Quantitative IgE- and IgG-subclass responses during and after long-term ragweed immunotherapy

The role of IgG1 and IgG4 as dominant IgE-blocking antibodies shifts during allergen immunotherapy

BACKGROUND

The induction of allergen-specific IgE-blocking antibodies is a hallmark of allergen immunotherapy (AIT). The inhibitory bioactivity has largely been attributed to IgG₄; however, our recent studies indicated the dominance of IgG₁ early in AIT.

OBJECTIVES

Here, the IgE-blocking activity and avidity of allergen-specific IgG₁ and IgG₄ antibodies were monitored throughout 3 years of treatment.

METHODS

Serum samples from 24 patients were collected before and regularly during AIT with birch pollen. Bet v 1-specific IgG₁ and IgG₄ levels were determined by ELISA and ImmunoCAP, respectively. Unmodified and IgG₁- or IgG₄-depleted samples were compared for their inhibition of Bet v 1-induced basophil activation. The stability of Bet v 1-antibody complexes was compared by ELISA and by surface plasmon resonance.

RESULTS

Bet v 1-specific IgG₁ and IgG₄ levels peaked at 12 and 24 months of AIT, respectively. Serological IgE-blocking peaked at 6 months and remained high thereafter. In the first year of therapy, depletion of IgG₁ clearly diminished the inhibition of basophil activation while the absence of IgG₄ hardly reduced IgE-blocking. Then, IgG₄ became the main inhibitory isotype in most individuals. Both isotypes displayed high avidity to Bet v 1 ab initio of AIT, which did not increase during treatment. Bet v 1-IgG₁ complexes were enduringly more stable than Bet v 1-IgG₄ complexes were.

CONCLUSIONS

In spite of the constant avidity of AIT-induced allergen-specific IgG₁ and IgG₄ antibodies, their dominance in IgE-blocking shifted in the course of treatment. The blocking activity of allergen-specific IgG₁ should not be underestimated, particularly early in AIT.

Allergen-Specific Antibodies Regulate Secondary Allergen-Specific Immune Responses

Immunoglobulin E (IgE)-associated allergy is the most common immunologically-mediated hypersensensitivity disease. It is based on the production of IgE antibodies and T cell responses against per se innocuous antigens (i.e., allergens) and subsequent allergen-induced inflammation in genetically pre-disposed individuals. While allergen exposure in sensitized subjects mainly boosts IgE production and T cell activation, successful allergen-specific immunotherapy (AIT) induces the production of allergen-specific IgG antibodies and reduces T cell activity. Under both circumstances, the resulting allergen-antibody complexes play a major role in modulating secondary allergen-specific immune responses: Allergen-IgE complexes induce mast cell and basophil activation and perpetuate allergen-specific T cell responses via presentation of allergen by allergen presenting cells to T cells, a process called IgE-facilitated antigen presentation (FAP). In addition, they may induce activation of IgE memory B cells. Allergen-induced production of specific IgGs usually exerts ameliorating effects but under certain circumstances may also contribute to exacerbation. Allergen-specific IgG antibodies induced by AIT which compete with IgE for allergen binding (i.e., blocking IgG) inhibit formation of IgE-allergen complexes and reduce activation of effector cells, B cells and indirectly T cells as FAP is prevented. Experimental data provide evidence that by binding of allergen-specific IgG to epitopes different from those recognized by IgE, allergen-specific IgG may enhance IgE-mediated activation of mast cells, basophils and allergen-specific IgE⁺ B cells. In this review we provide an overview about the role of allergen-specific antibodies in regulating secondary allergen-specific immune responses.

Modulation of Immune Mediators with MQT-based Immunotherapy

OBJECTIVE: Assess immune and clinical changes with immunotherapy based on modified quantitative testing (MQT).

BACKGROUND: Immunotherapy promotes immunomodulation that occurs over several years. Quantitative testing offers the advantage of initiating immunotherapy with robust antigen concentrations. This study assessed whether changes in immune mediators and allergy symptoms occur rapidly using quantitative techniques.

