute numbers of Tregs (CD3+CD4+CD25+FoxP3+), transitional Bregs (tBregs) (CD24++CD38++), memory Bregs (mBregs) (CD24++CD27+), and plasmablasts before (T0) and six months (T6) after transplantation. Additionally, we aim to investigate any correlation between Tregs and tBregs, mBregs, or plasmablasts and their relationship with graft function. Methods: Flow cytometry was used to immunophenotype cells from 50 kidney recipients who did not experience rejection. Renal function was assessed using the estimated glomerular filtration rate (eGFR). Results: At T6, there was a significant decrease in the frequency of Tregs, plasmablasts, and tBregs, as well as in the absolute number of tBregs. The frequency of mBregs, however, remained unchanged. Graft function was found to have a positive correlation with the frequency of tBregs and plasmablasts. A significant correlation was observed between the frequency and absolute number of tBregs only when the eGFR was greater than 60 but not at lower values. At an eGFR greater than 60, there was a positive correlation between the absolute numbers of Tregs and mBregs but not between Tregs and tBregs. No correlation was observed for any cell population in dialysis patients. Conclusions: The data show a correlation between the frequency and absolute number of tBregs and the absolute number of Tregs and mBregs with good renal function in the early post-transplant period.

Majority of human circulating IgG plasmablasts stop blasting in a cell-free pro-survival culture

Following infection or vaccination, early-minted antibody secreting cells (ASC) or plasmablasts appear in circulation transiently, and a small fraction migrates to the spleen or bone marrow (BM) to mature into long-lived plasma cells (LLPC). While LLPC, by definition, are quiescent or non-dividing, the majority of blood ASC are thought to be "blasting" or proliferative. In this study, we find > 95% nascent blood ASC in culture express Ki-67 but only 6-12% incorporate BrdU after 4 h or 24 h labeling. In contrast, < 5% BM LLPC in culture are Ki-67+ with no BrdU uptake. Due to limitations of traditional flow cytometry, we utilized a novel optofluidic technology to evaluate cell division with simultaneous functional IgG secretion. We find 11% early-minted blood ASC undergo division, and none of the terminally differentiated BM LLPC (CD19-CD38hiCD138+) divide during the 7-21 days in culture. While BM LLPC undergo complete cell cycle arrest, the process of differentiation into an ASC or plasmablasts also discourages entry into S phase. Since the majority of Ki-67+ nascent blood ASC have exited cell cycle and are no longer actively "blasting", the term "plasmablast", which traditionally refers to an ASC that still has the capacity to divide, may probably be a misnomer.

Majority of human circulating plasmablasts stop blasting: A probable misnomer

Following infection or vaccination, early-minted antibody secreting cells (ASC) or plasmablasts appear in circulation transiently, and a small fraction migrates to the spleen or bone marrow (BM) to mature into long-lived plasma cells (LLPC). While LLPC, by definition, are quiescent or non-dividing, the majority of blood ASC are thought to be "blasting" or proliferative. In this study, we find >95% nascent blood ASC in culture express Ki-67 but only 6-12% incorporate BrdU after 4h or 24h labeling. In contrast, <5% BM LLPC in culture are Ki-67 + with no BrdU uptake. Due to limitations of traditional flow cytometry, we utilized a novel optofluidic technology to evaluate cell division with simultaneous functional Ig secretion. We find 11% early-minted blood ASC undergo division, and none of the terminally differentiated BM LLPC (CD19 - CD38 hi CD138 + ) divide during the 7-21 days in culture. While BM LLPC undergo complete cell cycle arrest, the process of differentiation into an ASC of plasmablasts discourages entry into S phase. Since the majority of Ki-67 + nascent blood ASC have exited cell cycle and are no longer actively "blasting", the term "plasmablast", which traditionally refers to an ASC that still has the capacity to divide, may probably be a misnomer.

CD40 signaling-mediated delay in terminal differentiation of B cells enables alternate fate choices during early divisions

Memory B cells and differentiated plasma cells combine to confer sustained humoral immunity. Nonetheless, we are yet to understand how B cells decide between these fates. Although pan-T cell help augments plasma cell differentiation, signaling via CD40 alone is considered to be inhibitory. Here, we examine the capacity of CD40 signaling to interfere with lipopolysaccharide-induced differentiation. Whereas lipopolysaccharide stimulation yielded only short-lived plasmablasts, co-stimulation of CD40 enhanced activation, proliferation, survival, and isotype-switching, leading to alternate fate choices such as germinal center and memory B cells during early divisions. Contrary to the notion that CD40 signaling simply arrests differentiation, the survivors, at later time points, developed into long-lived mature plasma cells, after progressively losing their ability to get restimulated. Counterintuitively, as constitutive lipopolysaccharide stimulation itself hampered differentiation, we identified that the proliferation potential of cells acted alongside CD40 signaling. Accordingly, we propose a bi-layered regulation of differentiation - CD40 signaling and proliferation potential of cells independently inhibit the commitment to and maturation of differentiation, respectively. Elucidating such cell fate decision mechanisms will aid in better vaccine design and disease management.

Histopathologic, immunophenotypic, and mutational landscape of follicular lymphomas with plasmacytic differentiation

Follicular lymphomas with plasmacytic differentiation (FL-PCD) include two major subtypes: one with predominantly interfollicular PCD that usually harbors a BCL2 rearrangement (BCL2-R), and a second that has predominantly intrafollicular PCD and the frequent absence of a BCL2-R. It is proposed that these latter cases share some features with marginal zone lymphomas (MZL). To further explore this hypothesis in an expanded cohort of FL-PCD, a clinicopathologic investigation of 25 such cases was undertaken including an analysis of their mutational landscape. The 10 interfollicular FL-PCDs exhibited typical intrafollicular centrocytes/centroblasts (90%), CD10 expression (90%), full PCD including expression of CD138 by the plasma cells (PC) (100%), and PCs with class-switched immunoglobulin heavy chains (70%). These cases were BCL2-R positive (100%), BCL6-R positive in 30%, lacked extra BCL2 copies, and only 22% had extra copies of BCL6. Similar to classic FLs, 80% of interfollicular FL-PCDs harbored mutations in epigenetic regulators KMT2D (70%), CREBBP (40%), and/or EZH2 (30%). In contrast, only 45% of 11 intrafollicular FL-PCDs demonstrated typical intrafollicular centrocytes/centroblasts, 55% were CD10(-), 80% contained IgM+ PCs, and only 27% harbored BCL2-Rs. BCL6-Rs were identified in 27% of intrafollicular FL-PCD, while 60% showed extra copies of BCL2 and 50% extra copies of BCL6, consistent with complete or partial trisomies of chromosomes 18 and 3, respectively. Only 54% of intrafollicular FL-PCDs showed mutations in epigenetic regulators. Both subtypes showed mutational differences compared to classic FL, but only the interfollicular subtype showed differences from what is reported for nodal MZL. Four additional cases showed mixed intra- and interfollicular PCD. These results suggest that FL-PCD has some distinctive features and supports the existence of two major subtypes. The interfollicular PCD subtype shares many features with classic FL. The intrafollicular FL-PCDs are more heterogeneous, have differences from classic FL, and have a greater morphologic, immunophenotypic, and genetic overlap with MZL.

