In patients with active systemic lupus erythematosus (SLE), a marked B lymphocytopenia was identified that affected CD19+/CD27− naive B cells more than CD19+/CD27+ memory B cells, leading to a relative predominance of CD27-expressing peripheral B cells. CD27high/CD38+/CD19dim/surface Iglow/CD20−/CD138+ plasma cells were found at high frequencies in active but not inactive SLE patients. Upon immunosuppressive therapy, CD27high plasma cells and naive CD27− B cells were markedly decreased in the peripheral blood. Mutational analysis of V gene rearrangements of individual B cells confirmed that CD27+ B cells coexpressing IgD were memory B cells preferentially using VH3 family members with multiple somatic mutations. CD27high plasma cells showed a similar degree of somatic hypermutation, but preferentially employed VH4 family members. These results indicate that there are profound abnormalities in the various B cell compartments in SLE that respond differently to immunosuppressive therapy.

Maintenance of protective humoral immunity depends on the generation and survival of antibody-secreting cells. The bone marrow provides niches for long-term survival of plasma cells generated in the course of systemic immune responses in secondary lymphoid organs. Here, we have analyzed migratory human plasma blasts and plasma cells after secondary vaccination with tetanus toxin. On days 6 and 7 after immunization, CD19 ؉ / CD27 high /intracellular immunoglobulin G high (IgG high )/HLA-DR high /CD38 high /CD20 ؊ / CD95 ؉ tetanus toxin-specific antibodysecreting plasma blasts were released in large numbers from the secondary lymphoid organs into the blood. These cells show chemotactic responsiveness toward ligands for CXCR3 and CXCR4, probably guiding them to the bone marrow or inflamed tissue. At the same time, a population of CD19 ؉ /CD27 high /intracellular IgG high /HLA-DR low /CD38 ؉ /CD20 ؊ /CD95 ؉ cells appeared in the blood in large numbers. These cells, with the phenotype of long-lived plasma cells, secreted antibodies of unknown specificity, not tetanus toxoid. The appearance of these plasma cells in the blood indicates successful competition for survival niches in the bone marrow between newly generated plasma blasts and resident plasma cells as a fundamental mechanism for the establishment of humoral memory and its plasticity. IntroductionProtective humoral memory is conferred by stable titers of specific antibodies (Abs) and can last for years. 1 Although primary contact with an antigen (Ag) leads to the formation of Ab-secreting plasma blasts (PBs) with a lifespan of less than 1 week in extrafollicular foci and results in short Ab responses, 2 most Ab-secreting cells (ASCs) generated during secondary (memory) immune response leave the follicles of the secondary lymphoid tissues as PBs. Specific ASCs are later found in the bone marrow (BM), [3][4][5] mucosa-associated tissues, chronically inflamed tissues, 6 or, to a lesser extent, the red pulp of spleens, 7 with the phenotype of mature plasma cells (PCs) and a potential lifespan of more than 18 months. 3,8,9 Indeed, specific Ab titers, mostly of immunoglobulin G (IgG) and IgA subclasses, can be stable for years 10 and are produced mainly by resident PCs of the BM. 10,11 The survival of PCs within the bone marrow (BM) is not an intrinsic capability of these cells but, rather, is regulated by the local microenvironment, 7 which provides a limited number of survival niches for PCs. [12][13][14] Because Abs of the IgG subclass have only a half-life of 3 weeks, 12-14 the survival of PCs in the BM is prerequisite for the maintenance of Ab titers over long time periods (ie, protective immunity and memory). Release from secondary lymphoid organs, migration of PBs to the BM, and competition for the apparently limited number of survival niches with resident PCs generated earlier control the establishment and persistence of protective humoral memory.Chemokines and their receptors are crucial for the control of lymphocyte trafficking. In mouse, CX-chemokine-re...

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