Objective: To set up a sensitive triple-color flow cytometric assay (FCM) for detection of residual leukemia cells.
Methods: Application of triple-color flow cytometry to the patients for detecting CD(10)(+)CD(22)(+)CD(45)(- or dim) leukemic cells in acute B lymphoblastic leukemia (B-ALL).
Results: Leukemic cells in B-ALL patients' bone marrow (BM) consistently showed the CD(10)(+)CD(22)(+)CD(45)(- or dim) phenotype. FCM analysis could detect leukemic cells at the level of 1 per 10(4) cells. The CD(10)(+)CD(22)(+)CD(45)(- or dim) cell population was absent in normal BM, regenerating BM, and BM from leukemia patients in continuous complete remission. This assay could identify residual leukemic cells in 50 days after starting induction chemotherapy. Furthermore, a gradual increase of leukemic cell population could be monitored by this assay before morphological confirmation of BM relapse.
Conclusion: Triple-color FCM was a sensitive method for detecting BM CD(10)(+)CD(22)(+)CD(45)(minus sign or dim) leukemic cells and could be an additional useful tool to monitor MRD in B-ALL patients.