Increased Serum IgE Levels Research Articles

Reduced Serum Antibody Production and Acute Airway Inflammation in Interleukin 6-deficient Mice Challenged with Ovalbumin

ABSTRACT Background: IL-6 is a unique cytokine that has pro- and anti-inflammatory property. The purpose of this study was to clarify the role of IL-6 in the allergic airway inflammation. Methods: We challenged wild-type and IL-6-deficient mice with ovalbumin (OVA) inhalation after sensitization to OVA. Results: OVA challenge induced an intrapulmonary eosinophil infiltration and airway hyperresponsiveness in wild-type mice with increased serum IgE levels and enhanced intrapulmonary mRNA expression of T helper type 2 (Th2) cytokines, IL-5 and IL-13. IL-6-deficient mice developed a similar level of airway hyperresponsiveness despite an attenuated eosinophil infiltration and reduced elevation in serum IgE levels after oVa challenge. After OVA challenge, intrapulmonary IL-5 and IL-13 mRNA expression was less evident in IL-6-deficient mice than wild-type mice, while intrapulmonary IFN-y mRNA expression was more enhanced. Intravenous administration of anti-IL-6 antibodies during sensitization period in wild-type mice caused similar effects as observed in IL-6 deficient mice. Conclusions: Endogenous IL-6 may have important roles in Th2 polarization in sensitization period accompanied by eosinophil infiltration after acute exposure to aerosolized antigen.

Melkersson‐Rosenthal Syndrome

A 13 year‐old boy presented with a six‐month history of severe lip swelling. His past medical history was significant for eczema, multiple episodes of urticaria, and two episodes of anaphylaxis. Physical exam revealed severe cheilitis and labial angioedema. The cranial nerves were intact, and there was no evidence of a fissured tongue. A lip biopsy showed noncaseating granulomas throughout the dermis, with extension into the underlying skeletal muscle. Other features included dilated lymphatic channels, some closely approximating the granulomas, and a mild perivascular lymphoplasmacytic infiltrate. The epidermis was acanthotic with parakeratosis and focal acantholysis. Methenamine silver and acid‐fast stains were negative. A laboratory work‐up revealed an increased total eosinophil count, an increased serum IgE level, and a low complement C1q level. All other complement levels were normal. The patient also had an unremarkable chest x‐ray and a normal angiotensin converting enzyme level. This case represents the monosymptomatic form of Melkersson‐Rosenthal syndrome (MRS), also known as cheilitis granulomatosa Meischer. MRS is classically known as a triad of granulomatous cheilitis, facial nerve palsy, and fissured tongue. The onset of granulomatous cheilitis typically precedes the other symptoms, and when present alone, it is known as the monosymptomatic form of MRS.

Elevated expression of CD23 on peripheral blood B lymphocytes from patients with bullous pemphigoid: correlation with increased serum IgE

Background: Increased serum IgE levels are occasionally found in patients with severe bullous pemphigoid (BP). CD23, a low affinity Fc receptor for IgE, is mainly expressed on mature B lymphocytes. Studies have suggested that serum levels of soluble CD23 (sCD23) correlate with serum IgE levels and disease severity in BP. Objective: The purpose of our study is to examine whether the expression of CD23 is elevated in BP and whether this expression correlates with serum IgE levels and disease severity. Methods: We measured CD23 expression on B cells from patients with active BP, pemphigus vulgaris, pemphigus foliaceus, and atopic dermatitis (AD), as well as healthy control subjects, using a flow cytometer. Serum levels of IgE and sCD23 were also measured. Results: The expression of CD23 was significantly higher in BP patients compared with healthy control subjects ( P<0.05), whereas the levels were normal in the other bullous diseases. CD23 expression tended to be higher in severe BP compared with moderate BP, and the levels in severe BP were comparable to the levels in AD. Furthermore, CD23 expression correlated positively with serum IgE levels ( P<0.002), and the IgE levels were significantly higher in severe BP than in moderate BP ( P<0.01). CD23 expression in BP did not correlate with sCD23 levels. Conclusions: These results suggest that the up-regulated surface CD23 on B cells may be involved in IgE synthesis and inflammatory events in BP.

