Interferon gamma is effective for BM purging in a patient with CML

We report a case of Ph-positive CML where the BM was incubated for 24 h with 10(3) IU/ml IFN gamma and then cultured in liquid media for 4 weeks. After 24 h incubation, there was no differential sensitivity of CML CFU-GM to IFN gamma compared with untreated BM. Subsequent long-term culture (LTC) of the IFN gamma treated CML BM, however, demonstrated a 75% inhibition of production of CFU-GM from the second week onwards. Using PCR, we were able to demonstrate two types of BCR-ABL transcript in the diagnostic BM. After 4 weeks of LTC, the J(bcr b3/ABL II) RNA transcript persisted in the untreated BM, whereas neither BCR/ABL RNA transcripts were detected in the culture established with IFN gamma-treated CML BM. This study has two points of interest with the demonstration of (1) a possible antileukaemic effect of IFN gamma on the progenitors generated in the LTC system, and (2) the use of highly sensitive PCR technology to evaluate the effectiveness of IFN gamma to purge CML BM of Ph-positive cells.