Rheumatoid arthritis fibroblast‐like synoviocytes co‐cultured with PBMC increased peripheral CD4+CXCR5+ICOS+ T cell numbers

‘Circulating’ T follicular helper cells (Tfh), characterized by their surface phenotypes CD4⁺chemokine receptor 5 (CXCR5)⁺ inducible co‐stimulatory molecule (ICOS)⁺, have been identified as the CD4⁺ T cell subset specialized in supporting the activation, expansion and differentiation of B cells. Fibroblast‐like synoviocytes (FLS) are critical in promoting inflammation and cartilage destruction in rheumatoid arthritis (RA), and the interaction between FLS and T cells is considered to facilitate FLS activation and T cell recruitment. However, it remains unknown whether RA‐FLS co‐cultured with activated peripheral blood mononuclear cells (PBMC) has immunoregulatory effects on peripheral Tfh. In the present study, we co‐cultured RA‐FLS with or without anti‐CD3/CD28‐stimulated PBMC. The results showed that RA‐FLS co‐cultured with stimulated PBMC could increase the numbers of CD4⁺CXCR5⁺ICOS⁺ T cells of RA PBMC possibly via the production of interleukin (IL)‐6, a critical cytokine involved in the differentiation of Tfh cells. We also observed increased reactive oxygen species (ROS) levels in the co‐culture system of RA‐FLS and PBMC. The percentage of CD4⁺CXCR5⁺ICOS⁺ T cells was decreased when ROS production was inhibited by N‐acetyl‐L‐cysteine (NAC), a specific inhibitor which can decrease ROS production. In addition, we showed that the higher levels of tumour necrosis factor (TNF)‐α and IL‐1β in the co‐culture system and the blocking of TNF receptor 2 (TNF‐R2) and IL‐1β receptor (IL‐1βR) both decreased the numbers of CD4⁺CXCR5⁺ICOS⁺ T cells. Our study reveals a novel mechanistic insight into how the interaction of RA‐FLS and PBMC participates in the RA pathogenesis, and also provides support for the biologicals application for RA.     

Aberrant T-regulation in rheumatoid arthritis and IgA nephropathy affects CD5+ and CD5- B lymphocytes equally.

T-suppressor function and T-helper function in healthy adults, elderly patients with non-immune diseases, and patients with rheumatoid arthritis (RA) and IgA nephropathy (IgAN) were titrated by adding graded concentrations of CD8+ cells to autologous CD8-depleted peripheral blood mononuclear cells (PBMC), or CD4+ cells to CD8- 4- PBMC, respectively. Following culture with pokeweed mitogen (PWM), numbers of CD5+ and CD5- immunoglobulin-secreting cells were determined using a combination of rosetting with anti-CD5-coated Dynabeads and reverse haemolytic plaque formation (Jones, 1990). Of 11 RA patients studied, eight had slightly reduced suppressor activity for CD5+ and CD5- IgM-secreting cells, and three with active disease and high serum levels of C-reactive protein, could not suppress IgG, IgA or IgM secretion by either B subset. Helper activity for both CD5+ and CD5- B cells was slightly but significantly increased in RA patients. One of eight patients with IgAN could not suppress IgG, IgA or IgM production by CD5+ or CD5- B cells, and all IgAN patients required strikingly fewer CD4+ cells for PWM-induced activation of CD5+ and CD5- B cells than controls. It was concluded that in two immunologically mediated diseases in which some patients have raised numbers of circulating CD5+ B cells, aberrant T-regulation affects CD5+ and conventional CD5- B cells equally.     

