IL-5 is essential for vaccine-induced protection and for resolution of primary infection in murine filariasis

The pathways conferring immunity to human filariases are not well known, in part because human-pathogenic filariae do not complete a full life cycle in laboratory mice. We have used the only fully permissive infection of mice with filariae, i.e., infection of BALB/c mice with the rodent filarial nematode Litomosoides sigmodontis. Our previous results showed that worm development is inversely correlated with Th2 cytokine production and eosinophilia. The scope of the present study was to directly elucidate the role of interleukin-5 (IL-5) and eosinophils in controlling the development of L. sigmodontis after vaccination and in primary infection. BALB/c mice immunized with irradiated third-stage larvae (L3) were confirmed to have elevated IL-5 levels as well as high subcutaneous eosinophilia and to attack and reduce incoming larvae within the first 2 days, resulting in 70% reduction of worm load. Treatment of vaccinated mice with anti-IL-5 antibody (TRFK-5) suppressed both blood and tissue eosinophilia and completely abolished protection. This demonstrates, for the first time in a fully permissive filarial infection, that IL-5 is essential for protection induced by irradiated L3 larvae. In contrast, in primary-infected mice, anti-IL-5 treatment did not modify filarial infection within the 1st month, most likely because during primary infection IL-5-dependent mechanisms such as subcutaneous eosinophilia are induced too late to disturb worm establishment. However, there is a role for IL-5 late in primary infection where neutrophil-dependent worm encapsulation is also under the control of IL-5. Received: 30 March 2000     

Injection of recombinant interleukin 3 hastens worm expulsion in mice infected with Trichinella spiralis

 The effects of interleukin 3 (IL-3) on worm expulsion were studied in mice infected with Trichinella spiralis. C3H/He mice were treated with a total of 10⁴ U IL-3 or saline by daily peritoneal injection from day-5 to day-1. Muscle larvae were given orally to both groups of mice on day 0. The muscle worm burden in infected mice was assessed on day 28. The worm burden in mice treated with recombinant IL-3 (rIL-3) was significantly suppressed as compared with that in control mice. A reduction in the worm burden was observed in mice treated with rIL-3 from day-5 to day-1 but not in those treated day 16 to day 20. This suggests that IL-3 could up-regulate the host defense response to intestinal worms but not to parenteral stage worms. When various doses of rIL-3 were given to mice and the intestinal worm burden was assessed on day 5, protection was observed only in mice treated with a total of 10⁴ U rIL-3 but not in those given either 3.5×10³ or 10³ U. A kinetics study on the recovery of intestinal adult worms showed that rIL-3 treatment hastened worm expulsion. The mucosal mast-cell response observed in the small intestine of rIL-3-treated mice was induced earlier and was greater than that seen in the control. The host defense response induced by rIL-3 could not be inhibited by treatment with anti-IL-4 or anti-IL-5 monoclonal antibody. Under such an experimental condition in this study, at least, the numbers of mast cells per villus crypt unit observed in mice treated with rIL-3 and anti-IL-4 antibody were slightly lower than those seen in mice treated with rIL-3, but the difference was not significantly different. These results suggest that IL-3 can induce the expulsion of T. spiralis worms without the cooperation of IL-4 or IL-5 in mice. Received: 24 March 1995 / Accepted: 20 May 1995     

Limited involvement of interleukin-6 in the pathogenesis of lethal septic shock as revealed by the effect of monoclonal antibodies against interleukin-6 or its receptor in various murine models.

