BCL6 and infection: Later work by the group of André Ballesteros-Tato demonstrated that high IL-2 levels during the peak of an influenza virus infection prevented the development of Tfr, but that concomitant with the resolution of the infection, Treg cells downregulated CD25, upregulated Bcl-6, and differentiated into Tfr, which subsequently prevented the expansion of autoreactive B cells.32