METHODS: Sixteen allergic adults were tested using MQT. Subjects had serum drawn for immunoglobulins E and G4 (IgE, IgG4) to 3 antigens, Der p1, Der f1, and Fel d1, and for interleukins IL-1β, IL-2, IL-4, IL-5, IL-10, IL-12, and IL-13, and IL-1 receptor antagonist (IL-1RA). Subjects also completed the Sino-Nasal Outcome Test-20 (SNOT-20), the Allergy Outcome Scale (AOS), and the Rhinosinusitis Disability Index (RSDI). They underwent MQT-based immunotherapy and completed outcome measures again at 6 and 12 weeks.

RESULTS: Nine subjects completed the study. Analysis demonstrated significant increases in IgG4 levels to all antigens, significant decreases in serum levels of IL-1β and IL-5, and significant increases in levels of IL-1RA. Improvement was also noted in AOS and RSDI subscales.

CONCLUSION: Immunotherapy based on MQT demonstrates significant changes in immunoglobulin and cytokine levels by 12 weeks following initiation. In addition, improvement in symptom and quality-of-life measures occurs by 12 weeks. These findings support the rapid onset of clinical effects with MQT-based treatment of inhalant allergy.

EBM rating: C-4

Allergenic profile to Phleum pratense and immunological changes induced after grass allergen-specific immunotherapy

BACKGROUND

The introduction of molecular diagnoses has provided evidence of the existence of several different allergenic profiles in grass-sensitised individuals, reflecting the large number of allergens involved. This methodology has become a potent tool for a correct diagnosis and for the selection of the most appropriate immunotherapy. Based on these concepts, the objectives of this study were to determine the sensitisation profile of a grass-allergic population, and to treat them with specific immunotherapy.

METHODS

Patients suffering from rhinitis and/or asthma associated with grass pollen were recruited. The active group was treated with depigmented-polymerised allergenic extract of mixed grass pollen. sIgE and sIgG4 to Phleum pratense, and to its individual components (Phl p 1, 2, 4, 5b, 6, 7, 11 and 12) were determined at the beginning and end of the study.

RESULTS

The inclusion criteria were fulfilled by 139 individuals (36 in the control group and 103 in the active group). Phl p 1 (96.4%) and Phl p 4 (91.2%) were the most recognised allergens, and 15.3% of individuals had positive IgE to cross-reactive carbohydrate determinants. Levels of antigen-specific IgG4 increased significantly after treatment, and the IgE/IgG4 ratio decreased significantly in all allergens after receiving allergen-specific immunotherapy. Non-significant differences were observed in the control group.

CONCLUSIONS

A high percentage of sensitisation to Phl p 4 was observed. Immunological efficacy was studied by measuring sIgG4 levels and the IgE/IgG4 ratio before and after treatment. Sensitisation profiles should be taken into consideration to prepare the most appropriate immunotherapy containing all the relevant and needed allergens.

Basophil reactivity, wheal size, and immunoglobulin levels distinguish degrees of cow's milk tolerance

BACKGROUND

In our previous study about 75% of children with cow's milk allergy tolerated baked milk products, which improved their prognosis and quality of life.

OBJECTIVE

We sought to identify biomarkers of varying degrees of clinical tolerance among a cohort of children with cow's milk allergy.

METHODS

One hundred thirty-two subjects were initially classified as baked milk-reactive, baked milk-tolerant, or having "outgrown milk allergy" based on the results of oral food challenges. The baked milk-tolerant group was then divided into 3 groups based on the amount and degree of heat-denatured milk protein that they could tolerate. Serum was analyzed for allergen-specific IgE and IgG(4) levels, basophil reactivity was assessed in whole blood stimulated with serial 10-fold dilutions of milk protein, and skin prick tests (SPTs) were performed to commercial milk extract. Activated basophils were defined by using flow cytometry as CD63(bright)CD203c(+)CD123(+)HLA-DR(dim/-)CD41a(-)lineage(-). Data were analyzed by using the Jonckheere-Terpstra test.

RESULTS

Significant differences across the 5 clinical groups were seen for median casein- and milk-specific IgE levels, casein-specific IgG(4) levels, and casein IgE/IgG(4) ratios; milk-specific to nonspecific basophil activation ratio, median basophil reactivity, and spontaneous basophil activation (CD203c expression after stimulation with RPMI); and milk SPT wheal diameters. Casein- and milk-specific IgE level, milk-specific basophil reactivity, and milk SPT wheal diameter are all significantly greater among patients with milk allergy who react to baked milk than among those who tolerate it.

