Screening of immune-enhancing Lactobacillus in mice by using a cell-line

In this study, we found that it is possible to screen Lactobacillus strains that enhance the immune function of mice using HCT-8 cells. Lactobacillus were co-incubated with intestinal epithelial HCT-8 cells to detect and screen the strains that induced more interleukin-6 (IL-6) in the culture supernatant. Simultaneously, a mouse model of low immunity was established to administer the screened lactobacilli by gavage. After 4 weeks of continuous gavage, related cytokines in blood and immune cell indexes in organs were detected to comprehensively evaluate the feasibility of in vitro cell culture model for screening immune-enhancing strains. The content of IL-6 in the culture supernatant of HCT-8 cells induced by the three tested strains increased approximately 5, 8 and 15 fold compared with that of the control group. IL-6 content in serum of mice was significantly higher than that of the control group provided with cyclophosphamide (CTX). Lactobacillus paracasei ZLPC01 presented a higher ability to protect against the immune damage of CTX by decreasing the serum IgG level, increasing the transformation of mouse splenocytes, and the activity of NK cells. Furthermore, L. paracasei ZLPC01 increased cytokine content in serum (IL-6, IL-2, TNF-α and IFN-γ) and colon (IL-6 and TNF-α) in CTX-treated mice. Screening strains that enhance immunity via an in vitro cell-line is simple in operation, and the results are well correlated with those of animal experiments, which is feasible and effective in practice. In addition, L. paracasei ZLPC01 could have the potential to enhance the immunity of mice effectively through inducing intestinal cells to produce IL-6, TNF-α and other cytokines.