Egg Yolk Protein Water Extracts Modulate the Immune Response in BALB/c Mice with Immune Dysfunction Caused by Forced Swimming

The objective of this study was to determine the immunomodulatory effects of egg yolk protein–water extract (EYW) on splenocyte proliferation, cytokine secretion, immunoglobulin production, and NK cell cytotoxic activity in BALB/c mice. The forced swimming test (FST) was used to provide a model for suppressing immune regulation. The proliferation of B cells in the EYW supplementation group was significantly increased from the level to which it was reduced by the FST (from 40.9% to 81.8%, p < 0.05). EYW supplementation affected cytokine secretion of splenocytes. Levels of interleukin (IL)-2 and IL-10—as Th1 and Th2 cytokines, respectively—were decreased after the FST. However, EYW supplementation showed that secretion levels of these cytokines were significantly increased to pre-FST levels (p < 0.05). The production of immunoglobulins (IgA and IgG) was increased abnormally after the FST, whereas EYW supplementation significantly decreased it to pre-FST levels (p < 0.05). EYW supplementation also improved NK cell cytotoxic activity against YAC-1 tumor cells compared to the PC group (p < 0.05). These data suggest that EYW has potential as an immunomodulatory agent in the food and/or pharmaceutical industries.