Inhibitors of protein tyrosine kinases and protein tyrosine phosphatases suppress IL-4-induced CD23 expression and release by human B lymphocytes

The pleiotropic lymphokine IL-4 is a growth and differentiation factor for human B cells. IL-4 induces the expression of the CD23 (Fc epsilon RII) molecule on B lymphocytes and promotes the release of its soluble form (sCD23); the cleavage fragments of the latter have been reported to modulate IL-4-dependent IgE biosynthesis. In the present work, we have tested the effects of inhibitors of protein tyrosine kinases (PTK) and protein phosphatases (PP) on the induction by IL-4 of the membrane and soluble forms of CD23. The PTK inhibitors genistein and lavendustin A were found to suppress, in a dose-dependent way, the induction by IL-4 of CD23 membrane expression as well as CD23 release by resting and SAC-preactivated B lymphocytes. No such suppression was detected with inhibitors of serine and threonine kinases. The addition of the protein tyrosine phosphatase (PTP) inhibitor sodium orthovanadate also resulted in a marked decrease in CD23 induction by IL-4. Cell viability was little affected by these inhibitors. However, a diminution of the large activated B cell population was observed, which correlated with an inhibition of the entry in the S phase. Partial inhibition of sCD23 release was also observed with okadaic acid and calyculin A, two inhibitors of serine/threonine PP, but only at concentrations which block PP1 in addition to PP2A. These results suggest that protein tyrosine phosphorylation and dephosphorylation may play a major role in IL-4 signalling. This conclusion was strengthened by the observation that a mAb anti-CD45, a membrane tyrosine phosphatase, inhibited IL-4-induced sCD23 release by B lymphocytes.

Effects of IL-4 depletion on the antibody response to Pseudomonas aeruginosa lipopolysaccharide in mice

These studies were done to examine the role of interleukin-4 (IL-4) in the generation of isotype specific antibody responses of mice to Pseudomonas aeruginosa lipopolysaccharide (PALPS) by neutralization of IL-4 in vivo using anti-IL-4 antibody (11B11). We found that the administration of anti-IL-4 antibody (11B11) 24 h before immunization with PALPS resulted in a decreased PALPS-specific antibody response for all isotypes examined (IgM, IgG1, IgG2a, IgG2b, IgG3). By contrast, we observed that the non-antigen-specific (polyclonal) IgM response of mice following treatment with 11B11 antibody and PALPS was increased while the polyclonal responses for the other isotypes were unaffected. When mice were given recombinant IL-10 at the time of immunization with PALPS there was a decrease in the PALPS-specific antibody response but an increase in the polyclonal IgM, IgG2a, IgG2b, IgG3 response whereas the polyclonal IgG1 response was decreased by a five-fold margin. The results of these studies suggest that both the antigen-specific and the polyclonal response can be influenced in a different manner by IL-4 or by IL-10.

Evidence that rapamycin has differential effects of IL-4 function. Multiple IL-4 signaling pathways and implications for in vivo use

The immunosuppressive drug rapamycin, which inhibits the response of T cells to growth-promoting lymphokines, has been considered to act as a general inhibitor of cytokine action. Our investigations into the effect of rapamycin on human IL-4, a cytokine controlling B and T cell function, show this not to be the case. Unexpectedly, rapamycin actually synergized with IL-4 in both the upregulation of CD23 expression and the down-regulation of the type II (p75) TNF receptor, while in the same B cell line, rapamycin simultaneously inhibited the IL-4-dependent production of TNF alpha and beta. These results raise the possibility that multiple IL-4 signaling pathways may be responsible for the pleiotropic effects of IL-4, and have important implications for both the experimental and possible clinical in vivo use of rapamycin as a selective immunosuppressant.

