Sustaining exposure to high concentrations of bifidobacteria inhibits gene expression of Mouse's mucosal immunity

Sahar El Hadad; Ayeshah Zakareya; Ahmed Al-Hejin; Alia Aldahlawi; Mona Alharbi

doi:10.1016/j.heliyon.2019.e02866

Sustaining exposure to high concentrations of bifidobacteria inhibits gene expression of Mouse's mucosal immunity

Heliyon. 2019 Dec 12;5(12):e02866. doi: 10.1016/j.heliyon.2019.e02866. eCollection 2019 Dec.

Authors

Sahar El Hadad^{1

2

3}, Ayeshah Zakareya¹, Ahmed Al-Hejin^{1

4}, Alia Aldahlawi^{1

3

5}, Mona Alharbi¹

Affiliations

¹ Department of Biological Science, Faculty of Science, King Abdulaziz University, Jeddah, Saudi Arabia.
² Research Center of Genetic Engineering and Bioinformatics, VACSERA, Cairo, Egypt.
³ Immunolgy Unit, King Fahad Medical Research Center, King Abdulaziz University, Jeddah, Saudi Arabia.
⁴ Microbiology Unit, King Fahad Medical Research Center, King Abdulaziz University, Jeddah, Saudi Arabia.
⁵ Inflammatory Bowel Disease Research Group, King Abdulaziz University, Jeddah, Saudi Arabia.

Abstract

Numerous dietary products are supplemented with probiotics that may be beneficial for human health. Recently, bifidobacteria have received increasing attention as a genus of probiotic bacteria with high efficiency and few side effects. To examine potential effects of different bifidobacteria concentrations on the mucosal immune response, we fed mice with (a) 10⁸ colony-forming units (CFU) of bifidobacteria (group 10⁸ B), and (b) with 10¹² CFU of bifidobacteria (group 10¹² B) over 42 days and assessed gene expression in intestinal mucosa and immune marker concentrations in serum samples; ten untreated female mice were used as a control. Continuous exposure to 10⁸ CFU of bifidobacteria activated both macrophages and T_reg immune cells through significantly increasing the expression of mucosal TLR2 and IL10-mRNA genes, but inhibited Th1 and Th2 cells via significant downregulation of IL4 and IFNγ gene expression, compared to untreated mice. Interestingly, group 10¹² B showed down-regulated expression of TLR2, IL10, and IL4 genes but up-regulated expression of IFNγ, compared to group 10⁸ B and to the control. Also, polyclonal immunoglobulins IgG, IgM, and IgA showed a significant increase in all treated mice compared to the control. We conclude that high concentrations of bifidobacteria reduced innate immune functions. Furthermore, adaptive immunity seemed to be enhanced by increasing stimulation of T and B lymphocytes, suggesting aberration of the immune system following intestinal inflammation due to constant exposure to high concentrations of bifidobacteria. Both experimental bifidobacteria concentrations increased the total levels of circulating Igs, particularly of IgA.

Keywords: Bifidobacteria; IFN gamma; IL10.; IL4; Mice; Microbiology; Mucosal immunity; Probiotics; TLR2.