Immunomodulation of mixed postbiotics produced from Lactiplantibacillus plantarum KLDS1.0318 and KLDS1.0386 in vitro and in vivo.

Postbiotics can modulate immune responses by regulating immune cell functions and promoting the secretion of immune-related cytokines. However, most studies have focused on postbiotics from single strains, while the effects of mixed postbiotics remain underexplored. This study used RAW 264.7 cells and cyclophosphamide-induced immunosuppressed mice to investigate the immunomodulatory effects of postbiotics derived from mixed Lactiplantibacillus plantarum (L. plantarum) (KLDS1.0318 + KLDS1.0386). In vitro, heat-inactivated mixed L. plantarum (HK-Mix) and its cell-free supernatant (CFS-Mix) exhibited no cytotoxic effects and significantly enhanced the phagocytic activity of RAW 264.7 cells, as well as the secretion levels of NO and cytokines (IL-6, IL-1β, and TNF-α) (P < 0.05). In vivo, HK-Mix and Post-Mix (HK-Mix + CFS-Mix) significantly alleviated cyclophosphamide-induced weight loss, increased immune organ indices, and promoted splenic lymphocyte proliferation and NK cell activity (P < 0.05). Principal component analysis revealed that HK-Mix and Post-Mix showed higher comprehensive scores in vitro and in vivo, respectively, and correlation analysis demonstrated positive correlations among indicators within each experimental setting. Therefore, mixed L. plantarum postbiotics exhibit promising immunomodulatory potential by enhancing macrophage phagocytosis, promoting the secretion of TNF-α, IL-1β, and IL-6, and improving splenic lymphocyte proliferation and NK cell activity.