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Ding et al. Microbiome Res Rep 2024;3:16 https://dx.doi.org/10.20517/mrr.2023.64 Page 5 of 16

Figure 1. Effect of B. longum subsp. infantis on the percentage of B, T, and Th cells in mesenteric lymph nodes of female and male mice.
(A and C) the positive peak of T cells (CD3 marker); B cells (CD19 marker), and Th cells (CD4 marker) of female and male mice,
* ** ***
respectively; (B and D) Bar plot of percentage of B, T, and Th cells of female and male mice, respectively. P < 0.05; P < 0.01; P <
0.001, compared to corresponding gender control group. The mean ± SEM (n = 8 per group) was used to represent the data. Th: T
helper; SEM: error of the mean.

the percentage of B cells (P < 0.05, respectively), and I2MI and B6MNI increased the percentage of Th cells
significantly (P < 0.05 for all, Figure 1B). For male mice [Figure 1C], B. longum subsp. infantis I4MI, I5TI,
I8TI, and B6MNI significantly increased the percentage of T cells (P < 0.05), I4MI and I8TI significantly
increased the percentage of B cells (P < 0.05), and I4MI and B6MNI significantly increased the percentage of
Th cells (P < 0.05, respectively, Figure 1D).

Effects of B. longum subsp. infantis on cytokines and immunoglobulins in the colon of mice
The ability of eight B. longum subsp. infantis strains to stimulate immune cells capable of producing Th1/
Th2-associated gene proteins was first assessed by immunofluorescence and flow cytometry. The balance of
Th1/Th2 was assessed by cytokines and immunoglobulins. B. longum subsp. infantis B6MNI increased the
level of IFN-γ and IgG2a significantly (P < 0.05, Figure 2A and B) in the colon of female mice. No significant
differences were found in the levels of IL-4 and IgE in the colon of female mice [Figure 2C and D]. B6MNI
increased the ratio of IgG2a/IgE (P < 0.05, Figure 2E) in the colon of female mice. For male mice, no
significant differences were found in the levels of IFN-γ and IgG2a in the colon for female mice [Figure 2F