Identification of the novel null allele HLA-DPB1*1449:01N by next-generation sequencing.

The novel HLA-DPB1*1449:01N allele differs from HLA-DPB1*16:01:01:01 by a nucleotide at codon 92 in exon 2.

Laboratory and clinical practices in antinuclear antibody detection and related antigens: recommendations from a Spanish multicentre survey.

Antinuclear antibodies (ANA) are the most widely used immunological test for the diagnosis of autoimmune diseases. Despite the recommendations of experts, there is some variability in performing and interpreting this test in routine practice. In this context, the Spanish Group on Autoimmune Diseases (GEAI) of the Spanish Society of Immunology (SEI) conducted a national survey of 50 autoimmunity laboratories. Here we report the survey results on ANA testing, detection of related antigens, and our recommendations. The survey showed that most of the participating laboratories use a similar approach for most key practices: 84% perform ANA by indirect immunofluorescence (IIF) on HEp-2 cells as the screening methodology while the other laboratories use IIF to confirm positive screens; 90% report ANA test results as either negative or positive with titer and pattern; 86% indicated that the ANA pattern conditioned follow-up testing for specific antigen-related antibodies; and 70% confirm positive anti-dsDNA. However, testing practices were highly heterogeneous for certain items, such as sera dilutions and the minimum time period for repeating ANA and related antigen determinations. Overall, this survey shows that most autoimmune laboratories in Spain use a similar approach but that further standardization of testing and reporting protocols is needed.

The age again in the eye of the COVID-19 storm: evidence-based decision making.

BACKGROUND: One hundred fifty million contagions, more than 3 million deaths and little more than 1 year of COVID-19 have changed our lives and our health management systems forever. Ageing is known to be one of the significant determinants for COVID-19 severity. Two main reasons underlie this: immunosenescence and age correlation with main COVID-19 comorbidities such as hypertension or dyslipidaemia. This study has two aims. The first is to obtain cut-off points for laboratory parameters that can help us in clinical decision-making. The second one is to analyse the effect of pandemic lockdown on epidemiological, clinical, and laboratory parameters concerning the severity of the COVID-19. For these purposes, 257 of SARSCoV2 inpatients during pandemic confinement were included in this study. Moreover, 584 case records from a previously analysed series, were compared with the present study data. RESULTS: Concerning the characteristics of lockdown series, mild cases accounted for 14.4, 54.1% were moderate and 31.5%, severe. There were 32.5% of home contagions, 26.3% community transmissions, 22.5% nursing home contagions, and 8.8% corresponding to frontline worker contagions regarding epidemiological features. Age > 60 and male sex are hereby confirmed as severity determinants. Equally, higher severity was significantly associated with higher IL6, CRP, ferritin, LDH, and leukocyte counts, and a lower percentage of lymphocyte, CD4 and CD8 count. Comparing this cohort with a previous 584-cases series, mild cases were less than those analysed in the first moment of the pandemic and dyslipidaemia became more frequent than before. IL-6, CRP and LDH values above 69 pg/mL, 97 mg/L and 328 U/L respectively, as well as a CD4 T-cell count below 535 cells/µL, were the best cut-offs predicting severity since these parameters offered reliable areas under the curve. CONCLUSION: Age and sex together with selected laboratory parameters on admission can help us predict COVID-19 severity and, therefore, make clinical and resource management decisions. Demographic features associated with lockdown might affect the homogeneity of the data and the robustness of the results.

Autoreactive B-lymphocytes in SLE and RA patients: Isolation and characterisation using extractable nuclear and citrullinated antigens bound to immunobeads.

