The mite alimentary canal contains plenty of microbiota. It is accepted that some of the microbial products function as adjuvants to speed up immune responses.
We identified five bacterial proteins from dust mite, and Enterobacterial fimbriae H (FimH) was one of them. This study aims to test a hypothesis that the FimH protein enforces immunotherapy in asthmatic mice.
Asthmatic mice were treated by allergen specific immunotherapy (ASIT) with rDer f1/f2 or rDer f1/f2 plus FimH. Changes in inflammatory cell infiltration, airway hyperreactivity, frequency of Tregs, splenic CD4IFN-γ cells, and serum levels of TGF-β, IL-10, IL-13 and IL-17A of asthmatic mice were checked.
ASIT with rDer f1/f2 plus FimH reduced inflammatory cell infiltration, airway hyperreactivity (AHR), and levels of IgE and IgG1 compared to ASIT with rDer f1/f2 alone, but the levels of IgG2a increased. Asthmatic mice that underwent ASIT with rDer f1/f2 plus FimH showed increased frequency of Tregs, splenic CD4IFN-γ cells, serum levels of TGF-β and IL-10; and deceased splenic CD4IL-4 cells, and serum levels of IL-13 and IL-17A. In vitro study showed FimH triggered IL-10 expression in a concentration dependent manner and facilitated the differentiation of Tregs.
Used as an adjuvant, FimH enforces the effect of ASIT in asthmatic mice via augmenting Tregs.

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