Fig 4. Analysis of global peripheral blood memory T cell populations with respect to protection status following superinfection challenge.

Memory subsets were defined on differential expression of CCR7 and CD28 within the CD95⁺ T cell population. Results are shown for individual animals on the day of superinfection challenge and at day 130, after challenge and as median and mean values with boxes showing 25^th and 75^th percentiles grouped according to outcome of challenge. Pre-vaccination frequencies are shown as box plots derived from 18 macaques entering the original study. a, b, & c show frequencies of T_CM, T_EM1 and T_EM2 subsets of CD4⁺ cells respectively; likewise d, e, & f show frequencies of T_CM, CD28⁺CCR7^-, and T_EM subsets of CD8⁺ cells respectively. All results were compared and statistically significant differences for groups are shown as ρ values determined by Mann-Whitney rank sum test.