CD4 and infection: Of note, the frequency of FoxP3+ CD4+ T cells within the adoptively transferred host at day 28 post infection was not indicative of the level of adoptive protection provided (CD4+ naïve, 3.5±0.87; CD4+ “recipient”, 0.2±0.07; CD4+ RTE, 1.47±0.56) or different between mice receiving CD4+ RTEs and mature recipient CD4+ T cells.