Dilutional sensitivity of anti-inv16 antibody versus RT-PCR for detection of type A fusion. (A) Dilutional sensitivity of anti-inv16 Ab. PN 19 AML cells were serially diluted into normal bone marrow cells and analyzed by flow cytometry. The black trace represents isotype control. The gray trace represents anti-inv(16) Ab. (A) Undiluted PN 19 AML cells; (b and C) Cell dilutions shown to level of undetectable fluorescence shift (1:20). The D-values for results in (A), (B), and (C) are 0.71, 0.58, and 0.06, respectively. (B) Single-round RT-PCR of PN 19 AML sample [inv(16)+ with type A fusion] and serial normal bone marrow dilutions, using primers C1 and M1. PCR products were hybridized with a type A junction specific oligonucleotide probe. Lanes 1 through 6, undiluted PN 19 sample, 1:10 dilution, 1:20 dilution, 1:100 dilution, 1:10³dilution^., and 1:10⁴ dilution, respectively; lane 7, pure normal marrow; lane 8, negative control (no RNA).