In vivo sites and cellular mechanisms of T reg cell–mediated suppression

Abstract

Regulatory CD4 T (T reg) cells control immune responses to self-antigens and pathogens. However, where T reg cells act to curtail effector T cells in vivo and what stage of effector T cell activation or differentiation is targeted by T reg cells remain unknown. Furthermore, a requirement for direct effector T cell–T reg cell contact in vivo has not been ascertained. Varying answers to these important questions have been provided by several new studies.