Maturation trajectories and transcriptional landscape of plasmablasts and autoreactive B cells in COVID-19

In parasite and viral infections, aberrant B cell responses can suppress germinal center reactions thereby blunting long-lived memory and may provoke immunopathology including autoimmunity. Using COVID-19 as model, we set out to identify serological, cellular, and transcriptomic imprints of pathological responses linked to autoreactive B cells at single-cell resolution. We show that excessive plasmablast expansions are prognostically adverse and correlate with autoantibody production but do not hinder the formation of neutralizing antibodies. Although plasmablasts followed interleukin-4 (IL-4) and BAFF-driven developmental trajectories, were polyclonal, and not enriched in autoreactive B cells, we identified two memory populations (CD80⁺/ISG15⁺ and CD11c⁺/SOX5⁺/T-bet^+/−) with immunogenetic and transcriptional signs of autoreactivity that may be the cellular source of autoantibodies in COVID-19 and that may persist beyond recovery. Immunomodulatory interventions discouraging such adverse responses may be useful in selected patients to shift the balance from autoreactivity toward long-term memory.

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Plasmablast expansions correlate with disease severity and autoantibodies in COVID-19

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Patients with high plasmablast levels exhibit IGHV4-34 skewing

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Autoreactive BCRs are enriched in atypical memory, not plasmablast populations

Increased levels of circulating class-switched memory B cells and plasmablasts are associated with serum immunoglobulin G in primary focal segmental glomerulosclerosis patients

BACKGROUND

Focal segmental glomerulosclerosis (FSGS) is a kidney-specific autoimmune disease, but its pathogenesis is not fully known. The present study detected the frequencies of circulating memory B cells and plasmablasts and other clinical parameters in FSGS.

METHODS

We monitored 16 primary FSGS patients and 23 healthy controls (HC). Flow cytometry was used to analyze circulating memory B cell and plasmablastspercentages. Serum IgG levels were detected using a cytometric bead array (CBA).

RESULTS

The proportions of CD27 + IgD- class-switched memory B cells (P = 0.0002), CD27 + IgD-IgG + class-switched memory B cells (P < 0.0001), CD27hiCD38hi plasmablasts (P < 0.0001) and CD138 + plasma cells (P < 0.0001) were markedlyelevated in FSGS patients, and the frequency of CD38 + IgG + plasmablasts (P < 0.0001) and serum IgG levels (P < 0.0001) were lower compared to HC. In the FSGS patients, the frequency of CD27 + IgD-IgG + class-switched memory B cells negatively correlated with CD38 + IgG + plasmablasts (P = 0.0183, R = -0.3375), serum IgG levels (P = 0.0061, R = -0.4263) and estimated glomerular filtration rate (eGFR) (P = 0.0074, R = -0.4114) but positively correlated with 24-h urinary protein levels (P = 0.0077, R = 0.4085). The proportion of CD38 + IgG + plasmablasts positively correlated with serum IgG levels (P = 0.0151, R = 0.3538).

CONCLUSIONS

We speculate that alterations in the frequencies of CD27 + IgD-IgG + class-switched memory B cells and plasmablasts may be responsible for the etiopathogenesis of FSGS.

Germinal Center and Extrafollicular B Cell Responses in Vaccination, Immunity, and Autoimmunity

Activated B cells participate in either extrafollicular (EF) or germinal center (GC) responses. Canonical responses are composed of a short wave of plasmablasts (PBs) arising from EF sites, followed by GC producing somatically mutated memory B cells (MBC) and long-lived plasma cells. However, somatic hypermutation (SHM) and affinity maturation can take place at both sites, and a substantial fraction of MBC are produced prior to GC formation. Infection responses range from GC responses that persist for months to persistent EF responses with dominant suppression of GCs. Here, we review the current understanding of the functional output of EF and GC responses and the molecular switches promoting them. We discuss the signals that regulate the magnitude and duration of these responses, and outline gaps in knowledge and important areas of inquiry. Understanding such molecular switches will be critical for vaccine development, interpretation of vaccine efficacy and the treatment for autoimmune diseases.

Automated digital enumeration of plasma cells in bone marrow trephine biopsies of multiple myeloma

AIMS

Determination of the number of plasma cells in bone marrow biopsies is required for the diagnosis and ongoing evaluation of plasma cell neoplasms. We developed an automated digital enumeration platform to assess plasma cells identified by antigen expression in whole bone marrow sections in multiple myeloma, and compared it with manual assessments.

METHODS

Bone marrow trephine biopsy specimens from 91 patients with multiple myeloma at diagnosis, remission and relapse were stained for CD138 and multiple myeloma oncogene 1 (MUM1). Manual assessment and digital quantification were performed for plasma cells in the entire trephine section. Concordance rates between manual and digital methods were evaluated for each antigen by intraclass correlation analyses (ICC) with associated Spearman's correlations.

RESULTS

The digital platform counted 16 484-1 118 868 cells and the per cent CD138 and MUM1-positive plasma cells ranged from 0.05% to 93.5%. Overall concordance between digital and manual methods was 0.63 for CD138 and 0.89 for MUM1. Concordance was highest with diffuse plasma cell infiltrates (MUM1: ICC=0.90) and lowest when in microaggregates (CD138: ICC=0.13). Manual counts exceeded digital quantifications for both antigens (CD138: mean=26.4%; MUM1: mean=9.7%). Diagnostic or relapse threshold counts, as determined by CD138 manual assessments, were not reached with digital counting for 16 cases (18%).

CONCLUSIONS

Automated digital enumeration of the entire, immunohistochemically stained bone marrow biopsy section can accurately determine plasma cell burden, irrespective of pattern and extent of disease (as low as 0.05%). This increases precision over manual visual assessments which tend to overestimate plasma burden, especially for CD138, and when plasma cells are in clusters.

