Production of cytokines by human B cells in health and disease

[Platelets cytokines and their effects on platelet transfusion]

Platelets have long been confined to haemostasis only. However, novel functions for platelets have been identified recently. Those non-nucleated cells indeed participate to inflammation and also they produce and release numerous factors with known immunomodulatory functions. Among those factors are cytokines and chemokines and the like, such as soluble CD40-Ligand (CD154), which are key molecules in that they bridge innate and adaptative immunity; sCD40L is active on T cells, B cells, monocytes and macrophages, dendritic cells and endothelial cells lining the blood vessels. This means that when a platelet concentrate is transfused to a recipient, a huge amount of cytokines and chemokines is also infused. In this state of the art review, we will present arguments on the role of platelet secretory products in modulating cellular parameters of immunity, and--very likely--in altering functions of those immune cells upon encounters while infusing platelets in blood recipients. We aimed at summarizing data that have been made available on the issue of cytokines/chemokines released by stored platelets prior to delivery. We will focus on the suspected role of the CD40/CD40L tandem in postplatelet transfusion reactions or incidents. We will present recent data on the role of pathogen inactivators on the docking and/or release of cytokines/chemokines by platelets.

Polarization of B effector cells in Sjögren's syndrome

Analysis of salivary glands of patients with primary Sjögren's syndrome has yielded conflicting results with respect to T helper (Th)1/Th2 polarization. This balance might parallel the progress of the local lesions. B-cells are now taking center stage in this disease. They can also be primed to differentiate into two cytokine-production pathways, dubbed B effector (Be) 1 and Be2 cells. This is discussed in the light of our recent finding that Be1 accompany Th1, while Be2 accompany in the tissue lesions.

CD5 provides viability signals to B cells from a subset of B-CLL patients by a mechanism that involves PKC

B-chronic lymphocytic leukaemia (B-CLL) is a heterogeneous disease characterized by an accumulation of B lymphocytes expressing CD5. To date, the biological significance of this molecule in B-CLL B cells remains to be elucidated. In this study, we have analysed the functional consequences of the binding of an anti-CD5 antibody on B-CLL B cells. To this purpose, we have measured the percentage of viability of B-CLL B cells in the presence or in the absence of anti-CD5 antibodies and also examined some of the biochemical events downstream the CD5-signalling. We demonstrate that anti-CD5 induces phosphorylation of protein tyrosine kinases and protein kinase C (PKC), while no activation of Akt/PKB and MAPKs is detected. This signalling cascade results in viability in a group of patients in which we observe an increase of Mcl-1 levels, whereas the levels of bcl-2, bcl-x(L) and XIAP do not change. We also report that this pathway leads to IL-10 production, an immunoregulatory cytokine that might act as an autocrine growth factor for leukaemic B cells. Inhibition of PKC prevents the induction of Mcl-1 and IL-10, suggesting that the activation of PKC plays an important role in the CD5-mediated survival signals in B cells from a subset of B-CLL patients.

Murine isolated lymphoid follicles contain follicular B lymphocytes with a mucosal phenotype

Isolated lymphoid follicles (ILFs) are organized intestinal lymphoid structures whose formation can be induced by luminal stimuli. ILFs have been demonstrated to act as inductive sites for the generation of immune responses directed toward luminal stimuli; however, the phenotype of the immune response initiated within ILFs has largely been uninvestigated. To gain a better understanding of the immune responses initiated within ILFs, we examined phenotypic and functional aspects of the largest cellular component of the murine ILF lymphocyte population, B lymphocytes. We observed that murine ILF B lymphocytes are composed of a relatively homogenous population of follicular B-2 B lymphocytes. Consistent with their proximity to multiple stimuli, ILF B lymphocytes displayed a more activated phenotype compared with their counterparts in the spleen and Peyer's patch (PP). ILF B lymphocytes also expressed higher levels of immunomodulatory B7 and CD28 family members B7X and programmed death-1 compared with their counterparts in the spleen and PP. ILF B lymphocytes preferentially differentiate into IgA-producing plasma cells and produce more IL-4 and IL-10 and less interferon-gamma compared with their counterparts in the spleen. Immunoglobulin repertoire analysis from individual ILFs demonstrated that ILFs contain a polyclonal population of B lymphocytes. These findings indicate that murine ILFs contain a polyclonal population of follicular B-2 B lymphocytes with a phenotype similar to PP B lymphocytes and that, in unchallenged animals, ILFs promote immune responses with a homeostatic phenotype.

Pathogenic role of B cells in anti-CD40-induced necroinflammatory liver disease

Activated B cells function in antibody production and antigen presentation, but whether they perform any pathophysiological functions at sites of inflammation is not fully understood. Here, we report that intravenous injection of an agonistic anti-CD40 monoclonal antibody (alphaCD40) causes a biphasic inflammatory liver disease in inbred mice. The late phase of disease was suppressed in B-cell-deficient mice and by the depletion of macrophages, but not T cells or natural killer cells. We also report that SCID mice were not susceptible to alphaCD40-induced liver disease unless they were reconstituted with normal B cells and that B cells as well as macrophages played key roles in alphaCD40-induced late phase of liver inflammation. Finally, liver disease and the recruitment of inflammatory cells into the liver were mediated by interferon-gamma and tumor necrosis factor-alpha, but not by Fas. In conclusion, these results indicate that CD40 ligation can trigger a B-cell-mediated inflammatory response that can have pathogenic consequences for the liver.

Cutting edge: the development of IL-4-producing B cells (B effector 2 cells) is controlled by IL-4, IL-4 receptor alpha, and Th2 cells

Although IL-4-producing B cells (B effector 2 cells) are found following infection and immunization, the signals regulating IL-4 production by Be2 cells are unknown. We show that culturing naive B cells with Th2 cells induces up-regulation of IL-4 in the B cells with a concomitant down-regulation of T-bet, IL-12Rbeta2, and IFN-gamma. Up-regulation of IL-4 in the Be2 cells is dependent on both T cells and IL-4 as IL-4Ralpha-deficient B cells primed with Th2 cells did not transcribe IL-4, and B cells primed in the presence of IL-4-deficient Th2 cells produced IFN-gamma instead of IL-4. Likewise, the in vivo development of IL-4-expressing B cells in a nematode infection model was dependent on both T cells and IL-4Ralpha-mediated signals. Thus, the differentiation of naive B cells into IL-4-expressing Be2 cells is regulated by a combination of T cell-dependent signals and the cytokine environment and this process is critically dependent upon the IL-4/IL-4R signaling pathway.

Heterogeneity of IgG glycosylation in adult periodontal disease

Periodontal disease is a chronic inflammatory disease of bacterial etiology. In many other chronic inflammatory diseases, IgG glycans are galactose-deficient and thus capable of complement activation through the lectin pathway. In this study, we examined whether IgG in serum and gingival crevicular fluid, and IgG locally produced by plasma cells in gingiva of periodontal disease patients, display altered glycosylation. We developed a lectin-ELISA to measure levels of galactose-deficient IgG in the fluids and immunofluorescence staining to detect galactose-deficient IgG-producing cells in gingiva. Our results indicated higher levels of galactose-deficient IgG in sera and gingival crevicular fluid from periodontal disease patients, compared with levels in healthy controls. Furthermore, gingivae from periodontal disease patients exhibited infiltration of IgG-producing plasma cells; many of them contained galactose-deficient IgG in the cytoplasm. Analysis of our data suggests that IgG secreted by B-cells was aberrantly glycosylated, which resulted in the production of pro-inflammatory galactose-deficient IgG.

