Lacticaseibacillus paracasei LPB27: Effectively Enhances the Immune System by Improving the Intestinal Environment

Lacticaseibacillus paracasei LPB27 is a novel probiotic isolated from the intestines of healthy infants and young children. In this study, healthy mice were used as a model to systematically investigate the immune regulatory effects of LPB27 mediated by the microbiota–gut–immune axis, with a focus on evaluating its immune-enhancing potential. The safety evaluation showed that, at a dose of 0.50 g/kg/day, LPB27 caused no observable toxicity or adverse reactions. The evaluation of immune function indicated that in terms of cellular immunity, high-dose LPB27 increased the delayed-type hypersensitivity response and lymphocyte proliferation by 69% and 35%, respectively; in terms of humoral immunity, the number of hemolytic plaques and hemolysin titer increased by 42% and 36%, respectively; in terms of innate immunity, the carbon clearance capacity, CRBC phagocytosis rate, and macrophage phagocytic index increased by 13%, 33%, and 66%, respectively. Serum IgA, IgG, and IL-6 levels were significantly elevated in the high-dose group, whereas TNF-α was significantly reduced. Overall, LPB27 supplementation enhanced multiple immune indicators in mice. By comparing the gut microbiota composition at different time points, the study found that continuous intake of LPB27 was associated with an enrichment of multiple beneficial bacterial genera, including Akkermansia, Lactobacillus, Muribaculum, and Lachnospiraceae_NK4A136_group, together with a reduction of potentially pathogenic taxa, indicating an overall improvement in the intestinal microbial ecology. Changes in the abundance of these beneficial taxa were positively correlated with the predicted activation of metabolic pathways related to the synthesis of immune-related proteins. These findings support the further development of LPB27 as an immune-regulating ingredient.