Relationship of CD146 expression to secretion of interleukin (IL)‐17, IL‐22 and interferon‐γ by CD4+ T cells in patients with inflammatory arthritis

Expression of the adhesion molecule, CD146/MCAM/MelCAM, on T cells has been associated with recent activation, memory subsets and T helper type 17 (Th17) effector function, and is elevated in inflammatory arthritis. Th17 cells have been implicated in the pathogenesis of rheumatoid arthritis (RA) and spondyloarthritides (SpA). Here, we compared the expression of CD146 on CD4⁺ T cells between healthy donors (HD) and patients with RA and SpA [ankylosing spondylitis (AS) or psoriatic arthritis (PsA)] and examined correlations with surface markers and cytokine secretion. Peripheral blood mononuclear cells (PBMC) were obtained from patients and controls, and synovial fluid mononuclear cells (SFMC) from patients. Cytokine production [elicited by phorbol myristate acetate (PMA)/ionomycin] and surface phenotypes were evaluated by flow cytometry. CD146⁺CD4⁺ and interleukin (IL)‐17⁺CD4⁺ T cell frequencies were increased in PBMC of PsA patients, compared with HD, and in SFMC compared with PBMC. CD146⁺CD4⁺ T cells were enriched for secretion of IL‐17 [alone or with IL‐22 or interferon (IFN)‐γ] and for some putative Th17‐associated surface markers (CD161 and CCR6), but not others (CD26 and IL‐23 receptor). CD4⁺ T cells producing IL‐22 or IFN‐γ without IL‐17 were also present in the CD146⁺ subset, although their enrichment was less marked. Moreover, a majority of cells secreting these cytokines lacked CD146. Thus, CD146 is not a sensitive or specific marker of Th17 cells, but rather correlates with heterogeneous cytokine secretion by subsets of CD4⁺ helper T cells.     

Elevated circulating Th17 and follicular helper CD4+ T cells in patients with rheumatoid arthritis

It remains not fully elucidated the potential functions of Th17 cells and follicular helper T (Tfh) cells and secreting cytokines in the pathogenesis of rheumatoid arthritis (RA) and their association with disease activity. In this study, the frequencies of Th17 and Tfh cells were determined by flow cytometry, and the levels of interleukin (IL)‐17, IL‐21, and IL‐22 were measured by ELISA in RA patients with different disease activities. The dynamic changes of cell subsets were also detected in response to disease‐modify antirheumatic drugs (DMARDs) therapy. The percentages of CD3⁺CD4⁺IL‐17A⁺ (Th17) cells and CD3⁺CD4⁺CXCR5⁺ICOS^high (Tfh) cells, as well as the concentrations of IL‐17, IL‐21, and IL‐22 were significantly elevated in RA patients than those in healthy individuals. Furthermore, Tfh cells, IL‐21, and IL‐22 in the serum was positively correlated with the values of disease activity score. Concentrations of IL‐21 and IL‐22 in the serum were remarkably reduced following the DMARDs therapies. Our data suggested that Th17 cells, Tfh cells as well as the secreting cytokines may be involved in the pathogenesis of RA. The frequency of circulating Tfh cells and the productions of IL‐21 and IL‐22 were associated with the disease activity of RA patients, and might be potential therapeutic targets for treatment of RA.     

High frequencies of activated B cells and T follicular helper cells are correlated with disease activity in patients with new‐onset rheumatoid arthritis