Differential cytokine regulation by eicosanoids in T cells primed by contact sensitisation with TNP

Eicosanoids are important mediators of inflammation, but also play a role in regulation of lymphocyte function. In this study we have examined the function of both prostaglandins (PGs) and leukotrienes in regulating the release of a set of cytokines produced by T cells from mice primed with the contact-sensitising agent picryl chloride. Various patterns of response by different cytokines in response to exogenous eicosanoids were observed. Both interleukin-2 (IL-2) and interferon-gamma (IFN-gamma), two cytokines involved in activating the cellular contact sensitivity reaction, were downregulated by prostaglandin E2 (PGE2) and to a lesser extent by 6-keto PGF2 alpha (PGI2). In contrast, both PGE2 and PGI2 potentiated the release of IL-3 and IL-6 which both play an important role in stimulating haemopoesis after inflammation. Unexpectedly, IL-4 release was strongly inhibited by exogenous PGI2, while remaining unaffected by PGE2. This inhibition, in contrast to the PG-mediated effects on IL-2, IL-3, IL-6, and IFN-gamma was not due to increased intracellular levels of cAMP. In contrast to the strong immunomodulatory effects of PGs, leukotrienes B4 and C4 had only small and rather variable effects on any cytokine release.

Receptors for interleukin-13 and interleukin-4 are complex and share a novel component that functions in signal transduction

Interleukin-4 (IL-4) and interleukin-13 (IL-13) are two cytokines that are secreted by activated T cells and have similar effects on monocytes and B cells. We describe a mutant form of human interleukin-4 (hIL-4) that competitively antagonizes both hIL-4 and human interleukin-13 (hIL-13). The amino acid sequences of IL-4 and IL-13 are approximately 30% homologous and circular dichroism (CD) spectroscopy shows that both proteins have a highly alpha-helical structure. IL-13 competitively inhibited binding of hIL-4 to functional human IL-4 receptors (called hIL-4R) expressed on a cell line which responds to both hIL-4 and IL-13. Binding of hIL-4 to an hIL-4 responsive cell line that does not respond to IL-13, and binding of hIL-4 to cloned IL-4R ligand binding protein expressed on heterologous cells, were not inhibited by IL-13. hIL-4 bound with approximately 100-fold lower affinity to the IL-4R ligand binding protein than to functional IL-4R. The mutant hIL-4 antagonist protein bound to both IL-4R types with the lower affinity. The above results demonstrate that IL-4 and IL-13 share a receptor component that is important for signal transduction. In addition, our data establish that IL-4R is a complex of at least two components one of which is a novel affinity converting subunit that is critical for cellular signal transduction.

Increased interleukin-4 production by atopic mononuclear leukocytes correlates with increased cyclic adenosine monophosphate-phosphodiesterase activity and is reversible by phosphodiesterase inhibition

Previous studies have shown that leukocytes from patients with atopic dermatitis have increased levels of cyclic adenosine monophosphate (cAMP)-phosphodiesterase activity. This increased activity accounts for subnormal cAMP responses and correlates with increased in vitro immunoglobulin E production. To better understand the mechanism of this effect, we studied the relationship between phosphodiesterase activity and interleukin-4, a T-cell-derived cytokine that is a major regulator of immunoglobulin E production. Cultures stimulated with anti-CD3 or with phorbol myristate acetate plus ionophore significantly increased interleukin-4 production, and levels were consistently highest in cells from atopic subjects. Interleukin-4 production was higher, on a per T-cell basis, in mononuclear leukocyte cultures than in cultures of pure T cells, suggesting the possibility of a monocyte factor acting to increase interleukin-4 production. We next examined the effect of the phosphodiesterase inhibitor Ro 20-1724 on interleukin-4 production and found a significant reduction in cultures of atopic mononuclear leukocytes. This phosphodiesterase inhibitor effect appeared to act primarily on monocytes and correlated with increased intracellular cAMP levels. These studies demonstrate increased interleukin-4 production by atopic T cells. This abnormality can be reversed by inhibition of cAMP-phosphodiesterase, suggesting a possible therapeutic target for control of atopic disease.

Transforming growth factor-beta (TGF beta) inhibition of Epstein-Barr virus (EBV)- and interleukin-4 (IL-4)-induced immunoglobulin production in human B lymphocytes

This study reports on the effects of TGF beta on the secretion of Ig isotypes by highly purified (> 99% CD20-positive) human peripheral blood B cells. Stimulation of these B cell preparations with EBV resulted in the secretion of IgM, IgG, and IgA and the addition of IL-4 induced readily detectable levels (> 100 ng/ml) of IgE between 10 and 25 days of culture. TGF beta 1 and TGF beta 2 showed similar dose-dependent suppression of IgM, IgG, and IgA, and the relative proportion of IgG and IgA remained unchanged in the presence of TGF beta. IgE production induced by EBV and IL-4 was significantly inhibited by TGF beta. TGF beta effects on Ig secretion were not related to inhibition of B cell proliferation by this cytokine. In contrast to these TGF beta effects on EBV activation of primary B cells, the constitutive Ig secretion by EBV-transformed B cells was resistant to TGF beta, while the increase in Ig secretion induced by IL-6 was inhibited by TGF beta. Thus, TGF beta inhibits the EBV-induced secretion of the major Ig isotypes in peripheral blood B cells and has differential effects on Ig secretion by transformed B cells.

