CD4 and infection: At day 14 p.i., we sorted CD45.1+CD45.2+CD44+Tigit+IL-7Rα–PD-1+CXCR5+ and CD45.1+CD44+Tigit–IL-7Rα+PD-1+CXCR5+ CD4+ T cells and co-transferred them into CD45.2+ recipient mice followed by PR8 infection.