While CAR T cells targeting CD19 have been successful owing to plentiful extracellular expression of CD19, tumor antigens in solid tumors are often intracellular, and thus inaccessible to CAR T cells (unlike endogenous tumor-specific T cells that can recognize intracellular peptides in the context of MHC I presentation with their T cell receptors) (5). The gene discussed is CD19; the disease is neoplasm.