Systemic lupus erythematosus and rheumatoid arthritis are autoimmune diseases characterised by B-cell hyperactivation and production of autoantibodies (AutoAbs) against various self-antigens, including extractable nuclear antigens and citrullinated peptides. Therefore, B lymphocytes and antibody-secreting cells are considered relevant targets for therapies. However, isolation and characterisation of auto-reactive specific B lymphocytes are limited, primarily due to technical issues. In this work, we purified extractable nuclear antigen-specific and citrullinated peptide-specific auto-reactive B lymphocytes by magnetic selection with ENA- and citrullinated peptide-bound immunobeads. We obtained blood auto-reactive B lymphocytes from most patients. Their nature was primarily naïve B cells, some of them in an active status, with low levels of somatic hypermutations in the immunoglobulin heavy-chain variable regions. Their presence correlated with serum levels of autoAb. Auto-reactive B lymphocytes were able to differentiate into auto-reactive antibody-secreting cells under conditions of stimulation. In addition, based on the presence of circulating auto-reactive B cells and/or antibody-secreting cells, four different profiles were described in lupus patients. Thus, tracking auto-reactive B cells and/or antibody-secreting cells in patient blood could represent a biomarker for deciding whether to use therapies blocking either B cells, plasma cells or both, as well as a new tool for monitoring minimal residual autoimmune disease in patients.

Talleres de Autoinmunidad: Anticuerpos antinucleosomas y otras especificidades nucleares / No disponible

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The transcriptional profiling of human in vivo-generated plasma cells identifies selective imbalances in monoclonal gammopathies.

Plasma cells (PC) represent the heterogeneous final stage of the B cells (BC) differentiation process. To characterize the transition of BC into PC, transcriptomes from human naïve BC were compared to those of three functionally-different subsets of human in vivo-generated PC: i) tonsil PC, mainly consisting of early PC; ii) PC released to the blood after a potent booster-immunization (mostly cycling plasmablasts); and, iii) bone marrow CD138+ PC that represent highly mature PC and include the long-lived PC compartment. This transcriptional transition involves subsets of genes related to key processes for PC maturation: the already known protein processing, apoptosis and homeostasis, and of new discovery including histones, macromolecule assembly, zinc-finger transcription factors and neuromodulation. This human PC signature is partially reproduced in vitro and is conserved in mouse. Moreover, the present study identifies genes that define PC subtypes (e.g., proliferation-associated genes for circulating PC and transcriptional-related genes for tonsil and bone marrow PC) and proposes some putative transcriptional regulators of the human PC signatures (e.g., OCT/POU, XBP1/CREB, E2F, among others). Finally, we also identified a restricted imbalance of the present PC transcriptional program in monoclonal gammopathies that correlated with PC malignancy.

Clinical relevance of circulating anti-ENA and anti-dsDNA secreting cells from SLE patients and their dependence on STAT-3 activation.

Disturbances of plasma cell homeostasis and auto-antibody production are hallmarks of systemic lupus erythematosus. The aim of this study was to explore the presence of circulating anti-ENA and anti-dsDNA antibody-secreting cells, to determine their dependence on plasma cell-niche cytokines and to analyze their clinical value. The study was performed in SLE patients with serum anti-ENA and/or anti-dsDNA antibodies (n = 57). Enriched B-cell fractions and sorted antibody-secreting cells (CD19low CD38high ) were obtained from blood. dsDNA- and ENA-specific antibody-secreting cells were identified as cells capable of active auto-antibody production in culture. The addition of a combination of IL-6, IL-21, BAFF, APRIL, and CXCL12 to the cultures significantly augmented auto-antibody production and antibody-secreting cell proliferation, whereas it diminished apoptosis. The effect on auto-antibody production was dependent on STAT-3 activation as it was abrogated in the presence of the JAK/STAT-3 pathway inhibitors ruxolitinib and stattic. Among patients with serum anti-dsDNA antibodies, the detection of circulating anti-dsDNA-antibody-secreting cells was associated with higher disease activity markers. In conclusion, auto-antibody production in response to plasma cell-niche cytokines that are usually at high levels in SLE patients is dependent on JAK/STAT-3 activation. Thus, patients with circulating anti-dsDNA antibody-secreting cells and active disease could potentially benefit from therapies targeting the JAK/STAT3 pathway.

Survival of human circulating antigen-induced plasma cells is supported by plasma cell-niche cytokines and T follicular helper lymphocytes.