Several studies in human patients and in laboratory animals have revealed a correlation between serum interleukin (IL)-6 levels and outcome in clinical sepsis and in related animal models, respectively. In the present study, two monoclonal antibodies were used to investigate the contribution of IL-6 in the lethal action of tumor necrosis factor (TNF) and of lipopolysaccharide (LPS) in mice. We studied the potential protective properties of an anti-murine (m) IL-6 antibody and of an anti-mIL-6 receptor antibody. In controlled experiments, we observed that both monoclonal antibodies conferred a dose-dependent protection to a lethal dose of mTNF. Detailed studies with the monoclonal antibodies indicate, however, that protection was no longer observed when the mTNF dose was slightly higher than the lethal dose. Likewise, the anti-IL-6 monoclonal antibody protected against injections of LPS at a lethal-dose concentration, but here too failed to protect against higher doses of LPS. The anti-IL-6 monoclonal antibody was unable to protect against mTNF in mice sensitized by galactosamine, the corticoid receptor antagonist RU38486 or human (h) IL-1 beta. Protection did not correlate with the serum concentrations of IL-6. Finally, we demonstrate that hIL-6 injection did not change the sensitivity of mice towards mTNF. We conclude that, although IL-6 levels may be of value as a marker for the outcome in septic shock, this cytokine contributes only marginally in the pathogenesis leading to death. The small, but real, contribution of IL-6 in some situations might be due to its ability to up-regulate the level of TNF receptors.     

IL-6 induced by double-stranded RNA augments allergic inflammation via suppression of Foxp3+ T-cell/IL-10 axis

Activation of innate immunity against viruses in the respiratory tracts affects the development of asthma. Most respiratory viruses generate double-stranded (ds)RNA during their replication. We recently showed that a low-dose administration of polyinosinic polycytidylic acid (poly IC), a mimetic of viral dsRNA, during allergen sensitization augments airway eosinophilia and hyperresponsiveness in mice via enhanced production of IL-13 from T cells. However, a phenotype of asthma under severer load of dsRNA remains unknown. d-galactosamine (d-GalN) is known as a strong sensitizer of poly IC. Mice were treated with poly IC plus d-GalN during allergen sensitization. A sublethal dose of poly IC/d-GalN augmented airway eosinophilia and CD4(+) T-cell accumulation in the lungs but not airway hyperresponsiveness. The augmented inflammation was associated with decreased IL-10 in the bronchoalveolar lavage fluid and decreased Foxp3(+) regulatory T cells in the lungs. Serum IL-6 was prominently higher in the mice treated with poly IC/d-GalN than in that with poly IC alone or d-GalN alone. Poly IC/d-GalN did not affect IL-17-producing T cells in the lungs. Poly IC/d-GalN failed to augment airway eosinophilia after anti-IL-10 receptor monoclonal antibody treatment during allergen challenge. Finally, anti-IL-6 receptor monoclonal antibody treatment before poly IC/d-GalN completely prevented the decrease of IL-10 and Foxp3(+) regulatory T cells and the augmentation of airway inflammation. These results indicate that enhanced production of IL-6 by poly IC/d-GalN induces the augmentation of allergic inflammation via suppression of Foxp3(+) regulatory T-cell/IL-10 axis. IL-6 may be a target for preventing asthma augmentation related to severe virus infection.     

Rebound eosinophilia after treatment of hypereosinophilic syndrome and eosinophilic gastroenteritis with monoclonal anti-IL-5 antibody SCH55700

BACKGROUND: Hypereosinophilic syndrome and eosinophilic gastroenteritis with peripheral eosinophilia are characterized by sustained eosinophilia and eosinophil-mediated tissue damage. Although treatment with the humanized monoclonal anti-IL-5 antibody SCH55700 resulted in improvement of eosinophilia and clinical symptoms in 6 of 8 of patients with hypereosinophilic syndrome or eosinophilic gastroenteritis with peripheral eosinophilia for as long as 12 weeks, eosinophil counts subsequently rose above baseline levels, accompanied by an exacerbation of symptoms. OBJECTIVE: To identify the mechanism underlying this rebound eosinophilia. METHODS: Purified eosinophils from patients or normal donors were cultured with IL-5, patient serum, and/or anticytokine antibodies, and eosinophil survival was assessed by flow cytometry. Serum and intracellular cytokine levels were measured by multiplex sandwich ELISA and flow cytometry, respectively. RESULTS: Before treatment with SCH55700, in vitro eosinophil survival in media and in response to recombinant IL-5 was similar in patients and normal donors. At 1 month posttreatment, the eosinophil survival curves were unchanged in 4 of 5 patients in media and in all 5 patients in response to recombinant IL-5. Normal eosinophil survival was prolonged in cultures containing posttreatment but not pretreatment sera (pretreatment vs posttreatment, 10.74% vs 73.02% live cells; P = .01). This posttreatment serum effect on eosinophil survival was reversed by the addition of the monoclonal anti-IL-5 antibody TRFK5. Although increased levels of serum IL-5 were observed at 1 month compared with 2 to 3 days posttreatment in 5 of 6 patients ( P = .04), intracellular cytokine analysis did not reveal increased production of IL-5 by peripheral blood mononuclear cells. CONCLUSIONS: The rebound eosinophilia after SCH55700 treatment is a result of a serum factor that enhances eosinophil survival. Reversal of this effect by the addition of antibody to IL-5 suggests that this factor may be IL-5 itself.     

