Abstract
Foxp3(+) regulatory T cells (Tregs) balance the mammalian immune system by mechanisms that are yet to be elucidated in their entirety. Methods employed to quantify the regulatory activity of Tregs in vitro are an important tool in cellular immunology, but can be technically demanding and subjected to variation. In this manuscript, we describe in detail a robust Treg suppression assay based on the flow cytometric quantification of both CD4(+) and CD8(+) effector T cell functions. This method can provide valuable insights into the immunosuppressive activity of Foxp3(+) Tregs and is versatile with regard to genetic or pharmacologic manipulations. Additionally, novel regulatory immune cells can be characterized by using this assay.