Low versus high density of immobilized anti-CD3 influences IL-4 regulation of T-cell immune responses

Varying the concentration of anti-CD3 immobilized on Sepharose beads allowed us to study both the inhibitory and the stimulatory effects of IL-4 on purified T cells and contrast IL-4 versus IL-2-driven T-cell proliferative responses. In the presence of low density immobilized anti-CD3, IL-4 was unable to stimulate purified T cells and was inhibitory to IL-2-driven T-cell responses. The inhibitory effects of IL-4 were enhanced by preincubation of T cells with IL-4 prior to stimulation. In contrast, the inhibitory effects of IL-4 could be avoided by delaying the addition of IL-4 until Days 3-5 of culture or they could be reversed by the addition of IL-1. In the presence of high-density anti-CD3, IL-4 elicited an IL-2-independent proliferative response by purified T cells or sorted CD8+ cells. Comparison of IL-4-driven versus IL-2-driven T-cell responses demonstrated that IL-2 was able to upregulate mRNA for IL-4 receptors and interferon-gamma, while IL-4 had minimal effects on upregulating mRNA for either the p55 or the p75 IL-2 receptor subunits or interferon-gamma. The timing of the presence of IL-4, the state of T-cell activation, and the nature and strength of the stimulatory signal influenced the regulatory effect of IL-4 on the immune response.

Anti-IL-4 diminishes in vivo priming for antigen-specific IL-4 production by T cells

Treatment of mice with neutralizing monoclonal anti-IL-4 antibodies at the time of immunization with keyhole limpet hemocyanin causes significant inhibition of priming of T cells for the production of IL-4 upon subsequent in vitro challenge. BALB/c mice received a single injection of anti-IL-4 at the time of immunization. T cells purified from spleen and lymph nodes were obtained at 6 to 7 days and at 30 to 75 days after priming. In the 6- to 7-day group, IL-4 production in response to keyhole limpet hemocyanin among the recipients of anti-IL-4 was reduced by more than twofold in four of four experiments, when low density T cells were challenged. In some, but not all, of these experiments, production of IFN-gamma was enhanced at least twofold. Measurement of frequency of IL-4-producing, keyhole limpet hemocyanin-specific T cells indicated a twofold reduction in the anti-IL-4-treated mice. Among cells obtained between 30 and 75 days after priming, production of IL-4 was diminished in four of four cases in high density cells and three of four cases in low density cells. T cells were also prepared from mice that received a secondary in vivo challenge 90 to 105 days after priming. T cells from boosted donors that had received a single injection of anti-IL-4 at the time of priming showed diminished production of IL-4 in each experiment. By contrast, treatment with anti-IL-4 at the time of secondary challenge did not diminish IL-4-producing capacity of cells from mice that were primed in the absence of anti-IL-4. These results indicate that IL-4 is important in vivo in priming T cells to develop into IL-4-producing cells and indicate an important physiologic role for IL-4 in the establishment of lymphokine-producing phenotype.

Multiple effects caused by anti-IL-4 mAb inoculation in the thymus and spleen of adult mice

We investigated the physiological role of IL-4 in the thymus and spleen by administering a neutralizing monoclonal anti-IL-4 antibody (11B11 mAb) into adult mice for 7 or 14 days. After this treatment the thymus decreased in size, this was mainly attributed to a decrease in the CD4+CD8+ subset after 7 days and both the CD4+CD8+ and the CD4+CD8- subsets after 14 days. These data suggest that IL-4 has a role in CD4+CD8+ thymocyte development and can differentially modulate the maturation of CD4+CD8- thymocytes in adult mice. Conversely, anti-IL-4 inoculation induced an increase in spleen size. After 7 days of treatment this enlargement appeared to be due to a increase in number of immature cells, the majority of which were CD4-CD8-alpha beta TCR-B220-slg-Ia-Mac-1-Pgp1 positive. After 14 days, an expanded spleen size was mainly due to inflated numbers of mature CD4+CD8-, B and Mac-1+ cells. In addition, we showed that anti-IL4 mAb in vivo enhanced the CD4-CD8-alpha beta TCRlow subset within the spleen after 7 days which is also observed at 14 days of treatment. Finally, we demonstrated that anti-IL-4 mAb treatment is highly stimulatory for hemopoietic activity in the adult spleen. Taken together, these results support the notion that IL-4 acts in vivo, directly or indirectly, on T cell differentiation in the thymus and T subsets homeostasis as well as on other cell types in the spleen of adult mice.

