Objective: In allergic asthma, regulatory T cell (Treg) number and function are decreased. Antigen-primed CD8+ T cells play an indispensable role in the full development of airway inflammation and airway hyper-responsiveness (AHR) occurring in asthma. In this study, we investigated the relationship between subpopulations of CD8+ T cells and CD39+ Tregs.
Methods: Female C57BL/6 mice were used to develop the model of allergic asthma. Experimental mice were immunized with ovalbumin (OVA) by intra-peritoneal (i.p) injection and then challenged with OVA by intra-tracheal administration. Control mice were immunized with vehicle by i.p injection and challenged with OVA. Airway inflammation was determined by histology and AHR was measured by an invasive method. Levels of interferon (IFN)-γ, IL-4, and IL-17 in bronchoalveolar lavage fluid (BALF) were determined by enzyme-linked immunosorbent assay. The frequencies of CD8+IFN-γ+ cells (Tc1), CD8+IL-4+ cells (Tc2), CD8+IL-17+cells (Tc17), and CD39+Tregs were measured by flow cytometry. The correlation between CD39+Tregs and Tc subsets was analyzed by Pearson's test.
Results: Experimental mice displayed phenotypes of allergic asthma, including inflammatory cell infiltration into the lungs, goblet cell hyperplasia, increased airway resistance, and increased IL-4 and IL-17 in BALF. Compared to control mice, experimental mice displayed lower CD39+Tregs and Tc1 but higher Tc2 and Tc17. There was a negative correlation between CD39+Tregs and Tc2 or Tc17.
Conclusion: In allergic asthma, increased Tc2 and Tc17 are possibly related to insufficient CD39+Tregs.
Keywords: Allergic asthma; CD39+Tregs; CD8+IFN-γ+cells; CD8+IL-17+cells; CD8+IL-4+cells.