This study aimed to examine the frequency of different subsets of circulating B and T follicular helper (Tfh) cells in patients with new-onset rheumatoid arthritis (RA) and following standard therapies. Twenty-five RA patients and 15 healthy controls (HC) were recruited for characterizing the frequency of CD27⁺, immunoglobulin (Ig)D⁺, CD86⁺, CD95⁺, Toll-like receptor (TLR)-9⁺ B cells and inducible T cell co-stimulator (ICOS) and programmed death 1 (PD-1)-positive Tfh cells and the level of serum interleukin (IL)-21. The potential correlation between the frequency of different subsets of B and Tfh cells and the values of clinical measures in RA patients was analysed. In comparison with HC, significantly higher percentages of circulating IgD⁺CD27⁻CD19⁺ naive B, CD86⁺CD19⁺ and CD95⁺CD19⁺ activated B, CD3⁺CD4⁺CXCR5⁺, CD3⁺CD4⁺CXCR5⁺ICOS⁺, CD3⁺CD4⁺CXCR5⁺PD-1⁺ and CD3⁺CD4⁺CXCR5⁺ICOS⁺PD-1⁺ Tfh cells but lower IgD⁺CD27⁺CD19⁺ preswitch memory B cells were detected, accompanied by significantly higher levels of serum IL-21 in the RA patients. Furthermore, the percentages of CD95⁺ B cells were correlated positively with the frequency of PD-1⁺ Tfh cells, but negatively with ICOS⁺ Tfh cells. The percentages of CD86⁺ B cells and ICOS⁺ Tfh cells were correlated positively with the values of disease activity score 28 (DAS28). Following the drug therapies for 1 month, the percentages of CD86⁺ B and PD-1⁺ Tfh cells were reduced significantly in the drug-responding patients. Our data suggest that activated B and Tfh cells may contribute to the pathogenesis of RA and the frequency of activated B and Tfh cells may be used as biomarkers for evaluating the therapeutic responses of individual patients with RA.     

CD21−/low B cells associate with joint damage in rheumatoid arthritis patients

Depletion of B cells is beneficial in rheumatoid arthritis (RA) patients with autoantibodies to citrullinated proteins (ACPA) and/or the Fc portion of immunoglobulins (rheumatoid factor [RF]), suggesting a role for B cells in disease pathogenesis. To date, however, the identity of specifically pathogenic B cell subsets has not been discovered. One candidate population is identified by the low expression or absence of complement receptor 2 (CD21^?/low B cells). In this study, we sought to determine whether there was any correlation between CD21^?/low B cells and clinical outcome in patients with established RA, either ACPA⁺/RF⁺ (n = 27) or ACPA^?/RF^? (n = 10). Healthy donors (n = 17) were included as controls. The proportion of the CD21^?/low CD27^?IgD^? memory B cell subset in peripheral blood (PB) was significantly increased in ACPA⁺/RF⁺ RA patients compared with healthy donors, and the frequency of this subset correlated with joint destruction (r = 0.57, P < 0.04). The levels of the chemokines CXCL‐9 and CXCL‐10 were higher in synovial fluid than in plasma, and PB CD21^?/low cells expressed the receptor, CXCR3. In synovial fluid, most of the B cells were CD21^?/low, approximately 40% of that population was CD27^?IgD^?, and a third of those expressed the pro‐osteoclastogenic factor receptor activator of the nuclear factor κB ligand (RANKL). This subset also secreted RANKL, in addition to other factors such as IL‐6, even in the absence of stimulation. We interpret these data as reason to propose the hypothesis that the CD27^?IgD^? subset of CD21^?/low B cells may mediate joint destruction in patients with ACPA⁺/RF⁺ RA.     

Increased numbers of CD5+ B cells and T cell receptor (TCR) γδ+ T cells are associated with younger age of onset in rheumatoid arthritis (RA)

