Specifically, in engineered AML cell lines, a reduced degree of antigen modulation relative to wild-type CD33 was noted in sublines expressing CD33 isoforms containing exon 7a; by comparison, in engineered ALL cell lines, a reduced degree of antigen modulation relative to wild-type CD33 was noted in sublines expressing CD33 isoforms that lack exon 2 (Figure 8). Here, CD33 is linked to acute lymphoblastic leukemia.