HDACi promote the rapid down-regulation of CD62L, a marker of naive T cells. Freshly isolated murine CD4⁺ and CD8⁺ T cells, and Tregs, exposed to low, nontoxic concentrations of a pan-HDACi showed CD62L down-regulation within 2 hours of exposure, illustrating the potential for phenotypic modulation of T cells independently of their cell division.