Patients presenting with RA before the age of 45 years (younger onset) are known to have more aggressive disease compared with patients presenting after the age of 65 years (older onset). Coordinated expansion of circulating CD5⁺ B cell and TCR γδ⁺ T cell levels has been reported in patients with RA. This study assesses the peripheral blood levels of these two cell types in RA patients with younger and older onset of disease. CD5⁺ B cell levels were significantly elevated in the younger onset RA group (26·6 ± 4·5%) compared with the older onset RA group (14·2 ± 1·2%; P <0·01). TCR γδ⁺ T cell levels were also significantly raised in the young patients (4·0 ± 0·9%) compared with elderly patients (1·6 ± 0·2%; P <0·01). T cell levels (CD3⁺) were similar in both groups (young 66·4 ± 3·3%; old 74·3 ± 3·4% (mean ± s.e.m.); NS). Total B cell levels (CD19⁺) were also similar in these groups (7·7 ± 0·7% versus 8·9 ± 1·8%; NS). A significant positive correlation was observed between the CD5⁻ B and TCR γδ⁺ T cell types in the patients (r = 0·72, P <0.05). Compared with age-matched normal controls, the younger onset patients had similar CD5⁺ B cell and TCR γδ⁺ T cell levels to the elderly controls (CD5⁺ B cells 30·2 ± 3·0%; TCR γδ⁺ T cells 3·0 ± 0·8%). Conversely, older onset RA patients had CD5⁺ B cell levels similar to the young controls (12·3 ± 1·9%). Spontaneous in vitro synthesis of immunoglobulins (IgM, IgA and IgG) and rheumatoid factors (IgM and IgA isotypes) were not significantly different in both patient groups. The coordinate expansion of circulating CD5⁺ B cells and γδ⁺ T cells seen in patients with RA presenting before 45 years of age and not after 65 years of age may suggest a potential role for these cells in more aggressive disease states.     

Expression of CD5 and CD38 by human CD5− B cells: Requirement for special stimuli

In this study the mode of expression of CD5 by human tonsillar CD5^? B cells after stimulation with different agents was investigated. Resting B cells were separated into CD5⁺ and CD5^? cells and the two cell fractions exposed to phorbol 12-myristate 13-acetate (PMA). CD5^? B cells expressed CD5 and maximum CD5 expression was achieved after approximately 60 h of culture. Based upon the proportions of cells that express CD5 as well as those of the cells surviving in culture, it was calculated that 15–25 % of the total CD5^? B cells were induced to express CD5. Unlike CD5^? B cells, CD5⁺ B cells proliferated vigorously in response to PMA as assessed by [³H] thymidine incorporation and cell cycle analysis in vitro. However, the expression of CD5 by CD5^? B cells was not related to the selective expansion of some CD5⁺ B cells left over as contaminant cells since this occurred in the absence of cell proliferation. Upon exposure to PMA, CD5^? B cells remained in the G0-G1 phases of the cell cycle and did not express the Ki67 antigen or incorporate [³H] thymidine. Furthermore, mitomycin C treatment of the CD5^? B cells did not prevent CD5 expression. Phenotypic studies disclosed that CD5⁺ B cells but not CD5^? B cells expressed CD39. This finding offered the opportunity to carry out an additional control experiment. Separation of the two populations according to the expression of CD39 confirmed the finding obtained by fractionating the cells into CD5⁺ and CD5^? B cells. The cells induced to express CD5 also expressed CD38 that was not detected on resting CD5^? B cells. In this respect, the CD5^? B cells that converted into CD5⁺ cells (inducible CD5⁺ B cells) resembled the cells from the CD5⁺ B cell fractions that up-regulated CD5 and also expressed CD38 upon exposure to PMA alone. Another example of coordinate expression of these two antigens was the finding that exposure to PMA in the presence of recombinant interleukin-4 (rIL-4) resulted in inhibition of the expression of CD5 and CD38. Although virtually all of the tonsillar CD5^? B cells expressed the CD69 activation marker, no cells other than those co-expressing CD5 and CD38 were induced to express CD5 by PMA alone. Resting CD5^? B cells failed to express CD5 and/or CD38 when cultured with PMA in the presence of EL4 T cells and IL-4-free T cell supernatants. Although this combination of stimuli induced a vigorous cell proliferation, the failure to express CD5 and CD38 was not related to cell cycling, since mitomicyn C-treated CD5^? B cells also failed to express CD5 or CD38 when exposed to PMA in the presence of EL4 cells with or without T cell supernatants. Thus, exposure to T cells alone was sufficient to down-regulate CD5 and CD38 expression. Collectively, the above findings indicate that mature CD5^? B cells can follow distinct pathways of differentiation depending upon the nature of the stimuli encountered, and that CD5 expression may identify a special B cell subset or a particular stage of B cell differentiation.     

