Differential regulation of mast cell cytokines by both dexamethasone and the p38 mitogen-activated protein kinase (MAPK) inhibitor SB203580

Activated mast cells generate multiple cytokines but it is not known if these can be differentially regulated by pharmacological agents. We report here that the glucocorticoid dexamethasone (DEX) preferentially inhibited Ag-induced expression of IL-4 and IL-6 mRNA relative to TNF-alpha mRNA in RBL-2H3 cells. Likewise, the drug more readily inhibited release of IL-4 than TNF-alpha protein. SB203580, an inhibitor of p38 mitogen-activated protein kinase (MAPK), enhanced Ag-induced TNF-alpha mRNA expression without affecting IL-4 or IL-6 mRNA. At the protein level, SB203580 exerted little effect on TNF-alpha release but inhibited IL-4 release; notably, the ratio of TNF-alpha : IL-4 increased markedly with the concentration of SB203580, confirming the differential regulation of these cytokines. PD98059, an inhibitor of MAPK kinase (MEK), a component of the p44/42 MAPK pathway, partially inhibited Ag-induced expression of mRNA for all three cytokines while cyclosporin A inhibited Ag-induced IL-4 and IL-6 mRNA more readily than TNF-alpha mRNA. Ag activation of the cells led to phosphorylation of p38 and p44/42 MAPK but this was not influenced by DEX. In conclusion, mast cell cytokines can be differentially regulated pre- and post-translationally by DEX and SB203580 but there does not appear to be a direct mechanistic link between the actions of these two drugs.

Benzylpenicillin differentially conjugates to IFN-gamma, TNF-alpha, IL-1beta, IL-4 and IL-13 but selectively reduces IFN-gamma activity

It is known that beta-lactam antibiotics can conjugate to lysine and histidine residues on proteins via the carbonyl group of the opened beta-lactam ring. However, it is not known which proteins these drugs target and there is little work addressing whether conjugation is preferential for some proteins over others or if conjugation has functional consequences for the protein. We have previously shown that the beta-lactam antibiotic benzylpenicillin (BP) conjugates to IFN-gamma and reduces its activity. This interaction demonstrates selectivity, as BP does not bind to IL-4. Here, we extend our study to include other Th1 and Th2 cell-associated cytokines and two cytokines associated with inflammatory responses. We demonstrate by Western blotting that BP also conjugates to IL-1beta, IL-2, IL-5, IL-13 and TNF-alpha but not to IL-10. Densitometric analysis of leading cytokine bands on blots revealed that IFN-gamma always gave more intense BP-positive bands than any other cytokine analysed. Cytokines pre-incubated with BP at 37 degrees C in a protein-containing, serum-free medium were assayed for their biological activity. By in vitro bioassay, BP inhibited the ability of IFN-gamma but not IL-1beta or TNF-alpha to induce CD54 expression on epithelial cells. In addition, BP did not affect IL-4 or IL-13 inhibition of mast cell proliferation. When the pre-incubation temperature was reduced to 4 degrees C, BP did not conjugate to IFN-gamma or modulate its activity. BP retained its inhibitory effect on IFN-gamma activity when 20% FCS was added to the pre-incubation medium. In conclusion, BP conjugates to some cytokines but not others and this does not appear to be related to primary protein structure. Furthermore, of the cytokines studied, conjugation only to IFN-gamma is accompanied by inhibition of activity. This phenomenon is temperature dependent and occurs in the presence of serum. These findings provide further evidence for differential, direct drug-cytokine interactions. Such interactions may have therapeutic implications in terms of targeting cytokines to regulate their activity.

Nitric oxide: a regulator of mast cell activation and mast cell-mediated inflammation

Nitric oxide (NO) plays diverse roles in physiological and pathological processes. During immune and inflammatory responses, for example in asthma, NO is generated at relatively high and sustained levels by the inducible form of nitric oxide synthase (NOS-2). NOS-2 derived NO regulates the function, growth, death and survival of many immune and inflammatory cell types. In the case of mast cells, NO suppresses antigen-induced degranulation, mediator release, and cytokine expression. The action of NO on mast cells is time dependent, requiring several hours, and noncGMP mediated, most probably involving chemical modification of proteins. NO inhibits a number of mast cell-dependent inflammatory processes in vivo, including histamine mediated vasodilatation, vasopermeation and leucocyte-endothelial cell attachment. In human asthma and animal models of lung inflammation the role of NO is harder to define. However, although there are conflicting data, the balance of evidence favours a predominantly protective role for NO. Mimicking or targeting NO dependent pathways may prove to be a valuable therapeutic approach to mast cell mediated diseases.

Characterization of specific IgE response in vitro against protein and drug allergens using atopic and normal donors

BACKGROUND

As the incidence of allergy to different compounds increases in society, the need to understand and characterize specific IgE responses becomes obvious. Different cell culture systems have been evaluated for their ability to support such IgE secretion.

METHODS

One system employed human peripheral lymphocytes (PBL) from normal donors stimulated with anti-CD3 activated T cells with or without the presence of allergens like benzylpenicillin (BP) and Phlenum pratense (PP). Secretion of IgE was analyzed in ELISA and compared to the IgG response to the nonallergenic antigen tetanus toxoid (TT). Another system employed stimulation of T and B cells with a heterotope, consisting of a T helper cell epitope derived from TT, and a B cell allergen epitope derived from BP. The specific IgE secretion was compared, using lymphocytes from normal as well as BP-allergic donors.

RESULTS

Anti-CD3 stimulated T cells supported BP-specific IgE secretion in six of 11 normal donors. This response was inhibited in four donors and enhanced in two donors by the addition of the BP-allergen to the culture. In contrast, addition of the protein allergen (PP) or antigen (TT) to the same culture system inhibited both IgE and IgG synthesis in all experiments. Cells from the majority (10/16) of the BP-allergic donors failed to produce BP-specific IgE in vitro, when cultured in the presence of allergen.

CONCLUSIONS

An allergen specific immune response is readily generated in vitro. The differential response against benzylpenicillin between different donor categories most probably reflects the level of pre-exposure to this allergen in vivo.

Penicillin conjugates to interferon-gamma and reduces its activity: a novel drug-cytokine interaction

Beta-lactam antibiotics are the class of drug most frequently associated with IgE-mediated allergy but the mechanisms underlying this response are poorly understood. IFN-gamma is a key cytokine in immunity with regulatory actions on monocytes, NK cells, epithelial cells, and T and B lymphocytes. IFN-gamma promotes Th1 responses and inhibits Th2- and IgE-mediated responses. In this study we show, by Western blotting, that the prototype beta-lactam benzylpenicillin (BP) conjugates to human IFN-gamma but not to IL-4. The interaction of BP with IFN-gamma inhibited the cytokine's detection by immunoassay and impaired its activity, as assessed in three different assays: upregulation of MHC molecules on monocytes plus induction of nitric oxide synthesis and expression of monocyte chemoattractant protein-1 mRNA by epithelial cells. This is the first reported example of a direct drug-cytokine interaction and suggests a mechanism by which penicillin may disrupt IFN-gamma-dependent immune responses and promote allergy.