Detection of Circulating Tumor Plasma Cells in Monoclonal Gammopathies: Methods, Pathogenic Role, and Clinical Implications

Cancer dissemination and distant metastasis most frequently require the release of tumor cells into the blood circulation, both in solid tumors and most hematological malignancies, including plasma cell neoplasms. However, detection of blood circulating tumor cells in solid tumors and some hematological malignancies, such as the majority of mature/peripheral B-cell lymphomas and monoclonal gammopathies, has long been a challenge due to their very low frequency. In recent years, the availability of highly-sensitive and standardized methods for the detection of circulating tumor plasma cells (CTPC) in monoclonal gammopathies, e.g., next-generation flow cytometry (NGF), demonstrated the systematic presence of CTPC in blood in virtually every smoldering (SMM) and symptomatic multiple myeloma (MM) patient studied at diagnosis, and in the majority of patients with newly-diagnosed monoclonal gammopathies of undetermined significance (MGUS). These methods set the basis for further detailed characterization of CTPC vs. their bone marrow counterpart in monoclonal gammopathies, to investigate their role in the biology of the disease, and to confirm their strong impact on patient outcome when measured both at diagnosis and after initiating therapy. Here, we review the currently available techniques for the detection of CTPC, and determine their biological features, physiopathological role and clinical significance in patients diagnosed with distinct diagnostic categories of plasma cell neoplasms.

Increased Non-switched Memory B Cells are Associated with Plasmablasts, Serum IL-6 Levels and Renal Functional Impairments in IgAN Patients

Background: Circulating B cells are crucial for the pathogenesis of IgA nephropathy (IgAN). This study aimed at investigating the relationship between frequency of different subsets of circulating B cells and clinical measures in IgAN patients.Methods: The percentages of different subsets of circulating B cells in 23 IgAN patients and 14 healthy controls (HC) were determined by flow cytometry. Their serum IL-6 levels were measured by Cytometric Bead Array (CBA). Clinical parameters in five patients were measured before and after treatment for 8-12 weeks. The potential relationship between variants was analyzed.Results: In comparison with the HC, the frequency of CD3-CD19+ CD27+ IgD+IgM+ non-switched memory B cells (P = .0038) and CD3-CD19+ CD27hiCD38hi plasmablasts (P = .0467) and serum IL-6 (P = .0392) levels significantly increased in IgAN patients. The percentages of non-switched memory B cells were positively correlated with plasmablasts (R = 0.5781, P = .0039) and serum IL-6 levels (R = 0.6663, P = .0005) in the patients. The percentages of non-switched memory B cells (R = 0.8399, P < .0001), plasmablasts (R = 0.4486, P = .0318) and the levels of serum IL-6 (R = 0.5461, P = .0070) were positively correlated with the values of 24-h urine proteins in IgAN patients. The serum levels of IL-6 were negatively correlated with the eGFR values. Following standard treatment, the frequency of non-switched memory B cells and plasmablasts and the levels of 24-h urine proteins (P = .0317, P = .0079, P < .05) significantly decreased in IgAN patients.Conclusions: Abnormally higher frequency of non-switched memory B cells and plasmablasts may contribute to the pathogenesis of IgAN and be potential biomarkers for IgAN.

Next generation flow for minimally-invasive blood characterization of MGUS and multiple myeloma at diagnosis based on circulating tumor plasma cells (CTPC)

Here, we investigated for the first time the frequency and number of circulating tumor plasma cells (CTPC) in peripheral blood (PB) of newly diagnosed patients with localized and systemic plasma cell neoplasms (PCN) using next-generation flow cytometry (NGF) and correlated our findings with the distinct diagnostic and prognostic categories of the disease. Overall, 508 samples from 264 newly diagnosed PCN patients, were studied. CTPC were detected in PB of all active multiple myeloma (MM; 100%), and smoldering MM (SMM) patients (100%), and in more than half (59%) monoclonal gammopathy of undetermined significance (MGUS) cases (p <0.0001); in contrast, CTPC were present in a small fraction of solitary plasmacytoma patients (18%). Higher numbers of CTPC in PB were associated with higher levels of BM infiltration and more adverse prognostic features, together with shorter time to progression from MGUS to MM (p <0.0001) and a shorter survival in MM patients with active disease requiring treatment (p ≤ 0.03). In summary, the presence of CTPC in PB as assessed by NGF at diagnosis, emerges as a hallmark of disseminated PCN, higher numbers of PB CTPC being strongly associated with a malignant disease behavior and a poorer outcome of both MGUS and MM.

Reactive plasmacytosis mimicking multiple myeloma associated with SFTS virus infection: a report of two cases and literature review

Background

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging infectious disease caused by a novel bunyavirus named SFTS virus (SFTSV), which is classified into the genus Phlebovirus and family Phenuiviridae. Reactive plasmacytosis mimicking multiple myeloma is a very rare condition in association with SFTS. Here, we describe two SFTS cases who presented with hyperimmunoglobulinemia, as well as extensive bone marrow and peripheral blood plasmacytosis, which mimicked multiple myeloma (MM).

Case presentation

We report two cases who presented with fever and blood routine abnormity which were conformed as SFTS eventually. They were performed bone marrow aspiration and were admitted to the department of hematology with a preliminary diagnosis of MM. They all had hyperimmunoglobulinemia, extensive bone marrow and peripheral blood plasma cells, prolonged activated partial thromboplastin time (APTT), elevated hepatic enzyme. The two patients recovered with treatment of doxycycline, human immunoglobulins, plasma transfusion, and other supporting treatments. But case 1 occurred lymphoma 8 months later and died.

Conclusion

SFTS might be one of differential diagnosis of MM in certain endemic area. We also conclude that SFTSV is a pantropic virus that could injure most tissues and cells of the human body.

Interleukin-6: designing specific therapeutics for a complex cytokine

Interleukin-6 (IL-6) is a pivotal cytokine with a diverse repertoire of physiological functions that include regulation of immune cell proliferation and differentiation. Dysregulation of IL-6 signalling is associated with inflammatory and lymphoproliferative disorders such as rheumatoid arthritis and Castleman disease, and several classes of therapeutics have been developed that target components of the IL-6 signalling pathway. So far, monoclonal antibodies against IL-6 or IL-6 receptor (IL-6R) and Janus kinases (JAK) inhibitors have been successfully developed for the treatment of autoimmune diseases such as rheumatoid arthritis. However, clinical trials of agents targeting IL-6 signalling have also raised questions about the diseases and patient populations for which such agents have an appropriate benefit-risk profile. Knowledge from clinical trials and advances in our understanding of the complexities of IL-6 signalling, including the potential to target an IL-6 trans-signalling pathway, are now indicating novel opportunities for therapeutic intervention. In this Review, we overview the roles of IL-6 in health and disease and analyse progress with several approaches of inhibiting IL-6-signalling, with the aim of illuminating when and how to apply IL-6 blockade.