CONCLUSIONS

The majority of patients with milk allergy are able to tolerate some forms of baked milk in their diets. Different phenotypes of children with cow's milk allergy can be distinguished by casein- and milk-specific IgE levels, milk-specific basophil reactivity, and milk SPT mean wheal diameters. Spontaneous basophil activation is greater among patients with more severe clinical milk reactivity.

Immunological approaches for tolerance induction in allergy

Allergy is the consequence of an inappropriate inflammatory immune response generated against harmless environmental antigens. In allergic disorders such as asthma and rhinitis, the Th2 mediated phenotype is a result of loss of peripheral tolerance mechanisms. In cases such as these, approaches such as immunotherapy attempt to treat the underlying cause of allergic disease by restoring tolerance. Immunotherapy initiates many complex mechanisms within the immune system that result in initiation of innate immunity, activation of both cellular and humoral B cell immunity, as well as triggering T regulatory subsets which are major players in the establishment of peripheral tolerance. Though studies clearly demonstrate immunotherapy to be efficacious, research to improve this treatment is ongoing. Investigation of allergenicity versus immunogenicity, native versus modified allergens, and the use of adjuvant and modality of dosing are all current strategies for immunotherapy advancement that will be reviewed in this article.

Immunotherapy in food allergy

Food allergies are caused by immune responses to food proteins and represent a breakdown of oral tolerance. They can range from mild pruritus to life-threatening anaphylaxis. The only current consensus for treatment is food avoidance, which is fraught with compliance issues. For this reason, there has been recent interest in immunotherapy, which may induce desensitization and possibly even tolerance. Through these effects, immunotherapy may decrease the potential for adverse serious reactions with accidental ingestions while potentially leading to an overall health benefit. In this review, we discuss the mechanisms of food allergy and give an overview of the various immunotherapeutic options and current supporting evidence, as well as look towards the future of potential novel therapeutic modalities.

Birch pollen immunotherapy leads to differential induction of regulatory T cells and delayed helper T cell immune deviation

Correction of an imbalance between allergen-specific T cell subsets is considered a critical event in establishing allergen tolerance by specific immunotherapy (SIT). In a comprehensive, longitudinal study, distinct T cell populations and Ig subtypes were analyzed in subjects allergic to birch pollen during decisive time points of SIT (i.e., induction and maintenance phase), as well as in and out of birch pollen season. An increase in Bet v 1-specific, IL-10-secreting T cells, fulfilling the criteria of inducible type 1 regulatory T (Tr1) cells, was observed by the end of the induction phase; this resulted in a decreased ratio of allergen-specific IL-5(+) Th2/Tr1 cells. In contrast, CD4(+)CD25(+)CD127(low) regulatory T cell numbers did not change. Furthermore, enhanced concentrations of allergen-specific IgG Abs were observed, whereas allergen-specific IgE and IgA levels remained unchanged. After 1 y of SIT, a reduced ratio of allergen-specific Th2/IFN-gamma(+) Th1 cells was apparent. Although untreated and SIT-treated allergic subjects developed enhanced Th2 cell responses during birch pollen season, only SIT-treated patients experienced elevated numbers of allergen-specific Tr1 cells, which were associated with reduced skin prick test reactivity and diminished clinical symptoms. In coculture assays, allergen-specific Tr1 cells showed an IL-10- and dose-dependent inhibition of CD4(+)CD25(-) T effector cells. Thus, SIT has differential effects on regulatory T cell subsets, resulting in an early induction of allergen-specific Tr1 cells associated with an increase in allergen-specific IgG, and it leads to a delayed shift from an allergen-specific Th2- to a Th1-dominated immune response.

Injection and sublingual immunotherapy in the management of allergies affecting the unified airway

The spectrum of allergic disease involves both the upper and lower airways. Immunotherapy has been shown to produce immunologic changes that can result in the improvement of allergic diseases. Numerous clinical trials have demonstrated the effectiveness of injection and sublingual immunotherapy in the treatment of rhinitis and asthma. Recent data suggest that immunotherapy may have a role in preventing the development of new sensitizations or in decreasing the progression of allergic disease from rhinitis to asthma. Models of immunotherapy may therefore transition from symptom-relieving treatments to preventive methodologies for the management of allergic disease.