Nitric oxide in immunity and inflammation

Nitric oxide (NO) is synthesised by many cell types involved in immunity and inflammation. The principal enzyme involved is the inducible type-2 isoform of nitric oxide synthase (NOS-2), which produces high-level sustained NO synthesis. NO is important as a toxic defense molecule against infectious organisms. It also regulates the functional activity, growth and death of many immune and inflammatory cell types including macrophages, T lymphocytes, antigen-presenting cells, mast cells, neutrophils and natural killer cells. However, the role of NO in nonspecific and specific immunity in vivo and in immunologically mediated diseases and inflammation is poorly understood. NO does not act through a receptor-its target cell specificity depends on its concentration, its chemical reactivity, the vicinity of target cells and the way that target cells are programmed to respond. At high concentrations as generated by NOS-2, NO is rapidly oxidised to reactive nitrogen oxide species (RNOS) that mediate most of the immunological effects of NOS-2-derived NO. RNOS can S-nitrosate thiols to modify key signalling molecules such as kinases and transcription factors. Several key enzymes in mitochondrial respiration are also inhibited by RNOS and this leads to a depletion of ATP and cellular energy. A combination of these interactions may explain the multiple actions of NO in the regulation of immune and inflammatory cells.

Phenotypic variation in mast cell responsiveness to the inhibitory action of nitric oxide

OBJECTIVE AND DESIGN

The aim of this study was to investigate the possible phenotypic variations between mast cells in terms of their responsiveness to the inhibitory actions of nitric oxide.

MATERIALS

Unfractionated mouse peritoneal cells, purified rat peritoneal mast cells, mouse bone marrow-derived mast cells of the C1.MC/C57.1 line (cultured mouse mast cells, CMMC) and rat basophilic leukemia cells of the RBL-2H3 line were used.

METHODS

Mast cells were cultured with interferon-gamma (IFN-gamma)-stimulated mouse peritoneal cells as a source of nitric oxide, or with the nitric oxide donor S-nitrosoglutathione (SNOG). After 24 h culture, the mast cells were challenged with anti-IgE, antigen, or calcium ionophore A23187, and degranulation measured as release of [3H]serotonin.

RESULTS

Addition of IFN-gamma to mouse peritoneal cells led to nitric oxide synthesis and this was associated with decreased IgE-mediated mast cell degranulation. IFN-gamma did not induce nitric oxide production by CMMC and degranulation of CMMC was not inhibited by nitric oxide generated by co-cultured IFN-gamma-activated peritoneal cells. The nitric oxide donor SNOG inhibited degranulation of purified rat peritoneal mast cells, but not RBL-2H3 cells, stimulated by either IgE cross-linking or calcium ionophore.

CONCLUSIONS

The inhibitory effects of nitric oxide on mast cell degranulation are variable and selective for phenotype. Such phenotypic differences may reflect important variations in regulation of mast cell function.

Presentation of IFN-gamma to nitric oxide-producing cells: a novel function for mast cells

We report that mast cells can bind and present IFN-gamma in a functionally active form to macrophages. Flow-cytometric analysis revealed that biotinylated IFN-gamma bound equally well to purified peritoneal mast cells from both IFN-gammaR knockout and wild-type mice, indicating a non-IFN-gammaR binding site. Purified peritoneal mast cells, loaded with IFN-gamma for 30 min and washed, were able to induce NO synthesis by peritoneal macrophages. This response required cell contact and expression of IFN-gammaR on the responding macrophages, but not the mast cells. Human HMC-1 mast cells were also able to present IFN-gamma to mouse macrophages. Enzyme treatment of mouse mast cells revealed that binding of IFN-gamma was predominantly to chondroitin sulfate B (dermatan sulfate). Binding of IFN-gamma to dermatan sulfate was confirmed by inhibition ELISA. This study demonstrates for the first time that mast cells can present IFN-gamma to other cells via glycosaminoglycans. Mast cells may act as a reservoir of surface-stored functionally active cytokines.

Eotaxin and eotaxin receptor (CCR3) expression in Sephadex particle-induced rat lung inflammation

The beta chemokine eotaxin is a potent eosinophil activator and chemoattractant. We examined immunohistochemically eotaxin protein expression in a range of normal rat tissues and in rat lung during Sephadex particle-induced pulmonary inflammation. The time course of eotaxin expression in lung at various time points after Sephadex administration was related to the appearance of eosinophils in the bronchoalveolar lavage fluid and tissue distribution of eotaxin receptor (CCR3) positive cells. Results showed that eotaxin protein was constitutively expressed by both lung airway epithelial cells and gut epithelial cells in normal tissues in the absence of inflammation. During Sephadex induced pulmonary inflammation, eotaxin expression increased in alveolar macrophages prior to the major increase in eosinophil numbers which reached a peak at 72 h. The pattern of eotaxin pulmonary expression and the location of CCR3 receptor positive cells suggest a chemoattractant gradient resulting in migration firstly into the tissue and subsequently through the airway epithelium into the airways. Treatment of rats with the glucocorticoid dexamethasone or the immunosuppressant cyclosporin A reduced eosinophil entry into lung tissue and airways but had no apparent effect on eotaxin expression in vivo, indicating that both these drugs inhibit eosinophil recruitment either by an eotaxin-independent mechanism, or by targetting factors that synergise with eotaxin, or an event post eotaxin expression.

Poliomyelitis in intraspinally inoculated poliovirus receptor transgenic mice

Mice transgenic with the human poliovirus receptor gene develop clinical signs and neuropathology similar to those of human poliomyelitis when neurovirulent polioviruses are inoculated into the central nervous system (CNS). Factors contributing to disease severity and the frequencies of paralysis and mortality include the poliovirus strain, dose, and gender of the mouse inoculated. The more neurovirulent the virus, as defined by monkey challenge results, the higher the rate of paralysis, mortality, and severity of disease. Also, the time to disease onset is shorter for more neurovirulent viruses. Male mice are more susceptible to polioviruses than females. TGM-PRG-3 mice have a 10-fold higher transgene copy number and produce 3-fold more receptor RNA and protein levels in the CNS than TGM-PRG-1 mice. CNS inoculations with type III polioviruses differing in relative neurovirulence show that these mouse lines are similar in disease frequency and severity, demonstrating that differences in receptor gene dosage and concomitant receptor abundance do not affect susceptibility to infection. However, there is a difference in the rate of accumulation of clinical signs. The time to onset of disease is shorter for TGM-PRG-3 than TGM-PRG-1 mice. Thus, receptor dosage affects the rate of appearance of poliomyelitis in these mice.