Epidermal allergen sensitization primes for aeroallergen induced eosinophilic esophagitis (EE)

Rationale Aeroallergen induced experimental asthma is accompanied by esophageal eosinophilia, which mimics the pathophysiological changes observed in individuals with eosinophilic esophagitis (EE). Since epidermal allergen sensitization has been recently implicated in the pathogenesis of experimental asthma, we examined the ability of epidermal sensitization to also result in esophageal eosinophilia. Methods We developed a novel model for skin sensitization in which 100μg of Aspergilus fumigatus antigen (Asp) or Saline was topically applied to the shaved upper backs of mice on six occasions over the course of two weeks. One week following sensitization, mice from both groups were given a single intranasal challenge with Asp or Saline (n=4 mice per treatment). Results Epidermal sensitization to Asp caused a 4 to 5-fold increase in serum IgE levels compared to Saline. Additionally, following a single intranasal Asp challenge, epidermal sensitization to Asp resulted in pulmonary inflammation and significantly elevated eosinophils in both bronchoalveolar lavage fluid (BALF) (57.6 ± 8.4×104 vs. 0.2 ± 0.17×104 per lung) and in the esophagus (24.3 ± 7 vs. 4.4 ± 3 per mm2) compared to Saline-challenged mice (p=0.001). Conclusion Epidermal sensitization can prime for aeroallergen induced eosinophilic esophagitis providing a novel link between cutaneous and mucosal allergic responses.

Exacerbated and prolonged allergic and non-allergic inflammatory cutaneous reaction in mice with targeted interleukin-18 expression in the skin.

Interleukin 18 induces both T helper 1 and T helper 2 cytokines, proinflammatory cytokines, chemokines, and IgE and IgG1 production. A role of interleukin 18 in inflammatory cutaneous reactions is still unclear, however. Here we generated keratin 5/interleukin 18 transgenic mice overexpressing mature murine interleukin 18 in the skin using a human keratin 5 promoter. In the contact hypersensitivity model, trinitrochlorobenzene elicited a stronger ear swelling in keratin 5/interleukin 18 transgenic mice compared with control littermate wild-type or immunoglobulin/interleukin 18 transgenic mice in which mature interleukin 18 was expressed by B and T cells under the control of the immunoglobulin promoter. Application of an irritant, croton oil, induced stronger and more sustained ear swelling in keratin 5/interleukin 18 transgenic mice than in immunoglobulin/interleukin 18 transgenic or wild-type mice. Repetitive topical application (weekly for six consecutive weeks) of trinitrochlorobenzene to their ears also elicited a stronger cutaneous inflammation in keratin 5/interleukin 18 transgenic mice than seen in immunoglobulin/interleukin 18 transgenic or wild-type mice. After these six trinitrochlorobenzene applications, the expression of interferon-gamma, interleukin-4, and CCL20 mRNA in the ear tissue was increased and dermal changes, such as acanthosis and eosinophilic, neutrophilic, and mast cell infiltration, were greater in keratin 5/interleukin 18 transgenic mice than in wild-type mice. Furthermore, the repetitive application elicited a significant increase in serum IgE levels and the number of B cells in the draining lymph node in keratin 5/interleukin 18 transgenic mice. These results suggest that overexpression of interleukin 18 in the skin aggravates allergic and nonallergic cutaneous inflammation, which is accompanied by high expression of T helper 1 and T helper 2 cytokines and chemokines in the skin.

Return of the eosinophil question in asthma

Return of the eosinophil question in asthma

STAT6-independent regulation of TH2 cell development

STAT6-independent regulation of TH2 cell development

Association of alcohol consumption with total serum immunoglobulin E levels and allergic sensitization in an adult population-based survey.

Chronic alcoholism is associated with increased total serum IgE levels. The study aimed to investigate the relationship between alcohol intake and both total serum IgE levels and allergic sensitization in a general adult population. A total of 720 subjects was randomly selected (stratified by age) from the population older than 18 years of A-Estrada (Spain) and invited to participate in the study. From 697 eligible subjects, 469 (67%, median age 54 years, range 18 to 92 years, 44% males, 75% of cases from a rural environment) agreed to participate. A battery of 13 skin prick tests to common aeroallergens was performed in all subjects. Cases with at least one positive test (n = 121, 26%) were considered to have allergic sensitization. The most frequent sensitisers were mites and pollens (24% and 10% of subjects, respectively). Total serum IgE was measured in 465 subjects (99%). Alcohol consumption was registered as the number of standard (approximately 10 g) drinking units habitually consumed per week. A total of 244 subjects (52%) were alcohol consumers (median intake, 14 units/week, range 1 to 147 units/week). Abstainers (n = 225, 48%) constituted the reference category. Alcohol consumption of more than 14 units/week was associated with an increase in serum IgE levels after adjusting for age, gender, allergic sensitization and smoking (P = 0.02). Alcohol consumption was not significantly associated with either overall allergic sensitization or mite sensitization after adjusting for age, gender and smoking. However, alcohol consumption of more than 14 units/week was associated with an increased prevalence of pollen sensitization (adjusted OR 3.15, 95% CI 1.19 to 8.34, P = 0.02). Alcohol consumption above a certain threshold is associated with an increase in total serum IgE levels. Alcohol consumption may also be associated with an increased prevalence of pollen sensitization.