B-cell depletion inhibits arthritis in a collagen-induced arthritis (CIA) model, but does not adversely affect humoral responses in a respiratory syncytial virus (RSV) vaccination model

We report the development of a mouse B cell-depleting immunoconjugate (anti-CD22 monoclonal antibody [mAb] conjugated to calicheamicin) and its in vivo use to characterize the kinetics of CD22+ B-cell depletion and reconstitution in murine primary and secondary lymphoid tissues. The effect of B-cell depletion was further studied in a murine collagen-induced arthritis (CIA) model and a respiratory syncytial virus (RSV) vaccination model. Our results show that (1) the immunoconjugate has B-cell-specific in vitro and in vivo cytotoxicity; (2) B-cell reconstitution starts in the bone marrow and spleen around day 30 after depletion and is completed in all tissues tested by day 50; (3) B-cell depletion inhibits the development of clinical and histologic arthritis in the CIA model; (4) depletion of type II collagen antibody levels is not necessary for clinical and histologic prevention of CIA; and (5) B-cell depletion does not adversely affect memory antibody responses after challenge nor clearance of infectious virus from lungs in the RSV vaccination model. These results demonstrate for the first time that only B-cell reduction but not type II collagen antibody levels correlate with the prevention of arthritis and represent key insights into the role of CD22-targeted B-cell depletion in mouse autoimmunity and vaccination models.

Human mesenchymal stem cells modulate B-cell functions

Human mesenchymal stem cells (hMSCs) suppress T-cell and dendritic-cell function and represent a promising strategy for cell therapy of autoimmune diseases. Nevertheless, no information is currently available on the effects of hMSCs on B cells, which may have a large impact on the clinical use of these cells. hMSCs isolated from the bone marrow and B cells purified from the peripheral blood of healthy donors were cocultured with different B-cell tropic stimuli. B-cell proliferation was inhibited by hMSCs through an arrest in the G0/G1 phase of the cell cycle and not through the induction of apoptosis. A major mechanism of B-cell suppression was hMSC production of soluble factors, as indicated by transwell experiments. hMSCs inhibited B-cell differentiation because IgM, IgG, and IgA production was significantly impaired. CXCR4, CXCR5, and CCR7 B-cell expression, as well as chemotaxis to CXCL12, the CXCR4 ligand, and CXCL13, the CXCR5 ligand, were significantly down-regulated by hMSCs, suggesting that these cells affect chemotactic properties of B cells. B-cell costimulatory molecule expression and cytokine production were unaffected by hMSCs. These results further support the potential therapeutic use of hMSCs in immune-mediated disorders, including those in which B cells play a major role.

Differential production of immunoglobulin classes and subclasses by mucosal-type human B-lymphocytes exposed in vitro to CpG oligodeoxynucleotides

As B-lymphocytes play an important role in innate and adaptive immunity, we aimed to examine the effects of CpG oligodeoxynucleotides (ODNs) on purified tonsil-originating CD19+ B-cells, representing mucosal B-cells. We screened various K-type ODNs, reactive with human B-cells, and tested for the production of immunoglobulins in vitro. Using one CpG-ODN, DSP30, we observed that it could upregulate not only Toll-like receptor 9 (TLR9) mRNA expression in activated B-cells, but also the early expression of CD69 followed by the sequential expression of CD80, CD86 and the nuclear factor (NF)-kappaB pathway. Furthermore, mRNA expression of certain B-cell-derived cytokines was influenced by exposure to DSP30, with a strong upregulation of interleukin 6 (IL-6) and downregulation of IL1-beta. Stimulation of B-cells, co-stimulated with IL-2, IL-10 and soluble CD40 ligand (sCD40L) with different CpG-ODNs, had differing effects on the terminal differentiation in vitro of B-cells into immunoglobulin-secreting cells. TLR9 is involved in innate immunity and the recognition of bound CpG DNA from invading bacterial pathogens. As tonsillar B-cells are mucosal-type B-lymphocytes, this study suggests that CpG-ODNs show promise as mucosal adjuvants in modulating the local production of immunoglobulins of certain classes and subclasses, a crucial issue in vaccine perspectives.

Regulation of IFN-gamma production by B effector 1 cells: essential roles for T-bet and the IFN-gamma receptor

This manuscript systematically identifies the molecular mechanisms that regulate the ability of B cells to produce the critical type 1 cytokine, IFN-gamma. B cells produce IFN-gamma in response to IL-12 and IL-18 and when primed by Th1 cells. We show that development of IFN-gamma-producing B cells by either Th1 cells or IL-12/IL-18 is absolutely dependent on expression of the IFN-gammaR and the T-box transcription factor, T-bet. Interestingly, although T-bet up-regulation in developing B effector 1 (Be1) cells is controlled by IFN-gammaR-mediated signals, STAT1-deficient B cells up-regulate T-bet and produce IFN-gamma, indicating that additional transcriptional activators must be coupled to the IFN-gammaR in B cells. Finally, we show that although IL-12/IL-18 or IFN-gamma-producing Th1 cells are required to initiate transcription of the IFN-gamma gene in B cells, sustained expression of IFN-gamma and T-bet by B cells is dependent on an IFN-gamma/IFN-gammaR/T-bet autocrine feedback loop. These findings have significant implications, because they suggest that IFN-gamma-producing B cells not only amplify Th1 responses, but also imprint a type 1 phenotype on B cells themselves. In the case of immune responses to bacterial or viral pathogens, this B cell-driven autocrine feedback loop is likely to be beneficial; however, in the case of B cell responses to autoantigens, it may result in amplification of the autoimmune loop and increased pathology.

Bcl-2 regulatory pathway is functional in chronic lymphocytic leukemia

BACKGROUND

Chronic lymphocytic leukemia (CLL) is characterized by accumulation of clonal, malignant CD5(+), CD23(+) B cells. In vivo, these cells have an antiapoptotic phenotype (high levels of Bcl-2 and low levels of proapoptotic Bcl-2 family proteins, such as Bax). Abnormal B cells accumulate due to altered apoptosis regulation rather than to increased proliferation. However, it is unclear whether there are inherent Bcl-2 apoptotic pathway defects. With in vitro culture, these B cells rapidly apoptosis.

METHODS

To investigate apoptosis regulation, Bcl-2, Bax, mitochondrial membrane potential, annexin V, and caspase activation were simultaneous monitored in individual cells during in vitro apoptosis.

RESULTS

With in vitro culture, 30% to 50% of B cells were apoptotic at 24 h compared with fewer than 10% of T cells. Apoptotic B cells showed dramatic Bax upregulation and slight Bcl-2 decreases accompanied by decreased mitochondrial membrane potential and increased activated caspase-3 protein levels. Caspase-3 and caspase-9 activities were increased 18- to 51-fold and 6- to 11-fold, respectively, after 24 h of culture. Caspase-8 showed limited or no activation (less than fourfold).

CONCLUSIONS

These data show that in vitro apoptosis of CLL B cells occurs through a well-characterized Bcl-2 regulatory pathway consistent with that pathway being functional. Further, these cells' antiapoptotic phenotype is dependent on the in vivo environment, potentially involving paracrine/autocrine interactions.

