Cell penetrable-mouse forkhead box P3 suppresses type 1 T helper cell-mediated immunity in a murine model of delayed-type hypersensitivity

Forkhead box P3 (FOXP3), which is a transcription factor, has a primary role in the development and function of regulatory T cells, and thus contributes to homeostasis of the immune system. A previous study generated a cell-permeable fusion protein of mouse FOXP3 conjugated to a protein transduction domain (PTD-mFOXP3) that successfully blocked differentiation of type 17 T helper cells in vitro and alleviated experimental arthritis in mice. In the present study, the role of PTD-mFOXP3 in type 1 T helper (Th1) cell-mediated immunity was investigated and the possible mechanisms for its effects were explored. Under Th1 polarization conditions, cluster of differentiation 4+ T cells were treated with PTD-mFOXP3 and analyzed by flow cytometry in vitro, which revealed that PTD-mFOXP3 blocked Th1 differentiation in vitro. Mice models of delayed type hypersensitivity (DTH) reactions were generated by subcutaneous sensitization and challenge with ovalbumin (OVA) to the ears of mice. PTD-mFOXP3, which was administered via local subcutaneous injection, significantly reduced DTH-induced inflammation, including ear swelling (ear swelling, P<0.001; pinnae weight, P<0.05 or P<0.01 with 0.25 and 1.25 mg/kg PTD-mFOXP3, respectively), infiltration of T cells, and expression of interferon-γ at local inflammatory sites (mRNA level P<0.05) compared with the DTH group. The results of the present study demonstrated that PTD-mFOXP3 may attenuate DTH reactions by suppressing the infiltration and activity of Th1 cells.