Direct detection of Sabin poliovirus vaccine strains in stool specimens of first-dose vaccinees by a sensitive reverse transcription-PCR method

A multiplex reverse transcription-PCR method was optimized to monitor the duration of excretion of Sabin poliovirus strains in stools of vaccinees following administration of the first dose of the trivalent oral vaccine. The assay detected approximately 1 50% tissue culture infective dose of each poliovirus serotype spiked into cell culture media. Although PCR inhibitors were frequently encountered in the stool specimens, a 1:20 dilution of the extracted RNA was sufficient to obtain a positive PCR result. Analysis of 195 stool specimens collected from 26 vaccinees showed that poliovirus types 1, 2, and 3 were identified more frequently by PCR than by tissue culture isolation. The percentages of specimens positive by PCR for poliovirus types 1, 2, and 3 were 67.2, 82.6, and 53.8, respectively. In contrast, the culture method identified types 1, 2, and 3 virus in 55.4, 64.1, and 27.7% of the samples, respectively. Poliovirus type 2 excretion was detected by PCR in practically all of the oral poliovirus vaccine recipients for 4 to 8 weeks following vaccination. In contrast, excretion of type 1 and 3 viruses was more variable, with a range of 1 to 8 weeks. Shedding of type 3 virus ceased in approximately 70% of vaccinees within a week after immunization. In addition to an enhanced sensitivity for the detection of poliovirus, this PCR method permits the direct characterization of virus in stool specimens without further passage in culture, which may select for genetic variants that may not accurately reflect the virus composition in the original specimen.

Reciprocal effects of interleukin-4 and interferon-gamma on immunoglobulin E-mediated mast cell degranulation: a role for nitric oxide but not peroxynitrite or cyclic guanosine monophosphate

We report that cultured rat peritoneal cells spontaneously synthesize nitric oxide and this is associated with active suppression of mast cell secretory function. Addition of interleukin-4 (IL-4) or the nitric oxide synthase inhibitor N-monomethyl-l-arginine to peritoneal cells inhibited nitric oxide synthesis and enhanced anti-IgE-mediated mast cell degranulation, measured as serotonin release. Interferon-gamma (IFN-gamma) completely overcame the enhancement of serotonin release and suppression of nitrite production induced by IL-4. Over several experiments, with or without IL-4 and/or IFN-gamma, serotonin release correlated inversely with nitrite production. On a cell-for-cell basis, non-mast cells produced approximately 30 times more nitrite than mast cells in peritoneal cell populations, with or without IFN-gamma stimulation. The nitric oxide donor S-nitrosoglutathione inhibited anti-IgE-induced serotonin release from purified mast cells, whereas 8-bromo-cyclic GMP, the guanylate cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one, superoxide dismutase and the peroxynitrite scavenger uric acid, were without effect. We conclude that IL-4 and IFN-gamma reciprocally regulate mast cell secretory responsiveness via control of nitric oxide synthesis by accessory cells; the nitric oxide effect on mast cells is direct but does not involve cyclic GMP or peroxynitrite.

Characterization of mouse lines transgenic with the human poliovirus receptor gene

Two mouse lines transgenic with the human poliovirus receptor gene (PVR), TGM-PRG-1 and TGM-PRG-3, were characterized to determine whether transgene copy number and PVR expression levels influence susceptibility to poliovirus. The mouse lines have been bred for more than 10 generations and the transgene was stably transmitted to progeny as determined by Southern blot hybridization and restriction fragment length polymorphism. The transgene copy number is 10 in the TGM-PRG-3 mouse line and one in the TGM-PRG-1 mouse line. Abundance of PVR RNA is on average three-fold higher in TGM-PRG-3 relative to TGM-PRG-1 tissues, and the abundance of the receptor molecule is three-fold higher in TGM-PRG-3 central nervous system tissues compared to TGM-PRG-1 tissues as determined by Western blot analysis. When TGM-PRG-1 and TGM-PRG-3 mice were inoculated intracranially with a neurovirulent type III poliovirus strain, they developed clinical symptoms and CNS lesions characteristic of human poliomyelitis. These results indicate that the PVR gene is expressed as a functional receptor in the CNS of both mouse lines rendering the mice susceptible to poliovirus infection. Even though the two mouse lines have different copy numbers of the transgene and different levels of PVR RNA and protein, they are similar in their susceptibility to poliovirus.

Tumour necrosis factor-alpha expression and cell recruitment in Sephadex particle-induced lung inflammation: effects of dexamethasone and cyclosporin A

1. Tumour necrosis factor-alpha (TNF-alpha) is a cytokine with diverse properties consistent with a possible role in inflammatory disease. We investigated whether TNF-alpha is induced during the progression of lung inflammation elicited by a particulate non-antigenic stimulus, and whether pharmacological control of TNF-alpha expression influences recruitment of specific inflammatory cell types. 2. A single intravenous injection of Sephadex particles into rats led to extensive granulomatous inflammation in lung alveolar and bronchial tissue that peaked in intensity after 24-72 h. Mononuclear cells were the principal component of granulomas, but neutrophils and eosinophils were also abundant. Numbers of mononuclear cells, neutrophils and eosinophils recovered by bronchoalveolar lavage (BAL) peaked at 72 h, 48 h and 72 h, respectively. 3. Messenger RNA encoding TNF-alpha was induced in lung epithelial cells, lung granulomas and BAL cells 6 h after Sephadex administration and remained elevated for 72 h before declining to baseline by 7 days. In BAL cell populations TNF-alpha protein was localized to mononuclear cells at all times points pre- and post-Sephadex administration. 4. Treatment of rats with dexamethasone significantly reduced the Sephadex-induced recruitment of mononuclear cells, neutrophils and eosinophils into the bronchoalveolar cavity, and significantly reduced TNF-alpha mRNA expression by BAL cells. 5. Treatment of rats with cyclosporin A was without effect on Sephadex-induced elevations of mononuclear cell numbers and expression of TNF-alpha, but did reduce significantly recruitment of neutrophils and eosinophils to BAL cell populations. 6. These results show that a sequential asthma-like recruitment of neutrophils, eosinophils and mononuclear cells into lung tissue can be induced by single exposure to a non-antigenic stimulus. Pharmacological and histological studies reveal that mononuclear cell mobilization relates closely to induced TNF-alpha expression, whereas mobilization of neutrophils and eosinophils appears secondary to expression of the cytokine.

Nitric oxide inhibits IgE-mediated degranulation of mast cells and is the principal intermediate in IFN-gamma-induced suppression of exocytosis

IFN-gamma regulates various aspects of rodent peritoneal mast cell function, including mediator release, cell growth, TNF-alpha-mediated cytotoxicity, and MHC class II expression. We investigated whether the suppressive action of IFN-gamma on IgE/Ag-mediated degranulation of mast cells is mediated via synthesis of nitric oxide. Incubation of mouse peritoneal cells with L-NMMA, an inhibitor of nitric oxide synthase, or in medium lacking the nitric oxide precursor L-arginine reversed the inhibitory effect of IFN-gamma on Ag-induced serotonin release. Furthermore, the nitric oxide donors sodium nitroprusside and S-nitrosoglutathione inhibited degranulation, and this effect was direct, since it was seen equally on purified and unfractionated mast cells and occurred independently of IFN-gammaR expression. Additional experiments revealed that accessory cells in peritoneal cell populations were the principal target for the action of IFN-gamma and the main source of nitric oxide; the cytokine was more potent on unfractionated compared with purified mast cells, and IFN-gamma induced detectable nitrite production in mixed peritoneal cells, but not in purified mast cells. These studies show that IFN-gamma induces nitric oxide production in peritoneal cell populations, and that synthesized nitric oxide directly inhibits the IgE-mediated secretory function of mast cells. The activation of nitric oxide-producing cells in the tissue microenvironment may be important in the control of mast cell-dependent allergic reactions.

