Development of in vivo and in vitro models to study the role of SIgA in modulating allergic types of immune responses.

Clémentine PERRIER (to September 2008), Anne-Christine THIERRY and Blaise CORTHESY, in collaboration with Annick Mercenier, Nestec Research Centre, Lausanne.

We have developed a model of food allergy using CT induced sensitization and a model of oral tolerance using the allergen ovalbumin (OVA) in the BALB/c background. In both models, we used the same administration mode, time frame and allergen doses in order to ensure a strict comparison of immune and physiologic responses at the systemic and mucosal level. Analysis of Abs, mast cells and cytokines underscored marked differences with previously published models. OVA-specific Abs (IgE, IgGs and IgA in serum and feces) were produced in sensitized mice exclusively. Upon intra-gastric challenge with OVA, sensitized mice developed anaphylactic reactions associated with a decline of temperature, diarrhoea, degranulation of mast cells, which were only moderately recruited in the small intestine, and increased intestinal permeability (Figure 1A-C). Cytokines produced by immune cells from sensitized mice included T-helper type 2 cytokines (IL-5, IL-13), but also IL-10, IFN- and IL-17. In contrast, all markers of allergy were totally absent in tolerized animals, and yet the latter were protected from subsequent sensitization, demonstrating that oral tolerance took place efficiently.

Together, this indicates that the mouse model is perfectly suited to investigate the effect of SIgA-bound OVA versus free OVA in the context of allergic responses.

In parallel, we designed an in vitro model in which polarized Caco-2 cell monolayers were conditioned by basolateral basophils and used to examine apical to basolateral transport of OVA by ELISA in the presence of probiotic microorganisms. Activation of basophils with translocated OVA reflecting permeability changes was measured by b-hexosaminidase release assay. Levels of pro-inflammatory IL-8 and dendritic cell-modulating thymic stromal lymphopoietin derived from Caco-2 cells exposed to bacteria were indicative of epithelial cell responsiveness. SIgA-based immune complexes will be compared with OVA alone to examine the protective function of SIgA toward the epithelial monolayer mimicking the intestinal barrier.presence of bound Ags, and adds to the known function of immune exclusion and mucus anchoring by SIgA.

Figure 1:
Allergic manifestations. Sensitized, tolerized andcholera toxin (CT) control groups were challenged intra-gastrically with 100mg ovalbumin (OVA) and allergic signs weremonitored. (a) Temperature variation observed 30 min afterchallenge. (b) Concentration of mouse mast cell protease-1(MMCP-1) before (small circles) and after (large circles)challenge. (c) Intestinal permeability is reflected by theconcentration of immunoreactive ovalbumin (OVA) present in theserum of mice one day before (small circles) and one hour afterchallenge (large circles). Sensitized mice are shown in black,tolerized in grey, and cholera toxin (CT) control in white.

References:

• Perrier C., Thierry A.-C., Mercenier A. and Corthésy, B. Allergen-specific antibody and cytokine responses, mast cell reactivity and intestinal permeability upon oral challenge of sensitized and tolerized mice. Clin. Exp. Allergy 2009, 40:153-162.
   
• Thierry A.-C., Bernasconi E., Mercenier A. and Corthésy B. Conditioned polarized Caco-2 cell monolayers allow to discriminate for the ability of gut-derived microorganisms to modulate permeability and antigen-induced basophil degranulation. Clin. Exp. Allergy 2009, 39:527-536.

Dernière modification le 31.08.2010 - Impressum - Informations juridiques