Cytokine mRNA expression in B cells from bovine leukemia virus-infected cattle with persistent lymphocytosis

We have characterized the expression of six cytokine mRNAs in highly purified B cells from bovine leukemia virus (BLV)-infected cows with persistent lymphocytosis. Selected cytokine mRNAs included those encoding tumor necrosis factor (TNF), lymphotoxin-alpha (LT-alpha), transforming growth factor-beta1 (TGF-beta1), interleukin-1beta (IL-1beta), interleukin-6 (IL-6) and interleukin-10 (IL-10). Fresh B cells from cows with persistent lymphocytosis constitutively transcribed TNF, LT-alpha and TGF-beta1 mRNAs. Although IL-1beta, IL-6 and IL-10 mRNAs were barely detectable in fresh B cells from cows with persistent lymphocytosis, transcripts encoding these cytokines were strongly and rapidly upregulated in B cells after cell culture. Results from this study provide the first evidence that B cells infected with BLV express specific cytokine mRNAs in vivo.

Interaction of bone marrow stromal cells with lymphoblasts and effects of predinsolone on cytokine expression

Cytokines play a key role in the differentiation, growth and survival of hematopoietic cells in the bone marrow (BM) stroma microenvironment. The mechanisms by which stromal derangements may contribute to the evolution of hematopoietic neoplasias are largely unknown. Here, we characterized BM stromal cells isolated from children with acute lymphoblastic leukemia and determined the effect of the interaction between stromal cells and lymphoblasts on cytokine expression as well as the effect of prednisolone using mono- and co-culture models. The analyses demonstrate that (1) stromal cells and lymphoblasts display different patterns of cytokine gene expression individually. (2) Stromal cells influence gene expression of cytokines in lymphoblasts and vice versa. (3) Glucocorticoid substitution inhibit cytokine gene expression in stromal cells. These findings indicate that stromal cells are important components involved in malignant hematopoiesis and also in response to therapy.

Cytokine/cytokine receptor gene expression in childhood acute lymphoblastic leukemia

BACKGROUND

Recent studies have shown that cytokines/cytokine receptors (C/CR) affect leukemic cell growth and survival. The goal of the current study was to investigate possible correlations between gene expression patterns of C/CR in leukemic cells, clinical features, and outcome in children with acute lymphoblastic leukemia (ALL) at first disease recurrence.

METHODS

Between January 1997 and December 2000, bone marrow (BM) samples were collected from 68 children with first ALL recurrence at diagnosis. These patients were enrolled in the ALL-REZ 95-96 disease recurrence trials of the Berlin-Frankurt-Munster study group. C/CR gene expression (interleukin [IL]-7, IL-10, IL-12p40, IL-15, IL-18, IL-7Ralpha, IL-10R1, IL-15Ralpha, interferon-gamma [IFN-gamma], vascular epithelial growth factor [VEGF], Flt1, and transforming growth factor-beta) was quantified by real-time reverse transcriptase-polymerase chain reaction and correlated with protein expression by immunofluorescence.

RESULTS

In comparison with T-lineage ALL specimens, expression of IL-10, IFN-gamma, IL-15Ralpha, and Flt1 was significantly higher in B-cell precursor (BCP) ALL specimens (P <0.01). Among BCP ALL samples, gene expression of IL-7Ralpha and Flt1 was higher in pre-B than in common or pro-B leukemic cells. Moreover, expression levels of VEGF, IL-7Ralpha, IL-10R1, and IL-15Ralpha were lower in lymphoblasts of patients with a combined BM recurrence than in those with an isolated recurrence (P <0.05). Children with IL-15Ralpha expression above the median level had a significantly better probability of event-free survival (0.65 vs. 0.34, P=0.04) and survival (0.71 vs. 0.37, P=0.02) at 5 years.

CONCLUSIONS

Expression of distinct C/CR in ALL cells was associated with lineage commitment and differentiation of leukemic cells, as well as with prognosis. It remains to be evaluated whether these prognostic and biologic findings of distinct C/CR expression in leukemic cells also have therapeutical implications for future antileukemic strategies.

Intracellular cytokine expression in peritoneal monocyte/macrophages obtained from patients with cirrhosis and presence of bacterial DNA

BACKGROUND

The detection of bacterial DNA in serum and ascitic fluid from patients with cirrhosis and ascites is interpreted as molecular evidence of intestinal bacterial translocation and considered sufficient to activate the cellular immune response. In vitro studies on ascitic fluid culture have shown a close relationship between the synthesis of several cytokines and nitric oxide and the presence of bacterial DNA. Since different cell types give rise to cytokines, flow cytometry becomes a powerful tool to discriminate between populations involved in a bacterial challenge.

OBJECTIVE

To study the pre-activation status of macrophage/monocyte population ex vivo according to the presence of bacterial DNA.

PATIENTS

Patients with cirrhosis and culture-negative, non-neutrocytic ascites, with or without the presence of bacterial DNA in blood and ascitic fluid were studied.

METHODS

Flow cytometry analysis of intracellular cytokine expression in monocyte/macrophages from ascitic fluid was performed in basal conditions and after 12 h of cell stimulation adding lypopolysaccharide.

RESULTS

Monocyte/macrophages from patients with bacterial DNA showed a significantly higher production of interleukin-6 and tumor necrosis factor alpha in basal conditions than that in cells from patients without the presence of bacterial DNA. The addition of lipopolysaccharide produced a non-significant increment in the expression of these cytokines in patients with the presence of bacterial DNA, while this increment became significant in the other group of patients.

CONCLUSIONS

Bacterial translocation in patients with cirrhosis and ascites increases the basal intracellular cytokine expression, reducing its functional reserve capability.

Investigation of the role of B-cells in type 1 diabetes in the NOD mouse

B-cells are important in the development of type 1 diabetes, but their role is not completely defined. Although B-cells produce autoantibodies, these are not thought to be pathogenic; however, their antigen-presenting function is postulated to be critical. To examine the relative importance of these functions of B-cells, we have generated nonobese diabetic (NOD) B-cell-deficient mice that express a transgene encoding a mutant heavy chain immunoglobulin transgene on the cell surface but cannot secrete immunoglobulins (mIgs). This allowed us to dissect the importance of the relative roles of antigen presentation, dissociated from antibody production. We found that the expression of the mIg transgene increased insulitis and the incidence of diabetes compared with transgene-negative NOD B-cell-deficient mice, indicating that the ability to produce antibodies is not necessary for B-cells to have some effect on the development of diabetes. However, diabetes was not restored to the level seen in normal NOD mice. This may relate to reduced ability to activate an islet-specific T-cell repertoire, presumably due to the reduced islet-specific B-cell repertoire. Our results implicate a specific antigen-presenting function for B-cells.

Heterogeneous expression of interleukin-18 and its receptor in B-cell lymphoproliferative disorders deriving from naive, germinal center, and memory B lymphocytes

PURPOSE

Dysregulated cytokine/cytokine receptor expression may occur in B-cell lymphoproliferative disorders. Little information is available on interleukin-18 receptor (IL-18R) and IL-18 expression in normal and malignant B cells. Our purpose was to investigate this issue in human naive, germinal center (GC) and memory B cells, and in their neoplastic counterparts.

EXPERIMENTAL DESIGN

We have evaluated IL-18 expression and production in tonsil naive, GC, and memory B cells and in their presumed neoplastic counterparts by reverse transcription-PCR and ELISA. Moreover, IL-18Ralpha and beta expression was investigated in the same cells by reverse transcription-PCR, flow cytometry, and immunohistochemistry.

