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Interleukin-13 effectively down-regulates the monocyte inflammatory potential during traumatic stress.

OBJECTIVES: To determine the potential of interleukin-13 (IL-13) to modify in vitro lipopolysaccharide-induced monocyte-macrophage (MO) activity in human cells from individuals who had sustained either major mechanical or burn injury and to investigate whether the effect of IL-13 is different on MOs that have been preactivated under traumatic stress than on monocytic cells from healthy volunteers. DESIGN: Peripheral MOs from 20 controls and 16 patients after major burn or mechanical trauma were separated on days 1, 3, 5, and 7 after injury and incubated with lipopolysaccharide (1 microgram/mL) in the presence or absence of IL-13 (10 ng/mL) for 4 hours and for 20 hours. Thereafter, the following measures were determined from the culture supernatants: neopterin, nitric oxide, tumor necrosis factor alpha, IL-1 beta, IL-6, and IL-8. RESULTS: Ex vivo lipopolysaccharide-activated MOs, compared with control cells, displayed considerably enhanced inflammatory activity during the immediate posttraumatic course, with a substantial and consistent elevation of levels of tumor necrosis factor alpha and IL-6. The addition of human recombinant IL-13 to the MO cultures resulted in an effective down-regulation of the synthesis of tumor necrosis factor alpha, IL-1 beta, and IL-6 as well as IL-8, showing an average reduction of mediator production to two thirds of the value found in corresponding sole lipopolysaccharide-stimulated cultures. The impact of human recombinant IL-13 on control MOs was almost identical for IL-6 and IL-1 beta, slightly lower for IL-8, and nonexistent for tumor necrosis factor alpha. CONCLUSION: From this study and preexisting findings, we conclude that, based on its biologic properties, IL-13 should be tested as a biologic response modifier for acute states of trauma-induced host defense deficiency.

Adult↗

The insulin receptor substrate-1-related 4PS substrate but not the interleukin-2R gamma chain is involved in interleukin-13-mediated signal transduction.

Interleukin-13 (IL-13) induced a potent mitogenic response in IL-3-dependent TF-1 cells and DNA synthesis to a lesser extent in MO7E and FDC-P1 cells. IL-13 stimulation of these lines, like IL-4 and insulin-like growth factor-1 (IGF-1), resulted in tyrosine phosphorylation of a 170-kD substrate. The tyrosine-phosphorylated 170-kD substrate strongly associated with the 85-kD subunit of phosphoinositol-3 (PI-3) kinase and with Grb-2. Anti-4PS serum readily detected the 170-kD substrate in lysates from both TF-1 and FDC-P1 cells stimulated with IL-13 or IL-4. These data provide evidence that IL-13 induces tyrosine phosphorylation of the 4PS substrate, providing an essential interface between the IL-13 receptor and signaling molecules containing SH2 domains. IL-13 and IL-4 stimulation of murine L cell fibroblasts, which endogenously express the IL-4 receptor (IL-4R alpha) and lack expression of the IL-2 receptor gamma subunit (IL-2R gamma), resulted in tyrosine phosphorylation of insulin receptor substrate-1 (IRS-1)/4PS. Enhanced tyrosine phosphorylation of IRS-1/4PS was observed in response to IL-4, but not IL-13 treatment of L cells transfected with the IL-2R gamma chain. These results indicate that IL-13 does not use the IL-2R gamma subunit in its receptor complex and that expression of IL-2R gamma enhances, but is not absolutely required for mediating IL-4-induced tyrosine phosphorylation of IRS-1/4PS.

Adaptor Proteins, Signal Transducing↗

Regulation of endothelial and mesothelial cell function by interleukin-13: selective induction of vascular cell adhesion molecule-1 and amplification of interleukin-6 production.