In vivo administration of antibody to murine IL-5 receptor inhibits eosinophilia of IL-5 transgenic mice

We investigated the in vivo role of interleukin 5 (IL-5) and its receptor (IL-5R) in eosinophil growth and differentiation. When mice were administered IL-5 i.p., an increase in the number of eosinophils was observed within 5 days in peripheral blood and the peritoneal cavity. Hypereosinophilia was observed in IL-5 transgenic mice who displayed constitutive production of IL-5. A binding assay with 35S-labeled IL-5 revealed the presence of two classes of IL-5 binding sites (low and high affinity) on the surface of eosinophils. IL-5Rs on eosinophils were recognized using mAbs against murine IL-5R. When the IL-5 transgenic mice were passively administered with anti-murine IL-5R mAbs, the number of recognizable eosinophils in peripheral blood dropped within 5 days to normal levels. The antibody treatment also prevented the increase in the number of eosinophils in IL-5-injected mice. The inhibition of the above experimental eosinophilia was also observed by the passive administration of anti-IL-5 mAb. The results of the in vivo experiments clearly demonstrate that IL-5 plays an essential role in in vivo eosinophilopoiesis and may be acting on eosinophils or their precursors directly through IL-5Rs, resulting in preferential growth of this lineage of hematopoietic cells. It can also be stressed that IL-5 regulates a specific lineage of hematopoietic cells (eosinophils).     

Cytokine Regulation of Human Immune Response to Schistosoma mansoni: Analysis of the Role of IL-4, IL-5 and IL-10 on Peripheral Blood Mononuclear Cell Responses

The role of cytokines on the in vitro proliferative response of peripheral blood mononuclear cells (PBMC) from Schistosoma mansoni infected patients to soluble egg (SEA) and adult worm antigens (SWAP) were evaluated. The results obtained demonstrated that the proliferative response of PBMC from chronic intestinal (INT) patients to SEA and SWAP is increased by the blockage of IL-10 with specific monoclonal antibodies (MAb). The effects of these antibodies were readily reversed by the addition of recombinant IL-10. In contrast, no effect was observed on the PBMC response of acute and hepatosplenic patients (HS) in the presence of anti-IL-10. Anti-IL-4 antibodies decreased the PBMC response of the intestinal (INT) and HS individuals to SEA and SWAP, and the PBMC response of acute patients to SEA but not to SWAP. Addition of anti-IL-5 MAb did not decrease the PBMC response of acute patients to SEA or SWAP. These results suggested that IL-10 has an important role in the modulation of the immune response in chronic asymptomatic patients and that this cytokine may be an important factor in controlling morbidity.     

Contrasting roles for IL-10 in protective immunity to different life cycle stages of intestinal nematode parasites

Expulsion of the gastro-intestinal nematode Trichinella spiralis is associated with a pronounced mastocytosis mediated by a T helper (Th) 2 type response involving interleukin (IL)-4 and IL-13. Here we demonstrate that IL-10 is a key regulator of protective immune responses against T. spiralis in vivo. IL-10 knockout mice or normal mice treated with a neutralizing anti-IL-10 receptor antibody are highly susceptible to a primary T. spiralis infection and show significantly delayed adult worm expulsion. Depletion of IL-10 resulted in elevated Th1 and Th2 cytokine responses but significantly reduced numbers of mucosal mast cells in the jejunum. Interestingly, the increase in IFN-gamma detected in the absence of IL-10 resulted in increased immunity to larval stages. Hence, IL-10 has a negative effect on immunity to the tissue dwelling larval stages of T. spiralis but plays a significant biological role as an in vivo regulator of intestinal mast cell responses and is crucially involved in protection against adult stages of intestinal parasites in vivo.     