RESULTS

We found that: (a) IL-18 mRNA was expressed in tonsil naive, GC, and memory B cells. Bioactive IL-18 was secreted by naive and GC, but not by memory B cells; (b) IL-18Ralpha and beta transcripts were expressed in the three B-cell subsets. IL-18Ralpha was detected on the surface of naive, GC, and memory B lymphocytes, and IL-18Rbeta was detected on GC and memory, but not naive, B cells; (c) mantle zone, follicular, marginal zone, Burkitt lymphoma (BL), and B-cell chronic lymphocytic leukemia (B-CLL) cells expressed IL-18 mRNA. B-CLL and BL cells did not produce bioactive IL-18; and (d) lymphoma B cells displayed heterogeneous expression of either or both IL-18R chain mRNA. In contrast, B-CLL cells expressed both IL-18R chains at the mRNA and protein levels.

CONCLUSIONS

Dysregulated expression of IL-18 and/or IL-18R in chronic B-cell lymphoproliferative disorders may sometimes contribute to tumor escape from the host immune system.

Critical role of the major histocompatibility complex and IL-10 in matrilin-1-induced relapsing polychondritis in mice

Relapsing polychondritis (RP) is an autoimmune disease that affects extra-articular cartilage. Matrilin-1-induced relapsing polychondritis (MIRP) is a model for RP and is useful for studies of the pathogenic mechanisms in this disease. There are indications that the major histocompatibility complex (MHC) class II plays a major role in RP, since DR4⁺ patients are more commonly affected than controls. We have now addressed the role of the MHC region, as well as the non-MHC contribution, using congenic mouse strains. Of the MHC congenic strains, B10.Q (H2^q) was the most susceptible, the B10.P (H2^p) and B10.R (H2^r) strains developed mild disease, while B10 strains carrying the v, b, f, or u H2 haplotypes were resistant. A slight variation of susceptibility of H2^q strains (B10.Q> C3H.Q> DBA/1) was observed and the (B10.Q × DBA/1)F₁ was the most susceptible of all strains. Furthermore, macrophages and CD4⁺ T cells were the most prominent cell types in inflammatory infiltrates of the tracheal cartilage. Macrophages are the major source of many cytokines, such as interleukin-10 (IL-10), which is currently being tested as a therapeutic agent in several autoimmune diseases. We therefore investigated B10.Q mice devoid of IL-10 through gene deletion and found that they developed a significantly more severe disease, with an earlier onset, than their heterozygous littermates. In conclusion, MHC genes, as well as non-MHC genes, are important for MIRP induction, and IL-10 plays a major suppressive role in cartilage inflammation of the respiratory tract.

Apoptotic Effect of Rituximab on Peripheral Blood B Cells in Rheumatoid Arthritis

Rituximab (RTX) has proven efficacious in the treatment of rheumatoid arthritis (RA). Herein, we assessed the apoptosis-inducing capability of RTX in vitro on RA peripheral blood B-cell subsets and also compared the effects of RTX on B cells from rheumatoid factor-positive (RF+) and RF- patients. The likely relevance of B cells in disease was assessed by measuring B-cell-modulating serum cytokines. Peripheral blood B cells were isolated and cultured with the presence or absence of RTX. The levels of apoptosis within the naïve, memory and IgD+CD27+ B-cell subpopulations were determined by cytofluorometric analysis and caspase 3/7 assays. Levels of serum cytokines were measured with a multiplex cytokine array system. RTX induced significant apoptosis in all B-cell subsets in both RA and controls. In naïve and memory B cells from RA patients, RTX induced significantly higher levels of apoptosis than in controls. RTX induced apoptosis of B cells in RF+ and RF- patients. Serum levels of interleukin-1beta (IL-1beta), IL-4, IL-10 and IL-13 were profoundly increased in RF+ patients compared to RF- patients and controls. Although our cohort was small (10 RA patients), the data suggest that RTX induces apoptosis in all investigated subsets of B cells from RA patients. Interestingly, memory B cells from RA patients were more sensitive to RTX than memory cells from normal controls, suggesting that the delay in treatment response to RTX observed in clinical trials may be due in part to memory cell depletion. The apoptotic effects of RTX were similar in RF+ and RF- patients, but serum levels of B-cell-activating cytokine levels were only elevated in RF+ but not RF- patients. These data suggest that RTX is less effective in RF- RA because B cells play a less significant role in RA pathogenesis in RF- patients.

Distinct profiles of human B cell effector cytokines: a role in immune regulation?

There is growing interest in the fundamental roles that B cells may play in regulating immune responses. Emerging animal studies point to an important contribution of B cell effector cytokines to immune modulation, yet little is known about the factors regulating such cytokine production. We report that the profile of human B cell cytokine production is context dependent, being critically influenced by the balance of signals through the B cell receptor and CD40. B cells appropriately stimulated by sequential B cell receptor and CD40 stimulation proliferate and secrete TNF-alpha, lymphotoxin, and IL-6, which can act not only as autocrine growth and differentiation factors, but also serve to amplify the ongoing immune response. In contrast, CD40 stimulation alone, a mimic of a B cell receiving bystander T cell help in the absence of specific Ag recognition, induces negligible proinflammatory cytokines, but significant production of IL-10 that serves to suppress inappropriate immune responses. We thus describe a novel paradigm of reciprocal regulation of B cell effector cytokines, and ascribe active roles for human B cells in either promoting or suppressing local immune responses through context-dependent cytokine production.

Production of intracellular IL-2, TNF-alpha, and IFN-gamma by T cells in B-CLL

BACKGROUND

Recent evidence indicates that the slowly expanding population of CD5(+) B cells that characterizes B-cell chronic lymphocytic leukemia (B-CLL) could be related to defects in the response to cytokine produced by T cells that regulate apoptosis. We studied the intracellular expressions of interleukin-2 (IL-2), tumor necrosis factor-alpha (TNF-alpha), and interferon-gamma (IFN-gamma) in T-helper 1 cells (Th1 response) of B-CLL.

METHODS

Peripheral blood mononuclear cells from 21 healthy individuals and purified T cells from 21 early-stage and 15 late-stage B-CLL patients were activated with phorbol myristate acetate and ionomycin. The Th1 cytoplasmic cytokines were evaluated in CD4(+) and CD8(+) T cells by flow cytometry.

RESULTS

The percentages of CD4(+) and CD8(+) T cells positive for IL-2 were significantly lower in B-CLL patients than in healthy individuals (P = 0.030 and 0.049, respectively). No significant differences in TNF-alpha or IFN-gamma intracellular expressions were found between patients and healthy individuals. TNF-alpha- and IFN-gamma-expressing CD8 T cells were disease stage dependent, being significantly higher in late-stage patients (P < 0.001 for both cytokines).

CONCLUSIONS

Our present observations suggested that Th1 cytokines may be of major importance in the pathogenesis of B-CLL.

CD8+ chronic lymphocytic leukemia: an extensive characterization of a bizarre hybrid neoplasia

Atypical chronic lymphocytic leukemia (CLL) expressing the CD8 antigen have a frequency of less than 0.5% of all cases, however, they are not yet been fully characterized. Herein a CD8+ CLL case was extensively studied. Besides the classical CLL antigen expression, an unusual presence of surface markers such as CD11c, CD56, and CD154 was observed. Moreover, gene expression of chemokine receptors belonging to the CCR family were clearly evidenced as well as mRNA for both, Th1 and Th2 cytokines. Likewise, granzyme A, B and perforin gene expression, cytotoxic T cell or NK enzymes were found. The intricate profile of membrane molecules and gene expression suggest that it could be favorable, rather than deletereous, for the maintainance of the neoplastic process.

