Immune Boosting Effect of Limosilactobacillus Reuteri in Immunocompetent C57BL/6J Mice

Probiotics are well-known to be directly or indirectly involved in the host immune system. In this study, we analyzed the immune-boosting effects of lactic acid bacteria, including Limosilactobacillus and Lactococcus, in immunocompetent C57BL/6J mice. Three different lactic acid bacteria strains were orally administered to C57BL/6J mice for 8 weeks. Then, liver, spleen, and whole blood were harvested after sacrificing the animals. There were no significant changes in whole-body weight, weight of organs, or complete blood cell count by oral administration of lactic acid bacteria. The frequencies of CD3⁺, CD4⁺, and CD8⁺ T cells were significantly increased in the Limosilactobacillus reuteri MG5462 group compared to control. The frequency of NK1.1⁺ cells was significantly increased in the Lactococcus lactis MG5474 group compared to control. On the other hand, splenocyte proliferations and natural killer cytotoxicity did not differ between groups. In addition, the MG5462 group had a significant increase in the production of TNF-a compared to the control, which is consistent with the upregulation of T cells in the MG5462 group. Therefore, Limosilactobacillus reuteri could be a functional food additive to boost immunity by positively affecting T cell populations.