Allergen injection immunotherapy for seasonal allergic rhinitis

BACKGROUND

Allergic rhinitis is the most common of the allergic diseases. Despite improved understanding of the pathophysiology of allergic rhinitis and advances in its pharmacological treatment, its prevalence has increased worldwide. For patients whose symptoms remain uncontrolled despite medical treatment, allergen injection immunotherapy is advised. An allergen-based treatment may reduce symptoms, the need for medication and modify the natural course of this disease.

OBJECTIVES

To evaluate the efficacy and safety of subcutaneous specific allergen immunotherapy, compared with placebo, for reducing symptoms and medication requirements in seasonal allergic rhinitis patients.

SEARCH STRATEGY

We searched the Cochrane Ear, Nose and Throat Disorders Group Trials Register, the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library, Issue 1 2006), MEDLINE (1950 to 2006), EMBASE (1974 to 2006), Pre-MEDLINE, KOREAMED, INDMED, LILACS, PAKMEDINET, Scisearch, mRCT and the National Research Register. The date of the last search was February 2006.

SELECTION CRITERIA

All studies identified by the searches were assessed to identify randomised controlled trials involving participants with symptoms of seasonal allergic rhinitis and proven allergen sensitivity, treated with subcutaneous allergen specific immunotherapy or corresponding placebo.

DATA COLLECTION AND ANALYSIS

Two independent authors identified all studies reporting double-blind, placebo controlled randomised trials of specific immunotherapy in patients with seasonal allergic rhinitis due to tree, grass or weed pollens. Two authors independently performed quality assessment of studies. Data from identified studies were abstracted onto a standard extraction sheet and subsequently entered into RevMan 4.2.8. Analysis was performed using the Standardised Mean Difference (SMD) method and a random-effects model; P values < 0.05 were considered statistically significant. The primary outcome measures were symptom scores, medication use, quality of life and adverse events.

MAIN RESULTS

We retrieved 1111 publications of which 51 satisfied our inclusion criteria. In total there were 2871 participants (1645 active, 1226 placebo), each receiving on average 18 injections. Duration of immunotherapy varied from three days to three years. Symptom score data from 15 trials were suitable for meta-analysis and showed an overall reduction in the immunotherapy group (SMD -0.73 (95% CI -0.97 to -0.50, P < 0.00001)). Medication score data from 13 trials showed an overall reduction in the immunotherapy group (SMD of -0.57 (95% CI -0.82 to -0.33, p<0.00001)). Clinical interpretation of the effect size is difficult. Adrenaline was given in 0.13% (19 of 14085 injections) of those on active treatment and in 0.01% (1 of 8278 injections) of the placebo group for treatment of adverse events. There were no fatalities.

AUTHORS' CONCLUSIONS

This review has shown that specific allergen injection immunotherapy in suitably selected patients with seasonal allergic rhinitis results in a significant reduction in symptom scores and medication use. Injection immunotherapy has a known and relatively low risk of severe adverse events. We found no long-term consequences from adverse events.

Mechanisms of immunotherapy in allergic rhinitis

Allergic rhinitis is a common condition, but many people still experience suboptimal control of symptoms despite measures such as allergen avoidance, intra-nasal steroids and antihistamines. Specific immunotherapy (SIT) has been used for many years, but though many studies show clinical efficacy, its mechanism of action is still not clearly understood. Earlier studies showed changes in antibodies and it may be that SIT works through mechanisms that alter the ratio of 'protective' IgG4 to 'pro-allergenic' IgE. Other studies have shown a reduction in eosinophil migration to nasal mucosa as well as a reduction in inflammatory mediator release including basophil histamine release. More recent studies have proposed that SIT works through inhibition of T-helper 2 lymphocytes (Th2) which preferentially produce cytokines that promote allergic responses. SIT may cause a deviation from Th2 to Th1 (T-helper 1 lymphocytes) or may induce T-regulatory cells (T-regs) which inhibit Th2 responses directly or through inhibitory cytokines.

Expression of interleukin 4 receptors in bronchial asthma patients who underwent specific immunotherapy

BACKGROUND

Interleukin (IL) 4 and IL-13 are crucial cytokines for the development of allergic reactions and have been shown to modulate the function of monocytes and macrophages.

OBJECTIVES

To evaluate the expression of IL-4Rs on peripheral blood monocytes and in the serum of patients with bronchial asthma who underwent specific immunotherapy (SIT).