Interleukin-10 therapy--review of a new approach

Interleukin (IL)-10 is an important immunoregulatory cytokine produced by many cell populations. Its main biological function seems to be the limitation and termination of inflammatory responses and the regulation of differentiation and proliferation of several immune cells such as T cells, B cells, natural killer cells, antigen-presenting cells, mast cells, and granulocytes. However, very recent data suggest IL-10 also mediates immunostimulatory properties that help to eliminate infectious and noninfectious particles with limited inflammation. Numerous investigations, including expression analyses in patients, in vitro and animal experiments suggest a major impact of IL-10 in inflammatory, malignant, and autoimmune diseases. So IL-10 overexpression was found in certain tumors as melanoma and several lymphomas and is considered to promote further tumor development. Systemic IL-10 release is a powerful tool of the central nervous system to prevent hyperinflammatory processes by activation of the neuro-endocrine axis following acute stress reactions. In contrast, a relative IL-10 deficiency has been observed and is regarded to be of pathophysiological relevance in certain inflammatory disorders characterized by a type 1 cytokine pattern such as psoriasis. Recombinant human IL-10 has been produced and is currently being tested in clinical trials. This includes rheumatoid arthritis, inflammatory bowel disease, psoriasis, organ transplantation, and chronic hepatitis C. The results are heterogeneous. They give new insight into the immunobiology of IL-10 and suggest that the IL-10/IL-10 receptor system may become a new therapeutic target.

Follicular lymphoma cell lines, an in vitro model for antigenic selection and cytokine-mediated growth regulation of germinal centre B cells

In the periphery, B cells differentiate in germinal centres (GCs) of secondary lymphoid organs. Isolated GC cells die quickly in vitro by apoptosis. Therefore, cell lines originating from follicular lymphomas, which are the malignant counterparts of GC B cells, would provide a stable in vitro model to study the immunobiology of GC B cells. We have established three novel human follicular lymphoma cell lines that were characterized with special reference to immunophenotypic features, response to B-cell receptor (BCR) triggering, response to cytokines and cytokine mRNA expression. One of the cell lines, HF-1A3, has a phenotype of a centrocyte. It expresses surface immunoglobulin G (sIgG) and dies by apoptosis following BCR cross-linking. Co-stimulation with interleukin-6 (IL-6), IL-15 or interferon-gamma (IFN-gamma) rescues HF-1A3 cells from BCR-induced apoptosis. The second cell line, HF-28, also represents phenotypically an IgG+ centrocyte. Ligation of its BCR leads to the cell-cycle arrest at G1 instead of apoptosis. HF-28 cells express both CD45RA and RO isoforms, which is unusual in B lymphocytes apart from plasma cells, thus suggesting a transition to plasma cell phenotype. The third cell line, HF-4.9, which phenotypically represents an sIgM+ centroblast, responds by proliferation to BCR cross-linking. These cell lines offer a unique in vitro model to study antigenic selection and cytokine-mediated growth regulation of human GC B cells.

HIV-gp160 modulates differentially the production in vitro of IgG, IgA and cytokines by blood and tonsil B lymphocytes from HIV-negative individuals

HIV1-gp160 holds promises in anti-HIV vaccinal strategies. However, this molecule has been described to exhibit superantigenic activities. The present study aimed at examining the effect(s) of HIV1-gp160 on human B cells and in particular on B cells originating from HIV- donors. We purified human B cells of various origins, i.e. from blood and from tonsils (representing a mucosal-type origin), and we tested these cells (stimulated with a polyclonal B cell activator, interleukin (IL)-2 and IL-10 as cytokines, and recombinant HIV1-gp160) for the production of IgG and IgA in an in vitro model. Gp160 induced significantly less total IgG by blood - but not tonsil-originating - B cells and did not affect total IgA production. Further, HIV1-gp160 up-regulated IL-2-, IL-4- and IL-10-mRNA levels in stimulated blood B cells (these cytokines are known to be active on B cell activation and differentiation). Interestingly, HIV1-gp160 also up-regulated IL-1beta-, transforming growth factor (TGF)-beta-, interferon (IFN)-gamma- and IL-12-mRNA levels in stimulated mucosal-type, tonsil-originating, B cells. As these latter cytokines are involved in proinflammatory activities, HIV-gp160 delivery at the mucosal sites would be compatible with an adjuvant activity.

Costimulation via OX40L expressed by B cells is sufficient to determine the extent of primary CD4 cell expansion and Th2 cytokine secretion in vivo

The development of effector and memory CD4 cell populations depends upon both T cell receptor (TCR) engagement of peptide/major histocompatibility complex (MHC) class II complexes and ligation of costimulatory molecules with counter receptors on antigen-presenting cells (APCs). We showed previously that sustained interactions with APCs could be crucial for optimal expansion of CD4 cells and for development of effectors that secrete cytokines associated with Th2 cells. Using an adoptive transfer model with TCR transgenic CD4 cells, we now show that responses of CD4 cells primed in B cell-deficient mice become aborted, but are fully restored upon the transfer of activated B cells. Although B cells have the capacity to secrete multiple cytokines that could affect CD4 priming, including IL-4, we were unable to distinguish a role for cytokines that are secreted by B cells. However, B cell costimulation via the OX40L/OX40 pathway that has been implicated in CD4 cell expansion, survival, and Th2 development was required. Th2 but not Th1 responses were impaired in OX40L-deficient recipients and normal responses were restored with OX40L sufficient B cells. The results suggest that without engagement of OX40L on B cells, CD4 cell responses to many protein Ag would be dominated by Th1 cytokines. These data have important implications for strategies to achieve optimal priming of CD4 subsets.

Ixodes ricinus tick salivary gland extract inhibits IL-10 secretion and CD69 expression by mitogen-stimulated murine splenocytes and induces hyporesponsiveness in B lymphocytes

Tick saliva contains immunosuppressive factors allowing this blood-feeding ectoparasite to remain on hosts and enhancing pathogen transmission. In this study, we examined the modulation of mitogen-induced activation of naive murine splenocytes by the saliva and salivary gland extract (SGE) of I. ricinus ticks. We found that saliva-specific factors reduced IL-10 production by both concanavalin A (ConA) and lipopolysaccharide (LPS) stimulated splenocytes. The LPS-induced IL-10 production is 10 times more sensitive to SGE than the ConA-induced IL-10 production. Flow cytometric analysis determined that SGE particularly inhibited B (B220+) cell IL-10 production in mitogen-stimulated splenocyte preparations. Moreover, SGE reduced the early activation marker CD69 expression on ConA-activated T cells and also on B cells in presence of ConA or LPS. Annexin V and Via-probe staining demonstrated that SGE did not increase cell death in activated splenocytes and slightly decreased apoptosis in B lymphocytes. By employing assays with isolated B cells, we further showed that SGE had a direct effect on B cells and inhibited LPS-induced B cell proliferation. Taken together, our results indicate that salivary immunomodulators induce hyporesponsiveness to mitogen in both T and B cells, and that a direct B-cell inhibitory activity is present in tick saliva.