Rheumatoid factor and glomerulonephritis

It is presently unknown whether rheumatoid factors have a pathogenic role in the development of various types of glomerulonephritis with immune deposits. Three isotypes of rheumatoid factors (RFs), which are autoantibodies to IgG, were measured using the solid-phase fluorescence immunoassay in sera from patients with diffuse proliferative lupus nephritis (DPLN), membranous lupus nephritis (MLN), IgA nephropathy (IgAN) and idiopathic membranous nephropathy (MN). RF activity of immunoglobulins deposited in the glomeruli from these patients was also studied by examining the binding of the FITC-conjugated human IgG and Fc portion of IgG to the glomeruli of renal biopsy specimens. IgG, IgA and IgM RFs were significantly increased in sera from patients with DPLN, and the increase was significantly lower in patients with MLN, IgAN and MN. Human IgG bound to immunoglobulin on the glomeruli only in DPLN, but not in MLN, IgAN or MN. The Fc portion of IgG was demonstrated to be involved in this reaction. It was suggested that RFs and IgG may play a major role in immune deposits on the glomeruli in DPLN and may be involved in the development of DPLN; however, this is not likely in MLN, IgAN or MN.     

The human immunomodulatory CD25+ B cell population belongs to the memory B cell pool

We have shown that human CD20⁺25⁺ B cells display immunomodulatory properties. The aim of this study was to investigate if CD25⁺ B cells are found within the CD27 memory B cell population, and to analyse pattern of their cytokine production. B cells isolated from healthy subjects, rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE) patients were analysed regarding the frequency of CD25⁺ B cells within certain B cell subsets. Purified CD25⁺ B cells from healthy subject were used in vitro to evaluate their production of immunomodulatory cytokines. In healthy subjects the majority (60%) of memory B cells (CD20⁺27⁺) also co‐expressed CD25 while only 10–20% of the naïve B cells (CD20⁺27⁻) and plasmablasts (CD20–27⁺) expressed CD25. In RA and SLE patients, we found that 51% and 48%, respectively, co‐expressed CD25 in the memory population, whereas only 11% and 9% co‐expressed CD25 in the naïve B cell population. Phenotypic analysis of the CD20⁺25⁺27⁺ and CD20⁺25⁺27⁻ cells using CD10, CD24, CD38, CD45, CD71, CD80, CD86, CD95, CD138, BAFF‐R, TACI, IgA, IgD, IgG and IgM showed that CD20⁺25⁺27⁺ B cells preferentially represent highly activated, Ig class switched memory B cells. Cytokine profile analysis showed that CD25⁺ B cells secreted significantly higher levels of IL‐10 versus CD25⁻ B cells. In contrast, TGF‐β1 secretion was similar between the CD25⁺ and CD25⁻ sub‐populations. In conclusion, CD20⁺25⁺ B cells constitute a unique subpopulation preferentially occurring among CD20⁺27⁺ memory B cells. We suggest that CD25 can be used as a marker for a memory B cell subset.     

