n-Butyrate Anergized Effector CD4+T Cells Independent of Regulatory T cell Generation or Activity

CD4+ T cell anergy reflects the inability of CD4+ T cells to respond functionally to antigenic stimulation through proliferation or IL-2 secretion. Histone deacetylase (HDAC) inhibitors have been shown to induce anergy in antigen-activated CD4+ T cells. However, questions remain if HDAC inhibitors mediate anergy through direct action upon activated CD4+ T cells or through the generation and/or enhancement of regulatory T (Treg) cells. To assess if HDAC inhibitor n-butyrate induces anergy independent of the generation or expansion of FoxP3+ Treg cells in vitro, we examine n-butyrate-treated murine CD4+ T cells for anergy induction and FoxP3+ Treg activity. Whereas n-butyrate decreases CD4+ T cell proliferation and IL-2 secretion, n-butyrate did not augment FoxP3 protein production or confer a suppressive phenotype upon CD4+ T cells. Collectively, these data suggest that HDAC inhibitors can facilitate CD4+ T cell functional unresponsiveness directly and independently of Treg cell involvement.