Interleukin-15 + thioredoxin induce DNA synthesis in B-chronic lymphocytic leukemia cells but not in normal B cells

We have previously shown that Staphylococcus aureus Cowan strain 1 particles (SAC) + thioredoxin (Trx) + IL-2 may induce B-chronic lymphocytic leukemia (B-CLL) cells to proliferate. In this paper we have examined IL-15, which has activities similar to IL-2, for its ability to stimulate B-CLL cells and compared its activity with that of IL-2. We found that B-CLL cells could be induced to DNA synthesis upon treatment with IL-15 + Trx. The presence of Trx was essential for the IL-15-induced DNA synthesis. This contrasts to the effect of IL-15 + Trx on normal CD5+ and CD5- B cells, where IL-15 + Trx alone only induced limited DNA synthesis. IL-15 was as effective in the induction of DNA synthesis in B-CLL cells as IL-2, but about 100-fold less potent with an EC50 of 200 ng/ml. In addition we found that the IL-15 + Trx-induced proliferation was inhibited by CD40 stimulation. We conclude that IL-15 together with a proper costimulus can induce B-CLL cells to proliferate in vitro.     

Autologous bone marrow support and bone disease in metastatic breast cancer

Production of IgM, IgG and IgA was induced from human blood B lymphocytes by culturing with a CD40 MoAb and IL-2 for 9 days. Replacement of IL-2 by IL-10 markedly enhanced production of all three isotypes. High levels of immunoglobulin production also occurred when activated irradiated autologous T cells replaced the CD40 MoAb, and when IL-10 replaced IL-2 in these cultures a spectacular increase in IgG production occurred. The effectiveness of the T cell stimulus depended on the mode of purification of the T cells and the nature of the stimulant used to activate them. Differences in the kinetics and level of expression of CD40L on the various T cell preparations were observed, but did not account for variations in immunoglobulin-inducing efficiency. Immunoglobulin production from sIgD+ and sIgD- B cells was investigated. IgG and IgA were found in sIgD+ cultures, indicating that some isotype switching had occurred, but the major part of the IgG and IgA secreted was from cells already committed to these isotypes. Anti-IgD or anti-IgM MoAbs enhanced the proliferation of B cells induced by anti-CD40 antibody, but immunoglobulin production was not enhanced. Factors affecting the balance of proliferation and differentiation are discussed.     

Human interleukin 10 induces naive surface immunoglobulin D+ (sIgD+) B cells to secrete IgG1 and IgG3

During antigen-induced immune responses, human B cells switch isotype from immunoglobulin M (IgM)-IgD to IgG1-4, IgA1-2, or IgE. In the human, no cytokines have yet been demonstrated to act as switch factors for IgG1, IgG2, and IgG3. In this paper, we report that in response to interleukin 10 (IL-10), anti-CD40 activated tonsillar surface IgD+ (sIgD+) B cells are induced to secrete large amounts of IgM, IgG1, and IgG3 but neither IgG2 nor IgG4. Cord blood purified B cells and lymphocytes from Hyper-IgM patients also produced IgG1 and IgG3 after culture with anti-CD40 and IL-10. In contrast, sIgD- isotype-committed B cells produce IgG1, IgG2, and IgG3 when activated through CD40 in the presence of IL-10. Thus, in addition to its growth-promoting and differentiating activities on human B cells, IL-10 may represent a switch factor for IgG1 and IgG3.     

