Employing cell surface proteomics combined with MS identification of surface proteins in histone-lysine N-methyltransferase 2 A (KMT2A)-rearranged B-ALL PDX samples, followed by extensive tissue-specificity analyses, we identified LILRB1 (also known as CD85j) as a potential novel CAR target. This evidence concerns the gene KMT2A and acute lymphoblastic leukemia.