Functional Implications of Regulatory B Cells in Human IgA Nephropathy

IgA nephropathy (IgAN) diagnosis remains largely based upon immunohistologic detection of IgA‐ and IgG‐containing glomerular deposits in renal mesangial cells, and little is known about the underlying pathogenic mechanisms. This study examines the putative contribution of B cell types, including the Breg type, to IgAN pathogenesis. Twenty‐four patients with IgAN and proteinuria (Group A: <3.5 g/24 h, n = 13; Group B: >3.5 g/24 h, n = 11) and 10 healthy controls were enrolled. The frequencies of B cell subtypes in venous blood were measured by flow cytometry. Galactose‐deficient IgA1 was measurement by ELISA. Needle biopsies were analysed by histology and immunofluorescence microscopy. Correlation between clinical features and B cell subtypes, including the regulatory B (Breg) cells, and Breg cell‐derived immunomodulatory cytokine IL‐10 was assessed by Spearman's rank correlation test. IgAN patients had significantly higher frequencies of CD27⁺CD19⁺, CD38⁺CD19⁺, CD86⁺CD19⁺ and CD5⁺CD19⁺ B cells than the healthy controls, but significantly lower levels of Breg cells and intracellular expression of IL‐10 protein in the Breg subtype. Serum IgA concentration positively correlated with CD27⁺CD19⁺ B cell frequency and negatively correlated with IL‐10⁺ Breg cell frequency in IgAN patients, and the percentage of CD19⁺CD5⁺CD1d⁺ in CD19⁺ cells was negatively correlated with the level of serum Gd‐IgA1. Furthermore, the frequencies of CD19⁺CD38⁺ and CD19⁺CD86⁺ in the CD19⁺ subpopulation negatively correlated with the estimated glomerular filtration rate of IgAN patients. Several of the CD19⁺ B cell subtypes and the IL‐10⁺ Breg cells are differentially expressed in IgAN patients and may contribute to the disease pathogenesis.     

CD4-negative cytotoxic T cells with a T cell receptor α/βintermediate expression in CD8-deficient mice

Targeted disruption of the CD8 gene results in a profound block in cytotoxic T cell (CTL) development. Since CTL are major histocompatibility complex (MHC) class I restricted, we addressed the question of whether CD8–/– mice can reject MHC class I-disparate allografts. Studies have previously shown that skin allografts are rejected exclusively by T cells. We therefore used the skin allograft model to answer our question and grafted CD8–/– mice with skins from allogeneic mice deficient in MHC class II or in MHC class I (MHC-I or MHC-II-disparate, respectively). CD8–/– mice rejected MHC-I-disparate skin rapidly even if they were depleted of CD4⁺ cells in vivo (and were thus deficient in CD4⁺ and CD8⁺ T cells). By contrast, CD8+/+ controls depleted of CD4⁺ and CD8⁺ T cells in vivo accepted the MHC-I-disparate skin. Following MHC-I, but not MHC-II stimulation, allograft-specific cytotoxic activity was detected in CD8–/– mice even after CD4 depletion. A population expanded in both the lymph nodes and the thymus of grafted CD8–/– animals which displayed a CD4^?8^?3^intermediateTCRα/β^intermediate phenotype. Indeed its T cell receptor (TCR) density was lower than that of CD4⁺ cells in CD8–/– mice or of CD8⁺ cells in CD8+/+ mice. Our data suggest that this CD4^?8^?T cell population is responsible for the CTL function we have observed. Therefore, MHC class I-restricted CTL can be generated in CD8–/– mice following priming with MHC class I antigens in vivo. The data also suggest that CD8 is needed to up-regulate TCR density during thymic maturation. Thus, although CD8 plays a major role in the generation of CTL, it is not absolutely required.     

CD147 modulates the differentiation of T‐helper 17 cells in patients with rheumatoid arthritis

