The invention provides compositions and methods for treating diseases associated with expression of CD19, e.g., by administering a recombinant T cell comprising the CD19 CAR as described herein, in combination with one or more B-cell inhibitors, e.g., inhibitors of one or more of CD10, CD20, CD22, CD34, CD123, FLT-3, ROR1, CD79b, CD179b, or CD79a. The disclosure additionally features novel antigen binding domains and CAR molecules directed to CD20 and CD22, and uses, e.g., as monotherapies or in combination therapies. The invention also provides kits and compositions described herein.