Nitric oxide inhibits IgE-mediated degranulation of mast cells and is the principal intermediate in IFN-gamma-induced suppression of exocytosis

IFN-gamma regulates various aspects of rodent peritoneal mast cell function, including mediator release, cell growth, TNF-alpha-mediated cytotoxicity, and MHC class II expression. We investigated whether the suppressive action of IFN-gamma on IgE/Ag-mediated degranulation of mast cells is mediated via synthesis of nitric oxide. Incubation of mouse peritoneal cells with L-NMMA, an inhibitor of nitric oxide synthase, or in medium lacking the nitric oxide precursor L-arginine reversed the inhibitory effect of IFN-gamma on Ag-induced serotonin release. Furthermore, the nitric oxide donors sodium nitroprusside and S-nitrosoglutathione inhibited degranulation, and this effect was direct, since it was seen equally on purified and unfractionated mast cells and occurred independently of IFN-gammaR expression. Additional experiments revealed that accessory cells in peritoneal cell populations were the principal target for the action of IFN-gamma and the main source of nitric oxide; the cytokine was more potent on unfractionated compared with purified mast cells, and IFN-gamma induced detectable nitrite production in mixed peritoneal cells, but not in purified mast cells. These studies show that IFN-gamma induces nitric oxide production in peritoneal cell populations, and that synthesized nitric oxide directly inhibits the IgE-mediated secretory function of mast cells. The activation of nitric oxide-producing cells in the tissue microenvironment may be important in the control of mast cell-dependent allergic reactions.

Selectivity of IgE responses, mast cell sensitization, and cytokine expression in the immune response of Brown Norway rats to chemical allergens

Sensitizing chemicals can induce various types of allergic disease, including contact dermatitis and occupational asthma. In the present study we have examined the nature of the immune response induced in Brown Norway (BN) rats by oxazolone (OX), a potent contact allergen, and by trimellitic anhydride (TMA), a chemical known to cause sensitization of the respiratory tract and occupational asthma. BN rats were exposed topically to either OX or TMA at doses selected to achieve similar levels of proliferative activity by draining LNC. Both chemicals stimulated hapten-specific IgG antibody responses, but only TMA induced specific IgE antibody, an increase in total serum IgE and active sensitization of mast cells. Draining LNC from OX-treated rats expressed elevated IFN-gamma mRNA, whereas those from TMA-treated rats expressed elevated IL-5 mRNA compared to controls. Furthermore, Con A-activated draining LNC from rats exposed to TMA, but not OX, released significantly increased concentrations of IL-4. In conclusion, different chemical allergens can induce in the BN rat divergent patterns of IgE response and cytokine expression.

Dexamethasone or cyclosporin A inhibits stem cell factor-dependent secretory responses of rat peritoneal mast cells in vitro

Stem cell factor (SCF) is potent activator of degranulation of rat peritoneal mast cells in vitro and may promote mast cell activation under certain circumstances in vivo. In this study we report that the anti-inflammatory glucocorticoid dexamethasone (DEX) and the immunosuppressive cyclosporin A (CsA) are both effective inhibitors of SCF-induced degranulation of rat peritoneal mast cells in vitro, measured as release of serotonin (5-HT). Of the two drugs, DEX was the more potent with near maximal inhibition reached at 10(-8) M, whereas a graded inhibition was seen with CsA in the range 10(-8)-10(-6) M. DEX was equally effective in inhibiting the release of 5-HT induced by either SCF or anti-IgE, but was less effective in inhibiting release induced by compound 48/80 or calcium ionophore A23187. CsA produced a similar degree of inhibition of degranulation induced by SCF, anti-IgE or ionophore, but was without effect on the response to compound 48/80. Neither DEX nor CsA had any significant effect on mast cell surface expression of the SCF receptor or IgE antibody. We conclude that both DEX and CsA inhibit components of the secretion-coupling pathways that are triggered following either SCF receptor engagement or cross-linking of IgE, but that these drug differentially influence mast cell secretion induced by compound 48/80 or the calcium ionophore A23187.

A comparative study of peritoneal mast cells from mutant IL-4 deficient and normal mice: evidence that IL-4 is not essential for mast cell development but enhances secretion via control of IgE binding and passive sensitization

IL-4 enhances the growth and secretory function of mouse connective tissue type mast cells in vitro. To examine further the mast cell regulatory role of IL-4 we compared certain phenotypic and functional characteristics of peritoneal mast cells from mutant IL-4 deficient (IL-4(-/-)) or normal wildtype (IL-4(+/+)) mice. No differences were seen between mast cells from the two types of mouse in terms of numbers, histamine content, cell size, ultrastructure and number and size of granules. Mast cells from IL-4 deficient or wildtype mice responded equally to specific IgE/antigen and IL-4. However, Fc epsilon RI of IL-4(-/-) (in contrast to wildtype) mast cells were not pre-loaded with IgE, which would be expected to facilitate passive sensitization. Moreover, the in vitro total IgE binding capacity of mutant mast cells was significantly less than that of wildtype. Further in vitro experiments showed that IL-4 selectively enhanced IgE/antigen- rather than anti-IgE-induced degranulation from normal mast cells, and this effect was accompanied by an IL-4 induced increase in IgE binding capacity. In conclusion, IL-4 is not essential for peritoneal mast cell growth and exocytosis but regulates secretion via control of IgE binding and sensitization.

The effects of mercuric chloride on growth, cytokine and MHC class II gene expression in a human leukemic mast cell line

We have examined the effects of mercuric chloride (HgCl2) on growth and IL-4, IL-8, TNF-alpha and MHC class II gene expression in the HMC-1 human leukemic mast cell line. Proliferation, measured by [3H]thymidine incorporation or production of a formazan product (MTT assay), was substantially inhibited by HgCl2 at concentrations of 10(-6) M and above. Inspection of the DNA by agarose gel electrophoresis from HgCl2-treated cells revealed that it was intact, indicating inhibition of DNA synthesis, but not denaturation. HgCl2 inhibited expression of mRNA for IL-8, TNF-alpha and MHC class II at 4 x 10(-6) M and inhibited expression of IL-4 mRNA at 8 x 10(-6) M and above. At a concentration of 10(-5)M, HgCl2 almost completely blocked mRNA expression for IL-4, IL-8, TNF-alpha and MHC class II, but produced negligible inhibition of expression of mRNA encoding the housekeeping gene beta-actin, thus demonstrating selective toxicity for the cytokine and MHC class II genes studied. Pre-exposure of the cells to human recombinant IL-4 prior to treatment with HgCl2 had no effect on expression levels of any of the genes examined. The effects seen in this study are consistent with previous reports showing immunotoxic effects of HgCl2 on other cell types, therefore, the HMC-1 mast cell line may prove useful in further studies of mast cell cytokine gene expression and the mechanisms involved in cytokine gene toxicity.

