Formaldehyde Exposure Induces Differentiation of Regulatory T Cells via the NFAT- mediated T Cell Receptor Signalling Pathway in Yucatan Minipigs

The use of minipigs ( Sus scrofa ) as a platform for toxicological and pharmacological research is well established. In the present study, we investigated the effect of formaldehyde (FA) exposure on helper T cell-mediated splenic immune responses in Yucatan minipigs. The minipigs were exposed to different concentrations of FA (0, 2.16, 4.62, or 10.48 mg/m 3 ) for a period of 2 weeks. Immune responses elicited by exposure to FA were determined by assessing physiological parameters, mRNA expression, and cytokine production. Additionally, the distribution of helper T cells and regulatory T cells (Treg) and expression of NFAT families, which are well-known T cell receptor signalling proteins associated with regulatory T cell development, were evaluated. Exposure to FA suppressed the expression of genes associated with Th1 and Th2 cells in minipigs in a dose-dependent manner. Subsequent production of cytokines also declined post-FA exposure. Furthermore, exposure to FA induced the differentiation of CD4 + Foxp3 + Treg cells with divergent expression levels of NFAT1 and NFAT2. These results indicated that exposure to FA increased the Treg cell population via the NFAT-mediated T cell receptor signalling pathway, leading to suppression of the effector T cell activity with a decline in T cell-related cytokine production.