Chimeric antigen receptor (CAR) T cell therapy can result in impressive remissions in hematological malignancies, but relapse is common because a minority of infused cells acquire a long-lived, memory-like state. All US Food and Drug Administration-approved CAR T cell products incorporate either 4-1BB or CD28 costimulatory domains, each conferring distinct phenotypic outcomes, but how these signals control early fate decisions is incompletely understood. Here we show that costimulatory domains control memory fate acquisition through asymmetric cell division. CD28 CAR T cells have higher CAR surface expression and enhanced surface proteome asymmetry after the first division, yet paradoxically they show muted transcriptional, epigenetic and metabolic divergence between daughter cells, correlating with reduced long-term persistence. Conversely, 4-1BB CAR T cells have less surface polarization but more pronounced transcriptional, metabolic and epigenetic divergence, yielding proximal effector-prone and distal persistence-prone daughters. Integrating surface proteomics, transcriptomics, metabolomics and chromatin accessibility, we show how costimulatory domains tune asymmetric cell division to shape CAR T cell fate, providing a mechanistic foundation for optimizing cellular immunotherapy.