NOG-hIL-4-Tg, a new humanized mouse model for producing tumor antigen-specific IgG antibody by peptide vaccination

Immunodeficient mice transplanted with human peripheral blood mononuclear cells (PBMCs) are promising tools to evaluate human immune responses to vaccines. However, these mice usually develop severe graft-versus-host disease (GVHD), which makes estimation of antigen-specific IgG production after antigen immunization difficult. To evaluate antigen-specific IgG responses in PBMC-transplanted immunodeficient mice, we developed a novel NOD/Shi-scid-IL2rγ^null (NOG) mouse strain that systemically expresses the human IL-4 gene (NOG-hIL-4-Tg). After human PBMC transplantation, GVHD symptoms were significantly suppressed in NOG-hIL-4-Tg compared to conventional NOG mice. In kinetic analyses of human leukocytes, long-term engraftment of human T cells has been observed in peripheral blood of NOG-hIL-4-Tg, followed by dominant CD4+ T rather than CD8+ T cell proliferation. Furthermore, these CD4+ T cells shifted to type 2 helper (Th2) cells, resulting in long-term suppression of GVHD. Most of the human B cells detected in the transplanted mice had a plasmablast phenotype. Vaccination with HER2 multiple antigen peptide (CH401MAP) or keyhole limpet hemocyanin (KLH) successfully induced antigen-specific IgG production in PBMC-transplanted NOG-hIL-4-Tg. The HLA haplotype of donor PBMCs might not be relevant to the antibody secretion ability after immunization. These results suggest that the human PBMC-transplanted NOG-hIL-4-Tg mouse is an effective tool to evaluate the production of antigen-specific IgG antibodies.

Expression of the IL-6 receptor alpha-chain (CD126) in normal and abnormal plasma cells in monoclonal gammopathy of undetermined significance and smoldering myeloma

IL-6 activity in normal plasma cells (nPCs) and abnormal plasma cells (aPCs) is CD126 (subunit of IL-6 receptor) dependent. We quantified CD126 expression on nPCs and aPCs in monoclonal gammopathy of undetermined significance (MGUS), smoldering myeloma (SMM), and multiple myeloma (MM). CD126 was detected on all nPCs and aPCs indicating that CD126 does not have diagnostic utility. CD126 expression was higher in aPCs than in nPCs in 85% SMM but only 41% MGUS and there was evidence that CD126 was higher in aPCs than nPCs in the SMM (p = .048) but not MGUS (p = .96) patients. There is also a greater association between nPC and aPC CD126 expression in low risk MGUS than observed in high risk MGUS and SMM, suggesting normal regulation of CD126 decreases with disease progression. Future studies need to elucidate the role of bone marrow milieu versus escape from normal CD126 regulation in malignant transformation of clonal plasma cells.

Flow cytometry-based immunophenotypic analysis of primary systemic light chain amyloidosis

Using flow cytometry, the present study aimed to investigate the immunophenotypic characteristics of malignant plasma cells (PCs) in the bone marrow of patients with primary systemic light chain amyloidosis (AL) compared with the characteristics of patients with multiple myeloma (MM). Flow cytometric results of 51 patients with AL and 150 patients with MM were reviewed. The proportion of total bone marrow PCs in the patients with AL was significantly lower than that in the patients with MM, 1.35% (0.3–9.5%) vs. 9.7% (0.4–75.7%); (P<0.001). The cells in 24/51 patients with AL comprised two distinct populations: Normal PCs and malignant PCs, whereas only 11/150 patients with MM exhibited two populations. Patients with AL exhibited an increased cluster of differentiation (CD)19 expression compared with patients with MM, 4.5% (0.1–80.9%) vs. 1.6% (0.1–33.6%; P<0.001) and reduced CD138, with 90.8% (30.4–99.9%) vs. 95.0% (40.7–100%; P=0.006) and CD56, with 61.0% (1.5–99.2%) vs. 98.3% (0.1–100%; P<0.001) expression in malignant PCs. Light chain restriction was identified in all patients with AL, and the proportion of λ light chain restriction was 72.5%. The immunophenotypic characteristics of patients with AL demonstrated by flow cytometry were different compared with the characteristics of patients with MM in the number and composition of plasma cells, and the intracellular and extracellular expression of antigens. These differences may be associated with a less malignant phenotype of clonal PCs in AL than MM.

Distinct Differentiation Programs Triggered by IL-6 and LPS in Teleost IgM(+) B Cells in The Absence of Germinal Centers

Although originally identified as a B cell differentiation factor, it is now known that mammalian interleukin-6 (IL-6) only regulates B cells committed to plasma cells in response to T-dependent (TD) antigens within germinal centers (GCs). Even though adaptive immunity is present in teleost fish, these species lack lymph nodes and GCs. Thus, the aim of the present study was to establish the role of trout IL-6 on B cells, comparing its effects to those induced by bacterial lipopolysaccharide (LPS). We demonstrate that the effects of teleost IL-6 on naïve spleen B cells include proliferation, activation of NF-κB, increased IgM secretion, up-regulation of Blimp1 transcription and decreased MHC-II surface expression that point to trout IL-6 as a differentiation factor for IgM antibody-secreting cells (ASCs). However, LPS induced the secretion of IgM without up-regulating Blimp1, driving the cells towards an intermediate activation state in which antigen presenting mechanisms are elicited together with antibody secretion and expression of pro-inflammatory genes. Our results reveal that, in trout, IL-6 is a differentiation factor for B cells, stimulating IgM responses in the absence of follicular structures, and suggest that it was after follicular structures appeared that this cytokine evolved to modulate TD responses within the GC.

