Background Dysregulation of the balance between different T cell populations is believed to be an important basis for asthma.
Objective To observe the changes in γδT subtypes in transgenic asthmatic mice after aerosol inhalation of Mycobacterium vaccae, and to further investigate the mechanism of M. vaccae in asthmatic mice and its relationship with γδT cells.
Methods TCR-β^-/- mice were exposed to atomized normal saline or M. vaccae for 5 days and the γδT cells from the lung tissues were isolated. Changes in γδT17 and γδTreg populations were detected. Asthma was induced in BALB/c mice using ovalbumin, which was then transplanted with control or M. vaccae-primed γδT cells. First we analyzed the content of γδT cells that secrete IL-17 (IL-17 γδT cells) and Foxp3⁺ γδT cells in lung tissues and then measured the content of IL-17 in the bronchoalveolar lavage fluid (BALF) by ELISA.
Results Exposure to M. vaccae increased and decreased the relative proportions of Foxp3⁺ γδT cells and IL-17⁺ γδT cells, respectively, thereby decreasing airway reactivity and inflammation levels in asthmatic mice, and significantly decreasing IL-17 levels in BALF. Furthermore, mice treated with these primed T cells showed a decrease in IL-17⁺ γδT cells, and a concomitant increase in Foxp3⁺ γδT cells in their lung tissues. Furthermore, adoptive transfer of M. vaccae-primed γδT cells decreased GATA3 and NICD and increased T-bet in lung.
Conclusions The M. vaccae-primed γδT cells alleviated the symptoms of asthma by reversing Th2 polarization in the lungs and inhibiting the Notch/GATA3 pathway.