Highly suppressive functional CCR7 low Treg subset cells may correlate with poor prognosis of B-ALL.

Regulatory T cells (Tregs) may influence prognosis in leukemia. This study aimed to explore the effects and mechanisms of Treg subclusters on the prognosis in B-cell acute lymphoblastic leukemia (B-ALL) using single-cell RNA sequencing (scRNA-Seq). scRNA-seq was performed on sorted T cells from adults with newly diagnosed (Dix) B-ALL and healthy donors (HD) to establish the training cohort. Treg phenotypes, functions, and prognostic relevance were evaluated. A scRNA-seq dataset from the GEO database, including Dix and relapsed B-ALL, served as the validation cohort. Key findings were confirmed by flow cytometry. Transcription factor and cell-cell interaction analyses were conducted to clarify the mechanisms linking Treg subsets to prognosis. Tregs were divided into CCR7high and CCR7low subclusters. The proportion of CCR7low Tregs was higher in B-ALL than in HD and in Rel than in Dix. Patients with higher CCR7low Treg signature scores had a poorer prognosis. Compared with CCR7high Tregs, CCR7low Tregs exhibited enhanced activation, proliferation, and immunosuppression. Trajectory analysis suggested differentiation from CCR7high to CCR7low Tregs. IKZF2 and JUNB showed consistently increased activity and expression in CCR7low Tregs across cohorts. CCR7low Tregs showed increased interactions with terminal effector and exhausted CD8+ T cells through the LGALS9-P4HB/HAVCR2/CD44 pathway. An increased proportion of CCR7low Tregs correlated with poor prognosis in B-ALL, potentially due to enhanced activation, proliferation, and immunosuppression. IKZF2 and JUNB upregulation may promote CCR7low Treg differentiation and function. Moreover, CCR7low Tregs may impair CD8+ T cell immunity through the LGALS9-P4HB/HAVCR2/CD44 signaling.