Distribution of the natural logarithm of the percentage (A) and absolute number (B) of CD28-CD8+ T cells according to histological groups. In each boxplot, the central line indicates the median of the data set, the shaded box represents the interquartile range (IQR) which means 25 percentile to 75 percentile or quartile 1 (Q1) to quartile 3 (Q3), and the lower and upper bars indicate Q1 - 1.5 IQR and Q3 + 1.5 IQR, respectively. Biopsy group 1: normal/sub-normal, group 2: IFTA grade 2/3, group 3: ABMR, group 4: TCMR, and group 5: borderline rejection. See also Supplementary Tables 2 and 3 for the unadjusted mean difference in the log percentage and log absolute number, respectively, between biopsy groups.