CXCR5 and viral infectious disease: During an acute viral infection, T cells that intermediately express IL-2 receptor α induces the expression of BCL-6 and CXCR5 through ICOS signaling leading to Tfh differentiation by 72 h of antigen challenge, without the help of B cell, whereas T cells expressing higher IL-2 receptor α induces Blimp-1 expression driving the cells toward other effector T cells subsets (70).