Circulating memory B cells and plasmablasts are associated with the levels of serum immunoglobulin in patients with ulcerative colitis

Humoural immunity is crucial for the pathogenesis of ulcerative colitis (UC), but the precise perturbation of B cell immunity is poorly understood. This study is aimed at evaluating the numbers of different subsets of circulating memory B cells, plasmablasts, and the levels of serum immunoglobulin in UC patients. Total of 23 patients with active UC and 14 healthy controls (HC) were examined for the numbers of different subsets of circulating memory B cells and plasmablasts before and after treatment with mesalazine for 8-12 weeks by flow cytometry. Disease activity was evaluated by the Mayo clinic score. The levels of serum immunoglobulin, C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) were measured in individual subjects. In comparison with that in HC, significantly reduced numbers of IgG(+) IgD(-) CD27(+) CD19(+) memory B cells, increased numbers of CD20(-) CD19(+) plasmablast subsets, and higher serum IgG levels were detected in UC patients. The concentrations of serum IgG, the numbers of CD138(+) CD38(+) CD20(-) CD19(+), and IgG(+) CD38(+) CD20(-) CD19(+) plasmablasts were negatively associated with the numbers of IgG(+) IgD(-) CD27(+) CD19(+) memory B cells. Furthermore, the values of Mayo clinic score, CRP, or ESR in UC patients were negatively correlated with the numbers of IgG(+) IgD(-) CD27(+) CD19(+) memory B cells, while positively correlated with the serum IgG levels and the numbers of plasmablast subsets. Following treatment with mesalazine, the numbers of circulating IgG(+) IgD(-) CD27(+) CD19(+) memory B cells were significantly increased, while the numbers of CD138(+) CD38(+) CD20(-) CD19(+) and IgG(+) CD38(+) CD20(-) CD19(+) plasmablasts were reduced in UC patients. These decreased IgG(+) IgD(-) CD27(+) CD19(+) memory B cells and increased plasmablasts may be involved in the pathogenic process of UC.

Distinctions among Circulating Antibody-Secreting Cell Populations, Including B-1 Cells, in Human Adult Peripheral Blood

Human Ab-secreting cell (ASC) populations in circulation are not well studied. In addition to B-1 (CD20(+)CD27(+)CD38(lo/int)CD43(+)) cell and conventional plasmablast (PB) (CD20-CD27(hi)CD38(hi)) cell populations, in this study, we identified a novel B cell population termed 20(+)38(hi) B cells (CD20(+)CD27(hi)CD38(hi)) that spontaneously secretes Ab. At steady-state, 20(+)38(hi) B cells are distinct from PBs on the basis of CD20 expression, amount of Ab production, frequency of mutation, and diversity of BCR repertoire. However, cytokine treatment of 20(+)38(hi) B cells induces loss of CD20 and acquisition of CD138, suggesting that 20(+)38(hi) B cells are precursors to PBs or pre-PBs. We then evaluated similarities and differences among CD20(+)CD27(+)CD38(lo/int)CD43(+) B-1 cells, CD20(+)CD27(hi)CD38(hi) 20(+)38(hi) B cells, CD20(-)CD27(hi)CD38(hi) PBs, and CD20(+)CD27(+)CD38(lo/int)CD43(-) memory B cells. We found that B-1 cells differ from 20(+)38(hi) B cells and PBs in a number of ways, including Ag expression, morphological appearance, transcriptional profiling, Ab skewing, Ab repertoire, and secretory response to stimulation. In terms of gene expression, B-1 cells align more closely with memory B cells than with 20(+)38(hi) B cells or PBs, but differ in that memory B cells do not express Ab secretion-related genes. We found that B-1 cell Abs use Vh4-34, which is often associated with autoreactivity, 3- to 6-fold more often than other B cell populations. Along with selective production of IgM anti-phosphoryl choline, these data suggest that human B-1 cells might be preferentially selected for autoreactivity/natural specificity. In summary, our results indicate that human healthy adult peripheral blood at steady-state consists of three distinct ASC populations.

Current and future immunotherapy targets in autoimmune neurology

Randomized controlled treatment trials of autoimmune neurologic disorders are generally lacking and data pertaining to treatment are mostly derived from expert opinion, large case series, and anecdotal reports. The treatment of autoimmune neurologic disorders comprises oncologic therapy (where appropriate) and immunotherapy. In this chapter, we first describe the standard acute and chronic immunotherapies and provide a practical overview of their use in the clinic (mechanisms of action, dosing, monitoring, and side effects). Novel approaches to treatment of autoimmune neurologic disorders, through new drug discovery or repurposing, are dependent on improved mechanistic understanding of immunopathology. Such approaches, with emphasis on monoclonal antibodies, are discussed using the paradigm of three autoimmune neurologic disorders whose immunopathogenesis is better understood, specifically myasthenia gravis, neuromyelitis optica, and chronic inflammatory demyelinating polyradiculoneuropathy. It is important to realize that the treatment strategy and management plan must be individualized for each patient. In general these are influenced by the following: clinical severity, antibody type, presence or absence of cancer, and prior treatment response, if known.

Flow cytometry in hematological nonmalignant disorders

Multiparameter flow cytometry (MFC) has become an integral part of the diagnosis and classification of hematological malignancies. However, several nonmalignant or premalignant disorders may benefit from this technology in hematology laboratories. This review provides information on the normal immunophenotypic characteristics of peripheral blood leukocyte subsets and their modifications in several clinical conditions. The usefulness of MFC and the specific markers that can be investigated in hyperlymphocytosis, infection, hypereosinophilia, paroxysmal nocturnal hemoglobinuria, and large granular lymphocyte disorders is described. Mention is also made of the developments of MFC for analyses of red blood cells or platelets.

Phorbol myristate acetate, but not CD40L, induces the differentiation of CLL B cells into Ab-secreting cells

In this study, we investigated the capacity of chronic lymphocytic leukemia (CLL) B cells to undergo terminal differentiation into Ig-secreting plasma cells in T cell-independent and T cell-dependent responses. We used a two-step model involving stimulation with phorbol myristate acetate (PMA) and CD40L, together with cytokines (PMA/c and CD40L/c), for 7 days. We describe immunophenotypic modifications, changes in the levels of mRNA and protein for transcription factors and morphological and functional events occurring during the differentiation of CLL B cells into antibody-secreting cells (ASCs). The induction of differentiation differed significantly between the CD40L/c and PMA/c culture systems. The PMA/c culture system allowed CLL B cells to differentiate into IgM-secreting cells with an immunophenotype and molecular profile resembling those of preplasmablasts. By contrast, CD40L/c-stimulated cells had a phenotype and morphology similar to those of activated B cells and resembling those of the CLL B cells residing in the lymph node and bone marrow. These data suggest that the CLL B cells are not frozen permanently at a stage of differentiation and are able to differentiate into ASCs as appropriate stimulation are provided. The data presented here raise questions about the molecular processes and stimulation required for CLL B-cell differentiation and about the inability of CD40 ligand to induce differentiation of the CLL B cells.