Suppression of chronic myelogenous leukemia colony growth by interleukin-4

Interleukin-4 (IL-4) is a cytokine with pleiotropic activities. In normal bone marrow cultures grown in the presence of either granulocyte-macrophage colony-stimulating factor (GM-CSF) or interleukin-3 (IL-3), IL-4 suppresses granulocyte-macrophage colony-forming unit (CFU-GM) proliferation but it enhances the colony-stimulatory effect of granulocyte colony-stimulating factor (G-CSF). We studied the effect of IL-4 on chronic myelogenous leukemia (CML) bone marrow or peripheral blood cells from 30 patients using the CFU-granulocyte-erythrocyte-monocyte-megakaryocyte colony culture assay. In several repetitive experiments, IL-4 inhibited CFU-GM colony replication by 24 to 65% in a dose-dependent fashion at concentrations ranging from 0.01 to 10 micrograms/ml when patients' cells were cultured in the presence of erythropoietin alone or with phytohemagglutinin-conditioned medium, GM-CSF, or IL-3. The addition of 100 U/ml of IL-1 beta to the CML cultures partially reversed the inhibitory effect of IL-4. Incubation of CML low-density peripheral blood cells with IL-4 resulted in down-regulation of IL-1 beta and IL-6 production in three of four samples, suggesting that the suppressive effect of IL-4 is mediated by inhibition of IL-1 and by other mechanisms including inhibition of IL-6 production. In contrast to the stimulatory effect exerted by IL-4 on G-CSF-dependent CFU-GM progenitor proliferation in normal marrow, the addition of IL-4 to CML cultures grown in the presence of G-CSF resulted in a divergent effect: suppression of CML CFU-GM in two, stimulation in three, and no significant effect in two CML patients' samples. It is therefore possible that IL-4 may have an in vivo antiproliferative effect in a subpopulation of CML patients.

Effect of anti-gamma-interferon and anti-interleukin-4 administration on the resistance of mice against infection with reticulotropic and myotropic strains of Trypanosoma cruzi

We studied the effect of in vivo administration of anti-gamma-IFN and anti-IL-4 monoclonal antibodies on the resistance of mice against myotropic and reticulotropic strains of Trypanosoma cruzi. Anti-gamma-IFN treatment augmented the susceptibility of mice when infected with the reticulotropic RA and Tulahuén strains of T. cruzi but did not alter the course of infection with the myotropic CA-I strain of the parasite. In vivo administration of anti-IL-4 enhanced the resistance of mice when infected with either Tulahuén or RA strains but did not affect the course of parasitemia when infected with CA-I. The possible biological relevance of these observations is discussed.

Intracellular signaling events associated with the induction of DNA synthesis in human B lymphocytes. II. Different pathways triggered by IL-2 and IL-4

In attempts to detect associations between early signaling events triggered by interleukins and the induction of DNA synthesis, inhibitors of various second messenger pathways were tested for their effects on IL-2- and IL-4-elicited mitogenesis in preactivated human B lymphocytes. Inhibitors of phosphoinositidase C and of InsP3-induced calcium release suppressed IL-4- but not IL-2-mediated proliferation. The response to both lymphokines was also impaired by an inhibitor of the calcium/calmodulin complex and was modulated by variations of the [Ca2+]i. PKC inhibitors and PK-C depletion did not significantly alter the response to IL-2 and IL-4. The response to IL-2, but not to IL-4, was inhibited by cAMP analogues or by agents that raise cAMP. In contrast, IL-4, but not IL-2, stimulated cAMP accumulation in activated B cells. Taken together, these observations indicate that IL-2 and IL-4 use different signaling pathways to induce the G1-->S transition in these cells and suggest that the IL-4 inhibition of the B cell response to IL-2 may result from its effect on cAMP generation.