From IgE to anti-IgE: where do we stand?

From IgE to anti-IgE: where do we stand?

Exposure to diesel exhaust enhances total IgE in non-atopic dockers.

Diesel exhaust particles (DEPs) containing polycyclic aromatic hydrocarbons stimulate the formation of IgE in humans following single and acute exposure. The aim of the present study was to ascertain whether long-standing occupational exposure to DEPs carries a risk of enhanced serum IgE, and of rhinitis or asthma. In this cross-sectional study, findings in 76 dockers were compared with those in 63 reference subjects. Among the dockers, drivers and laborers were exposed to diesel emission from forklifts or trucks in the ship-holds, where benzopyrene levels averaged 4.9 ng/m(3). Serum IgE levels were measured by the UNICAP method. Atopy, an evident source of high IgE levels, was assessed by the Phadiatop test. The subjects' clinical and occupational histories were collected. Interval variables were analyzed with Student's t- and Levene's F-tests. The odds ratio (OR) with the 95% confidence interval (CI) was obtained by the exact method at univariate and multivariate (logistic regression) analysis. In view of the large difference in serum IgE (P=0.00001) and the prevalence of respiratory diseases ( P=0.009) between atopic and non-atopic subjects, we analyzed their data separately. For non-atopic subjects, the risk of presenting high IgE was significantly higher (OR=11.4; CI=1.44-526; P=0.013) and the risk of respiratory disease was significantly lower (OR=0.09; CI=0.00-0.73; P=0.016) in drivers and laborers as a whole than in the reference subjects. None of the ORs was significant among atopic individuals. In non-atopic dockers, long-standing exposure to DEPs at concentrations similar to those in heavily polluted cities increased serum IgE levels but not the incidence of rhinitis or asthma.

E- and P-selectins are essential for the development of cockroach allergen-induced airway responses.

Peribronchial inflammation contributes to the pathophysiology of allergic asthma. In many vascular beds, adhesive interactions between leukocytes and the endothelial surface initiate the recruitment of circulating cells. Previous studies using OVA-induced airway hyperreactivity indicated that P-selectin, a member of the selectin family expressed by activated platelets and endothelium, contributed to both inflammation and bronchoconstriction. The current study used cockroach allergen (CRA), an allergen that induces asthmatic responses in both humans and mice, to further investigate the role of selectins in the development of peribronchial inflammation and airway hyperreactivity. P- and E-selectin mRNAs were detected in extracts of CRA-sensitized animals beginning shortly after intratracheal challenge with CRA. The P-selectin mRNA was transiently induced at early time points while up-regulation of the E-selectin mRNA was more prolonged. Mice with targeted deletions in E-selectin (E(-)), P-selectin (P(-)), and both genes (E(-)/P(-)) showed 70-85% reductions in airway hyperreactivity, peribronchial inflammation, and eosinophil accumulation. The P(-) and E(-)/P(-) groups showed the most profound reductions. The transfer of splenic lymphocytes from CRA-primed E(-)/P(-) into naive wild-type (WT) mice produced the same level of airway hyperreactivity as transfers from CRA-primed WT into naive WT hosts, indicating that peripheral immunization was similar. The observed changes in the selectin-deficient animals were not related to inadequate sensitization, because CRA priming and challenge increased serum IgE levels. Furthermore, pulmonary Th2-type cytokines and chemokines in the E-selectin(-/-) and WT animals were similar. The findings indicate that both P- and E-selectin contribute to CRA-induced peribronchial inflammation and airway hyperreactivity.

Serum IgE levels in Korean patients with human immunodeficiency virus infection.