Effect of B-cell receptor engagement on CD40-stimulated B cells

Activation of human B cells in vitro either by cross-linking of surface immunoglobulins (sIg) or by triggering CD40 antigen, in the presence of interleukin-10 (IL-10) and interleukin-2 (IL-2), may result in high levels of immunoglobulin secretion in vitro. We studied the combined effects of ligation of the B-cell receptor (BCR) and CD40 [with anti-CD40 monoclonal antibody (mAb)] on B-cell proliferation and production of human immunoglobulin. For this purpose highly purified splenic B cells were cultured with various combinations of anti-CD40 and IL-10/IL-2 or IL-4 in the presence of CD32-transfected L cells. Simultaneous cross-linking of the BCR was achieved by mAb held on CD32-L cells or Staphylococcus aureus (SA). We found that dual BCR and CD40 ligation with IL-10/IL-2 leads to reduced immunoglobulin G (IgG) secretion compared with B cells stimulated with either anti-CD40 and IL-10/IL-2, or compared with B cells stimulated with SA or anti-BCR mAb and IL-10/IL-2. Dual BCR and CD40 ligation with anti-immunoglobulin mAb (anti-kappa + anti-lambda light chains) but not with SA induced a similar reduction in IgM production. The reduced immunoglobulin secretion found during dual ligation is accompanied by increased proliferation. This was independent of cytokine stimulation but SA/CD40-induced proliferation was increased in the presence of IL-10/IL-2, although not with IL-4. The combination anti-kappa and anti-lambda with anti-CD40 showed a long-term suppression of IgG and IgM production (at least 14 days), while anti-kappa or anti-lambda alone, or SA, allowed a moderate recovery of immunoglobulin production by day 14. These results suggest that simultaneous B-cell antigen receptor cross-linking and CD40 engagement via CD40L on T cells induces strong initial proliferation. This may be followed later by antibody production depending on the strength of the BCR signal and the presence of the appropriate cytokines.     

Activation of thymic B cells by signals of CD40 molecules plus interleukin-10

We have previously found that thymic B cells, particularly thymic CD5+ B cells, show low responsiveness to the usual B cell stimulants such as lipopolysaccharide or anti-IgM plus interleukin (IL)-4, although they proliferate and produce antibodies after direct interaction with major histocompatibility complex class II-restricted T blasts. These findings raise the possibility that a CD40-CD40 ligand (L) interaction is involved in the activation of thymic B cells. In the present study, we therefore examine this possibility using CD40L-transfected Chinese hamster ovary (CHO) cells or anti-CD40 monoclonal antibody (mAb). When B cells in the spleen and peritoneal cavity were stimulated, they proliferated and produced immunoglobulin (Ig) in the presence of CD40L-CHO cells or anti-CD40 mAb alone. However, another signal delivered by IL-10 in addition to CD40L-CHO cells or anti-CD40 mAb was found to be necessary for thymic B cells to proliferate and secrete Ig. Other interleukins acting on B cells, such as IL-4, IL-5, and IL-6, had no effect on the activation of thymic B cells, which thus have unique characteristics not found in peripheral B cells. This report discusses the physiological significance of IL-10- and CD40-driven signals in the activation of thymic B cells.     

Mouse germinal center B cells with the xid mutation retain responsiveness to antimouse CD40 antibodies but diminish IL-5 responsiveness

The germinal center (GC) develops in secondary lymphoid tissues in response to thymus-dependent (TD) antigens. To investigate the molecular mechanism of B cell differentiation in GC, we enriched GC B cells from spleen of TD antigen-immunized wild-type and X-linked immunodeficient (XID) mice, and examined the differentiation of GC B cells into antigen-specific IgG1 antibody-forming cells (AFC) in response to anti-CD40 mAb and cytokines. A significant proportion of freshly purified GC B cells expressed receptors for IL-4 and IL-5. Anti-CD40 mAb sustained the viability of GC B cells and IL-4 co-operated with anti-CD40 mAb for further enhancement of the cell viability. Anti-CD40 mAb and IL-4 were essential for inducing differentiation of GC B cells into antigen-specific IgG1-AFC and IL-5 efficiently enhanced their differentiation. GC B cells with the xid mutation responded for proliferation to CD40 ligation to a lesser extent and for the IgG1-AFC response to anti-CD40 mAb together with IL-4, but they showed impaired responsiveness to IL-5, regardless of enhanced expression of IL-5R in response to anti-CD40 mAb and IL-4. These results suggest that anti-CD40 mAb, IL-4 and IL-5 play a critical role in the differentiation of mouse GC B cells. The GC B cells from XID mice show a functional defect with respect to IL-5-mediated differentiation.     