Conversion of human interleukin-4 into a high affinity antagonist by a single amino acid replacement

Interleukin-4 (IL-4) represents a prototypic lymphokine (for a recent review see Paul, 1991). It promotes differentiation of B-cells and the proliferation of T- and B-cell, and other cell types of the lymphoid system. An antagonist of human IL-4 was discovered during the studies presented here after Tyr124 of the recombinant protein had been substituted by an aspartic acid residue. This IL-4 variant, Y124D, bound with high affinity to the IL-4 receptor (KD = 310 pM), but retained no detectable proliferative activity for T-cells and inhibited IL-4-dependent T-cell proliferation competitively (K(i) = 620 pM). The loss of efficacy in variant Y124D was estimated to be greater than 100-fold on the basis of a weak partial agonist activity for the very sensitive induction of CD23 positive B-cells. The substitution of Tyr124 by either phenylalanine, histidine, asparagine, lysine or glycine resulted in partial agonist variants with unaltered receptor binding affinity and relatively small deficiencies in efficacy. These results demonstrate that high affinity binding and signal generation can be uncoupled efficiently in a ligand of a receptor belonging to the recently identified hematopoietin receptor family. In addition we show for the first time, that a powerful antagonist acting on the IL-4 receptor system can be derived from the IL-4 protein.

Mechanism of pokeweed mitogen inhibition of rhIL-4-induced human IgE synthesis

Pokeweed mitogen (PWM) suppressed rhIL-4-induced IgE synthesis in a concentration-dependent manner. When rhIL-4 was present from Day 0, PWM added to cultures on Day 0 or 3 inhibited MNC IgE synthesis but not when it was added on Day 6 or later. The concentration of interferon-gamma (IFN-gamma) in MNC culture supernatants varied directly with the quantity of PWM added. Conversely, rhIL-4-stimulated MNC culture IgE concentrations varied inversely with the dose of PWM added and the IFN-gamma concentrations induced. The addition of a rabbit polyclonal neutralizing anti-human IFN-gamma antibody to rhIL-4 plus PWM-stimulated cultures partially or completely reversed PWM-induced inhibition of rhIL-4-induced IgE synthesis. PWM failed to inhibit rhIL-4-induced IgE synthesis by isolated B cells cocultured with monocytes and T cells from a clone unable to produce IFN-gamma message or protein. These findings are consistent with the postulate that PWM inhibits rhIL-4-induced IgE synthesis by inducing the production of IFN-gamma.

Modulation of human IgE synthesis by transforming growth factor-beta

Exogenous transforming growth factor-beta 2 (TGF-beta 2) markedly inhibits the interleukin 4 (IL4)-stimulated synthesis of human IgE in three models where the B cell co-stimulation signals are contact dependent. This concerns T cell-dependent IgE production by (i) unfractionated peripheral blood mononuclear cells (PMBC) cultured with IL4 and (ii) highly purified B cells cocultured with irradiated EL4 thymoma cells in the presence of IL4 and phorbol myristate acetate, as well as monocyte-dependent IgE production by rigorously T cell-depleted PBMC cultured with IL4 and hydrocortisone. The suppression is not isotype specific. TGF-beta exerts its effect by inhibiting the proliferation of B cells and perhaps also the differentiation of proliferating B cells. However, at a later stage of differentiation, IgE B cells are refractory to the inhibitory effect of TGF-beta, as shown by the slight but significant increase of the spontaneous secretion of IgE by PBMC of atopic patients. This enhancement is due to the suppression of endogenous interferon-gamma production. Most interestingly the synthesis of IgE by highly purified B cells costimulated with IL4 and Epstein-Barr virus is unaffected by TGF-beta. It is concluded that TGF-beta mainly acts by inhibiting IL4-supported B cell proliferation; however, its effects depend upon the B cell costimulation signals that are required together with IL4 for the induction of IgE synthesis.