An analysis of beta-lactam-derived antigens on spleen cell and serum proteins by ELISA and Western blotting

Penicillins and related beta-lactam antibiotics are known to conjugate to proteins to generate potentially antigenic (haptenic) determinants. In the present study, we used a rabbit polyclonal antibody raised against benzylpenicillin (BP) to investigate the capacity of six penicillins and one cephalosporin to generate haptenic groups in vitro on cultured mouse spleen cells and on serum proteins in the culture medium. All of the drugs tested, namely, BP, amoxicillin (AMX), ampicillin (AMP), cephalothin (CEP), cloxacillin (CLX), flucloxacillin (FLX), and phenoxymethylpenicillin (PMP) generated antigens in a concentration-dependent manner on cell and serum proteins, which could be detected by ELISA, although antigens generated by BP, CEP, FLX, or PMP in either cell- or serum-conjugated form were more readily detected than those generated by AMX, AMP, or CLX. Western blot analysis revealed that BP-derived antigens were generated relatively slowly on cell proteins (maximum binding was not yet reached after 8 h), compared to serum proteins (maximum binding within 1 h). BP, CEP, and PMP all generated similar distinctive patterns of immunostaining of electrophoresed cell or serum proteins which did not reflect the relative abundance of different proteins as revealed by Coomassie brilliant blue staining. FLX, CLX, AMP, and AMX did not generate antigens that could be detected on Western blots. In conclusion, we have shown that various beta-lactam antibiotics generate antigens on cell and serum proteins that can be detected and characterized immunochemically with polyclonal antiserum. Further application of these methods may offer potential for further identification of immunologically relevant cellular and serum antigens generated by these drugs.

Stem-cell factor, the kit ligand, induces direct degranulation of rat peritoneal mast cells in vitro and in vivo: dependence of the in vitro effect on period of culture and comparisons of stem-cell factor with other mast cell-activating agents

We report that stem-cell factor (SCF), the ligand of the receptor encoded by the c-kit proto-oncogene, is a potent activator of degranulation of rat peritoneal mast cells in vitro and in vivo. Freshly isolated, purified mast cells were relatively unresponsive to SCF (4-500 ng/ml) but progressively acquired responsiveness to this agent, assessed as serotonin (5-HT) release, during 48 hr culture in vitro. The cells showed a similar kinetic pattern of acquisition of responsiveness to anti-IgE but responded fully to calcium ionophore A23187 or compound 48/80 regardless of time in culture. Acquisition of mast cell responsiveness to SCF or anti-IgE was not due to serum factors or to recovery from the Percoll purification procedure. During culture, mast cell expression of the SCF receptor (SCFR) increased, and this may explain in part the increased responsiveness to SCF. However, surface IgE expression remained constant, and the increased responses to anti-IgE therefore must reflect changes in components of the secretion-coupling pathway that are activated subsequent to IgE cross-linking. The unresponsiveness of freshly isolated peritoneal mast cells to SCF or anti-IgE does not reflect a state of in vivo unresponsiveness, as peritoneal mast cells degranulated in vivo in response to these agents. We conclude that in terms of their responsiveness to SCF or anti-IgE, cultured tissue mast cells may be more representative than freshly isolated mast cells of secretory function in vivo, and therefore may be more appropriate for physiological or pharmacological studies of SCF- or IgE-dependent secretory responses.

Induced expression of mRNA for IL-5, IL-6, TNF-alpha, MIP-2 and IFN-gamma in immunologically activated rat peritoneal mast cells: inhibition by dexamethasone and cyclosporin A

We examined the capacity of purified rat peritoneal connective tissue-type mast cells (PMC) to express mRNA for several cytokines. Stimulation of PMC with anti-IgE for 4 hr induced the expression of mRNA encoding interleukin-5 (IL-5), IL-6, tumour necrosis factor-alpha (TNF-alpha), macrophage inflammatory protein-2 (MIP-2) and interferon-gamma (IFN-gamma). Unstimulated PMC expressed detectable mRNA for TNF-alpha but not for the other four cytokines. Incubation of PMC with cyclosporin A (CsA) or dexamethasone (DEX), each at 10(-6) M for 24 hr, significantly inhibited the induced expression of mRNA for each of the five cytokines, and also inhibited release of biologically active TNF-alpha. Throughout these experiments mRNA levels of the housekeeping gene G3PDH were not altered by stimulation with anti-IgE or incubation with CsA or DEX. We conclude that immunological activation of rat PMC induces gene expression of several cytokines and that expression of these genes can be inhibited by immunosuppressive drugs.

Activation and hapten inhibition of mast cells sensitized with monoclonal IgE anti-penicillin antibodies: evidence for two-site recognition of the penicillin derived determinant

We utilized an in vitro mast cell activation assay and hapten inhibition of mediator release to characterize the fine specificity of two IgE anti-penicillin monoclonal antibodies (mAb). Cultured mouse mast cells were passively sensitized with IgE mAb anti-benzylpenicillin (BP) or anti-amoxicillin (AX) and challenged with a range of penicillin-human serum albumin (HSA) conjugates. Mast cells sensitized with IgE anti-BP degranulated in response to BP-HSA, but not to AX-HSA or ampicillin(AMP)-HSA, whereas mast cells sensitized with IgE anti-AX responded to AX-HSA but not to BP-HSA or AMP-HSA. Because BP, AX and AMP differ chemically only in the structure of their side chain, these results show that this part of the drug molecule is essential for recognition by IgE antibody. Unexpectedly, although IgE-sensitized mast cells responded to only one penicillin in protein-conjugated form, antigen-induced degranulation was inhibited by the monomeric derivative of more than one penicillin. Furthermore, antigen activation of IgE-sensitized cells was inhibited, although less potently, by haptens representative of the specific penicillin side chain or the binuclear portion of the drug molecule. These patterns of recognition and hapten inhibition were also seen in solid-phase enzyme-linked immunosorbent assay (ELISA), although all haptenic inhibitors were approximately 100 times less potent in the ELISA compared to the mast cell assay. To explain these findings we propose a model in which IgE binding to penicillin-protein antigen is dependent on recognition of two distinct epitopes on the drug molecule: the first comprising the side chain, and the second comprising the binuclear portion plus the proximal region of the side chain. This two-site hypothesis provides a generally applicable model of antibody recognition of penicillins and provides a rational basis for understanding the specificity and cross-reactivity of IgE-mediated allergic reactions to penicillins.