Evidence for a critical role for IL-2 in CD40-mediated activation of naive B cells by primary CD4 T cells

The interaction of CD40 on B cells with the CD40 ligand (CD40L) on preactivated CD4 T cells is critical for the initiation of T-dependent Ab responses. It is believed that signals via CD40 synergize with cytokines (e.g., IL-4 and IL-5) to drive B cell activation. However, primary T cells preactivated via CD3 alone cannot induce B cell proliferation; we have shown previously that costimulation of T cells via CD3 and CD28 stabilizes the expression of the CD40L, which we propose contributes to their capacity to act as competent helper-effector cells. Here we show that an additional, critical reason why CD3-stimulated CD40L-bearing T cells are incompetent helper cells is because they secrete insufficient IL-2. In contrast, CD28/CD3-activated T cells induce B cells to become IL-2 responsive via a combination of CD40L and IL-2-mediated signals, and these two stimuli subsequently drive B cell proliferation and IgM secretion. We therefore propose that T cells must first encounter Ag in conjunction with CD80/86 on APCs. This leads to the stable expression of CD40L and maximal secretion of IL-2, which together render primary T cells competent to activate B cells in an IL-2-dependent fashion.     

Studies on the induction of antigen-specific antibody in anti-CD40 cultured human B lymphocytes

Costimulatory signals provided by T cells are required for B cells to produce specific antibody to T-dependent antigen. We have investigated the suitability of using the CD40 culture system for the proliferation and differentiation of Ag-specific human B cells using cytomegalovirus (CMV) or tetanus toxoid (TT) as antigen. We modified the CD40 culture system (CD32-transfected L cells, anti-CD40, and IL-4) by applying a sequential cytokine stimulation and compared total B-cell cultures with antigen-specific B cells preselected by panning. The detection of specific antibody became possible when antigen-selected B cells were cultured for 7 days in the CD40 system to induce clonal expansion, followed by the addition of IL-2 and IL-10 for an additional 7 days to induce plasma-cell differentiation. We conclude that our initial inability to detect specific antibody in the CD40 system is due to overgrowth of nonspecific B-cell clones and that selection of antigen-specific B cells by panning overcomes this problem. Induction of antigen-specific antibody production was found to be optimal when the initial contact with antigen during panning was limited to between 1 to 24 hours.     

Inhibitory and stimulatory effects of IL-10 on human CD8+ T cells

IL-10 is a well-documented immunosuppressant that inhibits macrophage-dependent Ag presentation and CD4+ T cell proliferation in vitro. We report that IL-10 inhibits alloantigen-specific proliferative responses and induces a long lasting anergic state in human purified CD8+ T cells when added concomitantly with the Ag in the presence of APC. Moreover, the generation of allospecific cytotoxic activity is inhibited by IL-10. These effects are indirect and are mediated through inhibition of the costimulatory functions of APC. In contrast, IL-10 has no direct inhibitory effects on the proliferation of purified CD8+ T cells activated by anti-CD3 mAb and promotes the growth of activated CD8+ T cells in combination with low doses of IL-2. Taken together, these results indicate that IL-10 has differential effects on CD8+ T cells depending on their state of activation, which may explain both the enhancing and inhibitory effects observed after IL-10 treatment in different in vivo experimental models.     

IL-12 up-regulates CD40 ligand (CD154) expression on human T cells

IL-12 is a heterodimeric cytokine produced by APC that promotes the development of CD4+ Th1 cells and their IFN-gamma production after TCR/CD3 triggering. We here investigated the capacity of IL-12 to modify the expression on T cells of CD40 ligand (CD40L or CD154), a molecule transiently expressed on activated T cells and known to be of utmost importance for cognate interaction with B cells and for activation of dendritic cells and macrophages. Our data demonstrate that IL-12 up-regulates CD40L expression on anti-CD3-activated human peripheral blood T cells. For optimal induction of CD40L, IL-12 synergizes with IL-2 as well as with other costimulatory interactions, such as B7/CD28. The effect of IL-12 was observed at both the protein and the mRNA level. T cells costimulated by IL-12 provided more efficient help for IL-4-dependent B cell proliferation and for IgG production than when activated in the absence of IL-12. This helper activity was blocked by an mAb against CD40L, indicating that the effect of IL-12 on B cells is mediated indirectly through CD40L. The data thus suggest that the effects of IL-12 on cellular and humoral immune responses are partly mediated through CD40L induction.     

