CTLA4 and infection: Binding of gp120 to CD4 receptor of Tregs with consecutive upregulation of cAMP.Upregulation of CD39/adenosine axis and functional markers CTLA-4, TNFR, Foxp3, TGFβ, IDO.Increased expression of homing receptors CD62L and integrin alpha 4 beta in Tregs.Upregulation of Foxp3 expression in progressive infection.