Cytokines production is altered in mice exposed to airborne suspended matter

The production of IL-2 and IL-4 by thymocytes, spleen and axillary lymph node lymphocytes from female and male mice exposed to airborne suspended matter (ASM) was the scope of our investigations. Cytokines production by activated lymphocytes was determined by the estimation of the percentage of cells positive for intracellular cytokines and by the concentration of both cytokines secreted into the culture medium. Two models of mice exposure to ASM were used: 1/ intraperitoneal injection (acute exposure), and 2/ oral exposure (subacute model). ASM exposure affected both IL-2 and IL-4 production and IL-2R alpha expression on activated lymphoid cells isolated from different lymphoid organs of both female and male mice. The effect was dependent on the route and duration of exposure, ASM dose and the age and sex of mice. A wide panel of changes is discussed. The prolonged exposure to ASM resulted in overproduction of IL-2 in both female and male mice and in overproduction of IL-4 in male mice. Acute exposure to ASM strongly affected IL-2 and IL-4 production, and the effect varied among lymphocytes from different lymphoid organs. Intracellular cytokines expression and the level of secreted cytokines seem to be good tools for the assessment of toxic effects of environmental pollution on the function of the immune system.

Biological assays for interferons

Interferons (IFN) are potent biologically active proteins synthesised and secreted by somatic cells of all mammalian species. They have been well characterised, especially those of human origin, with respect to structure, biological activities, and clinical therapeutic effects. While structural differences are known to exist among the IFN species that constitute the "IFN family" and despite the existence of different receptors for type I and type II IFN, all species have been shown to exert a similar spectrum of in vitro biological activities in responsive cells. Principal among the biological activities induced by IFN is antiviral activity, the activity used to originally define IFN. Antiviral activity of IFN is mediated via cell receptors and is dependent on the activation of signalling pathways, the expression of specific gene products, and the development of antiviral mechanisms. Sensitivity of cells to IFN-mediated antiviral activity is variable, and depends on a number of factors including cell type, expression of IFN receptors and downstream effector response elements, effectiveness of antiviral mechanisms, and the type of virus used to infect cells. Nevertheless, by the judicious use of sensitive cell lines in combination with appropriate cytopathic viruses, effective assays to measure the antiviral activity have been developed. Historically, "antiviral assays" (AVA) were the first type of biological assays that were developed to measure the relative activity or potency of IFN preparations. However, the subsequent discoveries of several other biological activities of IFN has opened the way to the development of assays based on one or other of these activities. The latter include inhibition of cell proliferation, regulation of functional cellular activities, regulation of cellular differentiation and immunomodulation. More recently, the cloning of IFN responsive genes has led to the development of "reporter gene assays". In this case, the promoter region of IFN responsive genes is linked with a heterologous reporter gene, for example, firefly luciferase or alkaline phosphatase, and transfected into an IFN-sensitive cell line. Stably transfected cell lines exposed to IFN increase expression of the reporter gene product in direct relation to the dose of IFN, the readout being a measure of this product's enzymic action. The current review aims to give a critical overview of the development, specificity, standardisation and present use of the various biological assay methods now available for the quantification of IFN activity.

Recombinant Dirofilaria immitis polyprotein that stimulates murine B cells to produce nonspecific polyclonal immunoglobulin E antibody

Nonspecific immunoglobulin E (IgE) production is an event characteristically observed in parasitic helminth infections, but its mechanisms are still unclear. To define these mechanisms, we prepared a recombinant Dirofilaria immitis protein (rDiAg) and assessed its effect on nonspecific IgE production. rDiAg preferentially induced nonspecific IgE production, without eliciting specific IgE production, as well as a Th2-type cytokine profile (high interleukin-4 [IL-4] and IL-10 production but low gamma interferon production) in BALB/c mice. rDiAg significantly elicited the proliferative response of naive B cells. This response was not abolished by polymyxin B, an inhibitor of lipopolysaccharide (LPS), and rDiAg normally expanded splenic B cells from LPS nonresponder C3H/HeJ mice. Thus, the mitogenic effect of rDiAg was not due to LPS contamination. rDiAg also enhanced levels of CD23 expression on splenic B cells. Splenic B cells produced marked levels of IgE when cultured with the combination of rDiAg and IL-4 (rDiAg-IL-4), whereas peritoneal B cells produced negligible levels of IgE. rDiAg-IL-4-induced IgE production by splenic B cells was synergistically increased by coculture with peritoneal B cells. rDiAg-driven IL-10 secretion was higher in peritoneal B cells than in splenic B cells. IgE production by splenic B cells cocultured with peritoneal B cells was decreased to a level comparable to that by splenic B cells in the presence of a neutralizing anti-IL-10 monoclonal antibody. Collectively, these results suggest that rDiAg-induced polyclonal expansion and IgE class switching of splenic B cells contribute to nonspecific IgE production and that these responses are enhanced by peritoneal B-cell-derived IL-10.

CD19(+) cells produce IFN-gamma in mice infected with Borrelia burgdorferi

We have recently shown that production of IFN-gamma and IL-10, but not IL-4 is specifically induced in the lymph nodes of C3H/HeJ (disease susceptible) and C57BL/6J (disease resistant) mice 1 week after infection with Borrelia burgdorferi spirochetes. The present study was conducted to determine the phenotypes of ex vivo lymph node cells obtained from infected mice of both strains at this time point. The percentages of CD3(+), CD4(+), CD8(+), TCRalpha/beta (+) and TCRgamma/delta (+) cells decreased in both strains of mice compared to LN from naive mice. In contrast, there was a threefold increase in the proportion of CD19(+) cells. In view of this expansion of the B cell proportion, we examined the ability of purified CD19(+) cells and CD43(+) cells to produce both IL-10 and IFN-gamma when the cells were restimulated in vitro with B. burgdorferi freeze-thawed spirochetes. As expected, CD43(+) cells were able to produce both cytokines, but not IL-4. Surprisingly, CD19(+) (B) cells also were able to produce IFN-gamma in comparable amounts, in addition to IL-10. Intracellular staining of CD19(+) cells with anti-IFN-gamma antibody confirmed this finding. We discuss this novel phenomenon in terms of its possible underlying mechanisms and its relevance, both in the context of the immunology of Lyme disease and that of other infectious diseases.

Interleukin 4 content in chronic lymphocytic leukaemia (CLL) B cells and blood CD8+ T cells from B-CLL patients: impact on clonal B-cell apoptosis

B-chronic lymphocytic leukaemia (CLL) clonal B cells are characterized by resistance to apoptosis. We evaluated clonal B cells and blood T cells for interleukin 4 (IL-4) content as IL-4 is able to increase CLL cell resistance to apoptosis. The content of IL-4 in CD8+ T cells of CLL patients (n = 9) ranged from 37% to 63% of the total CD8+ T cells (mean level of 49% +/- 3.4) compared with a range of 5-10% for control CD8+ T cells. Clonal B cells positive for cytoplasmic IL-4 ranged from 1% to 97% (mean value 57.8 +/- 6.9%). CD8+ T cells and clonal B cells secreted detectable levels of IL-4, but only clonal CLL B cells (n = 4) secreted IL-4 in association with increasing cell numbers. Fludarabine (F-ara-AMP, 0.1-100 micromol/ml) was able to downregulate the IL-4 content of CD8+ T cells, but not clonal B-cell IL-4. Culture supernatant from CLL CD8+ T cells decreased the spontaneous apoptotic rate of clonal B cells that was reversed with anti-IL-4 and soluble IL-4 receptor. These findings show that IL-4 is present in the microenvironment of B-CLL. In addition, use of agents that can interfere with IL-4 presentation to clonal B cells can be effective in increasing clonal B-cell apoptosis.

