Shifts in expression of immunological cell markers in relapsed acute leukemia.

The immunophenotypic features of leukemia blast cells were analyzed in a group of 156 patients with different immunological subtypes of acute leukemia, both lymphoblastic and myeloblastic. Of the 58 patients for whom immunologic studies were performed at relapse, 42 (72%) showed changes in the expression of immunologic markers. The minor shifts in B-ALL were observed most frequently and concerned of the loss of CD34 antigen in 17 cases and the loss of cALLA (CD10) in 7 cases of B-ALL at the first relapse. The acquisition of cell markers was not frequently observed, only in four cases could be seen. HLA-DR molecules remained relatively constant from diagnosis to relapse. In 2 from 3 T-ALL cases the loss of CD1 and CD2 markers, respectively, was noticed at relapse. CD5 and CD7 markers were relatively stable. In AML cases at relapse the acquisition of CD13 marker (in 4 from 7 cases) was often observed. It was interesting that comparing to the B-ALL cases, the loss of CD34 marker in AML cases was stray. In one case the acquisition of this antigen at relapse was actually observed. The major interlineage shift was detected in one case of B-ALL, that was newly diagnosed at relapse as AML M4 and presented different cytogenetic features. This case provides strong connection with the treatment, as more recently epipodophyllotoxins (vumon in our patient) have been linked to the development of secondary AML associated with a shorter latency period. The immunophenotypic changes frequently occur at relapse in all acute leukemia types. The shifts (loss or acquisition) in expression of individual markers at relapse are bound with the first diagnosis and may have a relationship to the treatment and are important for correct assessment of minimal residual disease.