Susceptibility of BALB/c mice to nymphs and larvae of Ixodes ricinus after modulation of IgE production with anti-interleukin-4 or anti-interferon-γ monoclonal antibodies

BALB/c mice infested three times with nymphs or larvae of Ixdoes ricinus ticks do not acquire resistance as assessed by evaluation of both tick attachment and the weight of engorged nymphs or larvae. Tick challenge causes a gradual increase in total IgE antibody production from the first to the third infestation. Anti-tick IgG antibodies are never detected. When the mice are treated with anti-interleukin-4 (anti-IL-4) or anti-interferon-gamma (anti-IFN-γ) monoclonal antibodies (mAbs) 1 day before each infestation, they produce fewer or more IgE antibodies, respectively. No effect is observed on IgG antibodies. In IL-4-deficient mice, no IgE or IgG antibody is produced. However, these treatments and the use of IL-4-deficient mice have no negative effect on either tick attachment or the weight of engorged nymphs or larvae. Treatment with anti-IL-4 mAb and the use of IL-4-deficient mice inhibits and abolishes the switching of IgE, respectively, but these are apparently not sufficient to shift the response toward Th1 cells. Received: 18 July 1997 / Accepted: 12 November 1997     

Elimination of eosinophils using anti-IL-5 receptor alpha antibodies effectively suppresses IL-33-mediated pulmonary arterial hypertrophy

Interleukin (IL)-5 is a critical regulator of eosinophils and a therapeutic target for asthma. The administration of anti-IL-5 or anti-IL-5 receptor (IL-5R) antibodies has been shown to reduce eosinophil counts and ameliorate asthmatic symptoms in studies on animal models of allergy as well as in human clinical trials. In order to explore other potential clinical uses of IL-5R antibodies, we used an animal model of IL-33-mediated pulmonary arterial hypertrophy. We first generated chimeric monoclonal antibodies against the mouse IL-5 receptor α chain (IL-5Rα), which comprised an Fc region from human IgG1 and a Fab region from a previously established anti-mouse IL-5Rα monoclonal antibody. To investigate the role of antibody-dependent cell-mediated cytotoxicity (ADCC), chimeric antibodies that lacked ADCC were prepared. These antibodies recognized IL-5Rα to the same extent as the ADCC-sufficient antibodies. Administration of chimeric antibodies with ADCC resulted in the elimination of eosinophils from the lung and thus suppressed the development of arterial hypertrophy. This effect was attenuated in mice treated with antibodies lacking ADCC. Taken together, the results of this study provided a potential use for anti-IL-5Rα antibodies in the treatment of arterial hypertrophy, which leads to pulmonary hypertension.     

Innate and cognate mechanisms of pulmonary eosinophilia in helminth infection

Passage of helminth larvae through the lungs can cause pulmonary eosinophilia that may have evolved as a means of parasite attrition. If allergic responses represent a misdirected activation of this arm of the immune system, then mechanisms governing eosinophil recruitment during infection would be expected to be closely related to those seen in allergy. We studied primary Necator americanus infection and compared this to multiply-infected or vaccinated mice. The arrival of larvae in the lungs triggered rapid eosinophil recruitment, which was greatly enhanced in previously sensitized mice. Interestingly, the presence of larvae in the lung was sufficient to trigger eosinophil chemoattractant production, including the chemokines eotaxin and MIP-1alpha, and was not enhanced by prior exposure to the parasites. Infection stimulated IL-5 production in all groups; however, this and IgE production were greatly enhanced in sensitized animals. Elevated IL-5 increased bone marrow production of eosinophils, and eosinophilia was abrogated by treatment with anti-IL-5 antibody. Therefore, trapping of larvae in the pulmonary vasculature is sufficient to trigger eosinophil recruitment, by induction of chemokines and IL-5. Primed cognate Th2 immunity does not increase local chemokine production, but does increase IL-5 production, which greatly enhances the availability of eosinophils for recruitment to the lung.     

