FREQUENCY OF ABERRANT EXPRESSION OF CD MARKERS IN CASES OF ACUTE LEUKEMIA

SUMMARY: In the present study 100 patients of acute leukemia were studied to find out the frequency of aberrant antigens in AML, B-ALL and T-ALL of which 73% cases were of lymphoid lineage and 27% cases were of myeloid lineage. 74% cases showed expression of lineage specific markers and were considered as conventional immunophenotypes while 26% cases showed expression of CD antigens which were not of that lineage upon which they were expressing. Some myeloid lineage associated antigens were present on acute lymphoblastic leukemia cases and lymphoid associated antigens showed their expression on acute myeloid leukemia cases. These cases were considered as aberrant immunophenotypes. The cases of acute lymphoblastic leukemia were further subcategorized as B-cell and T-cell acute lymphoblastic leukemia. The data from this study suggested that either the commonly described myeloid, B-cell and T-cell differentiation pathways are incorrect or blasts from cases of acute leukemia do not represent their normal counterparts. To explain these mixed immunophenotypes it is suggested that leukemic cells may have aberrant markers because of their abnormal genetic programme resulting in lineage infidelity. In this scenario the precursor cells may retain features of one lineage that they should have lost during commitment to another cell line. As a result of the leukemic process cells with aberrant immunophenotypes are immortalized in a precommitment phase of differentiation resulting in lineage promiscuity. This study strengthens the theories of lineage infidelity and lineage promiscuity by taking a critical and comparative approach of frequencies of aberrant antigens in acuteleukemia in population of Pakistan.