Analysis of Antigen Expression in T-Cell Acute Lymphoblastic Leukemia by Multicolor Flow Cytometry: Implications for the Detection of Measurable Residual Disease.

Multicolor flow cytometry (MFC) is a key method for assessing measurable residual disease (MRD) in acute lymphoblastic leukemia (ALL). However, very few approaches were developed for MRD in T-cell ALL (T-ALL). To identify MRD markers suitable for T-ALL, we analyzed the expression of CD2, CD3, CD4, CD5, CD7, CD8, CD10, CD34, CD45, CD48, CD56, CD99, and HLA-DR in T-ALL patients at diagnosis. The median fluorescence intensities (MFIs) of surface CD3, CD4, CD5, CD7, CD8, CD45, CD48, CD99, and CD16+CD56 were also evaluated at Day 15 and the end-of-induction (EOI). The MFC data from 198 pediatric T-ALL patients were analyzed retrospectively. At diagnosis, the most common antigens were identified, and the MFI of T-lineage antigens in blasts was compared to that in T lymphocytes. At follow-up, the MFIs of the proposed MRD markers were compared to those observed at diagnosis. The most common T-ALL antigens were CD7 (100.0%), intracellular CD3 (100.0%), CD45 (98.5%), and CD5 (90.9%). The MFIs of T-lineage antigens in blasts differed significantly from those in T lymphocytes. By the EOI, a substantial modulation of sCD3, CD4, CD5, CD7, CD8, and CD45 was observed. CD48 and CD99 were the most stable markers. The proposed MRD markers (sCD3, CD4, CD5, CD7, CD8, CD45, CD48, CD99, CD16+CD56) enabled MFC-MRD monitoring in virtually all T-ALL patients.