Conditioned polarized Caco-2 cell monolayers allow to discriminate for the ability of gut-derived microorganisms to modulate permeability and antigen-induced basophil degranulation.
BACKGROUND
Food allergy is a common allergic disorder--especially in early childhood. The avoidance of the allergenic food is the only available method to prevent further reactions in sensitized patients. A better understanding of the immunologic mechanisms involved in this reaction would help to develop therapeutic approaches applicable to the prevention of food allergy.


OBJECTIVE
To establish a multi-cell in vitro model of sensitized intestinal epithelium that mimics the intestinal epithelial barrier to study the capacity of probiotic microorganisms to modulate permeability, translocation and immunoreactivity of ovalbumin (OVA) used as a model antigen.


METHODS
Polarized Caco-2 cell monolayers were conditioned by basolateral basophils and used to examine apical to basolateral transport of OVA by ELISA. Activation of basophils with translocated OVA was measured by beta-hexosaminidase release assay. This experimental setting was used to assess how microorganisms added apically affected these parameters. Basolateral secretion of cytokine/chemokines by polarized Caco-2 cell monolayers was analysed by ELISA.


RESULTS
Basophils loaded with OVA-specific IgE responded to OVA in a dose-dependent manner. OVA transported across polarized Caco-2 cell monolayers was found to trigger basolateral basophil activation. Microorganisms including lactobacilli and Escherichia coli increased transepithelial electrical resistance while promoting OVA passage capable to trigger basophil activation. Non-inflammatory levels of IL-8 and thymic stromal lymphopoietin were produced basolaterally by Caco-2 cells exposed to microorganisms.


CONCLUSIONS
The complex model designed in here is adequate to learn about the consequence of the interaction between microorganisms and epithelial cells vis-a-vis the barrier function and antigen translocation, two parameters essential to mucosal homeostasis. It can further serve as a direct tool to search for microorganisms with anti-allergic and anti-inflammatory properties.
Thierry
A-C
AC
R & D Laboratory of the Division of Immunology and Allergy, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland.
Bernasconi
E
E
Mercenier
A
A
Corthésy
B
B
D000818:Animals; D015549:Basophil Degranulation Test; D001491:Basophils / Q000276:immunology*; D018938:Caco-2 Cells; D045744:Cell Line, Tumor; D002463:Cell Membrane Permeability / Q000276:immunology*; D018920:Coculture Techniques; D016207:Cytokines / Q000276:immunology; D004926:Escherichia coli / Q000276:immunology; D005260:Female; D006801:Humans; D007413:Intestinal Mucosa / Q000276:immunology* / Q000382:microbiology*; D007778:Lactobacillus / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D018448:Models, Immunological; D010047:Ovalbumin / Q000276:immunology; D051381:Rats; D001619:beta-N-Acetylhexosaminidases / Q000032:analysis / Q000276:immunology
D016207:Cytokines; D010047:Ovalbumin; D001619:beta-N-Acetylhexosaminidases