The role of CD147 in regulation of rheumatoid arthritis (RA) is not fully elucidated. The aim of this study was to investigate the effect of cell‐to‐cell contact of activated CD14⁺ monocytes with CD4⁺ T cells, and the modulatory role of CD147 on T‐helper 17 (Th17) cells differentiation in patients with RA. Twenty confirmed active RA patients and twenty normal controls were enrolled. CD4⁺ T cells and CD14⁺ monocytes were purified by magnetic beads cell sorting. Cells were cultured under different conditions in CD4⁺ T cells alone, direct cell‐to‐cell contact co‐culture of CD4⁺ and CD14⁺ cells, or indirect transwell co‐culture of CD4⁺/CD14⁺ cells in response to LPS and anti‐CD3 stimulation with or without anti‐CD147 antibody pretreatments. The proportion of IL‐17‐producing CD4⁺ T cells (defined as Th17 cells) was determined by flow cytometry. The levels of interleukin (IL)‐17, IL‐6, and IL‐1β in the supernatants of cultured cells were measured by ELISA. The optimal condition for in vitro induction of Th17 cells differentiation was co‐stimulation with 0.1 μg/mL of LPS and 100 ng/mL of anti‐CD3 for 3 days under direct cell‐to‐cell contact co‐culture of CD4⁺ and CD14⁺ cells. Anti‐CD147 antibody reduced the proportion of Th17 cells, and also inhibited the productions of IL‐17, IL‐6, and IL‐1β in PBMC culture from RA patients. The current results revealed that Th17 differentiation required cell‐to‐cell contact with activated monocytes. CD147 promoted the differentiation of Th17 cells by regulation of cytokine production, which provided the evidence for pathogenesis and potential therapeutic targets for RA.     

Monoreactive and Polyreactive Rheumatoid Factors Produced by in Vitro Epstein-Barr Virus-Transformed Peripheral Blood and Synovial B Lymphocytes from Rheumatoid Arthritis Patients

The CD5 membrane molecule, initially identified as an exclusive T-cell marker, also defines a phenotypically and functionally distinct B-lymphocyte population. In normal individuals, CD5+ B cells are committed to secrete 'natural' polyreactive (auto)antibodies, that is antibodies, mainly IgM, endowed with multiple antigen-binding capabilities, including rheumatoid factor (RF) activity. At variance with this, in rheumatoid arthritis (RA) as well as in other autoimmune conditions, monoreactive autoantibodies binding with high affinity and specificity to a given self antigen have been isolated and the cells from which they originate differently related to the CD5+ B-lymphocyte subset. Here, we studied the proportions of CD5+ B cells and the characteristics, in terms of polyreactivity and monoreactivity, of RF produced by B lymphocytes in RA patients with classified disease activity. Our results suggest that patients with a more severe disease activity have higher proportions of CD5+ B cells and higher frequencies of B lymphocytes committed to secrete RF, with the characteristics of polyreactive antibodies. On the other hand, we did not find a significant difference between the proportions of peripheral B cells producing monoreactive RF in patients with high- versus patients with low-activity RA. However, in two highly active RA patients, we found that synovial fluid, compared with peripheral blood, was significantly enriched for (IgG and IgA) monoreactive RF-producing B cells.     

Co‐inhibitory profile and cytotoxicity of CD57+PD‐1– T cells in end‐stage renal disease patients

Blockade of the CD80/86‐CD28 pathway by belatacept after kidney transplantation is associated with an increased risk of rejection compared with standard, calcineurin inhibitor (CNI)‐based therapy. CD28^– T cells, which express CD57, are not susceptible to belatacept treatment. High numbers of CD4⁺CD57⁺programmed death 1 (PD‐1)^– T cells pretransplantation have been associated with a higher chance of rejection, although conflicting data have been reported. To investigate the working mechanism behind this possible higher chance of rejection, we studied the expression of co‐inhibitory molecules (CD223, CD244 and PD‐1), proliferative capacity and cytotoxic potential of fluorescence activated cell sorted (FACS) CD4⁺CD57⁺PD‐1^– and CD8⁺CD57⁺PD‐1^– T cells, and their CD57^– control populations, after alloantigen stimulation. The effect of belatacept on the cytotoxic capacity of pretransplantation peripheral blood mononuclear cells from 20 patients who received belatacept post‐transplantation was also tested. Expression of co‐inhibitory molecule CD223 increased by approximately 10‐fold after allogeneic stimulation in all four T cell subsets. Proliferation and up‐regulation of CD244 and PD‐1 was observed for CD4⁺CD57^‐PD‐1^– T cells after allogeneic stimulation, but no up‐regulation of these markers occurred on CD8⁺ T cells or CD4⁺CD57⁺PD‐1^– T cells. However, CD4⁺CD57⁺PD‐1^– T cells and, to a lesser extent, CD8⁺CD57⁺PD‐1^– T cells displayed higher cytotoxicity as indicated by granzyme B expression. Belatacept inhibited the cytotoxic potential of CD4⁺CD57⁺PD‐1^– T cells (median of inhibition 31%, P < 0·01) and CD8⁺CD57⁺PD‐1^– T cells (median of inhibition 10%, P < 0·05). In conclusion, alloantigen‐activated CD4⁺CD57⁺PD‐1^– T cells exhibited a less proliferative but more cytotoxic profile than their CD57^– counterparts. Their cytotoxic capacity can be inhibited partly by belatacept and was not associated with development of rejection after kidney transplantation.     