Phenotypic, genomic and functional characterization reveals no differences between CD138++ and CD138low subpopulations in multiple myeloma cell lines

Despite recent advances in the treatment of multiple myeloma (MM), it remains an incurable disease potentially due to the presence of resistant myeloma cancer stem cells (MM-CSC). Although the presence of clonogenic cells in MM was described three decades ago, the phenotype of MM-CSC is still controversial, especially with respect to the expression of syndecan-1 (CD138). Here, we demonstrate the presence of two subpopulations--CD138++ (95-99%) and CD138low (1-5%)--in eight MM cell lines. To find out possible stem-cell-like features, we have phenotypically, genomic and functionally characterized the two subpopulations. Our results show that the minor CD138low subpopulation is morphologically identical to the CD138++ fraction and does not represent a more immature B-cell compartment (with lack of CD19, CD20 and CD27 expression). Moreover, both subpopulations have similar gene expression and genomic profiles. Importantly, both CD138++ and CD138low subpopulations have similar sensitivity to bortezomib, melphalan and doxorubicin. Finally, serial engraftment in CB17-SCID mice shows that CD138++ as well as CD138low cells have self-renewal potential and they are phenotypically interconvertible. Overall, our results differ from previously published data in MM cell lines which attribute a B-cell phenotype to MM-CSC. Future characterization of clonal plasma cell subpopulations in MM patients' samples will guarantee the discovery of more reliable markers able to discriminate true clonogenic myeloma cells.

Clinical manifestation of angioimmunoblastic T-cell lymphoma with exuberant plasmacytosis

Angioimmunoblastic T-cell lymphoma (AITL) is a rare subtype of non-Hodgkin lymphoma characterized by aggressive symptoms and various abnormal laboratory test results. One of the rare immunologic abnormalities in AITL is exuberant polyclonal plasmacytosis, but its clinical significance has not been evaluated. This report concerns three AITL cases with exuberant polyclonal plasmacytosis and investigates its clinical impact by comparison with 12 patients without plasmacytosis. Our study found that the performance status (PS) of the former was significantly worse and their serum immunoglobulin levels were significantly higher. All other parameters, including B symptoms, various prognostic scores, blood cell counts other than plasmacyte, and serum levels of lactate dehydrogenase, C-reactive protein and soluble interleukin-2 receptor, showed no significant differences. More importantly, although the diagnosis of AITL with plasmacytosis was not straightforward in our series, outcomes of treatment with conventional chemotherapy or immunosuppressive therapy with cyclosporine A were favorable. To conclude, AITL should be considered a candidate underlying disease of exuberant polyclonal plasmacytosis. Provided a correct diagnosis is made early and is followed by adequate treatment, the prognosis for AITL with plasmacytosis may not be worse than that for those without plasmacytosis despite the severe exhaustion at first presentation.

Antibody-secreting cells with a phenotype of Ki-67low, CD138high, CD31high, and CD38high secrete nonspecific IgM during primary hepatitis A virus infection

Although studies investigating the nature of Ab-secreting cells (ASCs) during acute infection with influenza or dengue virus found that the ASC response was dominated by virus-specific IgG secretion, the Ag specificity and phenotype of ASCs during primary acute viral infection were not identified. To this end, we investigated the nature of ASCs in direct ex vivo assays from patients with acute hepatitis A caused by primary infection with hepatitis A virus (HAV). We found that the frequency of CD27(high)CD38(high) ASCs was markedly increased in the peripheral blood during the acute phase of HAV infection. Moreover, substantial numbers of ASCs were non-HAV-specific and dominantly secreted IgM. We detected HAV-specific ASCs by staining with fluorochrome-tagged HAV-VP1 protein. As compared with HAV-specific ASCs, non-HAV-specific ASCs were Ki-67(low)CD138(high)CD31(high)CD38(high), demonstrating that non-HAV-specific ASCs had a bone marrow plasma cell-like phenotype whereas HAV-specific ASCs had a phenotype typical of circulating plasmablasts. These data suggest that non-HAV-specific ASCs might be mobilized plasma cells from the bone marrow or the spleen, whereas HAV-specific ASCs were newly generated plasmablasts. In this study, we provide evidence that pre-existing plasma cells are released into the circulation and contribute to Ag-nonspecific secretion of IgM during primary HAV infection.

The proto-oncogene c-myc regulates antibody secretion and Ig class switch recombination

The immune response involves the generation of Ab-secreting cells and memory B cells through a process called terminal B lymphocyte differentiation. This program requires the transcriptional repressor Blimp-1, which inhibits c-myc expression and terminates proliferation. Although the role of c-Myc in cell proliferation is well characterized, it is not known whether it has other functions in terminal differentiation. In this study, we show that c-Myc not only regulates cell proliferation, but it is also essential for Ab-secreting cell function and differentiation in vivo. c-Myc-deficient B lymphocytes hypersecrete IgM and do not undergo Ig class switch recombination (CSR). CSR has been previously linked to proliferation, and in this study we mechanistically link class switching and proliferation via c-Myc. We observed that c-Myc regulates CSR by transcriptionally activating the B cell-specific factor activation-induced cytidine deaminase. By linking cell proliferation and CSR, c-Myc is thus a critical component for a potent immune response.

Inhibition of DEPDC1A, a bad prognostic marker in multiple myeloma, delays growth and induces mature plasma cell markers in malignant plasma cells

High throughput DNA microarray has made it possible to outline genes whose expression in malignant plasma cells is associated with short overall survival of patients with Multiple Myeloma (MM). A further step is to elucidate the mechanisms encoded by these genes yielding to drug resistance and/or patients' short survival. We focus here on the biological role of the DEP (for Disheveled, EGL-10, Pleckstrin) domain contained protein 1A (DEPDC1A), a poorly known protein encoded by DEPDC1A gene, whose high expression in malignant plasma cells is associated with short survival of patients. Using conditional lentiviral vector delivery of DEPDC1A shRNA, we report that DEPDC1A knockdown delayed the growth of human myeloma cell lines (HMCLs), with a block in G2 phase of the cell cycle, p53 phosphorylation and stabilization, and p21(Cip1) accumulation. DEPDC1A knockdown also resulted in increased expression of mature plasma cell markers, including CXCR4, IL6-R and CD38. Thus DEPDC1A could contribute to the plasmablast features of MMCs found in some patients with adverse prognosis, blocking the differentiation of malignant plasma cells and promoting cell cycle.

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.

