An exciting approach to treatment of childhood cancer is the use of autologous T-cells engineered to recognize tumor-associated antigens. This treatment, chimeric antigen T-cells (CAR T) has been most successful in the treatment of relapsed or refractory B cell acute lymphoblastic leukemia. Our laboratory is interested in examining immunophenotypic remodeling of leukemia populations under the pressure of antigen-specific therapies. Particularly of interest, is in cases which relapse following CAR-T therapy with cells that no longer express the target antigen or cases that relapse with a different lineage. We are also interested in applying high-parameter, single-cell technologies to identify new targets that may be amenable to CAR-T cells or other immunotherapies.