NGS-based IG/TR rearrangement profiling in acute lymphoblastic leukemia: age dependence of immunogenetic maturation

• Compared to low throughput methods, NGS-based IG/TR profiling enables also clonal evolution analysis and detection of non-malignant clones

• NGS-based IG/TR-rearrangement profiling provides hints towards a higher immunogenetic maturity in pediatric ALL

We comprehensively profiled the landscape of immunoglobulin (IG) and T-cell receptor (TR) rearrangements at diagnosis in 1212 acute lymphoblastic leukemia (ALL) patients (573 children, 639 adults) diagnosed in Germany between 2017 and 2022.Our findings indicate that immunogenetic maturity in ALL patients is age-dependent, with younger patients exhibiting more mature profiles. In fact, 68.7% of pediatric B-ALL and 85.7% T-ALL patients carried IGK, or complete TRB and/or TRD rearrangements, respectively; compared to 39.0% and 67.3% in adults (B-ALL: p<2.2e-16, T-ALL: p=6.7e-03). Additionally, children carried more IG/TR markers compared to adults (mean 6/patient versus 4/patient, respectively; p=2.5e-38). Only 0.5% of pediatric patients lacked markers, contrasted with 6.7% of adults.IGH clonal evolution was most pronounced among pro-B ALL cases (60.9%), with the V-to-DJ mechanism driving pro-B evolution (78.6%), while V-replacement dominated other immunophenotypes. Additionally, we observed that the presence of expanded accompanying T-cell clones of unknown significance in B-ALL patients increased with age.This next-generation sequencing (NGS)-based study offers an unprecedented characterization of IG/TR rearrangement patterns across ALL subtypes and age groups. It highlights the higher immunogenetic maturity in children, which may be explained by the infection-driven abnormal activity of the IG/TR recombination machinery in pediatric ALL.