Effects of Limosilactobacillus fermentum KBL375 on Immune Enhancement and Gut Microbiota Composition in Cyclophosphamide-Induced Immunosuppressed Mice.

This study evaluated the immune-enhancing efficacy of Limosilactobacillus fermentum KBL375 isolated from the feces of healthy Koreans. KBL375-treated splenocytes showed enhancement of cytotoxicity against YAC-1 cells, the target of natural killer (NK) cells, with an increase in CD335, granzyme B, perforin, and interferon-gamma (IFN-γ). Oral administration of KBL375 in mice with cyclophosphamide (CP)-induced immunosuppression improved body weight and immune functions, including immune organ indices, lymphocyte proliferations, and immunoglobulin (Ig) A levels. Notably, KBL375 increased NK cell cytotoxicity and proportion in immunosuppressed mice. Perforin/IFN-γ expression levels, which indicated NK cell activation, were also increased in KBL375-treated mice. Furthermore, KBL375 led to an increase in beneficial microbes, such as Bifidobacterium, in the gut microbiome of immunosuppressed mice, fostering a favorable intestinal microbial environment. These comprehensive results suggest that KBL375 exhibits potent immune regulatory functions and positively influences the gut microbiota, implying its potential as a probiotic agent for immune enhancement.