Evolution of the TCR β-chain repertoire in A2/Melan-A⁺ CD8⁺ T cells. (A) Longitudinal analysis of the distribution of TCR β-chain clonotypes amplified from graft inoculums and PBMC samples obtained from corresponding UCBT recipients (n = 11). Each bar represents a time point (ie, graft inoculum or time after UCBT), and each box within a bar represents a particular T-cell clonotype identified by a characteristic TCR β-chain CDR3 sequence. Open boxes represent unique clonotypes (ie, clonotypes that were not found at another time point). Colored bars represent persisting clonotypes, that is, clonotypes that were observed at more than 1 time point; identical colors correspond to identical clonotypes in within-patient but not between-patient analysis. Twenty to 35 independent recombinant clones were analyzed per time point. Patients 2, 8, and 20 (P2, P8, and P20, respectively) experienced leukemic relapse. (B) Simpson's diversity index (Ds)²⁴  was used to represent clonal diversity. Statistical significance was tested with 1-way ANOVA and Bonferroni multiple comparison test. *P < .05. Boxes represent median and interquartile range; error bars represent the range; and n represents the number of subjects.