The present study was designed to explore the interaction of interleukin-13 (IL-13) with vascular endothelial cells (EC). In vitro exposure to IL-13 of human umbilical vein EC induced surface expression of vascular cell adhesion molecule-1 (VCAM-1). At optimal concentrations (10 to 50 ng/mL) and exposure times (24 hours), IL-13 was a twofold to threefold less effective inducer of VCAM-1 than IL-1, which was used as reference EC activator. When IL-13 was combined with IL-1, an almost additive induction of VCAM-1 was observed. Induction of VCAM-1 by IL-13 was selective in that E-selectin and intercellular adhesion molecule-1 (ICAM-1) were unaffected. IL-13 caused a modest reduction of IL-1 induction of E-selectin and ICAM-1. Surface expression of VCAM-1 on IL-13-treated cells was associated with mRNA induction (as assessed by Northern analysis and reverse transcriptase-polymerase chain reaction), with predominance of transcripts encoding the 7 Ig domain form of this molecule. In agreement with previous reports, IL-13 inhibited cytokine production in human monocytes. In contrast, IL-13 was a weak inducer and an amplifier (in concert with IL-1) of IL-6 expression in EC. Mesothelial cells, which share properties with EC and regulate the traffic and function of leukocytes in serosal cavities, were stimulated to express VCAM-1 and IL-6 by IL-13. Thus, IL-13 elicits a spectrum of responses in vascular endothelium remarkably similar to that of IL-4 and IL-10. Interaction of these cytokines with vascular endothelium may play an important role in the induction and expression of Th2-dependent responses.

Base Sequence↗

Interleukin-13 induces rapid tyrosine phosphorylation and activation of Raf-1 kinase in human monocytic progenitor cell line U937.

IL-13 is a pleiotropic cytokine produced by Th0, Th1-like, and CD8 T cells in response to antigen stimulation. Its biological effects include suppression of cytotoxic activity of monocytes/macrophages and suppression of pro-inflammatory cytokine production. However, the mechanism of IL-13 remains unknown. In this study we investigated the effects of rhIL-13 on tyrosine phosphorylation in U937 monocytic progenitor cells by immunoblotting and immunocomplex kinase assays. We demonstrate that rhIL-13 stimulates dose-dependent tyrosine phosphorylation of several proteins of Mr. 93, 80, 74, 49.5, 42, 30, 22 and 18 kDa within 30 sec. The effect of IL-13 was blocked by the tyrosine kinase inhibitor erbstatin. Furthermore, IL-13 induces tyrosine phosphorylation and rapid activation of raf-1 kinase. These findings provide the first evidence that the mechanism of IL-13 involves rapid tryrosine phosphorylation and activation of raf-1 serine/threonine kinase.

Blotting, Western↗

Predictive modelling of the 3-D structure of interleukin-13.

Several atomic structures are now available for the family of helical cytokines, which includes growth hormone as well as many of the interleukins. Using structural information from five members of this family, two alternative models of interleukin (IL)-13 are proposed. IL-13 has biological properties similar to those of IL-4 and, like the other interleukins, is a potentially important pharmaceutical target. The model of IL-13 is discussed and compared with the known interleukin structures.

Amino Acid Sequence↗

IL-13 has only a subset of IL-4-like activities on B chronic lymphocytic leukaemia cells.

