B cell targeting in CAR T cell therapy: Side effect or driver of CAR T cell function?

Chimeric antigen receptor (CAR) T cell therapies targeting CD19 and CD22 have been successful for treating B cell cancers, but CAR T cells targeting non–B cell cancers remain unsuccessful. We propose that rather than being strictly a side effect of therapy, the large number of CAR interactions with normal B cells may be a key contributor to clinical CAR T cell responses.