Anti-interleukin-5 (mepolizumab) therapy for hypereosinophilic syndromes

BACKGROUND: IL-5 is a cytokine critically involved in regulating several aspects of eosinophils including their production, activation, and tissue recruitment. As such, IL-5 may be involved in the pathogenesis of hypereosinophilic syndromes, a group of poorly treated diverse disorders characterized by sustained peripheral blood and/or tissue eosinophilia. OBJECTIVE: We aimed to assess the safety and efficacy of a humanized blocking monoclonal antibody against IL-5 (mepolizumab) in patients with several forms of hyper-eosinophilic syndromes. METHODS: We performed an open-label trial of anti-IL-5 in which 3 intravenous doses (10 mg/kg, maximum 750 mg) were administered at 4-week intervals to 4 patients with hypereosinophilic syndromes (defined by peripheral blood and/or tissue eosinophilia). The effects of treatment on safety, eosinophil levels (in peripheral blood and/or diseased tissue), pulmonary function, and quality of life were measured over a 28-week period. RESULTS: Anti-IL-5 was well tolerated in all patients and lowered peripheral blood eosinophil counts despite ongoing systemic glucocorticoid therapy. The decline in circulating eosinophil counts was sustained for at least 12 weeks after the last dose of anti-IL-5. In addition, anti-IL-5 improved clinical and quality of life measurements. In one patient with striking tissue eosinophilia (eosinophilic esophagitis), anti-IL-5 resulted in a 10-fold reduction in tissue eosinophil levels. CONCLUSIONS: These results suggest that anti-IL-5 is safe, effective in lowering eosinophil levels, and has potential glucocorticoid-sparing effects in patients with a variety of hyper-eosinophilic syndromes. As such, anti-IL-5 may have significant therapeutic potential for hypereosinophilic syndromes.     

Echinostoma caproni in rats: worm population dynamics and host blood eosinophilia during primary infections with 6, 25 and 50 metacercariae and resistance to secondary and superimposed infections

Hooded-Lister rats were inoculated with 6, 25, 50 or 100 metacercariae of the intestinal trematodeEchinostoma caproni. Worm establishment and the pattern of egg excretion were followed during the course of primary infections with 6, 25 and 50 metacercariae. Peripheral blood eosinophilia was followed at all infecton levels. After 1 month, worm recovery and faecal egg output showed a gradual decline with increasing duration of infection. High worm burdens were expelled later than smaller worm burdens, and egg output persited longer in animals exhibiting a high initial egg out-put. The level of blood eosinophilia increased with increasing degree of infection and with the level of egg output. A marked concomitant resistance to superimposed infection was observed on the challenge of rats harbouring 21- and 49-day-old infections with 50 metacercariae. In addition, rats were partially resistant to secondary infection at challenge day 14 following anthelmintic removal of primary 7-day-old infections with 50 metacercariae and were completely resistant at challenge day 7 following elimination of a primary 14-day-old primary infection.     

Anti-interleukin (IL)-4 and -IL-5 antibodies downregulate IgE and eosinophilia in mice exposed to Aspergillus antigens

The effect of multiple divided doses compared with single-dose injections of antibodies to murine interleukin (IL)-4 and IL-5 in their respective downregulation of IgE and eosinophilia developing in a model of allergic aspergillosis is investigated. BALB/c mice were exposed to Aspergillus fumigatus antigens (Af) before and along with anticytokine antibodies. The kinetics of blood eosinophils, eosinophil peroxidase (EPO) in bone-marrow cells, scrum levels of IgE and Af-specific antibodies, Af-induced cytokine production and mRNA, and lung histology were studied. The results indicate that only multiple anti-IL-5 antibodies were effective in maintaining baseline levels of blood eosinophils. Multiple anti-IL-4 antibodies also downregulated eosinophils in the bone marrow, lung, and peripheral blood, although to a lesser extent than in anti-IL-5 antibody-injected mice. Significant correlation between the EPO activity and the eosinophil numbers in anticytokine antibody-treated mice was observed. The different anti-IL-4 antibody treatments downregulated IgE to the same extent. We conclude that multiple divided doses of anti-IL-5 antibodies arc required to sustain normal eosinophil levels in murine allergic aspergillosis. This information may be significant in the therapy of pulmonary allergic diseases.     