Characterization of cytokine, growth factor receptor, costimulatory and adhesion molecule expression patterns of bone marrow blasts in relapsed childhood B cell precursor all

Relapse of childhood acute lymphoblastic leukaemia (ALL) comprises a leading challenge of investigation. Characterization of leukaemic cells regarding their potency to express growth factors and surface molecules can provide insight into their aberrant biology. Thus, we analyzed bone marrow blasts from 10 children with relapsed B cell precursor ALL. The gene and protein expression of essential haematopoietic growth factors (IL-2, IL-4, IL-7, IL-10, IL-15, IFN-gamma, G-CSFR), their corresponding receptors as well as the expression pattern of adhesion molecules (ICAM-1, CD58) and costimulatory proteins (CD40, CD40L, B7.1, B7.2, CD28, MHC-I and II) was analyzed by RT-PCR and flow cytometry. Constitutive gene expression was found for IL-7, IL-10, IL-15 and IFN-gamma and their corresponding receptors. Flow-cytometric analysis showed that IL-10R, IL-7Ralpha, IL-4Ralpha and the gamma(c)chain are constitutively expressed, and that some cells bear the G-CSFR. IL-10 and IL-15 protein-producing leukaemic cells were easily detectable. The neoplastic cells mainly lack B7.1, and ICAM-1 is mostly decreased. Furthermore, high CD40, and, surprisingly, CD40L expression could be found. These studies show that ALL cells are likely to be sensitive to many growth factors and some factors are produced by the neoplastic cell itself. The secretion of IL-10 by leukaemic cells, and the absence or downregulation of conventional adhesion and costimulatory molecules might represent an effective mechanism of escape of immune surveillance in relapsed ALL.

Reciprocal regulation of polarized cytokine production by effector B and T cells

Although B cells produce cytokines it is not known whether B cells can differentiate into effector subsets that secrete polarized arrays of cytokines. We have identified two populations of "effector" B cells (Be1 and Be2) that produce distinct patterns of cytokines depending on the cytokine environment in which the cells were stimulated during their primary encounter with antigen and T cells. These effector B cell subsets subsequently regulate the differentiation of naïve CD4+ T cells to TH1 and TH2 cells through production of polarizing cytokines such as interleukin 4 and interferon gamma. In addition, Be1 and Be2 cells could be identified in animals that were infected with pathogens that preferentially induce a Type 1 and Type 2 immune response. Together these results suggest that, in addition to their well defined role in antibody production, B cells may regulate immune responses to infectious pathogens through their production of cytokines.

Molecular mechanisms of B lymphocyte activation by the immune response modifier R-848

The imidazoquinoline R-848, originally identified as a highly effective antiviral agent, has recently been shown to be capable of potent B lymphocyte activation. The B cell-activating properties of R-848 are strikingly similar to the effects of the CD40 ligand CD154. The present study demonstrates that this similarity extends to the intracellular signaling pathways triggered by the compound, although both overlapping and distinct mechanisms of signaling were seen. Like CD40 ligation, R-848 stimulated activation of the stress-activated protein kinases c-Jun kinase and p38 and activated the NF-kappaB family of transcription factors. Both R-848- and CD40-mediated B cell differentiation were dependent upon NF-kappaB activation, although the relative importance of individual NF-kappaB family members appeared to differ between R-848- and CD40-mediated signals. Both signals were partially dependent upon induction of TNF-alpha and IL-6, and the cytoplasmic adaptor molecule TNF receptor-associated factor 2 is involved in both R-848- and CD40-mediated differentiation.

B-cell chronic lymphocytic leukemia/small lymphocytic lymphoma involving bone marrow with an interfollicular pattern

B-cell chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) may involve the bone marrow in nodular, interstitial, diffuse, or mixed patterns. However, B-cell CLL/SLL associated with large reactive germinal centers (the so-called interfollicular pattern) involving the bone marrow is not reported. We describe 2 examples of B-cell CLL/SLL that subtotally replaced the bone marrow with an interfollicular pattern. In both cases, the neoplasms were composed of small round lymphoid cells; proliferation centers also were present. The neoplasms surrounded large reactive germinal centers that were devoid of peripheral mantle zones. The germinal centers were paratrabecular and nonparatrabecular in case 1 and nonparatrabecular in case 2. Flow cytometry immunophenotypic studies done on bone marrow aspiration samples of both cases showed a uniform population of neoplastic cells positive for pan-B-cell antigens and the CD5 and CD23 antigens. Immunohistochemical studies done on bone marrow biopsy sections supported the flow cytometry results and demonstrated that the germinal centers were negative for BCL-2. B-cell CLL/SLL may rarely involve the bone marrow with an interfollicular pattern. Knowledge of this pattern will prevent confusion with follicle center lymphoma and large cell transformation, both of which initially were considered in the differential diagnosis of these cases.

Pathogenetic role of autoantibodies in neurological diseases

Autoreactive B cells and antibodies can be detected in a variety of neurological diseases. Their causative role has been established in some disorders and they are obviously involved in the pathogenesis of others. Some mechanisms engendering B-cell autoimmunity in animal models have been shown to operate in humans. Factors that determine B-cell immune-response patterns and the effector pathways have been identified. B-cell responses to CNS-restricted autoantigens are governed by distinctive immune reactions. Evidence has accumulated that the CNS is a permissive and, under inflammatory conditions, even a B-cell-supporting micro-environment. Data from human and animal experiments have enhanced our understanding of B-cell physiology in health and neurological disease, which has relevant diagnostic and therapeutic implications.

Stromal cell-derived factor-1 as a chemoattractant for follicular center lymphoma B cells

BACKGROUND

Follicular center lymphoma displays widespread lymph node involvement at diagnosis. The chemoattractants that control the locomotion of follicular center lymphoma B cells have not been established. Stromal cell-derived factor-1 (SDF-1) is a CXC-class chemokine that enhances the migration of normal human B cells and is expressed in peripheral lymphoid tissues. Here we have investigated 1) whether SDF-1 stimulates the in vitro locomotion of follicular center lymphoma B cells and of their presumed normal counterparts (i. e., germinal center B cells) and 2) whether the same cells express SDF-1 transcripts.

METHODS

B cells were purified by immunomagnetic bead manipulation. Messenger RNA was detected by reverse transcription-polymerase chain reaction. Migration was assessed by the filter and collagen invasion assays. All P values were two sided.

RESULTS

Follicular center lymphoma B lymphocytes showed a statistically significant migratory response to 300 ng/mL SDF-1, both in the filter and in the collagen assays (P =.002 for each). Such response was mediated by the SDF-1 receptor, CXCR4. CD40 monoclonal antibody (MAb) and tonsillar germinal center B cells treated with CD40 MAb and recombinant interleukin 4, but not freshly isolated, migrated statistically significantly faster in the presence than in the absence of SDF-1 (P =.002 in both filter and collagen assays). Freshly isolated follicular center lymphoma and germinal center B cells expressed SDF-1 transcripts.

CONCLUSIONS

This study shows that SDF-1 substantially enhances the migration of follicular center lymphoma B cells but not the migration of freshly purified germinal center B cells. This difference may be related to the extended survival of follicular center lymphoma versus germinal center B cells. SDF-1 produced in follicular center lymphoma lymph nodes may play a role in the local dissemination of tumor cells.