BackgroundHuman immunodeficiency virus (HIV) infection results in a selective CD4+ T cell depletion and an impairment of T cell regulation. Despite the immune depletion, the progression of HIV infection is accompanied by the stimulation of antibody synthesis. Thus, the prevalence and amplitude of the increase of total serum IgE level and the relationship between the IgE levels and the degree of immunodeficiency were evaluated in patients with HIV infection.MethodTwenty-six Korean adults infected with HIV, in different stages, were evaluated for serum IgE level and CD4+ T cell count. Serum IgG, IgM and IgA levels were also determined. All subjects enrolled in this study denied an individual and familial history of atopic diseases. The possibility of parasitic infestation was also excluded by history and stool examination.ResultsThe mean serum IgE level was 473.5 IU/L with a standard deviation of 671.4 IU/L (range: 15.9–2000 IU/L) and increased serum IgE levels (>200 IU/L) were found in 38.5% of the study population. The mean serum IgG, IgA and IgM levels were 1,939.5±588.6 mg/dL (normal: 751–1,560 mg/dL), 388.9±216.7 mg/dL (normal: 82–453 mg/dL) and 153.6±75.3 mg/dL (normal: 46–304 mg/dL), respectively. The CD4+ T cell count was inversely correlated to the serum IgE level (r=−0.429, p<0.05), but not to the other isotypes of immunoglobulin.ConclusionSerum IgE levels are increased in adults with HIV infection and could be useful as a marker of disease progression. Further study is needed to elucidate the causes and clinical significance of these findings.

Increase in serum IgE levels following injection of syngeneic keratinocyte extracts in BALB/c mice.

Increased serum IgE levels are found in atopic diseases, especially atopic dermatitis. It is generally accepted that the high serum IgE levels are increased by exposure to exogenous antigens. However, exposure to antigens in the absence of proper adjuvants does not usually increase serum IgE. Here, we studied the involvement of skin factor(s) in increasing serum IgE. The soluble fractions were obtained from two keratinocyte cell lines, PAM 212 and KCMH-1, derived from BALB/c and CBA/J mice, respectively. These were injected subcutaneously into parental mice strains at 2-week intervals. The levels of serum immunoglobulins and the release of IgE in vitro from spleen cells were measured by ELISA. The biological activity of the increased serum IgE was assessed by sensitization of RBL-2H3 mast cells with serum. Six injections of PAM 212-derived fraction (PAM extract) consistently increased the serum levels of IgE, IgG1 and IgG2b, but not those of IgM, IgG2a, IgG3 or IgA in BALB/c mice. The high serum levels of IgE were sustained for at least 10 weeks after one or two injections of PAM extract. When RBL-2H3 cells were sensitized with the serum from mice injected with PAM extract, they released histamine in response to anti-IgE. Moreover, spleen cells of these mice produced significantly higher amounts of IgE than those of uninjected mice in the presence of IL-4 and anti-CD40 antibody. On the other hand, no significant increase in immunoglobulins was observed following injection of the soluble fraction from KCMH-1 cells in CBA/J mice. These results suggest that the release of the soluble fraction of keratinocytes and its exposure to immunologically competent cells may induce an increase in serum IgE levels by a Th2-dominant mechanism.

Genetics of the neuronal NO synthase (NOS1) in the etiology of bronchial asthma

The free radical nitric oxide (NO) is endogenously produced by enzymes known as NO synthases. NO in the airways is involved in a number of pathophysiological processes, such as airway inflammation, allergic reactions, and asthma. Asthma is a multifactorial disease that is caused by environmental and genetic factors. Genome wide screening approaches in families revealed evidence for linkage between chromosomal region 12q and allergic diseases, increased serum IgE levels as well as the development of asthma. The gene encoding for neuronal NOS (NOS1) is an attractive candidate gene for asthma, not only because it is localized in chromosomal region 12q24. Experimental studies in animals and humans suggest that NOS1 plays an important role in asthma. For instance, in a murine model of allergic asthma, NOS1 has been shown to be important for the development of bronchial hyperresponsiveness, since mice deficient for the nos1 gene were less responsive to airway challenge than both wild-type mice and mice deficient for the nos2 gene. Case-control studies in humans revealed allelic associations between polymorphic markers in the NOS1 gene and the diagnosis of asthma. Furthermore, increased concentrations of NO in the airways of asthmatics are closely related to the size of an intronic (AAT)(n)-repeat polymorphism in the NOS1 gene. The purpose of this review is to summarize studies that provide evidence for an involvement of NOS1 in the genetics of asthma.

