Mechanisms of allergen-specific desensitization
Allergen-specific desensitization (SIT) is the most effective therapy for allergies. Although allergen-specific antibodies have an important role in the process, mechanisms of IgG-mediated inhibition of allergic reactions are not well defined.
We investigated mechanisms by which SIT-induced allergen-specific IgGs inhibit allergic reactions.
We generated mAbs that recognize 3 nonoverlapping epitopes of the major cat allergen Fel d 1. Each of the mAbs was produced as an IgE and different IgG isotype.
IgEs against 2 nonoverlapping epitopes on Fel d 1 are necessary and sufficient to sensitize mast cells for maximal FcepsilonRI signaling and degranulation on exposure to monomeric Fel d 1. IgE antibodies of a third specificity did not further increase mast cell degranulation, indicating that formation of large FcepsilonRI clusters are not required to induce maximal activation of mast cells. A single IgG that was specific for an epitope different from those recognized by the IgEs was a potent inhibitor of Fel d 1-mediated mast cell activation in vitro and in vivo. This inhibition required Fcgamma receptor-IIB. In human beings, IgGs of a single specificity were able to block degranulation of basophils from individuals with cat allergy. The inhibitory potential of these antibodies increased when larger allergen-IgG complexes were formed.
These data reconcile conflicting theories in the literature and might explain the reason IgE levels do not necessarily decrease during therapy, despite clinical efficacy. These findings have important implications for vaccine design.
Available from: Ana Lopes
- "Specific immunotherapy currently represents the only treatment that modifies the natural history of allergic rhinitis  with proven clinical effectiveness . However, despite the effects of this treatment being relatively well described, including important immunologic changes, like a modulation of the T-cell profile, with induction of allergen-specific Treg cells, that inhibit a proliferative and cytokine response to the allergen [31,32] or a local decrease in mast cell and basophil activity [33,34]. The systemic impact of SCIT in AR patients mono-sensitized to Dpt, as well as, the repercussion of long-term treatment on the effector cells of the allergic inflammation, are widespread under research. "
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Basophils are important effectors cells in allergic rhinitis (AR) since they are involved in immunoglobulin (Ig) E – mediated inflammation and in the release of pro-inflammatory mediators. Specific subcutaneous immunotherapy (SCIT) provides clear immunologic modulation in some immune cells, however its systemic effects on basophils are not well known.
Peripheral blood (PB) samples from 43 patients with allergic rhinitis mono-sensitized to Dermatophagoides pteronyssinus (Dpt) [33 of them under SCIT with allergoid Dpt extract, in maintenance dose (SCIT), with evaluation just before SCIT injection (SCIT-T0) and 4 hours later (SCIT-T4) and the other 10 Dpt allergic patients never having, in the past, undergone specific immunotherapy treatment (NSIT)], and 15 healthy age- and gender-matched controls (HG), were analyzed. For each sample, the total (t-IgE) and specific IgE (s-IgE) was performed, as well as, the relative frequency and absolute number of PB basophils and receptor-bound IgE and IgG expression were evaluated by flow cytometry and the Histamine N-methyltransferase (HNMT) and tryptase α/β1 (TPSAB1) gene expression was assessed by real-time PCR.
Higher levels of receptor-bound IgE were observed in SCIT patients, which are correlated with the levels of serum t-IgE and s-IgE, whereas no significant differences were observed for receptor-bound IgG. Regarding HNMT mRNA expression, significantly lower expression levels were detected in AR patients compared to HG, independently of type of therapy. Moreover a negative correlation was found between HNMT gene expression and time under SCIT. Conversely, tryptase gene expression was significantly up-regulated in NSIT when compared to HG; however in SCIT patients, tryptase gene expression was significantly decreased than in NSIT patients. No differences were found for any parameter between SCIT-T0 and SCIT-T4 with exception of a transient increased expression of tryptase in SCIT-T4.
PB basophils from patients with AR show altered functional features, which seems to be influenced by SCIT, suggesting that these cells could be useful to clarify the SCIT triggered mechanisms at a systemic level.
Allergy Asthma and Clinical Immunology 10/2013; 9(1). DOI:10.1186/1710-1492-9-40 · 2.03 Impact Factor
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ABSTRACT: An application of structural modeling and automated reasoning as
an intelligent software development environment for concurrent programs
is presented. This application, using an integration of software reuse
and theorem-proving methods, synthesizes an absolutely correct program
and increases software productivity. The concurrent programs are
described by a Prolog-based concurrent object-oriented language called
MENDEL/87. The functional part of the reusable component is generated by
structural modeling, and the synchronization part is synthesized from
temporal-logic specifications by the use of an automated-reasoning
mechanism. A description is also given of the MENDELS ZONE, implemented
on a Prolog machine, which is the working base of the method
System Sciences, 1989. Vol.II: Software Track, Proceedings of the Twenty-Second Annual Hawaii International Conference on; 02/1989
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ABSTRACT: We present an extension of the recently introduced hierarchical least mean square (HLMS) algorithm. The original algorithm suffers from two major drawbacks, namely the incapability to converge for every unknown channel and the dramatic deterioration of its performance as the number of levels increases significantly. To be able to cope with these, a novel global gradient descent algorithm is proposed. This algorithm converges for every class of unknown filters and it exhibits faster convergence than HLMS in any case.
Digital Signal Processing, 2002. DSP 2002. 2002 14th International Conference on; 02/2002
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