Difference between CD25⁺Tregs and Helios⁺Tregs in a murine model of allergic rhinitis

Regulatory T or Treg cells, balance the peripheral immune response to allergens in allergic rhinitis. Traditionally, Treg (CD25⁺ Treg) is identified by the coexpression of Foxp3 and CD25, but this strategy does not represent the true inhibitory function of Treg cells. Helios has been thought of as novel marker of activated Tregs, with an important inhibitory function. Consequently, Helios was proposed as a marker of Treg. Recent articles have shown that Foxp3 and Helios co-expression (Helios⁺Tregs) is an important functional stage of Treg.

To compare the prevalence of CD25⁺Tregs and Helios⁺Tregs using a mouse model of allergic rhinitis.

Twenty mice were randomized into two groups. The test group comprised 10 allergic rhinitis model mice exposed to ovalbumin; the control group was exposed to saline. The fractions of CD25⁺Tregs, Helios⁺Tregs, Helios⁺CD25⁺, and Helios⁺Foxp3⁺CD25⁺Tregs present in the two groups were determined using flow cytometry.

CD25⁺Tregs and Helios⁺Tregs were less abundant in the spleen and nasal mucosa cells of the allergic rhinitis model compared with the control. We also observed fewer Helios⁺Tregs than CD25⁺Tregs in nasal mucosa and splenic cells of both control and test groups. Moreover, we observed fewer Helios⁺Foxp3⁺, Helios⁺CD25⁺, and Helios⁺Foxp3⁺CD25⁺ Tregs in the nasal mucosa in the allergic rhinitis model. Helios was expressed the most in CD4⁺ CD25⁺Foxp3⁺ T-cells, followed by CD4⁺ CD25^-Foxp3^- T-cells. Approximately 75% of CD25⁺Tregs were Helios⁺ in spleens of allergic rhinitis and control mice.

This is the first report of the proportions of Helios⁺Tregs in nasal mucosa and spleens of allergic rhinitis mice. Gating true inhibitory Tregs with the coexpression of Foxp3 and Helios might be more useful than relying on the expression of CD25. This study provides a new insight for Treg studies of allergic rhinitis, and the potential utility of the marker as a therapeutic target.