Interleukin-17A is involved in enhancement of tumor progression in murine intestine

Interleukin (IL)-17A is a cytokine involved in neutrophilic inflammation but the role of IL-17A in anti-tumor immunity is controversial because both pro- and anti-tumor activities of IL-17A have been reported. We hypothesized that constitutive expression of IL-17A in intestinal environment modifies tumor growth. To address the issue, mice were inoculated into subserosa of cecum (i.c.) with murine EL4 lymphoma expressing a model tumor antigen, and tumor growth was monitored. IL-17A-producing cells were detected both in tumor mass and in normal intestinal tissue of i.c. tumor-bearing wild type mice. Tumor size in the wild-type mice was significantly higher than that in the cecum of IL-17A gene-knockout mice. Furthermore, anti-IL-17A monoclonal antibody treatment of wild-type mice resulted in decreased tumor size in the cecum. Model tumor-antigen-specific interferon-γ production was not modified in draining mesenteric lymph node cells in the absence or after neutralization of IL-17A. All the results suggest that constitutive expression of IL-17A in intestine enhances tumor growth, and anti-IL-17A antibody treatment is a candidate of a new anti-tumor immunotherapy against intestinal tumors.     

Trichinella spiralis infection in congenitally athymic (nude) mice. Parasitological, serological and haematological studies with observations on intestinal pathology.

In six experiments the course of a Trichinella spiralis infection in congenitally athymic (nu/nu) mice and their heterozygous thymus-bearing littermates (+/nu) was followed. In the +/nu mice worms were expelled at day 10 post infection. In nu/nu mice worms remained in the intestine until the end of the observation period (83 days post infection). In testing the yield of muscle larvae in +/nu and nu/nu mice 4--5 times more muscle larvae were isolated from nu/nu mice than from infected +/nu mice. The following phenomena were observed in +/nu mice only: anti-T. spiralis antibodies detected by immunofluorescence, intestinal plasma-cell production and intestinal eosinophilia. In nu/nu mice no blood eosinophilia was observed in contrast to the induction of eosinophilia both in infected +/nu and infected nu/nu mice reconstituted with thymuses from heterozygous littermates. Intra-epithelial lymphocytes, more numerous in +/nu than in nu/nu mice, were not attracted by Trichinella antigen. The data supported the hypothesis that worm expulsion is a T cell-dependent phenomenon. Plasma cell and antibody production as well as tissue and blood eosinophilia were shown to be thymus-dependent in a T. spiralis infection.     

Monoclonal antibody to CD4+ T cells abrogates genetic resistance to Haemonchus contortus in sheep.

The roles of CD4+ and CD8+ T cells in genetically determined resistance of sheep to Haemonchus contortus (a natural host-parasite relationship) was investigated by selectively depleting genetically resistant merino lambs of their CD4+ or CD8+ T cells by treatment with mouse monoclonal antibody (mAb) specific for the appropriate determinant before and during challenge infection. Administration of anti-CD4 mAb to genetically resistant lambs completely abrogated their expression of genetic resistance as indicated by significantly higher faecal egg output and worm burdens found in the CD4+ T-cell-depleted lambs compared with those of controls. Host responses associated with resistance to H. contortus including mucosal mast cell hyperplasia and tissue eosinophilia were also significantly suppressed in CD4-depleted lambs. The development of anamnestic anti-parasite antibody responses were also significantly inhibited by anti-CD4 mAb. Furthermore, anti-CD4 mAb abolished differences in host responses between genetically resistant and random-bred (susceptible) lambs. In contrast, depletion of CD8+ T cells had no effect on genetic resistance; faecal egg output, worm counts, mast cells and eosinophil responses in CD8-depleted lambs were not significantly different from those in controls. Together, these results suggest that CD4+ T cells play a pivotal role in mediating genetic resistance to H. contortus, and in the generation of mucosal mast cell hyperplasia, tissue eosinophilia and anti-Haemonchus antibody. CD8+ T cells appear to play no protective role. The possible mechanisms by which CD4+ T cells might mediate anti-parasite resistance are discussed.     

