Changes in intracellular cyclic adenosine monophosphate levels in peripheral blood leukocytes during immunotherapy with vespid venom

PDE3 Inhibition Reduces Epithelial Mast Cell Numbers in Allergic Airway Inflammation and Attenuates Degranulation of Basophils and Mast Cells

Epithelial mast cells are generally present in the airways of patients with allergic asthma that are inadequately controlled. Airway mast cells (MCs) are critically involved in allergic airway inflammation and contribute directly to the main symptoms of allergic patients. Phosphodiesterase 3 (PDE3) tailors signaling of cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP), which are critical intracellular second messenger molecules in various signaling pathways. This paper investigates the pathophysiological role and disease-modifying effects of PDE3 in mouse bone marrow-derived MCs (bmMCs), human LAD2- and HMC1 mast cell lines, human blood basophils, and peripheral blood-derived primary human MCs (HuMCs). In a chronic house dust mite (HDM)-driven allergic airway inflammation mouse model, we observed that PDE3 deficiency or PDE3 inhibition (PDE3i) therapy reduced the numbers of epithelial MCs, when compared to control mice. Mouse bone marrow-derived MCs (bmMCs) and the human HMC1 and LAD2 cell lines predominantly expressed PDE3B and PDE4A. BmMCs from Pde3^−/− mice showed reduced loss of the degranulation marker CD107b compared with wild-type BmMCs, when stimulated in an immunoglobulin E (IgE)-dependent manner. Following both IgE-mediated and substance P-mediated activation, PDE3i-pretreated basophils, LAD2 cells, and HuMCs, showed less degranulation than diluent controls, as measured by surface CD63 expression. MCs lacking PDE3 or treated with the PDE3i enoximone exhibited a lower calcium flux upon stimulation with ionomycine. In conclusion PDE3 plays a critical role in basophil and mast cell degranulation and therefore its inhibition may be a treatment option in allergic disease.

Birch pollen immunotherapy inhibits anaphylaxis to the cross-reactive apple allergen Mal d 1 in mice

BACKGROUND

Cross-reactive apple allergy is a common co-morbidity of birch pollen allergy, caused by the presence of a Bet v 1 homologue allergen in apple, Mal d 1. Treatment of tree pollen hay fever by immunotherapy is well established, but its effect on the accompanying apple allergy is debated.

OBJECTIVE

To establish a mouse model of birch pollen induced cross-reactivity to Mal d 1 and investigate the effect of birch pollen immunotherapy on the cross-reactivity to Mal d 1.

METHODS

Respiratory allergy was induced in Balb/c mice by intraperitoneal exposure to alum-adsorbed birch pollen extract (BPE) in combination with short or prolonged intranasal exposure to BPE. To evaluate the response to Mal d 1, mice were exposed intraperitoneally to Mal d 1. Immunoglobulin responses and cytokine production by splenocytes were measured by ELISA. Allergic symptoms were evaluated by measuring airway hyper-reactivity and hypothermia as a surrogate marker for anaphylaxis. Immunotherapy was performed subcutaneously with alum-adsorbed BPE.

RESULTS

Mice exposed to BPE develop cross-reactive IgE to Mal d 1. Early after exposure to BPE, this response is still weak and does not yet translate into anaphylaxis. Interestingly, later re-challenge with BPE increased cross-reactivity to a level where Mal d 1 exposure induced anaphylaxis. Cross-sensitization can also be induced by systemic Mal d 1 exposure. Birch pollen immunotherapy significantly reduced the anaphylactic response of mice to Mal d 1.

CONCLUSION & CLINICAL RELEVANCE

A mouse model mimicking birch pollen induced cross-reactivity to Mal d 1 was successfully established. In this model, birch pollen immunotherapy significantly ameliorated the anaphylaxis induced by Mal d 1. Our experimental data suggest that boosting of Mal d 1 recognizing immunoglobulins by BP SCIT is important for the amelioration of apple allergy in human.

Early suppression of basophil activation during allergen-specific immunotherapy by histamine receptor 2

BACKGROUND

Early desensitization of FcεRI-bearing mast cells and basophils has been demonstrated in allergen-specific immunotherapy and drug desensitization. However, its mechanisms have not been elucidated in detail. Histamine is one of the main mediators released on FcεRI triggering of basophils and mast cells, and it exerts its functions through histamine receptors (HRs).

OBJECTIVES

We sought to investigate HR expression on basophils of patients undergoing venom immunotherapy (VIT) and its effect on allergen, IgE, and FcεRI cross-linking-mediated basophil function and mediator release.

METHODS

Basophils were purified from the peripheral blood of patients undergoing VIT and control subjects and were studied functionally by using real-time PCR, flow cytometry and ELISA assays.

RESULTS

Rapid upregulation of H2R within the first 6 hours of the build-up phase of VIT was observed. H2R strongly suppressed FcεRI-induced activation and mediator release of basophils, including histamine and sulfidoleukotrienes, as well as cytokine production in vitro.

CONCLUSION

Immunosilencing of FcεRI-activated basophils by means of selective suppression mediated by H2R might be highly relevant for the very early induction of allergen tolerance and the so-called desensitization effect of VIT.

Hymenoptera venom immunotherapy

Subcutaneous venom immunotherapy is the only effective treatment for patients who experience severe hymenoptera sting-induced allergic reactions, and the treatment also improves health-related quality of life. This article examines advances in various areas of this treatment, which include the immunological mechanisms of early and long-term efficacy, indications and contraindications, selection of venom, treatment protocols, duration, risk factors for systemic reactions in untreated and treated patients as well as for relapse following cessation of treatment. Current and future strategies for improving safety and efficacy are also examined. However, although progress in the past few years has been fruitful, much remains to be accomplished.

Advances in hymenoptera venom immunotherapy

PURPOSE OF REVIEW

Venom immunotherapy is highly effective treatment, capable of improving health-related quality of life. This overview examines advances in various aspects of this treatment.

RECENT FINDINGS

New findings on the immunological mechanisms of the early and long-term efficacy of venom immunotherapy have been made. The decision to start and then to stop venom immunotherapy is best made on an individual case basis and should take into account medical and other factors, like the influence on patient quality of life. Venoms for use in immunotherapy should be selected according to the geographical distribution of each species and partial cross-reactivity between certain types of venom. Rapid protocols seem to be as safe as slower ones, though the major incidence of bee venom immunotherapy side-effects remains. Patients suffering from mast cell diseases seem to be at greater risk for an adverse reaction during treatment, without influencing its efficacy that much until the immunotherapy is actually ongoing. A number of new strategies for venom immunotherapy, mostly based on genetic engineering, have been described, and so far only a few have been used in humans.

SUMMARY

Although there has been progress in the past few years, much remains to be accomplished.