Compounds that induce autoimmunity in the brown Norway rat sensitize mast cells for mediator release and interleukin-4 expression

Brown Norway (BN) rats given mercuric chloride (HgCl2), gold (Au) salts or D-penicillamine develop a T helper 2 (Th2) cell-mediated autoimmune syndrome. The recent observation of tissue injury within 24 h of HgCl2 treatment suggested the involvement of a non-T cell. We therefore examined the effect of these compounds on rat mast cells in vitro. Incubation of BN rat peritoneal mast cells with HgCl2 enhanced the release of serotonin in response to IgE cross-linking agents. Mast cells from Lewis rats, a strain not susceptible to the autoimmune syndrome in vivo, were affected to a lesser extent. The effect was observed with purified BN mast cells, suggesting a direct action. Similar effects were seen with D-penicillamine in the presence of copper ions, a combination that produces hydrogen peroxide, and Au. HgCl2 caused significant induction of interleukin (IL)-4 mRNA in mast cells from BN, but not Lewis rats. The data demonstrate a novel enhancing effect of a number of compounds on mast cell mediator release, and an inducing effect of HgCl2 on mast cell IL-4, expression. These findings are consistent with our hypotheses that mast cells may contribute to early tissue injury, and also, via production of IL-4, may initiate and/or augment, the Th2 response in the BN rat model of chemical-induced autoimmunity.

Rat connective tissue-type mast cells express MHC class II: up-regulation by IFN-gamma

We studied MHC class II gene expression and its regulation by IFN-gamma in purified rat peritoneal connective tissue-type mast cells. Mast cells were cultured with or without recombinant rat IFN-gamma (70 ng/ml) for 48 hr and analyzed by RT-PCR for expression of mRNA encoding MHC class II and by fluorescence flow cytometry for surface expression of MHC class II protein product. Levels of MHC class II mRNA and cell-surface protein product in untreated mast cells remained constant throughout the culture period but increased progressively after treatment with IFN-gamma such that by 48 hr levels were significantly greater than those in untreated cells. Dual labeling confirmed that MHC class II product was coexpressed with IgE (a mast cell marker). To conclude, rat connective tissue-type mast cells express mRNA and surface product for the MHC class II gene which can be up-regulated by IFN-gamma.

Effects of interleukin-4 or stem cell factor on mast cell mediator release and cytokine gene expression

We have investigated the capacity of interleukin (IL)-4 or stem cell factor (SCF) to induce direct mediator release from rodent peritoneal mast cells, and also to induce or regulate cytokine gene expression in the human HMC-1 mast cell line. SCF, but not IL-4, induced low levels of serotonin release from mouse or rat peritoneal mast cells; rat mast cells acquired enhanced responsiveness to SCF during culture. IL-4, but not SCF, enhanced ionomycin-induced transcription and secretion of several genes, including the cytokines IL-3, IL-4, granulocyte/macrophage-colony-stimulating factor, IL-8 and the receptor for IL-6 in the human HMC-1 mast cell line.

IL-4 enhances IL-3 and IL-8 gene expression in a human leukemic mast cell line

We examined the capacity of interleukin (IL)-4 to induce or enhance the expression of certain cytokines in resting and activated cells of the HMC-1 human leukemic mast cell line. The HMC-1 mast cells were cultured with or without recombinant human IL-4 and then activated with the calcium ionophore ionomycin. Stimulation of non-IL-4-treated cells with ionomycin (10 microM) for periods of 30 min to 8 hr induced expression of mRNA encoding IL-3, IL-4 and IL-8 but was without effect on levels of mRNA for tumour necrosis factor (TNF)-alpha or beta-actin. Culture of the cells with IL-4 (100 ng/ml) for 24 hr led to a small increase in resting levels of mRNA for IL-3 and IL-8 but not for IL-4, TNF-alpha or beta-actin. More notably, the IL-4 treatment produced a pronounced elevation of mRNA for IL-3 and IL-8 when the cells were subsequently activated with ionomycin. The IL-4 treatment produced a negligible effect on IL-4 mRNA, and no effect on TNF-alpha or beta-actin mRNA levels in ionomycin-activated cells. Quantitation of cDNA by competitive polymerase chain reaction (PCR) revealed that the IL-4 treatment produced a sixfold increase in ionomycin-induced levels of cellular IL-3 mRNA, a fourfold increase in induced IL-8 mRNA and less than a twofold increase in induced IL-4 mRNA. The IL-4 treatment led to a 15- to 20-fold increase in ionomycin-induced secretion of IL-3 product and a doubling of induced IL-8 product. These effects of IL-4 were not associated with increased mast cell numbers. We conclude that IL-4 alone is a weak activator of IL-3 and IL-8 gene expression in mast cells, but is able to enhance activation signals in stimulated mast cells leading to transcription and secretion of these two cytokines.

Mast cell recovery following chronic treatment with compound 48/80

Histochemical and functional properties of mast cells (MC) in Brown Norway rats recovering from chronic treatment with the MC secretagogue compound 48/80 were examined. In the skin, treatment for 5 days with compound 48/80 resulted in a marked decrease in MC subpopulations defined by differential alcian blue/safranin staining. Both safranin-positive connective tissue MC and alcian blue staining MC were reduced in number. This was accompanied by significant decreases in skin histamine and rat MC serine protease I contents and a loss of specific IgE-mediated passive cutaneous anaphylaxis (PCA) activity. The PCA reaction did not return to normal before 2 months after stopping treatment and only when the numbers of safranin-positive connective tissue MC and skin histamine content reached pretreatment levels. The subepidermal alcian blue staining MC not eliminated by the compound 48/80 treatment were formalin resistant (unlike alcian blue staining mucosal MC of the intestine) and apparently played no role in the PCA response. MC numbers, histamine levels, and rat MC serine protease I content of the tongue were similarly decreased by compound 48/80. In contrast, mucosal MC of the gut were unaffected by the secretagogue treatment.

Interactions of IFN-gamma with IL-3 and IL-4 in the regulation of serotonin and arachidonate release from mouse peritoneal mast cells

We have examined the interactions between interferon-gamma (IFN-gamma), interleukin-3 (IL-3) and interleukin-4 (IL-4) in the regulation of IgE/antigen-induced secretory responses of mouse peritoneal mast cells. The cytokines were added either alone or in various combinations to cultured mast cells sensitized passively with IgE antibody. In experiments with unfractionated peritoneal cells (containing approx. 1% mast cells), IL-3 and IL-4 enhanced in an additive manner antigen-induced release of serotonin (5-HT), while IFN-gamma inhibited release regardless of whether IL-3 and/or IL-4 were present. In experiments employing mast cells purified to > 90%, IL-3 and IL-4 retained their enhancing activities whereas the inhibitory effect of IFN-gamma was considerably diminished. Nevertheless, IFN-gamma still inhibited significantly IL-4-enhanced secretion. The effects of IL-3 and IL-4 +/- IFN-gamma on arachidonate release were identical to those seen for 5-HT release, indicating that the secretion of both preformed mediators and newly synthesized eicosanoids is regulated in a similar way by these cytokines.

