Effects of soy and milk ferments on measures of innate immunity: a comparison of effects in normal and microgravity conditions

Abstract

Probiotics can influence intestinal responses and mucosal immunity either directly or indirectly through transient modulation of the endogenous microenvironment or the immune system. During space travel, astronauts experience various physiological stresses including putting them at risk for infections or inappropriate immune responses. Macrophages and monocytes are a key cell type involved in innate immunity. The effects of dairy milk or soy milk base fermented with S. thermophilus ST5 in combination with either B. longum R0175 or L. helveticus R0052 on the cell line U937 and all-trans retinoic acid differentiated U937 were examined under normal gravity and simulated microgravity conditions, in order to screen for effects on monocytes and macrophages. Soy and milk ferments demonstrated the ability to modulate certain aspects of the innate immune system, both in normal gravity and in simulated microgravity. These probiotics affected U937 cells differently depending on differentiation stage (monocyte or macrophage) and whether or not the cells were tested in regular gravity or in simulated microgravity conditions. These results provide insight into effects on this aspect of innate immunity and may provide guidelines to potential in vivo administration.