METHODS

The study was performed on 17 asthma patients with a typical clinical history and positive skin prick test results to Dermatophagoides pteronyssinus allergens. Five asthma patients who declined SIT were used as a comparator control group. Ten healthy persons served as negative controls. Flow cytometry analysis was performed on the whole blood samples using labeled monoclonal antibodies against CD14 and CD36 monocyte markers and against the CD124 alpha chain of IL-4R. The serum levels of soluble IL-4R were evaluated using an immunoenzymatic assay.

RESULTS

Compared with controls, bronchial asthma patients before SIT had a higher mean +/- SD percentage of CD14-positive cells that coexpressed CD124 (3.5% +/- 1.8% vs 18.6% +/- 7.9%; P < .01). After SIT, the mean +/- SD percentage of CD14 cells coexpressing CD124 decreased to 8.1% +/- 5.1%, which was significantly lower than before SIT (P < .01) but still significantly higher than in controls (P = .01). Changes in CD124 expression were associated with up-regulation of CD14 and down-regulation of CD36 expression on peripheral blood monocytes, suggesting that IL-4/IL-13-mediated signaling may be important for regulation of monocyte phenotype and function in asthma patients receiving SIT.

CONCLUSIONS

Even short courses of SIT are associated with a decrease in IL-4R expression on peripheral blood monocytes, which may cause decreased IL-4/IL-13-mediated effects in patients who undergo SIT.

The consideration of immunotherapy in the treatment of allergic asthma

BACKGROUND

Immunotherapy (IT) has undergone rigorous trials to evaluate its therapeutic benefit in the treatment of allergic respiratory disease. The tools of molecular biology have provided a framework with which to begin to understand the mechanistic effects of IT on the underlying inflammatory component of allergic respiratory disease.

RESULTS

The clinical relevance of these observations belies our understanding of allergic inflammation as the subsoil for the development of abnormal airway physiology, heightened bronchial reactivity, and the development of chronic asthmatic symptomatology.

CONCLUSIONS

IT provides the potential to downregulate this inflammatory cascade, reduce IgE antibody production, and attenuate symptoms. Conceptually, early intervention of allergic disease holds the most promise as a therapeutic intervention capable of arresting the progression of the disease, altering the severity of the disease, and/or preventing the development of the respiratory disease process.

Evaluation of the safety of an abbreviated course of injections of allergen extracts (rush immunotherapy) for the treatment of dogs with atopic dermatitis

OBJECTIVE

To evaluate the safety of an abbreviated course of injections of allergen extracts (rush immunotherapy) for the treatment of dogs with atopic dermatitis.

ANIMALS

30 dogs with atopic dermatitis examined at a veterinary dermatology referral practice for treatment with allergen-specific immunotherapy.

PROCEDURE

A catheter was placed in a vein in each dog. Dogs were constantly observed throughout the procedure. Allergen extracts were administered in increasing concentrations every 30 minutes for 6 hours to a maintenance concentration of 20,000 protein nitrogen units/ml. Epinephrine, oxygen, and emergency treatment were available as needed.

RESULTS

In 22 (73%) dogs, rush immunotherapy safely replaced the prolonged induction period (15 weeks) of weekly injections that consists of increasing concentrations of allergen extract. In 7 (23%) dogs, the induction period was abbreviated to 4 weeks. Of the 8 dogs that developed problems during rush immunotherapy, increased pruritus necessitated premature cessation of rush immunotherapy in 7, and 1 developed generalized wheals. Oral administration of prednisolone (1 mg/kg of body weight) resulted in resolution of adverse effects in all 8 dogs.

CONCLUSION AND CLINICAL RELEVANCE

Rush immunotherapy performed by personnel at a veterinary hospital is a safe method for treatment of dogs with atopic dermatitis.

The pharmacological basis of anti-IgE therapy

The treatment of asthma and allergic rhinitis using unique, humanized anti-IgE monoclonal antibodies with very particular binding specificities is now supported by the results of multiple phase II and III human clinical studies. The therapeutic efficacy of this approach is attributable to several pharmacological mechanisms. In addition to the expected effects of these monoclonal antibodies in neutralizing free IgE and inhibiting IgE production by B cells, several indirect biochemical and cellular effects have been uncovered during the course of the clinical trials. These include the accumulation of potentially beneficial IgE-anti-IgE immune complexes and the downregulation of the high-affinity IgE Fc receptors (FcvarepsilonRI) on basophils and mast cells. This article analyzes the structural basis of the specificity of the anti-IgE antibodies and pertinent results from in vitro experiments, animal model studies, and human clinical trials in an attempt to provide a cogent pharmacological interpretation of the therapeutic effects of anti-IgE therapy in both the near- and long term. The development of anti-IgE therapy over the past 10 years provides an interesting example of the emergence of a conceptually new, biotechnology-produced pharmaceutical.