A western blot approach to detection of human plasma protein conjugates derived from D-penicillamine

OBJECTIVES

To develop and apply an immunochemical approach to the study of drug-plasma protein conjugates derived from the anti-arthritic drug D-penicillamine (DP).

METHODS

An antiserum with specificity for protein-conjugated DP was raised in a rabbit. Plasma samples from patients receiving DP or from incubations of isolated normal plasma with DP were analysed for DP-derived conjugates by Western blotting using the anti-drug antibody.

RESULTS

A single DP-positive protein band was detected in plasma samples from 15/16 patients with rheumatoid arthritis receiving DP but in none of 20 patients of similar disease status who had not taken DP. The positive band appeared in patients' plasma during the course of treatment with DP. It was seen under nonreducing but not reducing conditions indicating that the drug is disulphide linked to the protein. The drug-modified protein migrated to a position intermediate between the trailing edge of albumin and the leading edge of transferrin (both non-reduced) suggesting a molecular weight of between 66 and 77 kDa. Incubations of normal human plasma, but not purified albumin or transferrin, with low concentrations of DP generated the same distinct band plus several less intense DP-positive bands.

CONCLUSIONS

Drug-plasma protein conjugates derived from DP in vivo and in vitro can be detected immunochemically by the Western blot method. Theories of DP immunotoxicity have implicated antigenicity of the drug, but this is the first immunochemical demonstration of a potential DP-derived antigen in human plasma. The method we describe may have application to studies of the relationship between DP antigenicity and toxicity.

Cytokine-mast cell interactions: relevance to IgE-mediated chemical allergy

Recent work has shown that certain cytokines (inducible secreted proteins) are potent regulators of mast cell development and secretory function. We know also that sensitization of mice to chemical allergens induces T cell-dependent immune responses in which cytokines play an important role. Combining these observations, we postulate that in vivo T cell responses might influence, via the production of cytokines, the behaviour of mast cells in situ. In support of this hypothesis we have found that mast cells isolated from chemical allergen-sensitized mice show enhanced responsiveness to IgE-dependent activation in vitro. This effect is seen with chemical allergens that are either contact or respiratory sensitizers in man. Although respiratory and contact allergens cannot be distinguished according to their ability to modulate mouse mast cell function in vivo, they can be separated on the basis of their differential ability to induce specific IgE-dependent mast cell sensitization. In conclusion, the mouse may offer a useful model for investigating and predicting the potential of chemicals to act as mast cell promoting agents and/or respiratory sensitizers.

Induction of an auto-anti-IgE response in rats. IV. Effects on mast cell degranulation

Induction of an auto-anti-IgE (auto-aIgE) response in the rat inhibits both total and specific IgE production and alters the distribution of mast cell (MC) subpopulations identified by differential Alcian blue/safranin staining. We have extended these observations by characterizing the auto-aIgE antibodies and determining their effects on MC degranulation in vitro and in vivo. An auto-aIgE response was induced in bacillus Calmette-Guérin (BCG)-primed rats by injecting a conjugate of highly purified rat IgE myeloma (IR2) coupled to tuberculin-derived purified protein derivative (PPD). Anti-IgE autoantibodies were almost exclusively IgG2a. The intradermal injection of auto-aIgE into untreated rats induced local MC degranulation as shown by a strong immediate skin response. Histologically there was evidence of significant degranulation of safranin staining connective tissue MC (SMC) in the skin but not of the Alcian blue staining MC (ABMC) in the sub-epidermal region. The induced degranulation was epsilon-chain specific; immunopurified anti-idiotypic antibodies raised to the IgE IR2 myeloma had no MC degranulating activity. When administered locally, auto-aIgE inhibited a subsequent passive cutaneous anaphylaxis (PCA) response elicited by anti-ovalbumin IgE. In addition, the PCA response was significantly decreased in animals with an ongoing auto-aIgE response. Immunopurified auto-aIgE also induced histamine release in vitro from rat peritoneal MC. These results are discussed in the context of naturally occurring autoantibodies to IgE present in patients with allergic disease.

Induction of mast cell sensitization by chemical allergens: a comparative study

In previous investigations we have shown that chemical allergens of different classes induce in mice qualitatively divergent immune responses. Respiratory allergens provoke substantial increases in total serum concentration of IgE. In contrast, contact allergens which are known or suspected not to cause respiratory sensitization or which at most have only a very limited potential to do so, have little or no effect on total serum IgE. Such differences, we propose, provide a novel approach for the prospective identification of chemicals with potential to cause respiratory allergy. In the absence of a robust method for the direct measurement of respiratory hypersensitivity reactions in mice we have sought in the present study to determine whether the IgE responses induced in mice by respiratory allergens are specific and of sufficient magnitude to cause the active sensitization of mast cells in vivo, a prerequisite for immediate hypersensitivity, including acute-onset respiratory hypersensitivity. Topical exposure of BALB/c mice to concentrations of > or = 10% of the human respiratory allergen trimellitic anhydride (TMA) caused the specific sensitization of peritoneal mast cells in situ as measured by the conjugate-induced release of [3H]-5-hydroxytryptamine in vitro. Experiments were performed also with 2,4-dinitrochlorobenzene (DNCB), a contact allergen that fails to induce respiratory hypersensitivity. Treatment of mice with concentrations of DNCB of comparable immunogenicity failed to cause mast cell sensitization. These data demonstrate that a known human chemical respiratory allergen induces in mice specific mast-cell-sensitizing IgE antibody and reinforce the value of the mouse as a model for the evaluation of respiratory sensitization potential.

Sensitization of mice to chemical allergens modulates the responsiveness of isolated mast cells to IgE-dependent activation

It is known that the release of granule-associated inflammatory amines by isolated mouse tissue-type mast cells is subject to regulation in vitro by a number of cytokines that are produced during the immune response. In this study we investigated whether mast cell secretory function might also be subject to regulation in vivo during active sensitization. Mice were sensitized with one of three chemical allergens (trimellitic anhydride, TMA; 2,4-dinitrochlorobenzene, DNCB; or oxazolone) all of which induce contact sensitization and one of which (TMA) in addition causes immediate hypersensitivity. Peritoneal mast cells isolated from treated mice and sensitized passively with IgE released a greater proportion of cellular serotonin (5-HT) on stimulation either by anti-IgE or by specific antigen than did cells isolated from vehicle-treated controls. These results show that the function of mast cells is susceptible in vivo to regulatory influences that result from induction of an immune response.