Human circulating Ag-induced plasma cells (PCs) contain a high proportion of cycling cells. This study reveals that these PCs spontaneously proliferate in culture during 72 h, as determined by BrdU-uptake detection. Transcriptome analysis indicates that, in comparison with tonsil and bone marrow (BM) PCs, these PCs distinctively upregulate genes involved in cell division. Blood PC proliferation occurs simultaneously with increasing apoptosis rates, and is associated with PC survival. In addition, the proliferating activity of these PCs is enhanced by the addition of cytokines present in PC survival niches. Moreover, blood Ag-induced, but not BM, PCs exhibit the expression of molecules involved in the interaction between memory B cells and T follicular helper (Tfh) cells. In fact, purified circulating and tonsil Tfh cells increased IgG secretion by blood Ag-induced, but not by BM, PCs. This effect is exerted by augmenting blood PC survival through a mechanism partly dependent on cell contact. These results strongly suggest that the proliferating capacity of circulating Ag-induced PCs contributes to their competitive migration to survival niches, either to long-living PC niches or to temporal niches present in reactive lymphoid organs and inflamed tissues, structures where Tfh cells appear to participate.

STAT-3 activation by differential cytokines is critical for human in vivo-generated plasma cell survival and Ig secretion.

Maturation and survival of plasma cells (PCs) depends on extrinsic factors provided in specialized niches. In addition, B lymphocyte differentiation into PCs requires the activation of the JAK-STAT-3 pathway. However, whether STAT-3 is needed only during the transition of B lymphocytes to PC, or it is also involved in the survival and function of PCs at different stages of maturation, has not been unequivocally clarified. This study analyzes the effect of IL-10, IL-21, and IL-6 on human in vivo-generated PCs isolated from secondary lymphoid organs, blood (circulating, recently Ag-induced PCs), and bone marrow. PCs from these different organs show specific profiles of receptors for, and responsiveness to, these cytokines required for their survival and sustained Ab secretion. However, IL-10, IL-21, and IL-6 commonly induce STAT-3 phosphorylation in the three PC subsets, and all of their effects are exerted strictly through the STAT-3 activation. The inhibition or nonactivation of this pathway in the three PC populations impairs not only the effect of STAT-3-activating cytokines, but also the action of other cytokines important at the PC level, including a proliferation-induced ligand, BAFF, insulin-like growth factor 1, vascular endothelial growth factor, and stromal cell-derived factor-1α. These results indicate that STAT-3 activation is critical for human PCs throughout their maturation.

Myeloma cells contain high levels of inorganic polyphosphate which is associated with nucleolar transcription.

BACKGROUND: In hematology there has recently been increasing interest in inorganic polyphosphate. This polymer accumulates in platelet granules and its functions include modulating various stages of blood coagulation, inducing angiogenesis, and provoking apoptosis of plasma cells. In this study we evaluated the characteristics of intracellular polyphosphate in myeloma cell lines, in primary myeloma cells from patients, and in other human B-cell populations from healthy donors. DESIGN AND METHODS: We have developed a novel flow cytometric method for detecting levels of polyphosphate in cell populations. We also used confocal microscopy and enzymatic analysis to study polyphosphate localization and characteristics. RESULTS: We found that myeloma plasma cells contain higher levels of intracellular polyphosphate than normal plasma cells and other B-cell populations. Localization experiments indicated that high levels of polyphosphate accumulate in the nucleolus of myeloma cells. As the principal function of the nucleolus involves transcription of ribosomal DNA genes, we found changes in the cellular distribution of polyphosphate after the inhibition of nucleolar transcription. In addition, we found that RNA polymerase I activity, responsible for transcription in the nucleolus, is also modulated by polyphosphate, in a dose-dependent manner. CONCLUSIONS: Our results show an unusually high accumulation of polyphosphate in the nucleoli of myeloma cells and a functional relationship of this polymer with nucleolar transcription.

Cutting edge: IL-21 derived from human follicular helper T cells acts as a survival factor for secondary lymphoid organ, but not for bone marrow, plasma cells.

IL-21 induces the differentiation of activated B lymphocytes into plasma cells (PC), but its direct effect on PC remains uncertain. This study analyzes the role of IL-21 on human in vivo-generated PC. IL-21R was clearly expressed on PC from the human tonsil, the lymph node, and the spleen (secondary lymphoid organs [SLO]) but barely on terminally mature bone marrow PC. IL-21 enhanced Ig secretion by isolated SLO PC but not bone marrow PC. Tonsillar T follicular helper (Tfh) lymphocytes are known to secrete IL-21. Purified Tfh cells induced a marked increase of Ig production by tonsillar PC, and this effect was impaired when endogenous IL-21 production was blocked. IL-21 provoked a rapid and transient phosphorylation of STAT3 in tonsillar PC. Tfh cells or exogenous IL-21 reduce tonsillar PC apoptosis and increases PC recovery but does not modify their nonproliferating status. These results suggest that IL-21 derived from Tfh cells acts as a survival factor for SLO PC in vivo.