Immune markers and correlates of protection for vaccine induced immune responses

Vaccines have been a major innovation in the history of mankind and still have the potential to address the challenges posed by chronic intracellular infections including tuberculosis, HIV and malaria which are leading causes of high morbidity and mortality across the world. Markers of an appropriate humoral response currently remain the best validated correlates of protective immunity after vaccination. Despite advancements in the field of immunology over the past few decades currently there are, however, no sufficiently validated immune correlates of vaccine induced protection against chronic infections in neither human nor veterinary medicine. Technological and conceptual advancements within cell-mediated immunology have led to a number of new immunological read-outs with the potential to emerge as correlates of vaccine induced protection. For T(H)1 type responses, antigen-specific production of interferon-gamma (IFN-γ) has been promoted as a quantitative marker of protective cell-mediated immune responses over the past couple of decades. More recently, however, evidence from several infections has pointed towards the quality of the immune response, measured through increased levels of antigen-specific polyfunctional T cells capable of producing a triad of relevant cytokines, as a better correlate of sustained protective immunity against this type of infections. Also the possibilities to measure antigen-specific cytotoxic T cells (CTL) during infection or in response to vaccination, through recombinant major histocompatibility complex (MHC) class I tetramers loaded with relevant peptides, has opened a new vista to include CTL responses in the evaluation of protective immune responses. Here, we review different immune markers and new candidates for correlates of a protective vaccine induced immune response against chronic infections and how successful they have been in defining the protective immunity in human and veterinary medicine.

[Plasmacytosis and dengue fever: an underestimated abnormality?]

INTRODUCTION

A significant peripheral blood plasmacytosis is a rare finding associated with viral infections. We reported five consecutive cases of dengue virus infection, with circulating plasma cells.

CASE REPORTS

Three women and two men, aged 26 to 75 years, had returned from French West Indies less than one week before the onset of the symptoms (mean: 2.5 days). The transient blood plasmacytosis was variable in intensity (0.1 to 0.8 G/L) with a maximal level between the fourth and the seventh day following the onset of the symptoms, and was associated in four patients, with activated lymphocytes and lympho-plasma cells.

CONCLUSION

Reactive plasmacytosis during dengue fever is common and probably underestimated because it is transient and only identified by careful microscopic examination of a blood smear. Plasmacytosis could be explained by the intensity of the immunological response and the production of large amount of interleukins.

IL-21 and IL-6 are critical for different aspects of B cell immunity and redundantly induce optimal follicular helper CD4 T cell (Tfh) differentiation

Cytokines are important modulators of lymphocytes, and both interleukin-21 (IL-21) and IL-6 have proposed roles in T follicular helper (Tfh) differentiation, and directly act on B cells. Here we investigated the absence of IL-6 alone, IL-21 alone, or the combined lack of IL-6 and IL-21 on Tfh differentiation and the development of B cell immunity in vivo. C57BL/6 or IL-21^−/− mice were treated with a neutralizing monoclonal antibody against IL-6 throughout the course of an acute viral infection (lymphocytic choriomeningitis virus, LCMV). The combined absence of IL-6 and IL-21 resulted in reduced Tfh differentiation and reduced Bcl6 protein expression. In addition, we observed that these cytokines had a large impact on antigen-specific B cell responses. IL-6 and IL-21 collaborate in the acute T-dependent antiviral antibody response (90% loss of circulating antiviral IgG in the absence of both cytokines). In contrast, we observed reduced germinal center formation only in the absence of IL-21. Absence of IL-6 had no impact on germinal centers, and combined absence of both IL-21 and IL-6 revealed no synergistic effect on germinal center B cell development. Studying CD4 T cells in vitro, we found that high IL-21 production was not associated with high Bcl6 or CXCR5 expression. TCR stimulation of purified naïve CD4 T cells in the presence of IL-6 also did not result in Tfh differentiation, as determined by Bcl6 or CXCR5 protein expression. Cumulatively, our data indicates that optimal Tfh formation requires IL-21 and IL-6, and that cytokines alone are insufficient to drive Tfh differentiation.

Molecular pathogenesis of multiple myeloma: chromosomal aberrations, changes in gene expression, cytokine networks, and the bone marrow microenvironment

This chapter focuses on two aspects of myeloma pathogenesis: (1) chromosomal aberrations and resulting changes in gene and protein expression with a special focus on growth and survival factors of malignant (and normal) plasma cells and (2) the remodeling of the bone marrow microenvironment induced by accumulating myeloma cells. We begin this chapter with a discussion of normal plasma cell generation, their survival, and a novel class of inhibitory factors. This is crucial for the understanding of multiple myeloma, as several abilities attributed to malignant plasma cells are already present in their normal counterpart, especially the production of survival factors and interaction with the bone marrow microenvironment (niche). The chapter closes with a new model of pathogenesis of myeloma.

High incidence of peripheral blood plasmacytosis in patients with dengue virus infection

Little is known about polyclonal peripheral blood plasmacytosis in dengue virus (DENV)-infected patients. We initiated this prospective observational study to quantify and describe the kinetics and phenotype of peripheral blood plasma cells (PCs) in these patients. Morphological examination and flow cytometric (FC) analysis for the characterization and immunophenotyping of lymphocyte subsets and PCs were performed in 35 and 31 patients suspected of DENV infection, respectively. Our results show that blood plasmacytosis is a very common haematological finding. Depending on the days of illness at presentation, blood plasmacytosis was observed in 64% to 73% of patients. Blood plasmacytosis was most pronounced before 7 days of illness and declined rapidly thereafter, to completely disappear after 14 days of illness. Blood plasmacytosis was higher in secondary DENV infection. The majority of CD138(+) PCs (89%) had a shared immunophenotype (CD45(+)/CD19(-)/CD56(-)) and in all cases the PCs were polyclonal. Blood plasmacytosis, characterized by a transient presence of polyclonal PCs in the circulation, is a common event in DENV infection.

Increased numbers of immature plasma cells in peripheral blood specifically overexpress chemokine receptor CXCR3 and CXCR4 in patients with ulcerative colitis

Ulcerative colitis (UC) is a chronic inflammatory bowel disease featuring infiltration by plasma cells producing immunoglobulins. We have reported previously the specific and significant proliferation of immature plasma cells in the inflamed colonic and pouch mucosa of UC patients. The aim of this study was to characterize peripheral blood immature plasma cells and the migration mechanisms of such immature plasma cells to inflamed sites in UC. The characteristics of peripheral blood immature plasma cells and chemokine receptor expression were examined by flow cytometry. Expression of mucosal chemokine was quantified using real-time reverse transcription-polymerase chain reaction and immunohistochemistry. The number of peripheral blood immature plasma cells was significantly higher in patients with active UC and active Crohn's disease (CD) than in healthy controls. The proportion of immature plasma cells was correlated positively with clinical activities of UC and CD. Many peripheral blood immature plasma cells were positive for CXCR3, CXCR4, CCR9 and CCR10. Expression of CXCR3 and CXCR4 in UC patients was significantly higher than in controls. CXCL9, CXCL10 and CXCL11 mRNA levels in colonic mucosa of inflamed IBD were higher than in controls. Immunofluorescence study also showed abundant CXCR3-positive immature plasma cells in the inflamed colonic mucosa of UC. Increased numbers of immature plasma cells may migrate towards inflammatory sites of UC via the CXCR3 axis, and may participate in UC pathogenesis.

