CD27 and infection: While the ratio for CD127, CD62L, and CD27 was greater than 1 (i.e., expression increased with time when expression at day 200 post infection was compared to expression at day 41) and the ratio for KLRG1 was less than 1 (i.e., expression decreased with time) in each individual inbred mouse and most outbred mice, the ratio for CD127, CD62L, and CD27 was near or below 1 and the ratio for KLRG1 was near or above 1 in some outbred mice (Figure 4B), suggesting that the phenotype of memory CD8 T cells does not progress or progresses very slowly with time after infection in some outbred mice.