Immunophenotyping in acute myeloid leukemia

The immunological phenotype of blast cells in myeloid leukemia is very diverse, and most often (in 80% of patients) aberrant expression of antigens is determined.

In other words, typical myeloid markers (CD11, CD13, CD14, CD15, CD33, CD36, CD41, CD42, CD65, HLA-DR; antigen of early CD34 precursor cells) can be expressed, first, together with antigens characteristic of lymphoid cells; secondly, their expression may be abnormal in the combination of early and late markers of cell differentiation; thirdly, over-expression of an antigen (for example, CD34) may be observed; fourth, there may be no expression of any antigen (for example, CD13 is expressed, but no CD33 is expressed). It is the aberrant immunophenotype that serves as a marker when monitoring minimal residual disease during remission.

In other cases, the detection of certain antigens on leukemic cells indicates only the aberrant immunophenotype and in some cases correlates with the prognosis.

For example, in acute myeloid leukemia, lymphoid markers occur in 14–60% of patients. According to German researchers, the CD2 antigen was expressed on blast cells in 57% of patients, CD5-y 60%, CD7-y 37%.

A study of the American group CALGB by definition of an immunophenotype in 339 patients with acute myeloid leukemia revealed the following frequency of lymphoid markers: CD2 (T-cell marker) was detected in 21% of cases (45 of 211 patients), CD19 (B-cell marker) – in 14 % (in 41 of 298 patients), CD2 and CD19, studied in combination, in 33% of cases (in 56 of 170 patients). Interestingly, with promyelocytic leukemia, a combination with lymphoid markers is noted 2 times more often, and with myelomonoblastic leukemia with eosinophilia (M4eo), 8 times more often than with other myeloid leukemias.

It is known that both M3 and M4eo are the most favorable variants of acute myeloid leukemia according to the effectiveness of treatment, therefore it is not surprising that in patients whose leukemic cells express, along with myeloid, lymphoid markers, the percentage of remissions was significantly higher (75 vs. 59%; р = 0.04) and overall survival over 2 years is better (43.8 ± 6.3% versus 29.8 ± 3.8%; p = 0.02). Detection of the early antigen of hematopoietic cells CD34 is also of prognostic significance: the prognosis in patients whose cells carry this marker is significantly worse than in those without it. It should be noted that this marker is most often determined in elderly patients with acute myeloid leukemia.

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