In vitro and in vivo analyses of regulatory T cell suppression of CD8+ T cells.

The study of regulatory T cells (Treg) requires methods for both in vivo and in vitro analyses, both of which have different limitations, but which complement each other to give a more complete picture of physiological function than either method alone. Our analyses have focused on Treg-mediated suppression of CD8(+) T cells, and in particular Tregs induced by viral infection. One of the unique characteristics of virus-induced Tregs is that they can suppress CD8(+) T cell function in vitro without the requirement for additional stimulation. This ability correlates with their suppressive capacity and activated status in vivo. Interestingly, while virus-induced Tregs suppress CD8(+) T cell function in vitro and in vivo, they do not suppress proliferation unless they are further activated in vitro.