Altered allergen binding capacities of Amb a 1-specific IgE and IgG4 from ragweed-sensitive patients receiving immunotherapy

BACKGROUND

The mechanisms for the effectiveness of allergen immunotherapy (IT) are not well understood. The binding potential for immunoglobulins is a function of both antibody concentration and affinity (K(A)).

PURPOSE

The purpose was to perform a cross-sectional preliminary study to investigate any differences in allergen-specific antibody affinity and concentration following ragweed immunotherapy by introducing a new concept of antibody binding capacity ([Ig] X K(A)).

METHODS

The binding capacity of allergen-specific IgE and IgG4 was determined for ragweed-allergic individuals undergoing ragweed immunotherapy and compared with the capacity of ragweed-specific IgE and IgG4 for allergic individuals not receiving immunotherapy.

RESULTS

The mean binding capacity for IgG4 after long-term immunotherapy was 1.6 log units higher (P < .0001) than for individuals not receiving IT. The binding capacity for allergen-specific IgE was 1.2 log units lower following long-term immunotherapy (P < .0001) compared with individuals not receiving ragweed IT.

CONCLUSIONS

We hypothesize that a primary effect of immunotherapy is to increase IgG4 binding capacity and concomitantly decrease IgE binding capacity.

The consideration of immunotherapy in the treatment of allergic asthma

Immunotherapy has undergone rigorous trials to assess its therapeutic benefit in the treatment of allergic respiratory disease. The tools of molecular biology have provided a framework with which to begin to understand the mechanistic effects of immunotherapy on the underlying inflammatory component of allergic respiratory disease. The clinical relevance of these observations belies our understanding of allergic inflammation as the subsoil for the development of abnormal airway physiology, heightened bronchial reactivity, and the development of chronic asthmatic symptoms. Immunotherapy provides the potential to downregulate this inflammatory cascade, reduce IgE antibody production, and attenuate symptoms. Conceptually, early intervention of allergic disease holds the most promise as a therapeutic intervention capable of arresting the progression of the disease, altering the severity of the disease, and/or preventing the development of the respiratory disease process.

Monitoring allergen immunotherapy of pollen-allergic patients: the ratio of allergen-specific IgG4 to IgG1 correlates with clinical outcome

BACKGROUND

Although allergen immunotherapy has been established as a treatment of type I allergy back in 1911, until now the underlying mechanisms have not been fully understood, nor are there any parameters which would allow one to monitor an ongoing treatment or to assess therapeutic success in the meantime.

OBJECTIVE

We wanted to define allergen-specific parameters that change due to treatment in correlation with the clinical outcome.

METHODS

We conducted a controlled study with grass pollen-allergic children and compared allergen-specific antibody titres before and 1 year after the onset of immunotherapy in contrast with untreated allergic and healthy children. Two recombinant forms of the major allergen group V of Phleum pratense (Phl p 5) served as model allergens.

RESULTS

No change in IgE levels and no significant reduction of skin prick test (SPT) reactivity were seen. On the other hand, a significant reduction of symptom scores in the treated group and a significant rise in allergen-specific IgG1, IgG2 and IgG4 due to the treatment could be observed, but in neither case could we establish a correlation between the increasing amounts of the single antibody classes and the reduction of symptom scores. But most interestingly, when comparing the ratio of IgG4 to IgG1 with the symptom scores, we found significant correlations. Nevertheless, treated allergic patients still differ considerably from healthy controls as nonatopics have hardly any measurable allergen-specific IgG antibodies and no IgE antibodies at all.

CONCLUSION

The ratio of IgG4 to IgG1 can serve as a valuable parameter that allows us to assess the success of immunotherapy already 1 year after the onset. The increase of specific IgG1 in relation to IgG4 during treatment reflects a possible influence of this subclass on the induction of tolerance towards allergens.

The kinetics of change in cytokine production by CD4 T cells during conventional allergen immunotherapy

BACKGROUND

The effect of conventional allergen immunotherapy on allergen-specific T lymphocyte cytokine production is incompletely understood, particularly during the initial phase of treatment.