The recently described interleukin-13 (IL-13) has been shown to share many of the effects of IL-4 on normal B cells, including growth-promoting activity and induction of CD23. In this study, we compared the effects of IL-13 and IL-4 on B chronic lymphocytic leukaemias (B-CLL) cells. After anti-CD40 activation, both IL-13 and IL-4 promoted the DNA synthesis of B-CLL cells and increased the recovery of viable cells. The time kinetics of the proliferative response of B-CLL cells to IL-13 or IL-4 were superimposable and showed the long-lasting effect of both cytokines. As on normal B cells, both IL-4 and IL-13 synergized with IL-10 to enhance B-CLL DNA synthesis. Moreover, IL-13, like IL-4, was able to increase CD23 expression on anti-CD40-activated leukaemic B cells. The CD23 up-regulation and the DNA synthesis induced by IL-13 on anti-CD40-activated B-CLL cells, were significantly reduced when B-CLL cells were cultured with anti-IL-4 receptor monoclonal antibody, suggesting a common pathway for IL-13 and IL-4 signalling. However, after cross-linking of surface IgM, IL-4 strongly inhibited the IL-2-induced DNA synthesis of B-CLL cells, whereas IL-13 did not inhibit IL-2-driven proliferation of anti-IgM-activated B-CLL cells. Furthermore, while IL-4 strongly up-regulated the expression of CD23 on anti-IgM-activated leukaemic B cells, IL-13 only marginally increased it. Finally, IL-13, in contrast to IL-4, did not prevent the entry of B-CLL cells into apoptosis. Thus IL-13 and IL-4 display comparable effects on anti-CD40-activated B-CLL cells, which are blocked by anti-IL-4 receptor (IL-4R) monoclonal antibodies. However, IL-13-dependent effects are absent or inefficient in non-activated or anti-IgM-activated B-CLL cells. This suggests that such cells may lack functional IL-13 receptors, though IL-13R and IL-4R on B-CLL cells share a common component.

Antibodies, Monoclonal↗

An interleukin 4 (IL-4) mutant protein inhibits both IL-4 or IL-13-induced human immunoglobulin G4 (IgG4) and IgE synthesis and B cell proliferation: support for a common component shared by IL-4 and IL-13 receptors.

Interleukin 4 (IL-4) and IL-13 share many biological functions. Both cytokines promote growth of activated human B cells and induce naive human surface immunoglobulin D+ (sIgD+) B cells to produce IgG4 and IgE. Here we show that a mutant form of human IL-4, in which the tyrosine residue at position 124 is replaced by aspartic acid (hIL-4.Y124D), specifically blocks IL-4 and IL-13-induced proliferation of B cells costimulated by anti-CD40 mAbs in a dose-dependent fashion. A mouse mutant IL-4 protein (mIL-4.Y119D), which antagonizes the biological activity of mouse IL-4, was ineffective. In addition, hIL-4.Y124D, at concentrations of up to 40 nM, did not affect IL-2-induced B cell proliferation. hIL-4.Y124D did not have detectable agonistic activity in these B cell proliferation assays. Interestingly, hIL-4.Y124D also strongly inhibited both IL-4 or IL-13-induced IgG4 and IgE synthesis in cultures of peripheral blood mononuclear cells, or highly purified sIgD+ B cells cultured in the presence of anti-CD40 mAbs. IL-4 and IL-13-induced IgE responses were inhibited > 95% at a approximately 50- or approximately 20-fold excess of hIL-4.Y124D, respectively, despite the fact that the IL-4 mutant protein had a weak agonistic activity. This agonistic activity was 1.6 +/- 1.9% (n = 4) of the maximal IgE responses induced by saturating concentrations of IL-4. Taken together, these data indicate that there are commonalities between the IL-4 and IL-13 receptor. In addition, since hIL-4.Y124D inhibited both IL-4 and IL-13-induced IgE synthesis, it is likely that antagonistic mutant IL-4 proteins may have potential clinical use in the treatment of IgE-mediated allergic diseases.

Antigens, CD↗

Differential regulation of IL-13 and IL-4 production by human CD8+ and CD4+ Th0, Th1 and Th2 T cell clones and EBV-transformed B cells.

In the present study, the requirements and characteristics for the production of IL-13 by human T cells, T cell clones and B cells were determined and compared with those of IL-4. IL-13 was produced by human CD4+ and CD8+ T lymphocyte subsets isolated from peripheral blood mononuclear cells and by CD4+ and CD8+ T cell clones. CD4+ T cell clones belonging to Th0, Th1-like and Th2-like subsets produced IL-13 following antigen-specific or polyclonal activation. In addition, EBV-transformed B cell lines expressed IL-13 mRNA and produced small amounts of IL-13 protein. Expression of IL-13 mRNA and production of IL-13 protein by peripheral blood T cells and T cell clones was induced rapidly and was relatively long lasting, whereas IL-4 production by these cells was transient. In addition, IL-13 mRNA expression was induced by modes of activation that failed to induce IL-4 mRNA expression. IL-13 shares many biological activities with IL-4 which is compatible with the notion that the IL-13 and IL-4 receptors share a common component required for signal transduction. However, IL-13 lacks the T cell-activating properties of IL-4. Here we have shown that this is related to the fact that T cells fail to bind radiolabeled IL-13 and do not express the IL-13-specific receptor component. Taken together, these results indicate that the differences in expression and biological activities of IL-4 and IL-13 on T cells may have consequences for the relative roles of these cytokines in the immune response.