IL-10-driven immunoglobulin production by B lymphocytes from IgA-deficient individuals correlates to infection proneness

In search for a possible explanation of the phenotypic heterogeneity in IgA deficiency, we studied the function of B cells from IgA-deficient (IgAd) individuals. Two groups of IgAd individuals, one frequently infected and one clinically apparently healthy, as well as normal controls, were studied. Peripheral blood mononuclear cells (PBMC) and B cells from IgAd individuals and controls were cultured with Staphylococcus aureus Cowan I strain and with anti-CD40 MoAb presented on the CD32-transfected fibroblast cell line in the presence of IL-10. In this experimental system PBMC and B cells from the infection-prone IgAd individuals produced only minute amounts of IgA. In contrast, PBMC and B cells from healthy IgAd subjects secreted significantly more IgA1 and IgA2 in comparison with infection-prone IgAd patients (P < 0.05). These data suggest that the abnormalities of B cell differentiation in IgAd could be of heterogeneous origin. Thus, whereas in healthy IgAd subjects IgA production may be efficiently up-regulated in vitro by addition of IL-10 to CD40-activated B cell culture, the corresponding B cell differentiation does not occur in infection-prone IgAd patients. These observations provide a conceptual framework for phenotypic heterogeneity in IgAd subjects.     

LPS-stimulated SJL macrophages produce IL-12 and IL-18 that inhibit IgE production in vitro by induction of IFN-gamma production from CD3intIL-2R beta+ T cells

SJL mice are known for their poor IgE production upon helminth infection. In this study, we have demonstrated that SJL standard B cells (85% IgM+ or B220+), prepared by complement-mediated T cell lysis, failed to proliferate and to produce IgE and IgG1 in response to LPS plus IL-4 in vitro. This diminished IgE production was restored by anti-IL-12 and enhanced by additional treatment with anti-IL-18, suggesting active suppression by the cells that produce IL-12 and IL-18. Indeed, SJL standard B cells were contaminated with Mac-1+ cells. Therefore, we removed macrophages by passing standard B cells through a Sephadex G-10 column (G10). Resultant cells (95% IgM+), designated as G10-B cells, responded to LPS and IL-4 by their proliferation and differentiation. G-10 treatment markedly diminished the proportion of B220- cells and Mac-1+ cells in SJL standard B cells. Furthermore, addition of SJL B220- cells dose dependently and MHC independently inhibited LPS plus IL-4-induced B cell growth and IgE production in SJL and BALB/c B cells. B220- cells in SJL standard B cells contained Mac-1+ cells (51%) and Fas ligand+ CD4-CD8- double-negative CD3intIL-2R beta+ T cells (26%). Thus, IL-12 and IL-18 produced by LPS-stimulated Mac-1+ cells stimulate this unique subpopulation of T cells to produce IFN-gamma, which in combination with Fas ligand, inhibits IgE production from the B cells. Our present results indicate that Mac-1+ cells and double-negative CD3intIL-2R beta+ T cells, uniquely abundant in the spleens of SJL mice, inhibit IgE production, indicating their new role in IgE response.     

