**Conflict of interest**

*Normal and Malignant B-Cell*

evaluation strategy.

absence of CD19+

based on CD7.

2009 therapy.

detection with CD7<sup>+</sup>

ing on T-cell ontogenesis.

into the high risk group.

based on detection of CD10<sup>+</sup>

Notwithstanding initial treatment results, some patients fail to respond to blinatumomab or develop progressive disease after initial response. Recurrence rate is 30%. Characterization of blast immunophenotype in recurrence on blinatumomab therapy discovered no CD19 expression on tumor cells. This interferes with BCP identification and requires new methodological approaches to MRD assessment. Inclusion of blinatumomab into B-ALL therapy requires an alternative MRD

There was one patient receiving blinatumomab in our study [47]. The MRD monitoring and immunophenotyping at second recurrence was difficult due to the

that was based on alternative B-lineage differentiation markers. Nuclear nuTdT in combination with cytoplasmatic CD22 as most stably expressed Ag were chosen. So, given the appearance of new targeted therapies, FC algorithms for both MRD

There is an equivocal situation with T-ALL. On the one hand, search for aberrant immunophenotype for TCP ended in failure. Expression of main Ag studied with respect to LAIP, that is, CD99 and nuTdT is variable [21]. On the other hand, taking into account normal T-cell ontogenesis, MRD assessment may be based on the

diagnosis and monitoring require certain flexibility and timely rational changes.

just to assess TCP number in order to quantify MRD at any therapy stage.

expression, while CD7 is needed to detect the membrane determinant.

Correct choice of antibody CD3 clone is of much importance for TCP identification. For instance, clone UCHT1 should be used to detect CD3 cytoplasmatic

The AIEOP-BFM protocol suggests that MRD detection in T-ALL should be

We compared the two approaches to TCP identification to find optimal TCP

All T-ALL patients in our study were stratified into the intermediate and high risk groups. According to MRD levels on day 15, most patients remained in the initial stratification group though 25.0% were transferred from the intermediate

Of note that all patients demonstrated MRD-positivity on day 15, that is, none of the T-ALL patients achieved complete leukemic cytoreduction on ALL-IC-BFM

So, clinical significance of MRD in ALL arises no doubt. It is reasonable to make

Since there are no normal BCP on day 15 of induction chemotherapy, MRD quantification in case of pre-pre-B and pre-B ALL immunosubtypes should be

pro-B (CD10<sup>−</sup> and/or CD34<sup>−</sup>), ALL immunosubtype MRD detection should be

During BM regeneration (end of remission induction therapy and long-term treatment stages), MRD quantification is based on identification of BCP with aberrant immunosubtype. Alongside with the most common CD58/CD38, the following Ag should be used in LAIP assessment: CD81, CD9, CD13, CD33, CD66c, CD123, and CD20. At the stage of diagnosis, the most informative personalized Ag combinations should be selected for further MRD monitoring to make a more accurate risk stratification of patients at different therapy stages and are an effective tool for its modification. Tumor immunophenotype in disease recurrence should be compared with that

In case of targeted therapy, for example, anti-recurrence treatment, FC protocol should be changed with respect to treatment features. For instance, BCP evaluation

absence of TCP of the cyCD3++smCD3−nuTdT+

/

++smCD3+

MRD quantification immunologically using FC assay.

in disease onset taking into account its possible changes.

/CD34+

based on expression of nuclear nuTdT in combination with cyCD22.

B-cells. An algorithm for BCP detection was proposed and tested

CD7+

immunophenotype within cyCD3+

population within CD19<sup>+</sup>

level in BM. One has therefore

population bas-

B-cells. In case of

**124**

The authors declare no conflict of interests.