Regulation of mouse peritoneal mast cell secretory function by stem cell factor, IL-3 or IL-4

We examined whether three cytokines that promote mouse mast cell development, the c-kit ligand stem cell factor (SCF), IL-3, or IL-4, also can directly stimulate or modulate mouse peritoneal mast cell (PMC) mediator release. Challenge of purified PMC with rat rSCF164 at 20 to 100 ng/ml for 30 min induced a modest release of serotonin (5-HT), whereas IL-3 or IL-4 did not directly stimulate 5-HT release. Experiments in which PMC were exposed to each cytokine for 15 min, and then to DNP-HSA Ag or anti-IgE antibody for a further 15 min, showed that SCF, but not IL-3 or IL-4, had an additive effect on the 5-HT release induced by either of the IgE cross-linking agents. In longer term experiments, SCF (0.16 to 500 ng/ml), IL-3 (2.5 to 100 ng/ml), or IL-4 (0.06 to 2.5 ng/ml) was added to peritoneal cell cultures for 48 h, during which the cells were passively sensitized with IgE anti-DNP antibody. Incubation of either unfractionated or highly purified PMC preparations with each of the three cytokines resulted in a concentration-related increase in 5-HT release upon subsequent challenge of the cells with DNP-HSA Ag. However, after pretreatment of peritoneal cells for 48 h with each cytokine, only IL-4 (10 ng/ml) enhanced release of 5-HT induced by calcium ionophore A23187 (0.25 microM); IL-3 (100 ng/ml) had no effect, whereas SCF (100 ng/ml) significantly inhibited ionophore-induced release. Although IL-3 or SCF up-regulate responsiveness to IgE-dependent stimuli, we detected no effect of these cytokines on the binding of [125I]IgE to PMC. This suggests that the enhancing effects of SCF or IL-3 on IgE-dependent 5-HT release did not simply reflect changes in the amount of IgE bound to the cells. In conclusion, we found that SCF, IL-3, or IL-4 each exerted a different spectrum of stimulatory, costimulatory, or regulatory effects on the secretory function of mouse PMC.

Regulation of mouse peritoneal mast cell secretory function by stem cell factor, IL-3 or IL-4

We examined whether three cytokines that promote mouse mast cell development, the c-kit ligand stem cell factor (SCF), IL-3, or IL-4, also can directly stimulate or modulate mouse peritoneal mast cell (PMC) mediator release. Challenge of purified PMC with rat rSCF164 at 20 to 100 ng/ml for 30 min induced a modest release of serotonin (5-HT), whereas IL-3 or IL-4 did not directly stimulate 5-HT release. Experiments in which PMC were exposed to each cytokine for 15 min, and then to DNP-HSA Ag or anti-IgE antibody for a further 15 min, showed that SCF, but not IL-3 or IL-4, had an additive effect on the 5-HT release induced by either of the IgE cross-linking agents. In longer term experiments, SCF (0.16 to 500 ng/ml), IL-3 (2.5 to 100 ng/ml), or IL-4 (0.06 to 2.5 ng/ml) was added to peritoneal cell cultures for 48 h, during which the cells were passively sensitized with IgE anti-DNP antibody. Incubation of either unfractionated or highly purified PMC preparations with each of the three cytokines resulted in a concentration-related increase in 5-HT release upon subsequent challenge of the cells with DNP-HSA Ag. However, after pretreatment of peritoneal cells for 48 h with each cytokine, only IL-4 (10 ng/ml) enhanced release of 5-HT induced by calcium ionophore A23187 (0.25 microM); IL-3 (100 ng/ml) had no effect, whereas SCF (100 ng/ml) significantly inhibited ionophore-induced release. Although IL-3 or SCF up-regulate responsiveness to IgE-dependent stimuli, we detected no effect of these cytokines on the binding of [125I]IgE to PMC. This suggests that the enhancing effects of SCF or IL-3 on IgE-dependent 5-HT release did not simply reflect changes in the amount of IgE bound to the cells. In conclusion, we found that SCF, IL-3, or IL-4 each exerted a different spectrum of stimulatory, costimulatory, or regulatory effects on the secretory function of mouse PMC.

The cellular and molecular basis for divergent allergic responses to chemicals

Chemicals vary with respect to the nature of allergic reactions which they will elicit preferentially. A wide variety of environmental and industrial chemicals are known to cause allergic contact dermatitis (contact sensitivity). Some of these are able also to induce respiratory allergy. This article reviews the characteristics of immune responses to different classes of chemical allergens and the role which functional subpopulations of T helper (TH) cells and their soluble cytokine products play in the induction of allergic sensitization. In addition, new opportunities to identify and classify chemical allergens based upon characterization of divergent allergic responses is discussed.

Cycloheximide treatment of mouse mast cells inhibits serotonin release. Evidence of a requirement for newly synthesized protein in the exocytotic response

Treatment of mouse peritoneal mast cells and mouse bone marrow-derived cloned mast cells with the protein synthesis inhibitor cycloheximide led to a marked abrogation of serotonin (5-hydroxytryptamine; 5-HT) release induced by a range of activators including antigen, anti-immunoglobulin E (anti-IgE) antibody, calcium ionophore A23187, and the polycation polylysine. Significant inhibition (28%) of IgE-mediated secretion was attained after incubation of peritoneal cells for only 2 hr, and inhibition progressed over a 24 hr period, reaching greater than 80% after 15 hr. When peritoneal mast cells were exposed to cycloheximide and then washed and returned to culture conditions, a substantial recovery of responsiveness to anti-IgE was seen after 5 hr. Under the same conditions to those used in functional studies, cycloheximide inhibited protein synthesis, measured as incorporation of [35S]-methionine, by purified peritoneal mast cells and cloned mast cells to 18.5% and 7.9% of control levels, respectively. These results show that synthesis of new protein over a period of a few hours is required to render mast cells fully responsive to stimuli that act via the IgE receptor, and to certain other stimuli that are receptor-independent.

A T-cell response to the anti-arthritic drug penicillamine in the mouse: requirements for generation of the drug-derived antigen

Mice primed with the anit-arthritic drug D-penicillamine (DP) developed DP-specific T cells in the draining lymph nodes (DLN) which responded to drug-haptenated stimulator cells, but not to untreated control cells nor to free drug, in in vitro proliferation assays. The responder cells were CD4+ and the response was major histocompatibility complex (MHC) class II restricted. The conditions required to generate efficient stimulator cells for in vitro proliferation assays were investigated. Drug-haptenated syngeneic spleen cells, but not thymocytes, were able to stimulate T cells from DP-sensitized mice. However, prolonged incubations of spleen cells with DP were required to generate the drug-derived T-cell antigen. Further experiments revealed that the generation of a DP-derived antigenic determinant for T cells did not require intracellular processing, as stimulator cells pretreated with fixative or lysosomotropic agents before drug haptenation were as effective as untreated DP-haptenated cells in stimulating the responder cells to proliferative in vitro. These findings show that the protein-reactive drug DP can generate a cellular antigen that is capable of stimulating a T-cell response. Furthermore, the generation of this antigen appears to bypass conventional antigen processing, suggesting perhaps a direct chemical modification of cell surface molecules that are involved in immune recognition. This process may underlie adverse reactions to DP that are believed to be mediated by the cellular immune system.