Spatial analysis reveals distinct immune phenotypes and tertiary lymphoid structure-like aggregates in pediatric AML

Pediatric cancers are characterized by a relatively low mutational burden and therefore, children are thought to be poor candidates for T cell-engaging immunotherapies. Here, we performed a multidimensional characterization of the tumor immune microenvironment in newly diagnosed children with acute myeloid leukemia (AML) and non-leukemic controls. We identified a subset of pediatric AML patients with remarkably high levels of T cell infiltration and a relatively low abundance of anti-inflammatory macrophages in the bone marrow. In addition, we detected large T cell networks that colocalized with B cells in immune-infiltrated samples, resembling tertiary lymphoid structures as described in solid tumors. Using spatial transcriptomics, we dissected the composition of these structures and revealed unique hotspots of anti-tumor immunity. This work raises the possibility that a subset of pediatric AML patients may benefit from T cell-engaging immunotherapies and encourages further study of these lymphoid structures in the context of immunotherapy in AML.