MODULATORY ROLES OF RANTES IN IL-4 PRODUCTION BY HUMAN BLOOD CD4+T CELLS

An increase in serum IgE levels has been reported in several thrombotic cardiovascular diseases. Since such diseases are associated with the activation of platelets, we hypothesized that platelets are implicated in a mechanism leading to heightened IgE synthesis. To this end, we performed an in vitro investigation of the effects on IL-4 production caused by several bioactive substances potentially released from platelets. Human blood CD4+T cells from blood donors were stimulated with anti-CD3 antibody and costimulatory signals delivered via CD58 and CD80 in the presence or absence of IL-4. One of the following test substances was also included in the culture: platelet factor-4, β-thromboglobulin, platelet-derived growth factor, serotonin, platelet activating factor, or RANTES. The cells were restimulated in the absence of IL-4 and test substances. Among the six substances, RANTES alone exhibited significant effects on IL-4 production. RANTES enhanced IL-4 production in the presence of IL-4, whereas it suppressed IL-4 production in the absence of IL-4. The enhancing effect of RANTES was positively correlated with plasma IgE levels in the donors. We concluded that RANTES may induce IgE synthesis by increasing IL-4 production in individuals predisposed to high IgE responses. Our observations indicate a link between platelets and immune phenomena associated with increased IgE responses.

Abrogation of lung inflammation in sensitized Stat6-deficient mice is dependent on the allergen inhalation procedure.

Conflicting results have been reported about the role of Stat6 in allergen-induced airway inflammation. We have studied the influence of the allergen inhalation procedure on the inflammatory response using wild-type and Stat6-deficient mice generated on a C57BL/6 background. Animals were immunized i.p. on day 0 and 7 with ovalbumin (OVA) and then received aerosolized OVA or phosphate buffer saline challenge (acute on day 14; chronic on day 14, 15, 16, 17 and 18) before being sacrificed at different time points. Following an acute challenge, Stat6-deficiency fully abrogated the increase in serum IgE levels and the development of lung inflammation (inflammatory cell infiltration, IL-4 and IL-5 release, and increase in plasma leakage). Following chronic challenge, despite the absence of IgE, IL-4 and IL-5, Stat6-deficient mice develop a characteristic lung inflammation, although the intensity was smaller when compared with the wild-type mice. OVA-induced early bronchoconstriction was observed in wild-type mice only after chronic challenge, and this was totally abrogated in the Stat6-deficient animals. These results suggest that Stat6 signalling is essential for the development of allergic airway inflammation following an acute allergen exposure. However, in a more chronic situation, the airway inflammatory response seems to be only partially mediated by Stat6.

In vivo administration of IL-18 can induce IgE production through Th2 cytokine induction and up-regulation of CD40 ligand (CD154) expression on CD4+ T cells.

IL-18 is considered to be a strong cofactor for CD4+ T helper 1 (Th1) cell induction. We have recently reported that IL-18 can induce IL-13 production in both NK cells and T cells in synergy with IL-2 but not IL-12, suggesting IL-18 can induce Th1 and Th2 cytokines when accompanied by the appropriate first signals for T cells. We have now found that IL-18 can act as a cofactor to induce IL-4, IL-10 and IL-13 as well as IFN-gamma production in T cells in the presence of anti-CD3 monoclonal antibodies (mAb). IL-18 can rapidly induce CD40 ligand (CD154) mRNA and surface expression on CD4+ but not CD8+ T cells. The administration of IL-18 alone in vivo significantly increased serum IgE levels in C57BL/6 (B6) and B6 IL-4 knockout mice. Furthermore, the administration of IL-18 plus IL-2 induced approximately 70-fold and 10-fold higher serum levels of IgE and IgG1 than seen in control B6 mice, respectively. IgE and IgG1 induction in B6 mice by administration of IL-18 plus IL-2 was eliminated by the pretreatment of mice with anti-CD4 or anti-CD154, but not anti-CD8 or anti-NK1.1 mAb. These results suggest that IL-18 can induce Th2 cytokines and CD154 expression, and can contribute to CD4+ T cell-dependent, IL-4-independent IgE production.