Age- and strain-related differences in murine spleen cell responses to different activation signals

The effect of age on the response of splenocytes to activation with anti-CD3 mAb and a combination of anti-CD3 mAb and TPA, as evidenced by interleukin-2 (IL-2) and interleukin-4 (IL-4) production and cell proliferation, was examined in the C57BL/6 and DBA/2 murine strains. Depending on the mode of activation, there were age and strain differences in IL-2 and IL-4 production. With all modes of activation, cells from the old C57BL/6 mice produced less IL-2 than their young counterparts. In DBA/2 mice there was no age-related difference in IL-2 production with anti-CD3 mAb activation alone, whereas when the same cell population was activated with anti-CD3 mAb and TPA an age-associated decrease in IL-2 production occurred. In both strains, there was an age-related increase in IL-4 production with anti-CD3 mAb activation. After addition of TPA, however, there was an age-related decrease in IL-4 production. An age-related decline in the proliferation occurred with all modes of activation in both mouse strains. There were also strain-related differences in proliferation after the addition of forskolin, an inhibitor of Th1-cell function. While forskolin inhibited the proliferation of cells from the young C57BL/6 mice only, in the DBA/2 mice proliferation of cells was inhibited in both age groups. There were no strain-related differences in inhibition by anti-transferrin receptor (TrfR) mAb, although cells from the old mice were slightly more sensitive to this inhibition.

Cyclosporine and FK506 inhibition of murine mast cell cytokine production

The ability of cyclosporine (CSA) and FK506 to inhibit cytokine production by factor-dependent murine mast cell lines was investigated. The mast cell clone, MC/9, and two mast cell lines, MCIII and MCVI, were stimulated to produce cytokines with phorbol myristate acetate plus the calcium ionophore A23187. The production of cytokines by stimulated mast cells cultured in the presence or absence of drug was monitored by bioassay of culture supernatants for induction of proliferation by factor-dependent cell lines and inhibition of these responses by neutralizing monoclonal antibodies. Both CSA and FK506 inhibited mast cell cytokine production at concentrations comparable to those observed with T cells. However, the degree of inhibition of cytokine production varied among the mast cell lines as well as between different cytokines produced by a given mast cell line. For example, CSA completely inhibited interleukin-2 (IL-2), IL-3, IL-4 and granulocyte-macrophage colony stimulating factor secretion by all three lines, with the exception that IL-2/IL-4 production by MCIII was partially resistant to inhibition by CSA. Similarly, FK506 completely inhibited cytokine production by MC/9, partially inhibited cytokine production by MCIII and had differential effects on IL-3/granulocyte-macrophage colony-stimulating factor and IL-2/IL-4 production by MCVI. Consistent with their ability to selectively inhibit cytokine gene transcription in T cells, neither CSA nor FK506 inhibited factor-dependent proliferation by these mast cell lines. In view of the putative role of cytokines in inflammation and late phase asthmatic reactions, these observations may be of particular significance in development of methods of pharmacologic intervention.

Functional assessment and partial characterization of [3H](+)-pentazocine binding sites on cells of the immune system

The existence of sigma receptors on lymphocytes and thymocytes was characterized using [3H](+)-pentazocine. [3H](+)-Pentazocine specifically labels high affinity sigma-type binding sites on T- and B-enriched lymphocyte membranes. The binding is saturable with T lymphocyte sites having a KD value of 401 +/- 85 nM and B lymphocyte sites having a KD value of 302 +/- 46 nM. Likewise, saturable high (KD1 277 +/- 92 nM) and low (KD2 2.5 +/- 1.2 microM) affinity sites for [3H](+)-pentazocine are found on thymocytes as well. In competition studies with lymphocytes, the rank order of potency for competing ligands is (+)-pentazocine = N-[2-(3,4-dichlorophenyl)ethyl]-N-methyl-2- (1-pyrrolidinyl)ethylamine (BD1008) greater than 1R,2S-(+)-cis-N-(2-(3,4-dichlorophenyl)ethyl]-2- (1-pyrrolidinyl)cyclohexylamine (LR132) greater than or equal to (-)-pentazocine greater than or equal to phenazocine greater than (+/-)-trans-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)cyclohexyl] benzeneacetamide methanesulphonate (U-50,488H) = phencyclidine greater than haloperidol = 1,3-di- (o)-tolylguanidine. In competition studies with thymocytes, the rank order of potency for competing ligands is (+)-pentazocine = BD1008 greater than or equal to phenazocine greater than haloperidol greater than 1,3-di-(o)-tolylguanidine greater than phencyclidine greater than (-)-pentazocine. These compounds were also investigated as potential regulatory molecules in mitogen-stimulated lymphocyte proliferation assays. Of the compounds tested, phencyclidine, 1,3-di-(o)-tolylguanidine, haloperidol, and (+)-pentazocine suppress concanavalin A-induced proliferation at high (10(-5) M) concentrations while (-)-pentazocine is inactive. When pokeweed mitogen or lipopolysaccharide are used, these compounds enhance or suppress lymphocyte proliferation depending on the mitogen and concentration of ligand. These results indicate a stereoselective receptor for (+)-pentazocine which is coupled to biological processes of lymphocytes.

