Background
Generation of CD8 T cell responses following viral infection or vaccination is indispensable for infection control. Regulatory CD4+ CD25+ T cells (Treg) are a key factor for the inefficiency of CD8 responses in viral persistence. The mechanisms of this suppression are not elucidated. Treg constitutively express the ectonucleotidase CD39, that generates immunosuppressive adenosine in the sites of immune activation.