B-Lymphocytes↗

Interleukin-2 secretion by human B lymphocytes occurs as a late event and requires additional stimulation after CD40 cross-linking.

While Epstein-Barr virus (EBV)-immortalized B cell lines have been shown to secrete interleukin (IL)-2 after stimulation with either teleocidin or phorbol myristate acetate (PMA) and ionomycin, experimental conditions leading to IL-2 production by normal human B cells have not been reported. In the present study we investigated various B cell activating conditions, including--by analogy to EBV-immortalized B lymphocytes--stimulation of B cells that are already proliferating (in cultures with IL-4 and immobilized anti-CD40 monoclonal antibody; the anti-CD40 system). This approach showed that B lymphocytes secreted IL-2 in the culture medium, but only if they were first activated for more than 24 h in the anti-CD40 system before exposure to PMA plus ionomycin. The production rate of IL-2 by B lymphocytes reached a maximum after 6 days of priming in such cultures followed by 48 h of stimulation with PMA plus ionomycin, corresponding to 7% or 15% of that of fresh CD4+ T cells activated, respectively, with phytohemagglutinin plus PMA, or with PMA plus ionomycin for 48 h. This IL-2 production could not be attributed to T cell contamination nor to EBV-infected B cells according to flow cytometric and reverse transcriptase-polymerase chain reaction analysis of cultured B cells. Lower IL-2 expression (detected only as mRNA synthesis) was also induced in the cultured B lymphocytes after incubation with cross-linking anti-IgM antibodies instead of PMA plus ionomycin. The appearance of IL-13 mRNA, but not IL-4 mRNA, was detected under the same stimulation conditions as for IL-2 mRNA. These results show that the production of IL-2 by normal B lymphocytes occurs as a late event relative to their activation and proliferation, and is in this respect subject to regulation different to that found in T lymphocytes.

Antibodies, Anti-Idiotypic↗

Not only Th2 cells but also Th1 and Th0 cells express CD30 after activation.

To investigate whether the CD30 molecule, expressed only by a minority of T and B cells, defines a subtype of T helper cells, Pityrosporum orbiculare-specific CD4+ T cell clones were assessed for CD30 protein and gene expression. The clones were defined as Th1, Th0, and Th2 according to their cytokine mRNA profile detected by reverse transcription PCR (RT-PCR). The kinetics of CD30 expression after OKT3 (anti-CD3) stimulation was analyzed by flow cytometry, immunocytochemistry, and RT-PCR. OKT3 activation induced a high expression of CD30 in cells of both Th1 and Th0 as well as Th2 type after 1-3 days. A difference between the clones was noted in that the Th2 clones remained highly positive in CD30 expression, whereas expression in the other clones started to decline from day 3. These data indicate that CD30 is expressed in activated CD4+ T cells of all three subtypes, and that the expression is sustained in Th2 cells.

Base Sequence↗

Tuft cell acetylcholine is released into the gut lumen to promote anti-helminth immunity.