Differential expression of SLAMS and other modulatory molecules by human plasma cells during normal maturation.

Plasma cells (PCs) are specialized in antibody (Ab) production and they are, therefore, responsible for maintaining humoral immune responses. The human PC compartment is heterogeneous. PCs from inductive secondary lymphoid organs and from peripheral blood (PB) show less capability for prolonged survival and Ab production than bone marrow (BM) PCs, a pool consisting of fully mature cells. The HLDA9 workshop has allowed the use of labeled-monoclonal Abs (moAbs) recognizing a variety of recently identified lymphocyte modulatory surface receptors. In this study, flow cytometry analysis has been used to define the presence of these receptors on human PCs obtained from human tonsil (as an example of inductive organ), from PB and from BM. It was found that human PCs commonly expressed SLAMF1 (CD150), SLAMF2 (CD48), SLAMF3 (CD229), SLAMF6 (CD352) and SLAMF7 (CD319), but not SLAMF4 (CD244). In addition, PCs distinctively showed a low level of SLAMF5 (CD84) and a very high level of SLAMF7 expression in comparison with earlier stages of B cell maturation. All PC subsets exhibited a similar pattern of expression of SLAMF receptors suggesting a stage-dependent role for these proteins. In addition, most circulating PCs clearly expressed TNFRSF14 (CD270), BTLA (CD272), B7-1 (CD80) and B7-2 (CD86), and a substantial fraction of them were also positive for TNFRSF18 (CD357), FCRL1 (CD307a) and LAIR-1 (CD305). In contrast, tonsil and BM PCs only exhibited partial expression of TNFRSF14 and B7-2, a pattern of molecular expression similar to that detected on germinal center (GC) B cells. Present results indicate that human PCs exhibit a common pattern of SLAMF proteins, but differ in the rest of the receptors examined; this difference might be associated with their distinctive homing and functional requirements.

Decreased frequency and activated phenotype of blood CD27 IgD IgM B lymphocytes is a permanent abnormality in systemic lupus erythematosus patients.

INTRODUCTION: Systemic lupus erythematosus (SLE) is characterized by B cell hyper-activation and auto-reactivity resulting in pathogenic auto-antibody generation. The phenotypic analysis of blood B cell subsets can be used to understand these alterations. METHODS: The combined detection of CD19, CD27 and IgD (or IgM) by flow cytometry (FC) analysis delineates five well-defined blood B cell-subsets: naive, switched (S) memory, double negative (DN) memory and CD27 IgD IgM (non-switched memory) B lymphocytes, and plasma cells (PCs). This phenotypic study was performed in 69 consecutive SLE patients and 31 healthy controls. RESULTS: SLE patients exhibited several abnormalities in the distribution of these B cell subsets, including elevated levels of DN memory B cells and PCs, and decreased CD27 IgD IgM B cells. Active SLE patients also showed decreased presence of S memory B cells and increased proportions of naive B lymphocytes. Nevertheless, when the patients in remission who did not require treatment were studied separately, the only remaining abnormality was a reduction of the CD27 IgD IgM B cell-subset detectable in most of these patients. The level of reduction of CD27 IgD IgM B cells was associated with elevated values of serum SLE auto-antibodies. Further analysis of this latter B cell-subset specifically showed increased expression of CD80, CD86, CD95, 9G4 idiotype and functional CXCR3 and CXCR4. CONCLUSIONS: The presence of a reduced blood CD27 IgD IgM B cell-subset, exhibiting an activated state and enriched for auto-reactivity, is a consistent B cell abnormality in SLE. These findings suggest that CD27 IgD IgM B lymphocytes play a role in the pathogenesis of this disease.

Increased survival is a selective feature of human circulating antigen-induced plasma cells synthesizing high-affinity antibodies.