Activating NK‐cell receptors co‐stimulate CD4+CD28− T cells in patients with rheumatoid arthritis

Effector T‐cell responses can be modulated by competing positive or negative signals transduced by NK‐cell receptors (NKR). In the CD4⁺ T‐cell population, the expression of NKR is primarily found in the CD4⁺CD28⁻ T‐cell subset, also known as CD28^null T cells. These T cells are frequently found in rheumatoid arthritis (RA) and other inflammatory disorders, suggesting that signaling through NKR may play a role in the autoimmune reaction. Here we aimed to dissect the phenotype and function of NKR‐expressing CD4⁺CD28⁻ T cells in patients with RA. By analyzing a broad array of NKR on CD4⁺CD28⁻ T cells we found a significant expression of the co‐activating receptors 2B4 (CD244), DNAM‐1 (CD226), and CRACC. Pair‐wise ligations of 2B4 with DNAM‐1 and/or NKG2D lead to increased effector functions of primary CD4⁺CD28⁻ T cells to suboptimal levels of anti‐CD3 stimulation. Using multi‐parameter flow cytometry, we demonstrate that such co‐ligation led to an increased magnitude in overall responsiveness without changing qualitative aspects of the response. Altogether these results demonstrate a pattern of additive effects in NKR‐mediated functional modulation of CD4⁺CD28⁻ T cells in RA. This may have consequences for the inflammatory responses imposed by these cells, thus influencing disease manifestations.     

CD21–/low B cells in human blood are memory cells

The complement receptor 2 (CR2, CD21) is part of a complex (CD21/CD19/CD81) acting as a co‐receptor to the B cell receptor (BCR). Simultaneous triggering of the BCR and CD21 lowers the threshold for B cell activation. Although CD21 is important, B cells that express low amounts or lack surface CD21 (CD21^–/low) are increased in conditions with chronic inflammation, e.g. autoimmune diseases. However, little is known about the CD21^–/low B cell subset in peripheral blood from healthy donors. Here, we show that CD21^–/low cells represent approximately 5% of B cells in peripheral blood from adults but are barely detectable in cord blood, after excluding transitional B cells. The CD21^–/low subset can be divided into CD38^–24⁺ and CD38^–24^low cells, where most of the CD38^–24⁺ are CD27⁺immunoglobulin (Ig)M⁺IgD⁺ and the CD38^–24^low are switched CD27^–. Expression levels of additional markers, e.g. CD95 and CD62L, are similar to those on classical memory B cells. In contrast to naive cells, the majority of CD21^–/low cells lack expression of the ABCB1 transporter. Stimulation with a combination of BCR, Toll‐like receptor (TLR)?7/8 and interleukin (IL)?2 induces proliferation and differentiation of the CD21^–/low B cells comparable to CD21⁺CD27⁺ memory B cells. The response excluding BCR agonist is not on par with that of classical memory B cells, although clearly above that of naive B cells. This is ascribed to a weaker response by the CD38^–24^low subset, implying that some memory B cells require not only TLR but also BCR triggering. We conclude that the CD21^–/low cells in healthy donors are memory B cells.