Role of CD4+ T lymphocytes and interleukin-5 in antigen-induced eosinophil recruitment into the site of cutaneous late-phase reaction in mice.

Previous studies suggested that the eosinophil recruitment into the site of cutaneous late-phase reaction (LPR) was dependent on IgE antibody and mast cells. In this study, we determined the role of CD4+ T cells and CD8+ T cells in causing antigen-induced eosinophil recruitment of LPR in mouse skin. Eosinophil infiltration into the subcutaneous tissue of ovalbumin (OVA)-sensitized BALB/c mice was biphasic, reaching the first peak at 6 h after the subcutaneous challenge with OVA and the second peak at 24 to 48 h. The in vivo depletion of CD4+ T cells by pretreatment with anti-L3T4 monoclonal antibody (mAb) significantly decreased the second peak (at 24 h and 48 h), but not the first peak (at 6 h), of OVA-induced eosinophil infiltration into the skin of OVA-sensitized mice. However, the depletion of CD8+ T cells by pretreatment with anti-Lyt-2 mAb had no significant effect on either the first peak or second peak of OVA-induced cutaneous eosinophilia. Pretreatment with anti-murine interleukin-5 (IL-5) mAb also decreased the second peak, but not the first peak, of OVA-induced cutaneous eosinophilia. In contrast to the inhibitory effects of depletion of CD4+ T cells and of anti-IL-5 mAb on the second peak of antigen-induced cutaneous eosinophilia, disodium cromoglycate and a selective antagonist for platelet activating factor (PAF) CV-6209 decreased the first peak of OVA-induced cutaneous eosinophilia in the mouse. These results indicate that CD4+ T cells, but not CD8+ T cells, cause the second peak of antigen-induced eosinophil recruitment of cutaneous LPR and that IL-5 mediates this eosinophil recruitment. In contrast, the first peak of antigen-induced eosinophil recruitment of cutaneous LPR is mediated by mast cells and PAF.     

In vivo treatment with anti-interleukin-13 antibodies significantly reduces the humoral immune response against an oral immunogen in mice.

Interleukin-13 (IL-13) is a cytokine which significantly enhances the proliferation and differentiation of B lymphocytes. We therefore evaluated its role in the formation of a humoral immune response in vivo. Upon oral immunization with the B subunit of Escherichia coli heat-labile enterotoxin (LT-B), rapid up-regulation of IL-13 mRNA expression in the mesenteric lymph nodes of LT-B intubated mice occurred. This result suggested that IL-13 might be involved in the formation of a mucosal antibody response against LT-B if this cytokine was in fact secreted. To test this possibility, the coding region for murine IL-13 was cloned into the pFLAG-1 expression vector. Recombinant murine IL-13 was purified from bacterial lysates and used as an immunogen to produce polyclonal anti-IL-13 antibodies. Groups of BALB/c mice treated in vivo with anti-IL-13 antibody 2 days before and on the day of oral immunization with LT-B had significantly reduced intestinal IgA and serum IgG and IgA anti-LT-B antibody responses when compared to mice treated with control antibody. Furthermore, groups of mice primed with LT-B and then treated with anti-IL-13 antibody prior to oral immunization with a second dose of LT-B also had significantly reduced intestinal IgA and serum IgG and IgA anti-LT-B antibody titres compared to controls. In vitro LT-B restimulation experiments using splenic mononuclear leucocytes isolated from LT-B primed mice treated with anti-IL-13 antibody demonstrated decreased expression of IL-4 and IL-13 mRNA and decreased IL-4 secretion when compared to controls. Together these results demonstrate an important role for IL-13 in the formation of a humoral immune response at mucosal surfaces.