The present study shows that tetanus toxoid (tet) booster releases to the human circulation 2 subsets of specific plasma cells (PCs), as defined by phenotype and morphology, which clearly differed in the staining capacity of their cytoplasmic antibodies (Abs) with fluorescein isothiocyanate (FITC)-labeled tet-fragment C (tetC). These cells, called tetCHIGH and tetCINT PCs according to their either high or intermediate FITC-tetC staining capacity, exhibit similar rapid temporary kinetics in the blood (5-8 days after boost), contain many cycling cells, express equivalent amounts of BLIMP-1 mRNA, and produce similar quantities of IgG. However, Abs synthesized by tetCHIGH PCs show a tetC affinity more than 10 times higher than that exhibited by tetCINT PC Abs, and indicated by IGVH sequence analysis. Chemotaxis to CXCL12, a requisite for bone marrow (BM) PC homing, is similar for both cell types. Circulating nonspecific and tetCINT PCs, but not tetCHIGH PCs, tend to undergo spontaneous apoptosis, as demonstrated by APO2.7 and activated caspase-3 expression, and cell recovery. These results indicate that tet booster generates 2 discrete subsets of specific PCs exhibiting different ranges of Ab affinity for the immunogen, and that only those synthesizing high-affinity Abs show enhanced survival. This inherent property may be essential for determining the BM fate of PCs secreting high-affinity Ab.

Autoantibodies against the chromosomal passenger protein INCENP found in a patient with Graham Little-Piccardi-Lassueur syndrome.

BACKGROUND: Graham Little - Piccardi - Lassueur (GLPL) syndrome is a rare dermatosis characterized by scarring alopecia, loss of pubic and axillary hair, and progressive development of variously located follicular papules. We report a first case ever of an autoimmune response in a patient suffering from GLPL syndrome. METHODS: Immunofluorescence and immunoblot analysis were used in a variety of cell cultures including human, monkey, hamster, mouse and bovine cells to analyze the presence of autoantibodies in a GLPL patient. RESULTS: The autoimmune serum showed a pattern of centromere and spindle microtubule staining resembling that of the chromosomal passenger protein complex. By using a complex of proteins expressed in baculovirus, immunoblot analysis demonstrated that the INCENP protein is a major autoantigen in this patient with GLPL syndrome. CONCLUSION: An autoimmune response in GLPL syndrome is reported against the INCENP centromere protein. The occasional development of autoimmunity in GLPL patients could serve as a test in continuing efforts to detect this disease and for a more directed therapy based on the autoantigen response.

CD95-Mediated control of anti-citrullinated protein/peptides antibodies (ACPA)-producing plasma cells occurring in rheumatoid arthritis inflamed joints.

OBJECTIVE: Serum anti-citrullinated protein/peptides antibodies (ACPA) are a valuable diagnostic parameter that might be involved in rheumatoid arthritis (RA) pathogenesis. CD95-dependent apoptosis is defective in RA synovium. The present study explores the occurrence of ACPA IgG, and the CD95-mediated control of ACPA IgG-secreting plasma cells (PC) in RA patients. METHODS: Mononuclear cells (MC) were purified from synovial fluid (SF) and peripheral blood (PB) of 15 RA patients. PC capable of secreting ACPA IgG were detected in MC cultures. ACPA IgG present in serum and SF, and PB and SF MC culture supernatant was measured by ELISA. CD95, CD27 and CD138 expression was examined on RA PC identified as CD19(low) CD38(high) cells by flow cytometry. CD95-ligation was obtained by treatment of cultured MC with the anti-CD95 Ab CH11. Apoptotic PC were identified as Annexin-V+. RESULTS: ACPA IgG level was found higher in patients' SF than in their serum. PC were detectable in SF and PB, and exhibited high CD95 and CD27 expression. In contrast, SF, but not PB, PC expressed elevated levels of CD138. SF, but not PB, PC actively secreted ACPA IgG in cultures, in a linear fashion for at least 14 days, and CD95-ligation markedly reduced this activity and provoked PC apoptosis. CONCLUSIONS: The results suggest that RA synovium is a prominent site for ACPA IgG formation and for the accumulation of ACPA IgG-secreting PC exhibiting prolonged survival, probably due to RA defective CD95-mediated control.