Upon parasitic helminth infection, activated intestinal tuft cells secrete interleukin-25 (IL-25), which initiates a type 2 immune response during which lamina propria type 2 innate lymphoid cells (ILC2s) produce IL-13. This causes epithelial remodeling, including tuft cell hyperplasia, the function of which is unknown. We identified a cholinergic effector function of tuft cells, which are the only epithelial cells that expressed choline acetyltransferase (ChAT). During parasite infection, mice with epithelial-specific deletion of ChAT had increased worm burden, fitness, and fecal egg counts, even though type 2 immune responses were comparable. Mechanistically, IL-13-amplified tuft cells release acetylcholine (ACh) into the gut lumen. Finally, we demonstrated a direct effect of ACh on worms, which reduced their fecundity via helminth-expressed muscarinic ACh receptors. Thus, tuft cells are sentinels in naive mice, and their amplification upon helminth infection provides an additional type 2 immune response effector function.

Animals↗

Interleukin 13: novel role in direct regulation of proliferation and differentiation of primitive hematopoietic progenitor cells.

The recently cloned interleukin 13 (IL-13) shares most investigated biological activities on B lymphocytes and monocytes with IL-4. In this study we investigated for the first time the potential role of IL-13 in the regulation of the growth of hematopoietic progenitor cells. IL-13 enhanced stem cell factor (SCF)-induced proliferation of Lin-Sca-1+ bone marrow progenitor cells more potently than IL-4. The effect of IL-13 was purely synergistic, since IL-13 alone stimulated no colony formation. Single cell experiments suggested that the synergistic effect of IL-13 on Lin-Sca-1+ progenitors was directly mediated. In contrast, IL-13 had no synergistic activity on SCF-induced proliferation of the more mature Lin-Sca-1- progenitor cells. Thus, the cloning frequency in response to SCF + IL-13 was at least 20-fold higher in the Lin-Sca-1+ than the Lin-Sca-1- progenitor cell population. Furthermore, IL-13 but not IL-4 synergistically enhanced colony formation of Lin-Sca-1+ progenitors in response to granulocyte/macrophage colony-stimulating factor (GM-CSF) (threefold), whereas both IL-4 and IL-13 enhanced G-CSF-induced colony formation (threefold), and neither of the two significantly affected CSF-1 and IL-3-induced proliferation. Finally, whereas stimulation of Lin-Sca-1+ progenitors by SCF + G-CSF resulted in the formation of 90% granulocytes, the addition of IL-13 resulted in the production of macrophages exclusively. This novel effect on differentiation was directly mediated, shared with IL-4, and could not be observed on Lin-Sca-1- progenitor cells. Collectively, these findings indicate a novel role of IL-13 in early myelopoiesis, partially overlapping but also different from that of IL-4.

Animals↗

Activated mast cells produce interleukin 13.

When mast cells are activated through their immunoglobulin (Ig)E receptors, release of low molecular weight mediators like histamine is followed by secretion of multiple cytokines, including interleukin (IL)-3, IL-4, IL-5, and granulocyte/macrophage colony-stimulating factor. Here we report that stimulated mast cells also synthesize IL-13 mRNA and protein; secretion of this cytokine may be of particular importance because of its ability to stimulate IgE expression. IL-13 transcripts detected by a semiquantitative reverse transcriptase-mediated polymerase chain reaction assay were induced within 30 min after stimulation of mast cells by dinitrophenyl plus monoclonal IgE anti-dinitrophenyl, and peaked at about 1 h. Within 3 h of IgE stimulation, secreted IL-13 bioactivity, estimated by proliferation of an IL-13-dependent cell line, reached levels equivalent to 1-2 ng/ml of IL-13. When added to human B lymphocytes, the mast cell-derived IL-13 activity (like bone fide IL-13) induced Ig C epsilon transcripts, DNA recombination characteristic of the isotype switch to C epsilon, and the secretion of IgE protein. These results suggest a model of local positive feedback interactions between mast cells and B cells, which could play a role in the pathogenesis of atopy.

Animals↗

Regulatory effects of IL-13 on synovial fluid macrophages and blood monocytes from patients with inflammatory arthritis.

