Establishment of an in vitro evaluation method for immunomodulatory functions of yeast strains

Saccharomyces cerevisiae, a widely studied yeast known for its industrial applications, is increasingly recognized for its potential in immunomodulation. This study aimed to systematically analyze and compare the immune-modulating properties of various S. cerevisiae strains under controlled experimental conditions. Three essential signals crucial for immune response activation were evaluated to elucidate the immunological responses elicited by these strains, i.e., dendritic cells (DC) cytokine secretion profiles, maturation status, and T cell polarization. Analysis of DC cytokine secretion profiles and maturation status revealed that all tested yeast strains induced DC activation, characterized by significant IL-6 secretion and modest IL-10 induction, as well as upregulation of MHC II molecules. Additionally, strain-specific effects were observed, particularly, strain AJM109 and Y1383 uniquely enhanced CD86 and PD-L1 expression, respectively, suggesting differential impacts on DC co-stimulatory signaling. Furthermore, strain Y1383 showed a unique capacity to support Treg-mediated immune suppression, demonstrating its potential in immune tolerance induction. These findings underscore the complexity of S. cerevisiae-based immune modulation and emphasize the importance of standardized evaluation methods to distinguish their specific immunological effects.