Activation of NMDA receptor-channels in human retinal Müller glial cells inhibits inward-rectifying potassium currents

No reliable culture system exists for B-lineage acute lymphoblastic leukaemia (ALL). Recently we found that many different mature B-cell malignancies proliferate upon stimulation via the CD40 antigen, and this led us to investigate whether a similar CD40 activation on ALL cells could also induce proliferation. First, we measured CD40 expression in 21 ALL cases; all were CD40+, although mostly weak. Next, we triggered the CD40 antigen by anti-CD40 antibodies and by a CD40 ligand-expressing cell line. In addition, we measured the influence of IL-3, IL-4 and IL-7 with and without these stimuli. In 8/10 cases proliferation, measured by 3H-thymidine incorporation, could be induced after CD40 crosslinking, especially in the presence of IL-3. Stimulation via the CD40 ligand was more successful than using crosslinked anti-CD40 antibodies. IL-4 inhibited the spontaneous proliferation found in three cases, but stimulated proliferation after CD40 crosslinking. IL-7 did not contribute to proliferation. Morphology, immunophenotyping and surface marker analysis, combined with DNA flow cytometry confirmed that the proliferation found could be ascribed to the ALL cells. In conclusion, B-lineage ALL cases are CD40+, and many can be cultured using CD40 stimulation and IL-3.     

IL-12 up-regulates IL-18 receptor expression on T cells, Th1 cells, and B cells: synergism with IL-18 for IFN-gamma production

IL-18 is a product of macrophages and with IL-12 strikingly induces IFN-gamma production from T, B, and NK cells. Furthermore, IL-18 and 1L-12 synergize for IFN-gamma production from Th1 cells, although this combination fails to affect Th2 cells. In this study, we show that IL-12 and IL-18 promptly and synergistically induce T and B cells to develop into IFN-gamma-producing cells without engaging their Ag receptors. We also studied the mechanism underlying differences in IL-18 responsiveness between Th1 and Th2 cells. Pretreatment of T or B cells with IL-12 rendered them responsive to IL-18, which induces cell proliferation and IFN-gamma production. These IL-12-stimulated cells had both high and low affinity IL-18R and an increased IL-18R mRNA expression. In particular, IL-12-stimulated T cells strongly and continuously expressed IL-18R mRNA. However, when T cells developed into Th1 cells after stimulation with anti-CD3 and IL-12, they lowered this IL-12-induced-IL-18R mRNA expression. Then, such T cells showed a dominant response to anti-CD3 by IFN-gamma production when they were subsequently stimulated with anti-CD3 and IL-18. In contrast, Th2 cells did not express IL-18R mRNA and failed to produce IFN-gamma in response to anti-CD3 and IL-18, although they produced a substantial amount of IFN-gamma in response to anti-CD3 and IL-12. However, when Th1 and Th2 cells were stimulated with anti-CD3, IL-12, and IL-18, only the Th1 cells markedly augmented IFN-gamma production in response to IL-18, suggesting that IL-18 responsiveness between Th1 and Th2 cells resulted from their differential expression of IL-18R.     

Heterogenous response of B lymphocytes to transforming growth factor-beta in B-cell chronic lymphocytic leukaemia: correlation with the expression of TGF-beta receptors

We investigated the potential role of transforming growth factor-beta (TGF-beta) on spontaneous and cytokine-induced proliferation of B-cell chronic lymphocytic leukaemia (B-CLL) cells in vitro. Purified B lymphocytes from 21 B-CLL patients were cultured for 5 d in the presence of medium alone, IL-2 and/or IL-10, in the presence or absence of TGF-beta, and proliferation was measured by 3H-thymidine incorporation. TGF-beta inhibited B-cell proliferation in the majority of patients (15/21) but no inhibition was detected in 6/21 patients whatever the type of stimulant used. Addition of neutralizing antibodies to TGF-beta increased spontaneous and cytokine-induced proliferation; this effect was dose dependent and specific because addition of an irrelevant chicken IgG had no effect on B-CLL proliferation. In resistant patients, neutralizing antibodies to TGF-beta did not increase the proliferation. The expression of TGF-beta receptors on B-CLL cells was significantly lower than the one observed on normal CD5+ B lymphocytes for which the sensitivity to TGF-beta inhibition was more marked than in CLL. In addition, we found a strong correlation between the response of leukaemic B cells to TGF-beta inhibitory action and the expression of TGF-beta receptors on these cells. In summary, TGF-beta appears to function in CLL as a negative regulator of B lymphocytes but loss of responsiveness to this factor accompanied by a decrease of TGF-beta receptor expression, might provide a selective advantage to B-CLL lymphocytes.     