OBJECTIVE

The purpose of this study was to prospectively follow the kinetics of change in CD4(+) T cell cytokine secretion during the course of conventional immunotherapy.

METHODS

Six allergic individuals were treated with extracts of Dermatophagoides farinae/Dermatophagoides pteronyssinus or with rye grass pollen (Lolium perenne) allergen, but not both, by using an internally controlled conventional immunotherapy protocol. CD4(+) T cells from peripheral blood were examined in vitro at varying intervals after the initiation of immunotherapy by stimulation with D farinae or L perenne group I antigen. The quantity of IL-4 and IFN-gamma produced and its relationship to clinical improvement was determined.

RESULTS

The ratio of allergen-specific IL-4/IFN-gamma production by CD4(+) T cells from 4 of 6 individuals receiving immunotherapy greatly increased during the period when the dose of allergen was increasing. However, after high-dose maintenance therapy was achieved, this ratio decreased in subjects responding clinically to, but not in those failing, immunotherapy. In addition, late-phase skin reactions and allergen-specific IgE levels in responding, but not in nonresponding, subjects diminished over the course of immunotherapy.

CONCLUSION

Conventional immunotherapy may initially exacerbate allergic disease by increasing allergen-specific IL-4 and allergen-specific IgE production. Later clinical improvement is associated with a reduction in allergen-specific IL-4 production and in allergen-specific serum IgE.

Physicochemical and immunologic characterization of low-molecular-weight allergoids of Dactylis glomerata pollen proteins

BACKGROUND

Orchard grass (Dactylis glomerata) pollen proteins were chemically modified by means of acid anhydrides (maleic and succinic anhydride) to obtain low-molecular-weight allergoids. Chemical modification in both cases led to the replacement of one positive charge (epsilon amino group of Lys) by one negative charge, yielding proteins with changed physicochemical properties in comparison to the native orchard grass-pollen proteins.

METHODS

Physicochemical characterization of derivatives was done by gel chromatography, SDS-PAGE, and isoelectric focusing. To examine the IgE-binding properties of these derivatives, we carried out immunoblotting. To examine the ability of derivatives to induce IgG production, we immunized rabbits. Skin prick testing with the allergoids was performed on 15 individuals allergic to orchard grass pollens and on two healthy subjects.

RESULTS

It was shown that the modified proteins retain their original molecular weights, but change pI to more acidic values. In the case of allergoids, a strong reduction in IgE binding was found. Immunization of rabbits with allergoids showed that the derivatives retain the ability to induce IgG production, and that the antisera obtained in such a way react to native (unmodified) extract. The ability of derivatives to induce allergic reaction was significantly reduced. The patients (86.6%) included in our study exhibited less than 50% of native extract response. Among them, 53.3% had no response to one or both allergoids.

CONCLUSIONS

These modification procedures yield allergoids with a reduced allergenic activity and preserved immunogenic potential suitable for use in immunotherapy.

Activation of B-lymphocytes during pollen season. Effect of immunotherapy

BACKGROUND

B-lymphocytes play an important part in the allergic reaction as producers of IgE antibodies.

OBJECTIVE

To investigate the cell surface expression of the activation antigens CD23, CD40 and HLA-DR on B-lymphocytes in birch pollen allergic patients before and during birch pollen season and to study the effect of immunotherapy.

METHODS

The study included 24 birch pollen allergic patients half of whom were treated with immunotherapy against birch pollen before the start of the season. Eleven of the 24 patients had asthma. Blood samples were taken and lung function was registered before the season began and before the immunotherapy treatment in January to February and during the season in May. The relative number of B-lymphocytes (CD19+) of the lymphocyte population and the cell surface expression of CD23, CD40 and HLA-DR on B-lymphocytes was measured by the use of flow cytometry.

RESULTS

In the control group of patients the relative number and concentration of B-lymphocytes, the cell surface expression of CD23, CD40 and HLA-DR on B cells, and the serum concentration of IgE increased during season compared with before season. In contrast, in the immunotherapy treated patients no changes in the number of B cells or cell surface expression of CD23, CD40 and HLA-DR were demonstrated.

