CD48 Is a Robust Marker and a Useful Addition for Assessment of Measurable Residual Disease in T-Cell Acute Lymphoblastic Leukemia.

To evaluate the utility of CD48 as a marker to distinguish T-lymphoblasts from mature T cells and NK cells in T-lineage acute lymphoblastic leukemia (T-ALL) for measurable residual disease (MRD) detection by flow cytometry. CD48 expression was assessed in T-lymphoblasts and mature T cells from 51 diagnostic T-ALL samples and 84 post-therapy samples. Normalized median fluorescence intensity (nMFI) of CD48 was calculated as the ratio of MFI in the population of interest to that in mature B cells. At diagnosis, the median CD48 nMFI in T-lymphoblasts was significantly lower (0.14) compared to mature T cells (1.29) (p < 0.0001). In MRD-positive post-therapy samples, T-lymphoblasts had a lower nMFI (0.22) than mature T cells (1.4), NK cells (1.06), and γδ T cells (1.09) (p < 0.0001). CD48 demonstrates consistent under-expression in T-lymphoblasts compared to mature T cells and NK cell cells, supporting its use as a reliable and informative marker for MRD detection in T-ALL. Its inclusion would enhance the accuracy of flow cytometry-based MRD panels.