Objective. Disease activity in systemic lupus erythematosus (SLE) is usually assessed with complex disease activity scores comprising a variety of different parameters. In order to determine whether SLE disease activity correlates with abnormal B lymphocyte activity, B cell subsets were analyzed, and their relationship to clinical and humoral measures of disease activity was assessed.Methods. The distribution of B cell subsets was determined by fluorescence-activated cell sorting analysis and assessed in relation to the autoantibody profile, disease activity measured by the SLE Disease Activity Index (SLEDAI) and the European Consensus Lupus Activity Measure scores, disease duration, and therapy.Results. The number and frequency of CD27 high plasma cells were significantly correlated with the SLE disease activity indices and with the titer of antidouble-stranded DNA (anti-dsDNA) autoantibodies. Circulating B cell subsets were not influenced by age or sex, but appeared to relate to the duration of disease and the therapeutic regimen, with the number and frequency of CD27 high plasma cells increasing and those of CD27؊ naive B cells decreasing over time. Patients were divided into those with a SLEDAI score of 0-8 (low disease activity) and those with SLEDAI score >8 (high disease activity). Patients with high disease activity had an increased frequency of both CD19؉ B cells and CD27 high plasma cells. By using a nonparametric data sieving algorithm, we observed that these B cell abnormalities provided predictive values for nonactive and active disease of 78.0% and 78.9%, respectively. The predictive value of the B cell abnormalities (78.9%) was greater than that of the humoral/clinical data pattern (71.4%), including anti-dsDNA antibody levels, circulating immune complexes, increased erythrocyte sedimentation rate, mucocutaneous involvement, and acute renal involvement.Conclusion. Flow cytometric monitoring of B cell subsets in the peripheral blood provides new insights into abnormalities of B cell function in SLE and may also be a diagnostically valuable option for monitoring the activity of this autoimmune disease.

Objective. Analysis of peripheral B cell subsets in patients with systemic lupus erythematosus (SLE) has provided evidence of specific alterations, such as an expansion of CD27؉؉ plasma cells/blasts and transitional B cells. However, memory B cells in lupus have not been thoroughly investigated, and only recently a CD27؊ memory B cell subset was identified in the peripheral blood of lupus patients. Focusing on CD27؊ B cells, this study aimed to identify abnormalities in peripheral B cell subsets in patients with SLE.Methods. Three independent cohorts of lupus patients were used to characterize CD27؊ memory B cells, using multiparameter flow cytometry and singlecell reverse transcription-polymerase chain reaction of heavy-chain transcripts.Results. We identified a homogeneous subset of CD27؊,IgD؊,CD95؉ memory B cells with an activated phenotype that was increased in patients with disease flares and that correlated with disease activity and serologic abnormalities. In contrast, the entire subset of CD27؊,IgD؊ B cells was found to be heterogeneous, did not correlate significantly with lupus activity, and was also increased in patients with bacterial infections. Conclusion. We conclude that CD95 is a useful marker to identify CD27؊ memory B cells with an activated phenotype, which might serve as a biomarker for lupus activity and as a target of further investigations aiming to elucidate the pathogenic potential of these cells and the mechanisms involved in the generation as well as regulation of this CD27؊,IgD؊,CD95؉ memory B cell subset.B cell monitoring has been extensively used recently to assess the effect of B cell-depleting or B cell-modulating therapies and the reconstitution of the peripheral blood B cell repertoire after treatment with B cell-depleting drugs. Expression of CD27 has been particularly useful to discriminate B cell subsets. Although CD27 was originally thought to distinguish between memory B cells and plasma cells and between memory B cells and naive B cells (1,2), more recently the heterogeneity of CD27Ϫ B cells has become apparent. The contribution of transitional B cells to this subpopulation has been shown to be high in some patients with systemic lupus erythematosus (SLE) (3). In this regard, after B cell depletion, immature and transitional B cells dominate the peripheral blood for months (4). Conversely, a recent analysis of B cell subsets in patients with Sjögren's syndrome demonstrated a predominance of CD27Ϫ B cells, of which ϳ10% were B cells with

Objective. To delineate the mechanism of the abnormalities in B cell biology found in patients with primary Sjögren's syndrome (SS).Methods

Objective. In systemic lupus erythematosus (SLE), the increased generation of memory B cells and plasma cells leads to autoimmune hypergammaglobulinemia and destructive immunoglobulin deposits in the kidneys. We undertook this study to determine the biologic mechanism driving this overactivation of the B cell compartment, which is the central issue in SLE. Methods. We used flow cytometry to analyze expression of the T cell-specific inducible costimulator (ICOS) and its ligand (ICOS-L) on B cells obtained from the peripheral blood of SLE patients. We correlated ICOS-L