CONCLUSION

The elevated expression of CD23, CD40 and HLA-DR on B cells, combined with increased levels of IgE in allergic patients during season could be explained by the effect of cytokines produced by activated TH2 cells. A shift from TH2 to TH1 cells might be the mechanism after the absence of signs of B-cell activation in immunotherapy treated patients. The prevention of increased cell surface expression on B cells by immunotherapy may constitute a significant mechanism behind the beneficial effects of immunotherapy in the treatment of pollen atopy.

A double-blind study of the discontinuation of ragweed immunotherapy

BACKGROUND

Immunotherapy effectively treats the symptoms of allergic rhinitis and improves its pathophysiology. We studied whether the effects of immunotherapy on the early response to nasal challenge with antigen and seasonal symptoms persist after discontinuation.

METHODS

Twenty subjects with ragweed allergy who were receiving immunotherapy and who had nasal challenges performed before initiation of treatment were selected. The patients had been receiving maintenance therapy with aqueous ragweed extract at a dose of 12 microg of Amb a 1 equivalent for a minimum of 3 years, at which point they were randomized to receive either placebo injections or to continue with the maintenance dose. Nasal challenges were performed before and 1 year after randomization. Nasal challenges were monitored by counting the number of sneezes and measuring histamine, N-alpha-tosyl-L-arginine methyl ester-esterase activity, and kinins in recovered nasal lavages. In the same year symptom diaries were collected during the ragweed season.

RESULTS

The initial immunotherapy significantly reduced responses to nasal challenge in both groups. The group continuing to receive active treatment showed no significant changes from the response before randomization. In contrast, the group randomized to placebo treatment showed a partial return of histamine, kinins, and N-alpha-tosyl-L-arginine methyl ester-esterase in nasal secretions and the numbers of sneezes. IgG antibodies to ragweed declined only in the group switched to placebo treatment. Seasonal rises of IgE antibodies to ragweed did not return during the first season after treatment was stopped. Symptoms reported during the ragweed season were not different between the groups.

CONCLUSIONS

One year after discontinuation of ragweed immunotherapy, nasal challenges showed partial recrudescence of mediator responses even though reports during the season appeared to indicate continued suppression of symptoms.

Immunologic effects of encapsulated short ragweed extract: a potent new agent for oral immunotherapy

BACKGROUND

Oral allergen immunotherapy with conventional allergens has not been a useful mode of treatment because of the lack of potency of allergens when administered by this route.

OBJECTIVE

To study the immunologic potency of short ragweed pollen extracts microencapsulated by a new technique administered orally to short ragweed pollen-sensitive humans and to establish the dose of oral microencapsulated short ragweed pollen extract required for these effects.

METHODS

Nine short ragweed pollen-sensitive patients were treated with a new oral agent for immunotherapy, microencapsulated short ragweed pollen extract, in an open study. The effectiveness of this treatment was determined by comparison to a group of nine matched short ragweed pollen-sensitive patients who received no treatment. Treated patients developed high titers of short ragweed-specific IgG and IgE antibodies and their expected seasonal increase in IgE antibodies was regulated. The dose of microencapsulated short ragweed pollen extract required to achieve these effects was only slightly higher than the dose of short ragweed pollen extract used in high dose subcutaneous immunotherapy. Furthermore, this dose was achieved in 7 weeks. There were no side effects other than mild gastrointestinal ones. The nine treated patients fared clinically better during the ragweed season than the untreated patients in this open study.

CONCLUSION

This study suggests that allergens microencapsulated by this new technique may make oral immunotherapy a practical mode of treatment.

IgG1 and IgG4 antibody responses to the dust mite Lepidoglyphus destructor in a naturally exposed farming population

The natural humoral immune response to the dust mite Lepidoglyphus destructor was assessed by comparing the IgG1 and IgG4 responses elicited in allergic (n = 44) and healthy (n = 16) individuals in a farming population chronically exposed to this allergen. With the aid of an immunoblotting technique and ELISA, the sera were analyzed for anti-L. destructor antibodies. While the majority of sera from the allergy group displayed several bands for both IgG1 and IgG4, the nonatopic healthy group was negative as analyzed in immunoblotting. When they were analyzed in ELISA, there was a significantly higher response in the allergy group than in the healthy group for IgG4, but not for IgG1. Taken together, these results imply that the immune system of individuals spared from allergic reactions to L. destructor not only lacks IgE antibodies but also seems largely to "ignore" these allergens/antigens despite exposure.