Nitrogen-containing bisphosphonate incadronate augments the inhibitory effect of farnesyl transferase inhibitor tipifarnib on the growth of fresh and cloned myeloma cellsin vitro

RAS gene mutations occur in 30 - 40% of multiple myeloma (MM) patients. Farnesylation is the first step in the post-translational modification of RAS proteins. Tipifarnib is a potent farnesyl transferase inhibitor, and incadronate prevents post-translational prenylation of GTP-binding proteins such as RAS proteins. We examined the effect of tipifarnib in combination with incadronate on the growth of fresh and cloned myeloma cells in vitro. Tipifarnib inhibited the growth of myeloma cells, and this inhibition was intensified when tipifarnib was combined with incadronate. Tipifarnib, in combination with incadronate, may have some benefits in MM patients.

B cell characterization and reactivity analysis in multiple sclerosis

B cells are one of the key players in the pathogenesis of multiple sclerosis (MS). The peripheral B cell distributions are similar in healthy persons and MS patients. In healthy controls, B cells are rarely present in the cerebrospinal fluid (CSF) while in MS patients, a clonally expanded B cell population is detected. This consists of memory B cells, centroblasts and antibody-secreting plasma blasts and plasma cells that are responsible for intrathecal immunoglobulin G production and oligoclonal band formation in more than 90% of MS patients. Unfortunately, the targets of the autoreactive B cells and antibodies remain largely unknown. Various candidate antigens have been identified but often their involvement in the disease process is still unclear. Most studies characterizing these target antigens examined autoantibodies by analyzing sera or CSF of MS patients. An alternative approach is focusing on the clonally expanded B cells. In this way B cells directed against myelin, astroglia and axons have been denoted in MS patients. B cell immortalization, that is based on the antibody-producing potential of Epstein–Barr virus (EBV) transformed B cells, can be used to expand B cells from MS patients for the production of antibodies, that ultimately can be analysed for target identification.

Bone-marrow immunophenotypic analysis allows the identification of high risk of progression and immune condition-related monoclonal gammopathy of undetermined significance

BACKGROUND

Monoclonal gammopathy of undetermined significance (MGUS) progresses to plasma cell dyscrasia at a rate of 1% per year. A high prevalence of MGUS has been noted in series of patients with immune disorders or chronic infections.

METHODS

Retrospective cohort and a cross-sectional study to analyze the prognostic value of aberrant (CD38(+ +)CD138(+) CD19(-)CD45(weak)) to normal phenotype (CD38(+ +)CD138(+) CD19(+)CD45(+)) bone-marrow plasma cells ratio (A/N ratio) for the development of a plasma cell dyscrasia and the association with the presence of a chronic immune disorder.

RESULTS

A total of 322 patients were included with a median follow-up of 46 months. Analysis for progression revealed an increased A/N ratio as the main independent prognostic variable. A significant association between a reduced A/N ratio and the diagnosis of a chronic immune condition was found. Using receiver-operating characteristic analysis we created an A/N ratio range from 4 to 0.20. Values of 4 or higher define a group at high risk of progression (OR 10.7). A/N values of 0.20 or lower are associated with immune disorders or chronic infections (OR 20.9).

CONCLUSIONS

Extreme values of the A/N ratio seem to be related with two different conditions: high risk of progression, and immune condition-related MGUS.

Evidence for a pathogenic determinant in HIV-1 Nef involved in B cell dysfunction in HIV/AIDS

B lymphocyte hyperactivation and elevated immunoglobulin levels (hypergammaglobulinemia) are pathogenic manifestations of HIV-1 infection. Here we provide evidence that these hallmarks are caused by a soluble factor whose production by infected macrophages is induced by the HIV-1 Nef protein. In vitro, HIV-1-infected macrophages or macrophages expressing Nef promoted B cell activation and differentiation to immunoglobulin-secreting cells. Nef-mediated activation of NF-kappaB in macrophages induced secretion of the acute-phase protein ferritin, and ferritin was necessary and sufficient for the observed Nef-dependent B cell changes. The extent of hypergammaglobulinemia in HIV-1-infected individuals correlated directly with plasma ferritin levels and with viral load. Furthermore, the induction of ferritin production and hypergammaglobulinemia was recapitulated when Nef was specifically expressed in macrophages and T cells of transgenic mice. Collectively, these results indicate that the HIV-1 Nef protein carries a pathogenic determinant that governs B cell defects in HIV-1 infection.

Proliferation of immature plasma cells in pouchitis mucosa in patients with ulcerative colitis

BACKGROUND

Pouchitis is the most common complication of restorative proctocolectomy in patients with ulcerative colitis (UC). The etiology of pouchitis is not known. We have previously reported the specific and significant proliferation of immature plasma lineage cells in the ulcer bases and inflamed mucosa of UC. In the present study we report the results of a phenotypic study of ileal pouch mucosa.

METHODS

Biopsy samples were taken from the ileal pouch of 22 patients with UC (12 with pouchitis, 10 with a normal pouch) and 5 patients with familial adenomatous polyposis (FAP) (with a normal pouch) who underwent restorative proctocolectomy, and normal ileum of 10 patients with UC yet to undergo pouch surgery. Frozen sections were cut from fixed samples and reacted with various lymphocyte markers and anti-Ki-67 antibodies. Ki-67+ cells, CD19+ cells, and CD138+ cells were significantly increased in the pouchitis mucosa of patients with UC.

RESULTS

Immunological double staining revealed significantly increased numbers of CD19+Ki-67+ cells and CD138+Ki-67+ cells in the pouchitis mucosa of patients with UC compared to noninflamed UC pouch, FAP pouch, and normal ileum of UC patients. The number of CD19+CD138+ cells was significantly increased in inflamed pouch mucosa. The increased number of CD19+CD138+ cells we observed represents proliferation of immature plasma cells. Moreover, the increase in labeling for Ki-67 among CD19 cells and CD138 cells suggests proliferative activity of these cells, consistent with their immaturity.

CONCLUSIONS

Proliferation of these immature plasma cells suggests the possibility of involvement of UC-derived abnormality in the pathogenesis of pouchitis.