Oral treatment with enrofloxacin early in life promotes Th2-mediated immune response in mice

Abstract

Background: Th2 lymphocytes play a crucial role in the development of allergy. These pathologies are caused by coordinated production of the cytokines IL-4, IL-5 and IL-13 that regulate the activity of eosinophils, basophils and B cells. According to the 'hygiene hypothesis', the reduced exposure to microorganisms favors allergy occurrence. The advances in medicine in the field of infection therapy promoted an increasing application of antibiotics which, apart from eliminating pathogens, also partially eliminate the microbiota.

Methods: Epicutaneous (EC) immunization with ovalbumin (OVA) followed by OVA challenge was used to study the influence of partial gut flora depletion by oral treatment with enrofloxacin on type-2 immune response.

Results: Current work describes the influence of enrofloxacin application on anti-OVA antibody production and cytokine synthesis in young and adult mice. Immune response in adult mice is less sensitive to modification of natural gut flora. We observed that enrofloxacin treatment of adult mice leads to significant decrease of anti-OVA IgG2a production while synthesis of anti-OVA IgE was not changed. The production of type-1 (IFN-γ), type-2 (IL-4, IL-5, IL-10, IL-13) and Th17-associated (IL-17A) cytokines was inhibited. On the other hand, treatment of young mice with enrofloxacin significantly upregulates the production of anti-OVA IgE and inhibits the secretion of anti-OVA IgG2a antibodies. Additionally, treatment with enrofloxacin early in life prior to OVA immunization results in increased production of type-2 (IL-4, IL-10 and IL-13) cytokines.

Conclusion: Our results clearly indicate that the immune system is more vulnerable to decreased bacterial exposure early in life that may promote development of allergy.

Keywords: Allergy; Antibiotic; Cytokines; IgE; Natural gut flora.