Biology of chronic lymphocytic leukemia

B-cell chronic lymphocytic leukemia (CLL) lies at the cross-roads of hematology, immunology and oncology for at least three major reasons: (a) it is the prototype of human malignancies that primarily involve defects in the induction of apoptosis; (b) CLL patients develop a severe immunodeficiency with progressive hypogammaglobulinemia; and (c) they have a high prevalence of autoimmune phenomena. Recent advances in the biology of the malignant cell in CLL lead to a scenario comprised of two basic elements: first, CLL cells are optimally organized to survive in their niches because their ability to undergo apoptosis is severely hampered; second, they have a microenvironment-dependence that promotes their extended survival, a situation that arises most probably through direct cell-to-cell contacts. In addition, CLL cells themselves are the major accessory cells in CLL, but are inefficient antigen-presenting cells. This latter defect may provide a clue to reinterpret the events of immunodeficiency and autoimmunity.

Induction of transforming growth factor-beta 1 production in human cells by herpes simplex virus

Transforming growth factor-beta (TGF-beta) is a cytokine of particular interest in human retrovirus infections because it can abrogate antigen-specific cellular activation. Although TGF-beta production has been observed in HIV infections, there is no evidence that herpes simplex virus (HSV)-stimulated human cells produce this cytokine. Here we present evidence, for the first time, that in vitro infection of human mononuclear cells with HSV type 1 (HSV-1) induced the release of TGF-beta1 protein. The production of this cytokine was time dependent and was found highly significant (p < 0.001) after 48 h. In addition, we observed that the secretion of TGF-beta1 was dependent on the concentration of human cells. It was found that virus needs to replicate in human cells for the production of TGF-beta1, as UV-inactivated virus did not induce significant production of cytokine protein. Interestingly, increased HSV-1-induced TGF-beta1 production in cultures containing antiinterleukin (IL)-12 or antiinterferon (IFN)-gamma antibodies was observed, whereas an irrelevant antibody had no effect on the production of this cytokine. Taken together, these findings indicate that human cells synthetize TGF-beta1 in response to HSV-1 and at the same time suggest that HSV-1-induced TGF-beta1 production may be one of the mechanisms by which HSV can at least partly evade activation of the host immune system.

Accessory cells, cytokine loops and cell-to-cell interactions in chronic lymphocytic leukemia

In addition to the extensive work that has been conducted in order to understand better the biological features of the leukemic population in B-cell chronic lymphocytic leukemia (CLL), over the years considerable interest has been directed towards other related studies that may have important implications for the accumulation of the leukemic clone and for the immunoparesis typical of this disease. In the present review article, we discuss some of these areas of investigation and, in particular, we focus on: (1) the multiple abnormalities recorded within the T and cytotoxic compartment of patients with CLL; (2) cytokine loops occurring in this disease, with particular emphasis on the cytokines that appear to play a more critical role; and (3) the cell-to-cell cross talk that may be actively operational in CLL. These findings will be discussed in relation with the possible implications that each of them have in the expansion and clinical behavior of a disease that is increasingly proving its heterogeneity.

Cytokine expression in B-CLL in relation to disease progression and in vitro activation

Earlier, we reported an association between low in vitro and in vivo IL-1 and IL-6 production, decreased IL-1beta and IL-10 mRNA expression and B cell chronic lymphocytic leukemia (B-CLL) disease progression. We have now further investigated cytokine mRNA transcription in B-CLL cells and cytokine serum levels in B-CLL patients. Reverse transcriptase polymerase chain reaction (RT-PCR) amplification of tumor necrosis factor (TNFalpha), IFNgamma, IL-6 and BCGF was equally often seen in non-progressive and progressive patients. However, 4 out of 23 non-progressive cases expressed mRNA for IL-12 while no IL-12 expression was seen in 15 progressive patients. No IL-12 was found in sera or supernatants from in vitro stimulated B-CLL cells, whereas TNFalpha and IL-10 were detected in sera from 51 and 31 of 65 B-CLL patients, respectively. TNFalpha values were significantly high in sera from patients in stages III and IV with disease progression. TNFalpha and IL-10 were also detected in culture supernatants from in vitro stimulated B-CLL cells, whereas IFNgamma was undetectable in these cultures and rarely positive in serum. Although further investigations are required, our data and that from previous reports indicate that B-CLL-derived cytokines are involved in B-CLL disease progression.

Dendritic Cell-Derived IL-12 Promotes B Cell Induction of Th2 Differentiation: A Feedback Regulation of Th1 Development

B cells convert what are normally conditions for Th1 differentiation into an environment suitable for Th2 development. This capacity is dependent on CD40 as B cells from CD40−/− mice do not elicit Th2 differentiation. To elucidate the basis of this effect, we surveyed cytokine RNA made by naive B cells after activation with anti-Ig and anti-CD40. Resting B cells make TGF-β message only, however, 4 days after activation, RNA encoding IL-6, IL-10, and TNF-α was found. The expression of these messages was accelerated by 2 days in the presence of IL-12. The relevance of these observations to T cell differentiation was investigated: addition of OVA peptide to splenic cells from DO.11.10 transgenic mice causes most T cells to make IFN-γ. Coactivation of B cells in these cultures reduces the number of IFN-γ-producing T cells and increases the number synthesizing IL-4. Abs to IL-6 and IL-10 block the IL-4 enhancement. Dissection of the component APC demonstrated that interaction of B cells with IL-12-producing dendritic cells is crucial for B cell-mediated IL-4 enhancement: Thus, B cells preactivated in the presence of dendritic cells from IL-12−/− mice show little IL-4-inducing activity when used to activate T cells. This immune regulation is initiated by IL-12 and therefore represents a feedback loop to temper its own dominant effect (IFN-γ induction).

The B-cell system of human mucosae and exocrine glands

The mucosae and exocrine glands harbour the largest activated B-cell system of the body, amounting to some 80-90% of all immunoglobulin (Ig)-producing cells. The major product of these immunocytes is polymeric (p)IgA (mainly dimers) with associated J chain. Both pIgA and pentameric IgM contain a binding site for the polymeric Ig receptor (pIgR), or secretory component (SC), which is a requirement for their active external transport through secretory epithelia. The pIgR/SC binding site depends on covalent incorporation of the J chain into the quaternary structure of the polymers when they are produced by the local immunocytes. This important differentiation characteristic appears to be sufficient functional justification for the J chain to be expressed also by most B cells terminating at secretory effector sites with IgD or IgG production; they probably represent a "spin-off" from sequential downstream CH switching on its way to pIgA expression, thus apparently reflecting a maturational stage of effector B-cell clones compatible with homing to these sites. Observations in IgA-deficient individuals suggest that the magnitude of this homing is fairly well maintained even when the differentiation pathway to IgA is blocked. Certain microenvironmental elements such as specific cytokines and dendritic cells appear to be required for induction of IgA synthesis, but it remains virtually unknown why this isotype normally is such a dominating product of local immunocytes and why they have such a high level of J chain expression. Also, despite the recent identification of some important requirements in terms of adhesion molecules (e.g. integrin alpha 4 beta 7 and MAdCAM-1) that explain the "gut-seeking" properties of enterically induced B cells, the origin of regionalized homing of B cells to secretory effector sites outside the gut remains elusive. Moreover, little is known about immune regulation underlying the striking disparity of both the class (IgD, IgM) and subclass (IgA1, IgA2, IgG1, IgG2) production patterns shown by local immunocytes in various regions of the body, although the topical microbiota and other environmental stimuli might be important. Rational design of local vaccines will depend on better knowledge of both inductive and migratory properties of human mucosal B cells.