Induced Pluripotent Stem Cell-Derived Dendritic Cells Provide a Reliable In Vitro Platform for Functional Screening of Immunoregulatory Probiotics

The immunoregulatory effects of probiotics have been widely studied, particularly in maintaining immune balance. Conventional in vitro functional screening of probiotics relies on fresh donor-derived primary immune cells, which often exhibit significant inter-individual and temporal variability, limiting reproducibility and interpretation. As an alternative, human-induced pluripotent stem cell (iPSC)-derived dendritic cells were co-cultured with five probiotic strains in the current study to evaluate their immunomodulatory interactions. To assess whether cytokines produced by probiotic-stimulated dendritic cells can influence T cell differentiation, human CD4⁺ T cells were exposed to the conditioned medium derived from co-cultures. Enzyme-linked immunosorbent assay results demonstrated that iPSC-derived dendritic cells secreted cytokines at distinct concentrations in response to different probiotic strains, suggesting that these cells can distinguish between different microbial stimuli, and supporting their use in functional probiotic screening. Among the five strains tested, <i>Lactiplantibacillus plantarum</i> LPA-56, <i>Limosilactobacillus reuteri</i> RU-23, and <i>Lactobacillus fermentum</i> Fem-99 induced cytokine production levels that promoted the differentiation of the human CD4⁺ T cells into regulatory T cells. These findings demonstrate that iPSC-derived dendritic cells have immunomodulatory potential, are reliable for in vitro screening of probiotics, and offer a promising strategy for selecting potent immunoregulatory probiotic candidates.