Differential inhibition of interleukin 2- and interleukin 4-mediated human B cell proliferation by ionomycin: a possible regulatory role for apoptosis

Surface immunoglobulin (Ig) cross-linking by anti-IgM (mu) antibodies leads to B cell activation resulting in numerous early biochemical events including an increase in intracellular [Ca2+]. Furthermore, anti-mu-activated B cells become able to proliferate in response to interleukin (IL)2 and IL4. These studies examined the effect of the calcium ionophore ionomycin, an enhancer of cytoplasmic [Ca2+] levels, on IL2 and IL4-mediated proliferation of anti-mu-stimulated normal human B cells. Ionomycin inhibited the proliferative response of anti-mu-activated B cells to IL4. In contrast, IL2 and phorbol 12,13 dibutyrate (PBu2)-mediated B cell proliferation was refractory to the growth inhibitory effects of ionomycin. In an attempt to delineate a possible mechanism(s) for this differential growth effect of ionomycin, we first studied direct effects of ionomycin on activated B cells. Our data suggested that ionomycin induced DNA fragmentation in anti-mu-costimulated B cells. Interestingly, in contrast to PBu2, IL4 did not prevent ionomycin-dependent DNA fragmentation. Importantly, H7, an inhibitor of protein kinase C activation, down-regulated only the IL2 and PBu2-driven B cell proliferation but not B cell proliferative response to IL4. These results suggest that putative protein kinase C activation, either by direct treatment with phorbol ester or during IL2 signaling, counteracts the inhibitory effects of ionomycin. In contrast, IL4 signaling does not exhibit the same protective properties.

IFN-gamma reverses IL-4 inhibition of fetal thymus growth in organ culture

IL-4 is known to inhibit the growth and differentiation of 14-day-old fetal mouse thymus in organ culture. Here we report that IFN-gamma reverses this IL-4-mediated growth inhibition. Thymus lobes from 14-day-old fetuses were cultured for 12 days in medium containing 100 IU/ml rIL-4 either in the absence or presence of rIFN-gamma (100 to 1000 IU/ml). After culture, the cell yields and the absolute numbers and frequencies of the major subpopulations according the coordinate expression of CD4 and CD8 were estimated. IL-4 treatment alone was found to result in a seven-fold decrease in cell yield and an almost complete absence of the CD4+CD8+ subpopulation. Addition of IFN-gamma reversed IL-4-mediated inhibition in a dose-dependent fashion, with an optimal dose ranging from 200 to 500 IU/ml. IFN-gamma exerted this effect only when added within the first 48 h of initiating the culture. The specificity of the reversal effect was ascertained by neutralization of the effect by a neutralizing anti-IFN-gamma mAb and by lack of activity of human IFN-gamma. In the absence of IL-4, IFN-gamma had a growth-promoting effect as evident from a threefold increase in cell numbers.

Regulation of murine in vivo IgG and IgE responses by a monoclonal anti-IL-4 receptor antibody

Although the cytokine interleukin 4 (IL-4) stimulates LPS-activated mouse B lymphocytes to secrete both IgG1 and IgE, an anti-IL-4 antibody completely inhibits IgE responses but has little or no effect on several in vivo IgG responses. IL-4 might, therefore, have a restricted role in the generation of in vivo humoral immune responses. Alternatively, IgG1 responses might be stimulated by IL-4 secreted by T cells that are interacting directly with B cells, so that anti-IL-4 antibody cannot neutralize IL-4 before it binds to a B cell IL-4 receptor. In contrast, an antibody that blocks the IL-4 receptor (IL-4R) should equally inhibit responses to IL-4 produced proximal to or distant from a B cell. This reasoning led us to determine the ability of an anti-IL-4R mAb to affect antibody production in mice injected with a goat antibody to mouse IgD (GaM delta) or inoculated with the nematode parasite Heligmosomoides polygyrus. Anti-IL-4R mAb, like anti-IL-4 mAb, blocked IgE responses by greater than 95% and enhanced IgG2a responses to a variable extent. Anti-IL-4R mAb, however, had only a modest and variable inhibitory effect on the induction of IgG1 responses, although it caused these responses to terminate more rapidly. A combination of anti-IL-4 and anti-IL-4R mAbs totally blocked goat anti-mouse IgD antibody (GaM delta)-induced IgE production but had no additive inhibitory effect on IgG1 production. These observations are most consistent with the view that IL-4 is required for a primary IgE response, but has relatively little role in the induction of IgG1 responses in the in vivo systems studied.

