Introduction
Many dietary products have complex bioactive macro- and micronutrient composition. Recent research highlighted the anti-inflammatory and pain-reducing properties of egg yolk. These effects have been attributed to specific lipid-soluble extracts and water-soluble proteins. Th17 cells are involved in the several autoimmune and inflammatory diseases. In the present study, we demonstrate for the first time that egg yolks significantly inhibited the generation of Th17 cells. Furthermore, we hypothesized that the administration of egg yolks to imiquimod (IMQ) induced ear edema animal model would suppress Th17 cell differentiation and eventually ameliorate edema.
Materials and methods
Murine splenocytes were stimulated under Th17-polarizing conditions (immobilized anti-CD3 and anti-CD28 antibodies with IL-6 plus TGF-b for 5 days) with or without egg yolks water soluble fraction. The cells were characterized for helper T cell subsets by flow cytometric analysis. Furthermore, we investigated the effects of egg yolks on the IMQ induced ear edema model mouse. The C57BL/6J mice were divided into three groups, including a control group, low-dose (5% w/w) and high-dose (10% w/w) egg yolks groups. The mice in the control group were fed a standard diet, AIN-93G (Oriental Yeast Co. Ltd., Tokyo) during experimental period. In the two egg yolk groups, the diet was prepared by adding egg yolk powder (Kewpie Co. Tokyo) to the standard diet.
Results and discussion
Egg yolks water soluble fraction reduced the frequency of IL-17 producing CD4 T cells under the Th17-polarizing conditions in vitro. The mice fed egg yolks showed significant lower severity of ear edema than those fed the control diet. The inhibitory effect of egg yolks on Th17 differentiation exhibited in vivo. These data suggest that the suppressive effect of egg yolks water soluble fraction on Th17 differentiation might be useful for controlling unbalanced cytokine networks in autoimmune diseases.