Activated macrophages are central to the destructive processes of chronic inflammatory arthritis. In this study, it was hypothesized that IL-13, a product predominantly of 'Th2-type' lymphocytes, may be used therapeutically to down-regulate monocyte/macrophage activities at sites of chronic inflammation. Synovial fluid mononuclear cells were isolated from 12 patients with chronic inflammatory arthritis. Peripheral blood mononuclear cells (PBMC) were isolated at the same time as synovial fluid cells from all 12 patients. IL-13 significantly inhibited lipopolysaccharide (LPS)-induced tumour necrosis factor-alpha (TNF-alpha) production by mononuclear cells from peripheral blood, but not synovial fluid. In contrast, IL-13 inhibited LPS-induced IL-1 beta production by all cells, and as a positive response to IL-13, CD23 expression was increased on both cell populations. Blood monocytes cultured for 7 days with granulocyte-macrophage colony-stimulating factor (GM-CSF) or M-CSF responded to IL-13 in a manner similar to that detected for synovial fluid-derived cells, with suppression of LPS-induced IL-1 beta, but not TNF-alpha, production. In all experiments, the responses to IL-13 were very similar to those detected to IL-4, but differed from those measured with IL-10. Thus, the responses to IL-13 by synovial fluid cells and cultured monocytes are not equal to those of blood monocytes. The similar responses to IL-4 and IL-13 support claims of a common element for signalling from the IL-4 and IL-13 receptors. Furthermore, the activity of a common receptor chain may be altered by monocyte activation and differentiation.

Antigens, CD↗

Brequinar sodium, mycophenolic acid, and cyclosporin A inhibit different stages of IL-4- or IL-13-induced human IgG4 and IgE production in vitro.

We investigated the effect of cyclosporin A (CsA), mycophenolic acid (MPA), and brequinar sodium (BQ) on human IgG4 and IgE synthesis induced by IL-4 or IL-13. BQ inhibited IL-4 and IL-13-induced IgG4 and IgE synthesis in cultures of peripheral blood mononuclear cells (PBMC) or highly purified B cells costimulated by anti-CD40 mAbs in a dose-dependent fashion. CsA and MPA had either suppressive or enhancing effects depending on the concentrations tested. Interestingly, BQ inhibited IgG4 and IgE synthesis at concentrations of 10(-6)-10(-8) M, which did not affect T or B cell proliferation, indicating that the inhibitory effects of BQ on Ig production were not directly related to inhibition of T or B cell proliferation. In contrast, the inhibitory effects of MPA on Ig production were directly associated with inhibitory effects on T and B cell proliferation. CsA blocked T and B cell proliferation at the same concentration (10(-7) M) which enhanced IgG4 and IgE synthesis, indicating that reduction in T or B cell proliferation correlated with enhanced IgE production. CsA also inhibited CD40 ligand expression and IL-2, IL-4, IL-5, IFN-gamma, and GM-CSF production by activated CD4+ T cell clones, whereas MPA and BQ were ineffective, indicating that these compounds do not inhibit early events in T cell activation. Collectively, our data indicate that BQ, MPA, and CsA block different stages of the IgG4 and IgE production process. In addition, we observed that CsA and MPA, in contrast to BQ, at lower concentrations can also have potentiating effects on the production of these Ig isotypes.

Antigens, CD↗

IL-13 and calpain-14 suppress the expression of SPINK7 by regulating OVOL1 in eosinophilic esophagitis.

Eosinophilic esophagitis (EoE) is a type 2 allergic disease characterized by esophageal inflammation and epithelial cell dysfunction. The acquired loss of the anti-serine protease of kazal type 7 (anti-SPINK7) in the squamous epithelium of the esophagus has a causal role in EoE pathogenesis. However, there is a limited understanding of the factors that regulate its expression and responsiveness to inflammatory stimuli. Herein, we have identified the transcription factor, ovo like transcriptional repressor 1 (OVOL1), as an esophageal selective gene product that regulates SPINK7 promoter activity. Overexpression of OVOL1 increased SPINK7 expression, whereas its depletion decreased SPINK7 expression, impaired epithelial barrier, and increased production of the proatopy cytokine thymic stromal lymphopoietin (TSLP). Stimulation with IL-13 abrogated the nuclear translocation of OVOL1 and promoted enhanced degradation of OVOL1 protein. This effect of IL-13 was dependent on the esophageal specific cysteine protease calpain-14 at least in part. Analysis of human esophageal biopsies demonstrated that the expression of esophageal OVOL1 correlated with SPINK7 transcript expression and was lost as a function of EoE disease activity. In summary, our study identifies key regulatory mechanisms in EoE pathogenesis, demonstrating that OVOL1 promotes SPINK7 transcription, whereas IL-13 suppresses this pathway in EoE.