Perspective evaluation of the post-graduate courses of the Nursing Department at UFRN (1980-1992)

Superantigens have been used to study peripheral tolerance in CD4+ T cells. The superantigen SEB induces T cell anergy by promoting the differentiation of SEB-activated virgin T cells into anergic memory T cells. Memory T cells from SEB or antigen-primed mice do not proliferate when they are cultured with SEB. The present studies were performed to determine whether memory T cells fail to interact with SEB antigen-presenting cells or whether SEB promotes incomplete or negative signals in memory T cells. When murine virgin and memory T cells were separated on the basis of CD45RB expression and cultured with SEB-pulsed B cells, SEB induced the expression of CD25, which then mediated proliferation when IL-2 was added to the cultures. In addition, SEB promoted the expression of the CD40L, which is required for T helper cell function. Finally, PMA induced a costimulatory signal leading to the proliferation of these cells. Surprisingly, the agents, i.e., IL-2 and PMA, which induced TM cell proliferation in conjunction with SEB failed to induce lymphokine secretion. However, in the presence of IL-4 plus IL-5, the T memory cells induced the SEB-pulsed B cells to secrete IgM and IgG. These results suggest that memory T cells are not simply unresponsive to SEB but are actively anergized.     

Deficient interleukin-10 production by neonatal T cells does not explain their ineffectiveness at promoting neonatal B cell differentiation

Neonatal T cells are poor promoters of Ig secretion by neonatal B cells. Since IL-10 has been shown to play a role in B cell differentiation, we investigated the relationship of IL-10 production by neonatal T cells and their ability to provide B cell help. Neonatal CD4+(CD8-) T cells and adult naive CD4+ (CD8-/CD45RO-) T cells activated with immobilized anti-CD3 produced consistently less IL-10 than adult memory CD4+(CD8-/CD45RA-) T cells. Production of IL-10 by adult and neonatal T cells was dependent on IL-2, but was unaffected by supplemental IL-4. Despite diminished IL-10 production, supplemental IL-10 increased neonatal T cell-dependent Ig secretion only modestly, but did not increase Ig heavy chain isotype switching. This contrasted with the ability of IL-10 to enhance the secretion of all Ig isotypes by adult B cells stimulated in the presence of either IL-2 or IL-4. These results suggest that IL-10 can promote T cell-dependent Ig secretion but not Ig heavy chain isotype switching by neonatal B cells. However, deficient IL-10 production alone does not account for the poor ability of neonatal T cells to support neonatal B cell Ig production.     

Telomerase activity is induced in human peripheral B lymphocytes by the stimulation to antigen receptor

To understand the molecular events for the proliferation of B cells, we studied the induction of telomerase activity in vitro after stimulation to B-cell antigen receptor (BCR) on human peripheral B cells. Although unstimulated purified B cells of tonsils and peripheral blood from healthy volunteers do not express detectable telomerase activity, anti-IgM beads induce telomerase activity in these B cells. Soluble anti-IgM antibody (Ab) alone does not induce telomerase activity, but the second signal, given by either one of the cytokines of interleukin-2 (IL-2), IL-4, and IL-13 or by anti-CD40 monoclonal Ab (MoAb), is effective as the costimulation for the induction of the activity. Stimulation with anti-IgM Ab and anti-CD40 MoAb induces telomerase activity in most mature B cells of the tonsils and peripheral blood. The stimuli to both IgM and IgD receptors similarly induce the activity. Induction of telomerase activity is accompanied with the proliferation of B cells, but is not absolutely correlated with the extent of B-cell growth. Phorbol dibutylate (PDB) plus calcium (Ca) ionophore (PDB/Ca), which replace the activation through BCR and the costimulatory molecules, also induce telomerase activity. Moreover, it is suggested that phosphoinositide (PI) 3-kinase plays a role for the induction of telomerase activity in B cells stimulated with anti-IgM Ab and anti-CD40 MoAb. These results suggest that telomerase activity is induced in the B-cell activation of the antigen specific immune response.