A recombinant extracellular domain of the human interleukin 4 receptor inhibits the biological effects of interleukin 4 on T and B lymphocytes

Human interleukin 4 (IL4) acts on various hematopoietic cell types through interaction with a specific cell surface receptor (IL4R), whose cDNA has been cloned. We have produced a cDNA encoding a soluble form of the extracellular domain of the human IL 4R (sIL4R) and describe here the capacity of sIL4R to antagonize the in vitro activities of IL4 on normal B and T lymphocytes. sIL4R inhibited IL4-induced proliferation of both phytohemagglutinin-preactivated peripheral blood mononuclear cells (PBMC) and anti-IgM co-stimulated tonsil B cells with similar efficiency. This inhibitory activity was specific since sIL4R did not affect IL2-dependent proliferation of these cells. sIL4R also blocked IL4-dependent induction of the low-affinity receptor for IgE on B cells and inhibited IgE production by IL4-activated PBMC. Thus, in contrast to the IL6R extracellular domain which stimulates IL6 biological activity, the IL4R extracellular domain is a powerful antagonist of its specific ligand.

Interferon-gamma inhibition of interleukin 4-induced hyperproliferation of resting B cell from NZB/NZW F1 mice

To characterize B cell hyperactivity in autoimmune NZB/NZW (B/W) F1 mice, we studied the effects of murine recombinant interferon gamma (IFN-gamma) on interleukin 4 (IL-4) induced resting B cell growth and differentiation. The number of resting B cells of B/W F1 mice were decreased, with more sensitivity to IL-4 than normal mice. Thus, resting B cell hyperresponsiveness to IL-4 was in a dose-dependent manner suppressed by IFN-gamma. This action was most noticeable when IFN-gamma was added to the culture system simultaneously with IL-4. As well, IFN-gamma did not exhibit cytotoxicity. These results suggest that IFN-gamma may have regulatory effects on IL-4 mediated B cell triggering.

Independent regulation of interleukin 4 (IL-4)-induced expression of human B cell surface CD23 and IgM: functional evidence for two IL-4 receptors

Activation of human B cells with interleukin 4 (IL-4) is known to result in increased expression of CD23 (the low-affinity receptor for IgE) and sIgM. However, whereas CD23 expression is increased by several B cell mitogens, including phorbol 12-myristate 13-acetate, Epstein-Barr virus, anti-immunoglobulin (Ig), and IL-4, surface IgM (sIgM) expression is increased only with IL-4, suggesting that expression of each surface antigen is regulated independently. This was confirmed in three different ways. First, in dose-response experiments, it was shown that 10 times the concentration of IL-4 was required for CD23 than for sIgM expression. Similar or even higher concentrations of IL-4 were required for proliferation. In fact, optimal sIgM expression was obtained in some experiments with concentrations of IL-4 (1-5 units/ml) which had little or no effect on either CD23 expression or B cell proliferation. Secondly, IL-4 is known to activate the phosphatidyl inositol pathway in human B cells followed 8-10 min later by an increase in cAMP. Pharmacologically mimicking this pathway by brief exposure of resting B cells to phorbol dibutyrate plus ionomycin followed 10 min later with dibutyryl cAMP resulted in an increase in expression of CD23 but not sIgM. Thirdly, CD19 monoclonal antibody, which inhibits B cell proliferation in response to IL-4 plus anti-Ig, was found to inhibit IL-4-induced CD23 but not sIgM expression. These results show that CD23 and sIgM expression are regulated independently and are consistent with the existence of two separate signal transduction pathways stimulated by IL-4, which may be coupled to distinct IL-4 receptors.