A cluster of seven tightly linked polymorphisms in the IL-13 gene is associated with total serum IgE levels in three populations of white children

Background: Increased levels of total serum IgE are a strong risk factor for the development of asthma. IgE is also involved in host defenses against parasites and fungi. Linkage of total serum IgE with markers located close to the 3 Mb cluster of cytokine genes in chromosome 5q31 has been reported. IL-4 or IL-13 are regarded as essential for IgE synthesis. Objective: We tested whether polymorphisms in the IL-13 gene might explain the linkage between chromosome 5q31 and total serum IgE levels. Methods: We used denaturing HPLC to detect polymorphisms in overlapping PCR fragments of the IL-13 gene including promoter and 3′ untranslated regions. After sequencing was performed to identify the locations of the polymorphisms, PCR and primer-induced restriction site assays were used to genotype subjects in 3 unselected populations. Results: We report here 7 polymorphisms (6 novel) in IL-13. Four of these polymorphisms are tightly linked to a variant in the terminal portion of the coding region of the gene that results in a predicted amino acid change in residue 130 (Arg130Gln). The Gln form is strongly associated (P = .000002) with increased serum IgE levels in 3 different populations comprising a total of 1399 children. Two additional polymorphisms in the promoter region of IL-13 are more loosely linked to Arg130Gln and are also less significantly associated with total serum IgE levels. Conclusion: These data suggest that the Arg130Gln polymorphism in IL-13, or others in close linkage with it, is associated with the development of the elevated serum IgE phenotype. (J Allergy Clin Immunol 2000;105:506-13.)

Induction of IgE synthesis by genetically modified CD8 + T cells of a patient with adenosine deaminase deficiency

We have previously reported that an adenosine deaminase (ADA)-deficient patient treated with T cell-directed gene therapy had an increase in serum IgE levels, despite a marked inversion of the CD4/CD8 ratio. In the present report, we have analyzed the phenotypic and functional profiles of the patient's lymphocytes obtained during the clinical trial. In peripheral blood mononuclear cells (PBMC) that were freshly prepared from the patient, both CD4+ and CD8+ T cell subsets were negative for CD40 ligand (CD40L; CD154) and Fas ligand (FasL; CD95L), while CD20+ B cells constitutively expressed CD40 and HLA-DR and were negative for CD80, CD86 and Fas (CD95). The expression of CD23 was detected on the majority of CD20+ B cells and expression was upregulated by interleukin (IL)-4. Furthermore, the patient's PBMC, which already expressed both germline and mature Ce transcripts in vivo, spontaneously secreted IgE and responded to IL-4 with increased IgE production during in vitro culture. When stimulated with anti-CD3ε monoclonal antibody (mAb), CD8+ T cells from gene-transduced T cells displayed high production of interferon (IFN)-γ, low production of IL-4 and IL-13 and comparable levels of CD40L and FasL expression; however, lined CD8+ T cells from circulating T cells expressing the transgene produced IL-4 and IL-13 together with smaller amounts of IFN-γ and preferably expressed CD40L rather than FasL. Two such CD8+ T cells, in conjunction with the presence of IL-4, supported CD40L-mediated B cell proliferation and IgE production after stimulation and fixation. These results indicate that ADA-deficient B cells are functionally mature and that gene-transduced CD8+ T cells and lined CD8+ T cells containing the transgene exhibit T helper 0- and T cytotoxic (c) 2-like phenotypes, respectively. Our data also suggest that immuno-logic reconstitution with genetically modified CD8+ T cells may promote IgE production.

Protection in lambs vaccinated with Haemonchus contortus antigens is age related, and correlates with IgE rather than IgG1 antibody.

Protection by vaccination with excretory-secretory products (ES) from Haemonchus contortus, containing predominantly proteins of 15 and 24 kDa, against an experimental challenge infection depends on the age of the sheep. Vaccinated sheep 9, 6 or 3 months of age were protected for 83%, 77% and -34%, respectively. There was a significant difference in ES-specific serum IgE response but not in IgG1 response, after the last vaccination between the different age groups. In the protected 9-month-old animals, there was an increase up to 18 times the prevaccination levels, while the increase in the unprotected 3-month-old animals was at most 1.4 times. The 6-month-old animals showed an intermediate increase of approximately six times the prevaccination level. There was no correlation within the 9-month-old sheep between ES-specific IgE levels and protection, measured as worm burden. However, when the different age groups were combined, there was a positive correlation (r = 0.38) between protection and ES-specific IgE levels 1 week after the vaccination. At the end of the experiment, peripheral blood eosinophils and mast cell counts in abomasal tissue were also significantly higher in the vaccinated and challenged 9-month-old sheep than in the vaccinated and challenged 3-month-old or than in the 9-month-old sheep with challenge, but without vaccination. Increased serum IgE levels, eosinophilia and mucosal mast cell hyperplasia are the hallmarks of a Th2 response and were all demonstrated in protected, older sheep, but not in unprotected, younger sheep.