Rechallenge with T cell-dependent Ags induces memory B cells to re-enter germinal centers (GCs) and undergo further expansion and differentiation into plasma cells (PCs) and secondary memory B cells. It is currently not known whether the expanded population of memory B cells and PCs generated in secondary GCs are clonally related, nor has the extent of proliferation and somatic hypermutation of their precursors been delineated. In this study, after secondary tetanus toxoid (TT) immunization, TT-specific PCs increased 17- to 80-fold on days 6–7, whereas TT-specific memory B cells peaked (delayed) on day 14 with a 2- to 22-fold increase. Molecular analyses of VHDJH rearrangements of individual cells revealed no major differences of gene usage and CDR3 length between TT-specific PCs and memory B cells, and both contained extensive evidence of somatic hypermutation with a pattern consistent with GC reactions. This analysis identified clonally related TT-specific memory B cells and PCs. Within clusters of clonally related cells, sequences shared a number of mutations but also could contain additional base pair changes. The data indicate that although following secondary immunization PCs can derive from memory B cells without further somatic hypermutation, in some circumstances, likely within GC reactions, asymmetric mutation can occur. These results suggest that after the fate decision to differentiate into secondary memory B cells or PCs, some committed precursors continue to proliferate and mutate their VH genes.

European duck meat production is based on the use of Pekin, Muscovy and Mule duck genotypes that vary in their behavioural and physiological characteristics. Furthermore, large differences exist in their housing and management conditions. The aim of this review is to discuss the welfare of these different genotypes in typical husbandry systems, focusing on ducks kept for meat production. Firstly, factors that can affect duck welfare, such as stocking density and group size, access to straw, an outdoor run, or open water, are described. Secondly, welfare problems such as feather pecking, fear and stress, and health problems are assessed. Thirdly, the various systems used in Europe are described for these aspects. Giving ducks access to straw, an outdoor run, or open water increases the behavioural opportunities of the ducks (foraging, preening, bathing, and swimming), but can also lead to poor hygiene and increased health-and food safety risks. Therefore, practical solutions that allow expression of natural behaviour, but do not lead to hygiene or health problems have to be found and some practical suggestions are provided.

Altogether, both B cell hyperactivity and striking abnormalities in peripheral B cell memory are indicated at the single-cell mRNA level in patients with primary SS. Detection of multiple Ig heavy-chain transcripts in peripheral CD19+,CD27+ memory B cells of patients with SS may represent the abnormal retention of pre-switch mRNA transcripts in circulating post-switch B cells.

IntroductionPlasmablasts are an immediate product of B-cell activation that home either to the bone marrow or to the mucosa to secrete antibody as terminally differentiated plasma cells. [1][2][3] In healthy persons, B cells and antibodies protect from pathogens, whereas loss of immunologic tolerance and malignant transformation result in the generation of autoreactive B cells and autoantibody production and development of lymphoma, respectively. Direct targeting of B cells by the chimeric anti-human CD20 antibody rituximab (RTX) has been developed for the treatment of rheumatoid arthritis (RA) and B-cell malignancies. 4,5 However, not all patients respond to RTX therapy, and the efficiency of B-cell depletion in lymphoid tissues as well as the susceptibility of different B-cell subtypes remain of central interest, in particular related to individual unresponsiveness.In RA, depletion of peripheral CD20 ϩ B cells reduces, but does not eliminate, autoimmunity, indicated by subsequent flares and continuous production of autoantibodies. 6 Persisting (auto-) antibodies in patients treated with RTX reflect the continued presence of antibody-secreting cells, whereas it remains unclear whether those are long-lived, CD20 Ϫ plasma cells, eg, residing in the bone marrow, or whether they have been generated de novo from B cells not depleted by RTX. In this context, germinal center B cells of the Peyer patches and peritoneal B1 B cells resisted to RTX treatment in human cd20 tg mice. 7 Depletion of B cells from human lymphoid tissues of systemic immunity, for example, the spleen and lymph nodes by RTX has been described in individual cases. [8][9][10] Thus, the efficiency of global or selective B-cell depletion remains of interest, in particular whether there is a distinct susceptibility of B-cell subsets to RTX within gut-associated lymphoid tissues (GALT).Here, we demonstrate the continued presence of dividing and migratory plasmablasts expressing a mucosal phenotype in the peripheral blood of patients with RA consistent with steady-state plasmablasts 1 after treatment with RTX. These data show that a subset of chronically activated mucosal B lymphocytes carrying highly mutated V H gene rearrangements and secreting antimicrobial immunoglobulin A (IgA) are not deleted by RTX. This reflects the robustness of humoral mucosal immunity during B-cell depletion with RTX and underscores the independent regulation of mucosal immune responses in steady state. The resistance of some mucosal B cells to RTX is apparently not stringently related to RA pathogenesis but could represent a mechanism underlying enhanced RTX resistance in some mucosa-associated lymphoid tissue lymphoma cases. 11,12 Methods A detailed description of the patients, samples, and methods are available as supplemental Methods (available on the Blood Web site; see the Supplemental Materials link at the top of the online article). An Inside Blood analysis of this article appears at the front of this issue.The online version of this article contains a data supplement....