CD4 and infection: Prior to LCMV challenge, a significantly greater percentage of CVB3-specific SMARTA memory cells were CD62Lhi compared to LCMV-specific SMARTA cells (Figure 9D, right panel); we speculate that a lower level of MHC class II antigen presentation, and/or a weaker (or more brief) period of stimulation during rCVB3 infection, permitted more rapid CD62L expression by CVB3-induced memory CD4+ T cells.