Humans↗

PredIL13: Stacking a variety of machine and deep learning methods with ESM-2 language model for identifying IL13-inducing peptides.

Interleukin (IL)-13 has emerged as one of the recently identified cytokine. Since IL-13 causes the severity of COVID-19 and alters crucial biological processes, it is urgent to explore novel molecules or peptides capable of including IL-13. Computational prediction has received attention as a complementary method to in-vivo and in-vitro experimental identification of IL-13 inducing peptides, because experimental identification is time-consuming, laborious, and expensive. A few computational tools have been presented, including the IL13Pred and iIL13Pred. To increase prediction capability, we have developed PredIL13, a cutting-edge ensemble learning method with the latest ESM-2 protein language model. This method stacked the probability scores outputted by 168 single-feature machine/deep learning models, and then trained a logistic regression-based meta-classifier with the stacked probability score vectors. The key technology was to implement ESM-2 and to select the optimal single-feature models according to their absolute weight coefficient for logistic regression (AWCLR), an indicator of the importance of each single-feature model. Especially, the sequential deletion of single-feature models based on the iterative AWCLR ranking (SDIWC) method constructed the meta-classifier consisting of the top 16 single-feature models, named PredIL13, while considering the model's accuracy. The PredIL13 greatly outperformed the-state-of-the-art predictors, thus is an invaluable tool for accelerating the detection of IL13-inducing peptide within the human genome.

Humans↗

IL-13 induces proliferation, Ig isotype switching, and Ig synthesis by immature human fetal B cells.

In this study it is demonstrated that the novel T cell-derived cytokine IL-13 induces proliferation, Ig isotype switching, and Ig synthesis by human immature B cells derived from fetal bone marrow (BM). IL-13 induced proliferation and IgM, total IgG, IgG4, and IgE synthesis when total fetal BM cells or highly purified s mu+, CD10+, CD19+ fetal B cells were cultured in the presence of anti-CD40 mAb or activated CD4+ T cells. Although the ratios of the different isotypes produced in response to IL-13 were similar to those induced by IL-4, the levels of Ig produced in response to IL-13 were generally 5- to 15-fold lower, indicating that IL-13 is less potent than IL-4. In addition, in co-cultures of fetal B cells and CD4+ T cell clones IL-13 was effective only in the presence of IL-7, which may be due to the fact that IL-13, in contrast to IL-4, does not act on T cells. IL-13- and IL-4-induced IgE synthesis by s mu+, CD19+ fetal B cells was enhanced by IL-6 and inhibited by IL-12, IFN-alpha, IFN-gamma, and transforming growth factor-beta, suggesting that IL-13 and IL-4 induce IgE synthesis via similar signaling pathways. Like IL-4, IL-13 also induced Ig production, including IgG4 and IgE synthesis, by highly purified s mu-, CD10+, CD19+ pre-B cells co-cultured in the presence of activated cloned CD4+ T cells and IL-7. However, in contrast to IL-4, IL-13 did not enhance CD23, CD40, and HLA-DR expression on cultured s mu- pre-B cells in the absence of other stimuli, suggesting that IL-13 alone does not activate pre-B cells. Taken together, our data indicate that IL-13 induces proliferation, Ig isotype switching, and Ig production by immature fetal B cells in the presence of costimulatory signals provided by activated CD4+ T cells or anti-CD40 mAb. IL-13 is another cytokine that, in addition to IL-4, can induce isotype switching to IgG4 and IgE synthesis in immature human B cells.

Antibody Formation↗