The Enhancement of Regulatory T Cell Maturation and Th1/Th2 Balance through FOXP3 Expression by Lactobacillus paracasei in an Ovalbumin-Induced Allergic Skin Animal Model.

Chronic allergic skin conditions, including atopic dermatitis (AD), are characterized by pruritus, erythema, xerosis, desquamation, and inflammation, significantly impacting quality of life. Long-term steroid use, while common in treatment, carries the risk of adverse effects. Previous studies have demonstrated the potential of Lactobacillus paracasei subsp. paracasei NTU 101 (NTU 101) in alleviating AD symptoms from a preventive perspective. This study, however, focuses on exploring NTU 101's therapeutic potential by investigating its effects on regulatory T cell (Treg) maturation and Th1/Th2 balance. The results revealed that NTU 101 administration effectively reduced serum IgE levels and inflammatory cell infiltration in the skin, leading to a significant improvement in both epidermal and dermal thickness in the AD model. Additionally, NTU 101 modulated the immune response by increasing the proportion of CD4+/IL-4+ (Th2) cells in the spleen and concurrently enhancing FOXP3 expression in CD4+/CD25+ cells, which is critical for Treg cell development. This immune modulation was further associated with a rebalancing of the Th1/Th2 ratio, achieved by increasing the proportion of CD4+/IFN-γ+ (Th1) cells. Moreover, NTU 101 influenced the proportion of CD4+IL-17+ (Th17) cells, thereby supporting neutrophil maturation and promoting allergen clearance, ultimately mitigating AD symptoms. These findings underscore the potential of NTU 101 not only in managing AD symptoms but also in modulating key immune pathways involved in the pathogenesis of the disease, offering a promising alternative or adjunct to conventional steroid therapies.