CCR9 is expressed on T-ALL blasts with limited expression on normal peripheral blood cells. (A) Heatmap showing genes that are solely expressed in MOLT-4 T-ALL cells (red) compared with 35 normal tissue (blue; n = 172 samples) using subtractive transcriptomics from data from the Human Protein Atlas.²³(B-C) CCR9 gene expression as determined by RNA-sequencing from pediatric patients with T-ALL from St. Jude’s Hospital (Memphis, TN).²⁴ Pie chart (B) shows distribution of patients considered CCR9⁺ (fragments per kilobase of exon per million mapped fragments [FPKM] >2.0), while scatter chart (C) shows CCR9 expression according to genetic subgroup. (D) Expression of CCR9 on 102 cases of primary T-ALL, proportion of positive blasts. (E) CCR9 antigen density of positive samples, antibodies bound per cell. (F) Expression of CCR9 on peripheral leucocytes in healthy donors. Mono, monocytes; mRNA, messenger RNA; NK, natural killer cells; RPKM, reads per kilobase of transcript per million reads mapped; TCM, T central memory; TEM, T effector memory; TEMRA, terminally differentiated effector memory; TSCM, T stem cell memory; UNK, unknown.